27th elementary school of piraeus final version

Activity report: Energy performance and
climatic conditions in public spaces in the
MED area / Step-by-Step Energy Retrofit
Methodology for the 27th Elementary
School of Piraeus, Greece according to the
Passive House Standard
Deliverable No. P8
Component No.5-Pilot testing of the methodology, Evaluation and Capitalization
Phase No. 5.6- Final set of applications and Development of a strategic plan to introduce
outcomes in the wider EU area
Contract No.: 1C-MED12-73
Axe2: Protection of the environment and promotion of a sustainable territorial development
Objective 2.2: Promotion of renewable energy and improvement of energy efficiency
Authors:
Submission date: 20/5/2015
Status: Final
May 2015

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Contents
1. General....................................................................................................................................................................... 3
2. Building description.................................................................................................................................................... 4
2.1 Building identification data ........................................................................................................................................ 4
2.2 Building operational schedule .................................................................................................................................... 6
2.3 Existing Building data................................................................................................................................................. 7
2.3.1 Design........................................................................................................................................................................7
2.3.2 Building Envelope....................................................................................................................................................10
2.3.3 Energy Balance Winter............................................................................................................................................17
2.3.5 HVAC- Lightning ......................................................................................................................................................20
3 The Passive House Standard .................................................................................................... 23
3.1 Introduction.............................................................................................................................................................. 23
3.2 Passive House Criteria .............................................................................................................................................. 26
3.3 EnerPHit Standard for existing buildings .................................................................................................................. 28
3.4 Occupant Satisfaction............................................................................................................................................... 32
3.6 Boundary conditions for the PHPP calculation.......................................................................................................... 36
3.7 Passive House Standard for Schools.......................................................................................................................... 39
3.7.1 The Air Quality Issue ...............................................................................................................................................39
3.7.2 The Requirements...................................................................................................................................................40
4 The Enerphit Procedure for the 27th
Elementary School............................................................ 43
4.1 General................................................................................................................................ 43
4.2 The building envelope .............................................................................................................................................. 46
4.2.1 The opaque elements .............................................................................................................................................46
4.2.2 Transparent Elements.............................................................................................................................................49
4.3 The new Ventilation System with Heat Recovery...................................................................................................... 52
4.4 Heating and cooling ................................................................................................................................................. 56
4.5 The overall results of the passive house retrofit ....................................................................................................... 57

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4.5.2 The summer situation (monthly method)..............................................................................................................58
5 Comparison of PASSIVE HOUSES Step-by-Step Approach & KENAK............................................ 62
Calculation of the primary energy use is reliable due to the use of the total unadjusted final energy
consumption and can be used successfully for checking compliance with the PE limit value............. 77
6 Conclusion............................................................................................................................... 84
7 How to go about it................................................................................................................... 85
8 References............................................................................................................................... 86
Stefanos Pallantzas, Civil Engineer, Certified Passive House Designer.............................................. 86

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1. General
In the present deliverable, a detailed presentation of the retrofit methodologies and results will be given,
concerning a selected building (the PILOT BUILDING) of the ones that are illustrated in the deliverable D.7.
The criteria for selecting one of the three potential buildings are the followings :
- Present building status (structural, schedule, operations, etc)
- Potential for retrofit results
- Complexity of the building envelope
- Potential of multiplication effect for the study outcomes for similar buildings in Municipality
- Available info for structural items (insulation studies, etc)
- Competence of building info folder
Based on the above info, the studding team, together with the technical board of the municipality of Piraeus,
has decided to run the retrofitting study for the case of the 27th
Elementary School (THE PILOT BUILDING).
Under the philosophy that moves the REPUBLIC-MED program and concerns the nomination of approaches and
methods to intensify the imagination and innovation that is documented with scientific approaches, will be
performed analysis, based on the principles of an international standard and Liabilities building, the existing
energy behavior and scenarios proposed situation the pilot building. For this building (the PILOT BUILDING), it
will be implemented the above actions (1) and (2), and based on the passive house standard and compare the
results obtained from the two methodologies as:
A) The accuracy of calculations the status quo: Comparison between measurements and calculations of the
National methodology and Passive House Standard.
B) The upgrading and investment cost measures: comparison between the measures and the costs provided by
the National methodology and Passive House Standard.
It will also investigate the feasibility and feasibility of the annual renovation of the building, with the following
actions:
• Hint energy upgrade measures that can be applied for each year until 01.01.2019.
• Identify the Cost per year.
• Description of measurements and control of energy efficiency of a building over the course of the progressive
project.
• Guidelines for identifying funding opportunities to implement progressive project with examples of similar
projects.
The application of models for both Passive House Standard and KENAK will be made by highly experienced and
certified designers, aiming at optimum efficiency models.

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2. Building description
2.1 Building identification data
The 27th elementary school in Piraeus is located at 37°57’ N and 23°37’ E. The school consists of two connected
buildings and a courtyard. The building consists of the ground floor, the first and the second floor. The boiler
room is located on the ground floor. The 27th elementary school was built in 1987.
Figure 1 : depicts the geographical location of the school
The basic data of the building (according to plans, data provided and on-site measurements) are :

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Location Piraeus Climatic Zone (PHPP) GR002a - Athinai
Total Floor area (m2) 1640 Treated Floor Area (PHPP,
m2)
1264
Total Volume (m3) 5014 Conditioned Volume
(PHPP,m3)
4044
Total Thermal Envelope
(PHPP,m2)
2913 Total Windows Area
(PHPP,m2)
335
Number of floors Ground Floor + 2
Table 1 : Info data for the building under consideration

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2.2 Building operational schedule
The school operates from the 11th of September until the 15th of June from Monday to Friday. During this
period, the school remains closed for approximately 15 days for Christmas holidays and 15 days for Easter
holidays.
The school operates in two shifts. The first shift operates from 08:00 until 14:00. The number of pupils and
teachers in the first shift is 237 and 24 respectively. The second shift operates from 14:00 until 16:15. The
number of pupils and teachers in the second shift is 45 and 2 respectively. In this shift, only two classrooms in
the ground floor are operational.
Each classroom accommodates approximately 20-23 pupils. The main operational characteristics of the 27th
elementary school are:
Occupancy schedule 08:00 – 14:00
14.00 - 16.15
Total number of pupils 237
45
Average occupancy hours 1st shift: 6h
2nd shift: 2h, 15 min
Total number of
teachers & staff
24
Table 2 : Schedule for the building under consideration

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2.3 Existing Building data
2.3.1 Design
The whole building is oriented in the north-south direction. The main entrance of the building is on the north
facade. The building envelope has not been renovated since its construction in 1987.
Figure 2 : North Façade Figure 3: South Façade
The layouts of the ground, first, second floors and the elevations are presented in the Figures 4, 5, 6 , 7 and 8
respectively.
Figure 4 : Ground floor

8
Figure 5: 1st
floor
Figure 6: 2nd
floor

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Figure 7: North and East Elevations
Figure 8 : South and West Elevations.

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2.3.2 Building Envelope
2.3.2.1 Opaque elements
The construction is a concrete-brick construction. Erker slabs have been used a lot as an architectural feature of
the building. The walls of the school are in a good condition without evident signs of moisture or leakage
problems. According to the plans and the building permission, the walls are built with bricks and are thermally
insulated.
Tables 3, 4 and 5 presents the thermal characteristics of the walls as inputted in the PHPP.
Bauteil Nr. Bauteil-Bezeichnung Innendämmung?
01ud Ext.wall_brick
Wärmeübergangsw iderstand [m²K/W]
Ausrichtung des Bauteils 2-Wand innen Rsi 0,13
Angrenzend an 1-Außenluft außen Rsa 0,04
Teilfläche 1 l[W/(mK)] Teilfläche 2 (optional) l[W/(mK)] Teilfläche 3 (optional) l[W/(mK)] Dicke [mm]
Plaster 0,872 20
Brick 0,523 90
Glass wool 0,041 50
Brick 0,523 90
Plaster 0,872 20
Flächenanteil Teilfläche 1 Flächenanteil Teilfläche 2 Flächenanteil Teilfläche 3 Summe
100% 27,0 cm
U-Wert-Zuschlag 0,10 W/(m²K) U-Wert: 0,662 W/(m²K)

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Concerning these figures, we have increased the U-values by 10% in order to include also all thermal bridges of
the outside walls. We also have decreased proportionally the insulation referring to the concrete elements,
because part of their surface is uninsulated.
Bauteil Nr. Innendämmung?
02ud Ext.wall_conc.
Plaster 0,872 20
Brick 0,523 60
Glass wool 0,041 50
Reinforced concrete 2,030 300
Plaster 0,872 20
70% 30,0% 45,0 cm
0,10 W/(m²K) U-Wert: 2,000 W/(m²K)
03ud Erker slab_
Ausrichtung des Bauteils 0,1 innen Rsi 0,10
Marble tiles 1,100 50
plaster 0,872 20
100% 22,0 cm
0,10 W/(m²K) U-Wert: 3,643 W/(m²K)

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Figure 9: Thermal bridges and uninsulated concrete elements
There are two types of roofs in the school; a flat roof mainly and a sloped roof only in a small part of the school.
Both roof types are thermally insulated. Table 6 and Table 7 present the thermal characteristics of the roofs.
05ud Flat roof
Ausrichtung des Bauteils 1-Dach innen Rsi 0,17
Plaster 0,870 10
Concrete slab 2,040 150
Light concrete 0,290 100
Cement mortar 1,400 20
Hydroinsulation 0,230 10
Extruded polystyrene 0,034 100
Gravel 2,000 50
100% 44,0 cm
0,10 W/(m²K) U-Wert: 0,373 W/(m²K)

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Figure 10: Flat Roof Figure 11: Sloped Roof
The floor in contact with the ground is covered by marble tiles and is thermally insulated. Table 8 presents the
thermal characteristics of the floor.
06ud Sloped roof
ALUMINIUM SHEET 160,000 5
Insul. Sandwich panel 0,025 100
ALUMINIUM SHEET 160,000 5
100% 11,0 cm
0,10 W/(m²K) U-Wert: 0,338 W/(m²K)

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2.3.2.2 Transparent Elements
There are three types of openings in the building: windows, doors and glass blocks. The windows are double
glazed with aluminum frame and the doors are made of steel. The U value of the windows is 3,7 W/m2K (12 mm
air gap), of the metal doors is 5,8 W/m2K and of the glass blocks is 3,5 W/m2K.
The total area of the building’s openings (including the glass blocks) is approximately 335 m2. The following
Figures depict views of the windows, doors and glass blocks.
Figure 12 : Aluminium windows Figure 13 : Steel Exterior Doors
04ud Ground Floor slab
Ausrichtung des Bauteils 3-Boden innen Rsi 0,10
Angrenzend an 2-Erdreich außen Rsa 0,00
Glass wool insulation 0,041 50
Sand 0,580 20
Concrete gravel 0,810 200
100% 47,0 cm
0,05 W/(m²K) U-Wert: 0,631 W/(m²K)

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Figure 14: Glass blocks Figure 15 : Glass blocks and Windows in the South facade
In the following table (9), one can see the characteristics of the transparent elements, as shown in the PHPP.
Verglasungen Verglasungen
Als Startkomponente für die Optimierung empfohlene Verglasung:
2-fach Wärmeschutzglas (Bitte Behaglichkeitskriterium beachten!)
ID Bezeichnung g-Wert Ug-Wert
W/(m²K)
01ud Existing double glazed windows 0,77 2,90
02ud Glass blocks 0,30 3,50
03ud Existing 5,70
Fensterrahmen Fensterrahmen
Uf-Wert Rahmenbreite Glasrand Wärmebrücke Einbau Wärmebrücke
ID Bezeichnung links rechts unten oben links rechts unten oben
YGlasrand
links
YGlasrand
rechts
YGlasrand
unten
YGlasrand
oben
YEinbau
links
YEinbau
rechts
YEinbau
unten
YEinbau
oben
W/(m²K) W/(m²K) W/(m²K) W/(m²K) m m m m W/(mK) W/(mK) W/(mK) W/(mK) W/(mK) W/(mK) W/(mK) W/(mK)
01ud Metal frame not insulated 5,50 5,50 5,50 5,50 0,060 0,060 0,080 0,080 0,030 0,030 0,030 0,030 0,088 0,088 0,088 0,088
02ud Glassblock 0,88 0,88 0,88 0,88 0,001 0,001 0,001 0,001 0,100 0,100 0,100 0,100 0,100 0,100 0,100 0,100

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2.3.2.3 Shading
The building is situated in a densely built urban area. Big Buildings are shading the school, especially the south
façade. The sloped roof of the Auditorium is blocking a big part of the south façade of the 1st
floor. There is no
external shading system for the windows in the building.
2.3.2.4 Airtightness
We have assumed in our calculations that the airtightness of the building is very poor, according to experience
from the majority of the existing building stock in Greece.
Orientation
Global-
Radiation
Shading
Ver-
schmut-
zung
Non-vertical
Radiation
Glass part g-Value Reductionfactor Radiation Window Area
Window
U-Value
Glass area
Average
radiation
Standardwerte → kWh/(m²a) 0,75 0,95 0,85 m2
W/(m2
K) m2
kWh/(m2
a)
Nord 25 0,56 0,95 0,85 0,75 0,65 0,34 158,39 3,95 118,61 25
Ost 50 0,10 0,95 0,85 0,78 0,77 0,06 13,50 3,68 10,47 50
Süd 95 0,53 0,95 0,85 0,78 0,61 0,33 124,19 3,94 96,63 95
West 49 0,29 0,95 0,85 0,93 0,38 0,22 38,11 3,85 35,35 46
Horizontal 80 1,00 0,95 0,85 0,00 0,00 0,00 0,00 0,00 0,00 80
Summe bzw. Mittelwert über alle Fenster 0,60 0,31 334,18 3,92 261,06

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2.3.3 Energy Balance Winter
According to the envelope characteristics and the airtightness of the building, the energy balance of the building
is shown in the following chart. In the left column the losses of the thermal envelope are shown. The main
problems are: windows, external walls and airtightness of the building. On the right column one can see that
the solar gains are very low. This is the reason why the energy demand, even in winter time, is very high.
Figure 16 : Energy Balance Winter by PHPP

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2.3.4 Energy Balance Summer
The following chart shows the temperature situation during summer. As one can see, the inside temperature
(yellow) of the building is often higher than the outside temperature (blue). This happens also during June and
September, when the school is operating.
Figure 17 : temperature situation during summer by PHPP
The energy balance of the Building during summer time is shown in the following chart. The same elements
(walls, roof, windows, lack of airtightness on the left column) lead to heat loads coming inside the building,
while huge internal heat gains (right column white) lead to a large cooling demand.

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Figure 18 : Energy Balance Summer by PHPP

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2.3.5 HVAC- Lightning
2.3.5.1 Heating / Cooling
The school has a central heating system. The central heating system dates back to the time when the school was
constructed in 1987. In 2004, there was a fuel switch from oil to natural gas by replacing the oil burner with a
natural gas burner. The boiler room is located on the ground floor of the school at the south side of the building.
The central heating system operates for approximately 4 months, from mid-November until the end of March
and the heating schedule daily is from 07.00 to 12.30, 5 days per week. The natural gas fired boiler is
manufactured by the Greek company “Therma”; its total heating capacity is 150.000 kcal/h (175 KW). This boiler
is extremely over-dimensioned, while the needs of the existing building are less than 75 KW.
A two-pipe system is used for hot water circulation throughout the building. The school building is heated by
cast iron radiators. The piping network in the boiler room, but also in the rest of the building, is not insulated. All
areas of the school are heated by radiators, including the circulation areas, except from the WC.
There is not any central cooling system in the school. A few old AC split units, with a total capacity of 26kW, are
located in the teachers’ offices and some other rooms. Some ceiling fans are also present.
Figure 19 : The Gas Boiler Figure 20 : Uninsulated pipes
Figure 21: Ceiling fans and splits Figure 22 : some fans in the Auditorium

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2.3.5.2 Lighting
The school is equipped with T8 fluorescent luminaires of 36 W with a cover. The average power in the
classrooms is approximately 13,5 W/m2 and in the circulating areas is 2,2 W/m2. It is noted that many of the
lighting fixtures are not operating and the lighting conditions are not sufficient.
Figure 23 : Insufficient lightning in all areas
Inserting all above data in the PHPP we’ve got the results for the energy consumption of the existing building as
follows:
Comments:
 The heating and cooling consumption were expected. The building is mainly uninsulated, the quality of
the windows is very poor and the airtightness is poor. The building has a good orientation but the solar
gains are low because of the surrounding buildings. The indoor air quality is only controlled by opening
the windows, but this causes more energy demand for heating and cooling. Interviews with teachers
gave us information about them not being satisfied from the heating and cooling system and the air
Builiding Energy Consumption according toTFA and Year
Treated Floor Area m² 1263,8 Criteria Ok?
Heating Heating Demand kWh/(m²a) 56 ≤ 15 -
Heating Load W/m² 62 ≤ - -
Cooling Cooling Demand kWh/(m²a) 49 ≤ 15 16
Cooling Load W/m² 42 ≤ - 11
Overheating >25 % - ≤ - -
Humidification G39 (> 12 g/kg) % 0 ≤ 10 ja
Airtightness Blowerdoor Test n50 1/h 7,0 ≤ 1,0 nein
PE-Bedarf kWh/(m²a) 195 ≤ 201,792951 ja
PER-Bedarf kWh/(m²a) 174 ≤ - -
kWh/(m²a) 0 ≥ - -
2
leeres Feld: Daten fehlen; '-': keine Anforderung
Non Renewavble Energy
Renewable
Primary Energy
(PER)
Erzeugung erneuerb. Energie
(Bezug auf überbaute Fläche)
-
nein
nein
Aleternative
Criteria

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quality. The final demand is on this level because of the climate conditions and due to the fact that the
school is closed during the hot period of summer.
 The Primary Energy demand is lower than expected. This is because the heating system, which has very
high losses due to the uninsulated pipe system, doesn’t work more than 4 hours/day and the lightning
system is very poor. The measured consumptions during the last years are even lower, because of the
financial crisis.
 There is a big potential to reduce the energy demand of the school using the passive house standard
and this is what will be analyzed in the following sections.

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3 The Passive House Standard
3.1 Introduction
Passive House is a building standard that is truly
energy efficient, comfortable and affordable at the
same time. Passive House is not a brand name, but
a tried and true construction concept that can be
applied by anyone, anywhere.
Yet, a Passive House is more than just a low-energy
building:
Passive Houses allow for space heating and cooling
related energy savings of up to 90% compared with
typical building stock and over 75% compared to
average new builds. Passive Houses use less than
1.5 l of oil or 1.5 m3 of gas to heat one square
meter of living space for a year – substantially less
than common “low-energy” buildings. Vast energy
savings have been demonstrated in warm climates
where typical buildings also require active cooling.
Passive Houses make efficient use of the sun, internal heat sources and heat recovery, rendering conventional
heating systems unnecessary throughout even the coldest of winters. During warmer months, Passive Houses
make use of passive cooling techniques such as strategic shading to keep comfortably cool.
Passive Houses are praised for the high level of comfort they offer. Internal surface temperatures vary little from
indoor air temperatures, even in the face of extreme outdoor temperatures. Special windows and a building
envelope consisting of a highly insulated roof and floor slab as well as highly insulated exterior walls keep the
desired warmth in the house – or undesirable heat out.
A ventilation system imperceptibly supplies constant fresh air, making for superior air quality without
unpleasant draughts. A highly efficient heat recovery unit allows for the heat contained in the exhaust air to be
re-used.

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Typical heating systems in
Central Europe, where the
Passive House Standard was
first developed and applied, are
centralized hot water heating
systems consisting of radiators,
pipes and central oil or gas
boilers. The average heating
load of standard buildings in
this area is approximately 100
W/m² (approx. 10 kW for a 100
m² apartment). The Passive
House concept is based on the
goal of reducing heat losses to
an absolute minimum, thus
rendering large heating systems
unnecessary. With peak heating
loads below 10 W per square meter of living area, the low remaining heat demand can be delivered via the
supply air by a post heating coil (see box below). A building that does not require any heating system other than
post air heating is called a Passive House; no traditional heating (or cooling) systems are needed.
The Passive House concept itself remains the same for all of the world’s climates, as does the physics behind it.
Yet while Passive House principles remain the same across the world, the details do have to be adapted to the
specific climate at hand. A building fulfilling the Passive House Standard will look much different in Alaska than
in Zimbabwe.
In ‘warm climates’, reducing the space heating demand is a concern but in addition, avoiding overheating in
summer by passive or active cooling strategies become highly relevant for the building optimization. The
improved building envelope of a Passive House helps to minimize external heat loads (solar and transmission).
In addition, well-known shading solutions in warm climates, such as fixed and moveable shading devices (in
order to minimize heat loads), as well as cross night ventilation (passive cooling) are important measures for
Passive Houses.
Regarding summer comfort, the internal heat loads must be minimized e.g. energy efficient appliances should
be focused on.
First certified Passive Houses in warm climates show the optimization potential in design and execution. While
lower levels of insulation are sufficient for moderate and warm climates such as the majority of the
Mediterranean region, high levels of insulation in opaque elements of the building envelope are required for
extremely hot climates.

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To achieve cost-efficient solutions, the resulting insulation thicknesses call for optimized compactness of the
building shape. Windows should meet the comfort and energy requirements, and the designer should be aware
of the high influence of the best orientation.
Very good airtightness is important in all climates, and especially for hot and humid climates [Schnieders et. al.
2012]. Active cooling could be avoided in so-called ‘Happy climates’, but is mandatory for very warm climates
(for instance Granada, Spain).
Ventilation strategies include natural ventilation in summer as well as mechanical ventilation (extract air system
only or ventilation system with heat exchanger and summer bypass). For cost effective Passive Houses in warm
climates component performance should be in the focus of all stakeholders.

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3.2 Passive House Criteria
Passive Houses are characterized by an especially high level of indoor comfort with minimum energy
expenditure. In general, the Passive House Standard provides excellent cost-effectiveness particularly in the
case of new builds. The categories Passive House Classic, Plus or Premium can be achieved depending on the
demand and generation of renewable primary energy (PER).
1
The criteria and alternative criteria apply for all climates worldwide. The reference area for all limit values is the
treated floor area (TFA) calculated according to the latest version of the PHPP Manual (exceptions: generation
of renewable energy with reference to ground area and airtightness with reference to the net air volume).
2
Two alternative criteria which are enclosed by a double line together may replace both of the adjacent criteria
on the left which are also enclosed by a double line.
3
The steady-state heating load calculated in the PHPP is applicable. Loads for heating up after temperature
setbacks are not taken into account.
4
Variable limit value subject to climate data, necessary air change rate and internal moisture loads (calculation
in the PHPP).
5
Variable limit value subject to climate data, necessary air change rate and internal heat and moisture loads
(calculation in the PHPP).
6
The steady-state cooling load calculated in the PHPP is applicable. In the case of internal heat gains greater
than 2.1 W/m² the limit value will increase by the difference between the actual internal heat gains and 2.1
W/m².

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7
Energy for heating, cooling, dehumidification, DHW, lighting, auxiliary electricity and electrical appliances is
included. The limit value applies for residential buildings and typical educational and administrative buildings. In
case of uses deviating from these, if an extremely high electricity demand occurs then the limit value can also be
exceeded after consultation with the Passive House Institute. Evidence of efficient use of electrical energy is
necessary for this.
8
The requirements for the PER demand and generation of renewable energy were first introduced in 2015. As
an alternative to these two criteria, evidence for the Passive House Classic Standard can continue to be provided
in the transitional phase by proving compliance with the previous requirement for the non-renewable primary
energy demand (PE) of QP ≤ 120 kWh/(m²a). The desired verification method can be selected in the PHPP
worksheet "Verification". The primary energy factor profile 1 in the PHPP should be used by default unless PHI
has specified other national values.

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3.3 EnerPHit Standard for existing buildings
The Passive House Standard often cannot be feasibly achieved in older buildings due to various difficulties.
Refurbishment to the EnerPHit Standard using Passive House components for relevant structural elements in
such buildings leads to extensive improvements with respect to thermal comfort, structural integrity, cost-
effectiveness and energy requirements.
The EnerPHit-Standard can be achieved through compliance with the criteria of the component method (Table
8) or alternatively through compliance with the criteria of the energy demand method (Table 9). Only the
criteria of one of these methods must be met. The climate zone to be used for the building's location is
automatically determined on the basis of the chosen climate data set in the Passive House Planning Package
(PHPP).
As a rule, the criteria mentioned in Table 8 correspond with the criteria for certified Passive House components.
The criteria must be complied with at least as an average value for the entire building. A higher value is
permissible in certain areas as long as this is compensated for by means of better thermal protection in other
areas.
In addition to the criteria in Table 8 or Table 9, the general criteria in Table 10 must always be met. The EnerPHit
categories Classic, Plus or Premium may be achieved depending on the demand and generation of renewable
primary energy (PER).

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Table 8 : EnerPhit criteria for the building component method
Table 9 : Enerphit criteria for the energy demand method

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Table 10 : General EnerPhit criteria
The PHI Low Energy Building Standard is suitable for buildings which do not fully comply with Passive House
criteria for various reasons.
Table 11 : PHI Low Energy Building Criteria
Besides a high level of energy efficiency, Passive House buildings and buildings refurbished to the EnerPHit
Standard offer an optimum standard of thermal comfort and a high degree of user satisfaction as well as
protection against condensate related damage. In order to guarantee this, the minimum criteria mentioned
below must also be complied with in addition to the criteria in Sections
 Frequency of overheating. Percentage of hours in a given year with indoor temperatures above 25 °C
o without active cooling: ≤ 10 %

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o with active cooling: cooling system must be adequately dimensioned
 Frequency of excessively high humidity. Percentage of hours in a given year with absolute indoor air
humidity levels above 12 g/kg
o without active cooling: ≤ 20 %
o with active cooling: ≤ 10 %
The criteria for the minimum level of thermal protection according to Table 12 are always applicable irrespective
of the energy standard and must be complied with even if EnerPHit exemptions are used. They apply for each
individual building component on its own (e.g. wall build-up, window, connection detail). Averaging of several
different building components as evidence of compliance with the criteria is not permissible.
Table 12 : Criteria for minimum thermal protection

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3.4 Occupant Satisfaction
All living areas must have at least one operable window. Exceptions are possible in justified cases as long as
there is no significant likelihood of occupant satisfaction being affected.
It must be possible for the user to operate the lighting and temporary shading elements. Priority must be given
to user-operated control over any automatic regulation.
In case of active heating and/or cooling, it must be possible for users to regulate the interior temperature for
each utilization unit.
The heating or air-conditioning technology must be suitably dimensioned in order to ensure the specified
temperatures for heating or cooling under all expected conditions.
Ventilation system:
o Controllability: The ventilation volume flow rate must be adjustable for the actual demand. In
residential buildings the volume flow rate must be user-adjustable for each accommodation unit
(three settings are recommended: standard volume flow / standard volume flow +30 % /
standard volume flow -30 %).
o Ventilation in all rooms: All rooms within the thermal building envelope must be directly or
indirectly (transferred air) ventilated with a sufficient volume flow rate. This also applies for
rooms which are not continuously used by persons provided that the mechanical ventilation of
these rooms does not involve disproportionately high expenditure.
o Excessively low relative indoor air humidity : If a relative indoor air humidity lower than 30 % is
shown in the PHPP for one or several months, effective countermeasures should be undertaken
(e.g. moisture recovery, air humidifiers, automatic control based on the demand or zone,
extended cascade ventilation, or monitoring of the actual relative air humidity with the option
of subsequent measures).
o Sound level: The ventilation system must not generate noise in living areas. Recommended
values for the sound level are ≤ 25 db(A): supply air rooms in residential buildings, and
bedrooms and recreational rooms in non-residential buildings ≤ 30 db(A): rooms in non-
residential buildings (except for bedrooms and recreational rooms) and extract air rooms in
residential buildings
o Draughts: The ventilation system must not cause uncomfortable draughts.

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3.5 The Passive House Planning Package (PHPP)
The Passive House Planning Package (PHPP) (order here) contains everything necessary for designing a properly
functioning Passive House. The PHPP prepares an energy balance and calculates the annual energy demand of
the building based on the user input relating to the building's characteristics.
The main results provided by this software programme include:
o The annual heating demand [kWh/(m²a)] and maximum heating load [W/m²]
o Summer thermal comfort with active cooling: annual cooling demand [kWh/(m²a)] and maximum
cooling load [W/m²]
o Summer thermal comfort with passive cooling: frequency of overheating events [%]
o Annual primary energy demand for the whole building [kWh/(m²a)]
The PHPP consists of a software program and a printed manual. The manual not only elucidates the calculation
methods used in the PHPP but also explains other important key points in the construction of Passive Houses.
The actual PHPP program is based on Excel (or an equivalent spreadsheet software programme) with different
worksheets containing the respective inputs and calculations for various areas. Among other things, the PHPP
deals with the following aspects:
o Dimensioning of individual components (building component assemblies including U-value calculation,
quality of windows, shading, ventilation etc.) and their influence on the energy balance of the building in
winter as well as in summer
o Dimensioning of the heating load and cooling load
o Dimensioning of the mechanical systems for the entire building: heating, cooling, hot water provision
o Verification of the energy efficiency of the building concept in its entirety

34
The calculations are instantaneous, i.e. after changing an entry the user can immediately see the effect on the
energy balance of the building. This makes it possible to compare components of different qualities without
great effort and thus optimize the specific construction project - whether a new construction or a refurbishment
- in a step-by-step manner with reference to energy efficiency. Typical monthly climatic conditions for the
building location are selected as the underlying boundary conditions (particularly temperature and solar
radiation). Based on this, the PHPP calculates a monthly heating or cooling demand for the entered building. The
PHPP can thus be used for different climatic regions around the world.
All calculations in the PHPP are based strictly on the laws of physics. Wherever possible, specific algorithms
resort to current international standards. Generalisations are necessary in some places (e.g. global established
routines for shading), and sometimes deviations may also be necessary (due to the extremely low energy
demand of Passive Houses, e.g. for the asymptotic formula for the utilisation factor), while for some areas there
are no internationally relevant standards (e.g. with reference to dimensioning of ventilation systems). This
approach has resulted in an internationally reliable calculation tool with which the efficiency of a construction
project can be evaluated more accurately than with conventional calculation methods. (Read more about this in
the section PHPP - validated and proven in practice)
The PHPP forms the basis for quality assurance and certification of a building as a Passive House or an EnerPHit
retrofit. The results of the PHPP calculation are collated in a well-structured verification sheet. In addition to the
basic components of the PHPP already mentioned, various useful additions have also been made for the user's
benefit. For example, the simplified calculation method based on the German energy saving ordinance EnEV has
been integrated into the PHPP. Preparing an energy performance certificate for a project is facilitated by an
additional tool.
A section of the PHPP “Verification”-sheet with the results for a sample detached house built to the Passive
House Standard.

35
Figure 24 : flow chart on how the PHPP works
The PHPP can be used all over the world and is now available in several languages. Some of the translated
versions contain additional calculations based on regional standards (similar to the German EnEV) in order to
allow use as official verification of energy efficiency in the respective countries.
The first edition of the Passive House Planning Package (PHPP) was released in 1998 and has been continuously
further developed since then. New modules which were important for planning were added later on, including
advanced calculations for window parameters, shading, heating load and summer behaviour, cooling and
dehumidification demands, cooling load, ventilation for large objects and non-residential buildings, taking into
account of renewable energy sources and refurbishment of existing buildings (EnerPHit). The PHPP is
continuously being validated and expanded in line with measured values and new findings.
The new PHPP 9 (2015) was launched at the 19th International Passive House Conference in April 2015.

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3.6 Boundary conditions for the PHPP calculation
When verifying the criteria using the Passive House Planning Package (PHPP), the following boundary conditions
must be fulfilled:
3.6.1 Zoning
The entire building envelope (e.g. a row of terraced houses or an apartment block or office building with several
thermally connected units) must be taken into account for calculation of the specific values. An overall
calculation can be used to provide evidence of this. If all zones have the same set temperature, then a weighted
average based on the TFA from individual PHPP calculations of several sub-zones may be used. Combination of
thermally separated buildings is not permissible. For the certification of refurbishments or extensions, the area
considered must contain at least one external wall, a roof surface and a floor slab or basement ceiling. Single
units inside a multi-storey building cannot be certified. Buildings which are adjacent to other buildings (e.g.
urban developments) must include at least one exterior wall, a roof area and a floor slab and/or basement
ceiling to be eligible for separate certification.
3.6.2 Calculaion method
The monthly method is used for the specific heating demand.
3.6.3 Internl heat gains
The PHPP contains standard values for internal heat gains in a range of utilization types. These are to be used
unless PHI has specified other values (e.g. national values). The use of the individually calculated internal heat
gains in PHPP is only permitted if it can be shown that actual utilisation will and must differ considerably from
the utilisation on which the standard values are based.
3.6.4 Internal moisture gains
Average value over all annual hours (also outside of the usage period): residential building: 100 g/(person*h)
non-residential building without significant moisture sources beyond moisture released by persons (e.g. office,
educational buildings etc.): 10 g/(Person*h) non-residential building with significant moisture sources beyond
moisture released by persons: plausible substantiated estimation based on the anticipated utilisation.

37
3.6.5 Occupancy rates
Residential buildings: standard occupancy rate in the PHPP; if the expected number of persons is significantly
higher than the standard occupancy rate, then it is recommended that the higher value should be used. Non-
residential buildings: Occupancy rates and periods of occupancy must be determined on a project-specific basis
and coordinated with the utilization profile.
3.6.6 Indoor design temperature
Heating, residential buildings: 20 °C without night setback, non-residential buildings: standard indoor
temperatures based on EN 12831 apply. For unspecified uses or deviating requirements, the indoor
temperature is to be determined on a project-specific basis. For intermittent heating (night setback), the indoor
design temperature may be decreased upon verification. Cooling and dehumidification: 25 °C for 12 g/kg
absolute indoor air humidity.
3.6.7 Climate data
Climate data sets (with a seven-digit ID number) approved by the Passive House Institute should be used. The
selected data set must be representative for the climate of the building's location. If an approved data set is not
yet available for the location of the building, then a new data set can be requested from an accredited Passive
House Building Certifier.
3.6.8 Average ventilation volumetric flow
Residential buildings: 20-30 m³/h per person in the household, but at least a 0.30-fold air change with reference
to the treated floor area multiplied by 2.5 m room height. Non-residential buildings: The average ventilation
volumetric flow must be determined for the specific project based on a fresh air demand of 15-30 m³/h per
person (higher volumetric flows are permitted in the case of use for sports etc. and if required by the applicable
mandatory requirements relating to labour laws). The different operation settings and times of the ventilation
system must be considered. Operating times for pre-ventilation and post-ventilation should be taken into
account when switching off the ventilation system. For residential and non-residential buildings, the mass flows
used must correspond with the actual adjusted values.

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3.6.9 Domestic hot water demand
Residential buildings: 25 litres of 60 °C water per person per day unless PHI has specified other national values.
Non-residential buildings: the domestic hot water demand in litres of 60 °C water per person per day must be
separately determined for each specific project.
3.6.10 Balance boundary for electricity demand
All electricity uses that are within the thermal building envelope are taken into account in the energy balance.
Electricity uses near the building or on the premises that are outside of the thermal envelope are generally not
taken into account. By way of exception, the following electricity uses are taken into account even if they are
outside of the thermal envelope:
o Electricity for the generation and distribution of heating, domestic hot water and cooling as well as for
ventilation, provided that this supplies building parts situated within the thermal envelope.
o Elevators and escalators which are situated outside provided that these overcome the distance in height
caused by the building and serve as access to the building
o Computers and communication technology (server including UPS, telephone system etc.) including the
air conditioning necessary for these, to the extent they are used by the building's occupants.
o Household appliances such as washing machines, dryers, refrigerators , freezers if used by the building's
occupants themselves
o Intentional illumination of the interior by externally situated light sources.

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3.7 Passive House Standard for Schools
The Passive House concept has been
undergoing a rapid expansion in the last few
years, also in the non-residential sector.
Administrative buildings, factory buildings,
community centers and many other buildings
have been realized. Some initial projects have
also been realized in the area of new school
construction and school modernization. The
systematically examined boundary conditions
for the construction of schools were published
in 2006 within the framework of the Protocol
Volume “Passive House Schools” in the
“Research Group for Cost-efficient Passive
Houses” [Feist 2006] . Experiences with initial
projects that have been realized were also
incorporated into this.
3.7.1 The Air Quality Issue
The pollution of the indoor air in schools consists mainly of the following:
o Outdoor air pollution
o Metabolic waste products of the occupants
o Emissions from building materials, furnishings and work
equipment (crafts, chemistry)
o Radon pollution
o Microorganisms (MVOC)

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3.7.2 The Requirements
o Each modern school should have controlled ventilation which meets the criteria for acceptable indoor
air quality.
o In the interest of a justified investment or technical expenditure, the air flow rates of the school's
ventilation system should be based on health and educational objectives and not on the upper limits
of the comfort criteria. The result is: CO2 limit values between 1200 and 1500 ppm and designed air
flow rates between 15 and 20 m³/person/h (possibly more for a higher average age of the pupils).
With these reference values, the result is a significant improvement in the air quality in comparison with
the values usually obtained in Germany, Austria and
Switzerland today. Experience with the Passive Houses
already built also shows that the designed values should
not be reduced even further. For increased air quantities
attention would have to be paid to the resulting reduction
in the relative air humidity in winter. If the per person air
flow rates are projected as 15 to 20 m³/(h pers) in the given
interval, the primary objectives of indoor air quality will
certainly be achieved and the problem of low relative
humidity does not even arise.
In comparison with residential buildings and office buildings, the overall air flow rates and air change
rates which have to be planned are considerably higher during use due to the increased number of
persons present in schools.
o In the interest of justifiable operational costs, the ventilation systems in schools must be operated
periodically or according to demand. Preliminary purge phases or subsequent purging periods ensue
before and after use for hygiene reasons. The easiest solution is to use time control.
A direct result of the designed high air change rates is that the operating times of the ventilation system
have to be restricted to the periods of use or the air quantities should at least be greatly reduced
outside of these times, because otherwise there will be very high electricity consumption values even
for efficient systems – this differs fundamentally from home ventilation in which the designed air
quantities are near those required for basic ventilation needed on a permanent basis (with 0.25 h-1).
In schools, for basic ventilation planned with 2 h-1, there are several possibilities, the most efficient
being a one-hour preliminary purge phase with designed volumetric air flows, with which the necessary
”double” exchange of the air volume can be achieved. After that, regulation of the air quantities
according to demand should be strived for, on which the occupancy density, the CO2 content of the air
or other representative air quality indicator can be based.
Without any ventilation, the air quality is poor. The CO2 concentration can be easily measured; and is
correlated to other indoor pollution substances e.g. Radon. With a ventilation system, all pollution is
reduced to a hygienically satisfactory level (subjectively, visitors note that “it doesn't smell like a school
here at all”).

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As shown by experience, it should be ensured that the technology used is robust and simple and, if
necessary, possible to operate manually (no “technological Christmas trees”). For intermittent operation
of the ventilation system, it is important that all system parts, especially the filters, are “run dry” before
switching off the air flows – this is achieved most easily by using the recirculation mode after the period
of use.
o Passive House schools should be designed so that besides the usual heating using supply air, it is also
possible to heat up the rooms to a comfortable level during the preliminary purge phase in the
morning. It is stated that heating classrooms using the supply air in schools is no problem because the
volumetric fresh air flow based on the useable area is very high. However, after the setback phase,
reheating to a comfortable level (particularly in relation to the radiation temperature asymmetry) is only
possible if the building's envelope surfaces have a high level of thermal protection. For schools this is
the decisive criterion.
Parametric studies with thermal simulation of school buildings show that under the given conditions the
level of thermal protection complying with the “residential Passive House Standard” is within the range
of optimum results. Nevertheless, for school buildings there is more scope than there is for residential
buildings, due to the many kinds of regulation possibilities and the high air changes available. Because
the buildings are generally comparatively large and compact, the designer is well-advised to approach
the optimum level by complying with the classic Passive House Standard while at the same keeping a
safety margin.
o The criteria given above can be met if, under the boundary conditions of use, the building envelope
and heat recovery are designed so that the annual heating demand according to the PHPP is less than
or equal to 15 kWh/(m²a) (based on the total net useable area).
A detailed analysis has confirmed the planning guidelines according to which some Passive House
schools had already been planned and built. This was by no means self-evident, as, due to the
completely different usage, this criterion is derived in a completely different way than the criterion
which applies to residential buildings.
Nevertheless, it is no coincident that this result is quantitatively comparable with that of the Passive
House residential building; the reason for this is that the temporal average values of the boundary
conditions (air quantities, internal heat sources, heat load) are very similar to those for residential use.
As shown by the examples of buildings which have already been built, applying these basic
recommendations and the components available on the market today, it is possible to realise Passive
House school buildings with various design concepts.
School refurbishment with Passive House components can be planned using the PHPP and that, except
for some clearly defined features, the same focal points had to be taken into consideration for these as
for residential or office buildings in the Passive House Standard.
An important boundary condition is the intermittent use with temporarily extremely high internal loads.
The temporal average value of the internal loads with 2.8 W/m² on average is not much more than the

42
values for residential use. Setback phases play an important role in school buildings. A tool is available
for determining the expected effective temperature reduction [PHPP 2007] .
In school buildings particular attention should be paid to specific use in summer. Sufficient shading,
night-time ventilation and high internal heat capacity are all imperatives. If it is not possible to meet one
of these requirements, equivalent compensation must be provided – this can be concrete core
temperature control or the use of adequate heat exchangers, for example.
For reheating after setback phases, the central heating generator must be able to provide a sufficiently
high output (in the range of 50 W/m² of heated useable area). The pre-heating phase must be regulated
via time control and internal temperature measurement.
Based on all previous experiences, the Passive House concept has proved to be just as successful for
schools, where it is particularly advantageous due to the ventilation system’s importance.

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4 The Enerphit Procedure for the 27th
Elementary School
4.1 General
Passive House school buildings are particularly interesting. Several school buildings have been realized using this
standard and experiences gained from their use are now available: The Passive House Standards allows for
energy savings of around 75% in comparison with average new school buildings - and of course there is no need
for an additional heating or cooling system. The additional investment costs are within reasonable limits. What
is important is the know-how - which can be obtained by every architect thanks to the “Passive House Schools”
Protocol Volume, funded by the Hessian Ministry of Economic Affairs.
While a comprehensive retrofit is always the best way to increase energy efficiency in existing buildings, it is
unfortunately not always possible. Often, financial or other challenges get in the way - the reality can be more
complex.
Figure 25 : Step-by-step approach of EnerPhit refurbishment plan

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Each part of a building has its own life span. While the facade may be crumbling, the roof tiles may still be in
great shape. Perhaps the heating system is shot, yet it will be another 20 years before the windows need to be
replaced. Renovation measures can be time and resource intensive, which is why they are typically only carried
out when absolutely necessary. Once the facade has been newly insulated and painted, it will typically stay that
way, for better or worse, for the next generation or two. At the same time, energy efficiency measures for any
one part of the building are always most affordable when that part is already in need of renovation.
Step-by-step renovation is the natural result. One of the additional benefits of such an approach is that it gets
the most out of each building component so that the initial investment is taken advantage of to its fullest. Also,
renovation work is spread over a variety smaller measures is easier to finance.
If You Do It, Do It Right From The Start!
It is important to avoid missed opportunities by carrying out every retrofitting measure with an eye to quality
and energy efficiency. It is also essential to remember that when we retrofit, we are not just improving
aesthetics and reducing energy losses – we are also directly affecting a building’s moisture balance, air-flow,
surface temperatures and much more besides.
Planning Your Retrofit
When conducting a step-by-step deep retrofit, a well-thought out plan can help ensure that the integrity of the
building envelope throughout the renovation process. Improving airtightness, for example, without taking the
insulation and ventilation into account, may lead to otherwise avoidable moisture problems. Especially if many
years lie between various renovation steps, a plan covering present and future steps is essential.

45
Figure 26 : Examples of EnerPhit results
A master plan can be tailored to fit the needs of the building and/or its owners/users. For example, it could
specify the replacement of various components at various points in time or go facade by facade. However the
plan is composed, it should define the type, quality and order of measures to be taken. The reward for steps
carried out following an integrated plan: a future-proof, comfortable, sustainable building with consistently low
running costs.

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4.2 The building envelope
The most important principle for energy efficient
construction is a continuous insulating envelope all
around the building (yellow thick line), which minimizes
heat losses like a warm coat.
In addition to the insulating envelope there should also
be an airtight layer (red line) as most insulation
materials are not airtight.
Preventing thermal bridges (circles) is essential – here
an individual planning method has to be developed,
according to the construction and used materials, in
order to achieve thermal bridge free design.
Independently of the construction, materials or building
technology, one rule is always applicable: both
insulation and airtight layers need to be continuous.
4.2.1 The opaque elements
Applying exterior wall insulation to an existing building when the plaster needs to be renewed can help reduce
the costs for the plaster significantly as plastering can be limited to rough filling where the old plaster is no
longer able to bear loads and needs to be chipped off.
There is no universal answer to the question whether a compound insulation system needs to be bonded to the
old plaster or even dowelled. Manufacturers are starting to offer strength tests for larger projects in order to
determine whether the old plaster is still able to bear loads. Additional dowelling may be dispensed with if such
guarantees are provided by manufacturers.
In our case we have added a 100mm external insulation layer (for example EPS 035) to all external walls of the
building (except from the eastern partition wall towards the neighboring building). The U-Value of the external
walls was improved as follows:

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08ud Ext.wall_brick_eps
Plaster 0,872 20
Brick 0,523 90
Glass wool 0,041 50
Brick 0,523 90
Plaster 0,872 20
eps 0,035 100
Acrylic plaster 0,350 4
100% 37,4 cm
W/(m²K) U-Wert: 0,215 W/(m²K)
09ud Ext.wall_conc._eps
Plaster 0,872 20
Brick 0,523 60
Glass wool 0,041 50
Plaster 0,872 20
eps 0,035 100
70% 30,0% 55,4 cm
W/(m²K) U-Wert: 0,286 W/(m²K)

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In the flat roof of the building we have added 100 mm of XPS 034
There is no need to put additional insulation on the sloped roof of the Auditorium. There is also no need to put
insulation on the ground floor slab, because the thermal bridges to the ground are not so important.
10ud Erker slab_eps
Ausrichtung des Bauteils 0,1 innen Rsi 0,10
plaster 0,872 20
eps 0,035 100
100% 32,4 cm
W/(m²K) U-Wert: 0,317 W/(m²K)
05ud Flat roof_eps
Plaster 0,870 10
Concrete slab 2,040 150
Light concrete 0,290 100
Cement mortar 1,400 20
Hydroinsulation 0,230 10
Extruded polystyrene 0,034 200
Gravel 2,000 50
100% 54,0 cm
W/(m²K) U-Wert: 0,151 W/(m²K)

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4.2.2 Transparent Elements
In new buildings, as well as in old buildings that have not been modernized, windows constitute a weak point in
terms of thermal protection as their thermal transmittance (heat transfer coefficient, U-value) is generally much
poorer than that of the wall, roof or floor constructions. As a rule, windows of old buildings also have massive
leaks which lead to high heat losses and to an impairment of comfort due to drafts, and they can also cause
building damage. On the other hand, windows are essential in providing solar gains and thus reducing the
overall heating demand.
One of the objectives of carrying out modernizations is to provide a comfortable indoor temperature for the
occupants. Half our perception of warmth is from the radiant temperature of our surroundings and the other
half from the air temperature. It will feel cold next to internal surfaces that are cold even if the air temperature
is normal just from the lack of radiant heat. So for comfort it is important that cold internal surface
temperatures are avoided as well as draughts and temperature stratification in the room.
In this context it is important to limit the difference between the operative or perceived indoor temperature
and the temperature of the individual surfaces enclosing the room volume (walls, ceiling, floor or windows). As
long as the operative temperature also remains within the comfortable range unpleasant temperature
differences between surfaces and uncomfortable radiant heat effects are avoided. Limiting the temperature
difference also reduces the effect of cold air descending from cold surfaces producing draughts and cold feet.
In the relevant literature, e.g. [Feist 1998] , it is stated that as soon as the temperature of individual surfaces
that enclose the room volume does not exceed a limit of 4.2 K below the operative temperature of the room,
the unpleasant effects mentioned above can no longer occur.
Thus the comfort requirement is: θsi ≥ θop – 4,2 K.
If the operative indoor temperature θop is assumed to be 22°C and the external temperature θa is –16°C, for an
internal heat transfer resistance Rsi = 0,13 m²K/W, the result is the well-known Passive House comfort criterion
Uw,installed ≤ 0,85 W/(m²K) which was introduced more than a decade ago.
If it is not possible to achieve this value, a heat source must be provided underneath the window in order to
prevent uncomfortable cold air descent and radiant heat deprivation, and to achieve the desired level of
comfort.
The heat transfer coefficient for the installed window is determined based on the U-values of the glazing (Ug)
and the frame (Uf) as well as the thermal bridge loss coefficient of the glazing edge (Ψg), the connection of the
adjacent building components (ΨInstall) and the respective areas or lengths:

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Orientation
Global
Radiation
Shadings Dirty
Non vertical
radiation
Glass area g-Value Reduction Factor Radiation Window area Uw Glass area
average
global
radiation
Standardwerte → kWh/(m²a) 0,75 0,95 0,85 m2
W/(m2
K) m2
kWh/(m2
a)
Nord 25 0,50 0,95 0,85 0,54 0,65 0,22 158,39 1,34 85,93 25
Ost 50 0,10 0,95 0,85 0,59 0,40 0,05 13,50 1,32 8,03 50
Süd 95 0,46 0,95 0,85 0,58 0,40 0,21 124,19 1,35 71,52 95
West 49 0,32 0,95 0,85 0,71 0,54 0,19 38,11 1,35 27,12 46
Horizontal 80 1,00 0,95 0,85 0,00 0,00 0,00 0,00 0,00 0,00 80
Summe bzw. Mittelwert über alle Fenster 0,53 0,21 334,18 1,34 192,60
All these values are required for the correct consideration of the heat losses of a window in the energy balance.
For the overall concept, not only the heat losses but also the solar gains through the windows are important.
Besides the orientation and shading of the windows, the total solar transmission factor of the glass and the
frame proportion also influence the solar gains. Since significant energy gains cannot be achieved through the
opaque frames, it is important to minimize the frame proportions (smaller facing widths, large windows, no
glazing bars, fewer glazing sections). The total solar transmission factor g refers to the proportion of incident
solar radiation which enters the building. If the g-value is 0,3 or 30%, for example, this means that 30% of the
solar radiation incident on the glass pane can reach the inside of the building. Modern standard triple-glazing
has g-values of around 50%. G-values of up to 60% are possible at moderate additional costs with the use of one
or more panes made of clear glass instead of float glass. The g-value is lower if there are special requirements in
terms of the robustness of the glass or fire protection regulations. This should be taken into consideration for
the energy balance at an early stage. In moderate climates, glass with lower g-values (solar protection glass)
should only be used if very high internal heat loads are expected.
In our building, windows are the main reason for the heat losses. So they have to be replaced with better,
thermal protected components. We have chosen the following values for the new components:
 South oriented double-glazed windows with Ug=1,30 W/m2K, g-Value 0,40 and Uf=1,00 W/m2K
 North oriented double-glazed windows with Ug=1,30 W/m2K, g-Value 0,60 and Uf=1,00 W/m2K
 The east and west windows have the same values as the south oriented
 All glass blocks will be replaced by double-glazed windows
 Shading of the south-east-west windows will be improved by 75% during summer

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The installation of the new windows will minimize the installation thermal bridges and improve their
airtightness.
The steel external doors of the building will also be
replaced by new with similar Uw values. The new doors
have to be double in order to improve the needed
airtightness.

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4.3 The new Ventilation System with Heat Recovery
Ventilation with heat recovery is a central requirement for the operation of Passive Houses. The significant
reduction in ventilation heat losses as a result of the heat recovery makes it possible to both simplify and reduce
the size of the heating system, thereby reducing investment costs as well.
Ventilation with heat recovery plays an important role in energetic refurbishment as well. Significant cost and
energy savings due to the lower ventilation heat losses combined with the resulting good indoor air quality
make such ventilation not only more attractive, but necessary for energy efficient construction.
Next to climatic conditions and the required ventilation rate, a building’s ventilation heat losses mainly depend
on:
 the heat recovery efficiency of the ventilation unit
 the airtightness of the building (the free infiltration and exfiltration)
 the forced infiltration and exfiltration caused by the volume flow balancing between exhaust and fresh
air
Beside the heat recovery of the ventilation unit and the airtightness of the building, the volume flow balancing
of exhaust air and fresh air also has an important influence on ventilation heat losses and, therefore, on the
energy balance of the whole building. Imbalances can be caused e.g. by improper commissioning of the
ventilation system or gradual clogging of the air filter.
In our case we have designed a simple ventilation system consisting of two main duct systems in each level, one
for the supply air into the north oriented classes and offices and one for the extract air from the south oriented
floors and sanitary rooms.
Figure 27 : Ground floor: the heat recovery unit is located in the former oil-tank room.

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Figure 28 : 1st
floor - Supply air goes to the classrooms, extract air comes from the corridors (the temperature
there is higher because of their south orientation) and the WC’s.
Figure 29 : 2nd
floor - same design as in 1st
floor.
The supply air volume is in general 18m3/h per person, so every classroom needs approximately 430m3/h. The
total capacity of the central unit is 5.000 m3/h. The heat recovery rate has to be >75%. There are certified units
with a rate of 85% in the market.

54
A ground heat exchanger, developed under the school yard, will
support the ventilation system and will adjust the air temperature
and humidity during the whole year. Ground-air heat exchangers
(also known as earth tubes) offer an innovative method of heating
and cooling a building and are often used on zero carbon /
Passivhaus buildings. The ventilation air is simply drawn through
underground pipes at a depth of 1.5m into the HRV, which pre-heats
the air in the winter and pre-cools the air in the summer. So the Heat
Recovery Rate will be as follows:
The Ventilation unit will have an automatic summer by-pass and an electrical heating registry. The unit will
operate 24h/day: 8 hours in full operation, 2 hours before the school opens at 77% and during the night at 40%.
The average ventilation volume will be 2.952 m3/h and the average air exchange will be 0,73 ach/h. The unit will
not operate during weekends and vacations. Preheating the air flow up to 38 Degrees Celsius will cover all the
heating demand of the building. It is proposed to use the existing conventional heating system of the building
every morning of a working day for an hour before the school opens. For the rest of the day the ventilation
system will cover the needs.
Selection of the ventilation unit with heat recovery
Location of the unit Inside the themal envelope
Heat recovery Humidity recovery Specific power Application range Frost protection
zur Lüftungsgeräte-Liste efficiency consumption required
Sortierung: WIE LISTE Unit hWRG hERV [Wh/m³] [m³/h]
Selection of unit 0,84 0,00 0,45 1300 - 5200 ja
Implementation of frost protection 1-Nein
Conductivity supply air duct Y W/(mK) 0,911 Temperature limit [°C] 2
Lenght of supply air duct m 5 Useful energy [kWh/a] 0
Conductivity extract air duct Y W/(mK) 0,911
Lenght of extract air duct m 5 Room temperature (°C) 20
Temperature of mechanical services room °C 20 Avg ambient temp. heat. period (°C) 12,9
(Enter only if the central unit is outside of the thermal envelope.) Avg ground temp (°C) 20,7
Effective heat recovery efficiency hWRG,eff 83,4%
Effective heat recovery efficiency subsoil heat exchanger
SHX efficiency h*EWÜ 85%
Heat recovery efficiency SHX hEWÜ 94%
0654vl03-LÜFTA - MAXK I3 6000 DC
1-Innerhalb therm.Hülle
Average air change rate calculation
Factors referenced to
Type of operation Daily operation times maximum Air flow rate Air change rate
h/d m³/h 1/h
Maximum 8,0 1,00 4680 1,16
Standard 2,0 0,77 3600 0,89
Basic 0,54 2520 0,62
Minimum 14,0 0,40 1872 0,46
Average air flow rate (m³/h) Average air change rate (1/h)
Average value 0,63 2952 0,73

55
During summer the ventilation rate will increase by 50%. Night ventilation
trough automatic opened windows will decrease the needs for cooling.
Heating Load PH = 16983 W
Heating Load according to Treated Floor Area PH / TFA = 13,4 W/m²
Input max. Supply air Temperature 38 °C °C °C
Max.Supply Air Temp. Jzu,Max 38 °C Supply air temperature without preheating Jzu,Min 19,7 19,7
For Comparison: Heating Load, transfelable by the Supply Air is PZuluft;Max
= 17835 W specified : 14,1 W/m²
(ja/nein)(yes/no)
Heatable with supply air? ja yes

56
4.4 Heating and cooling
The existing heating system will be
used only for the pre-heating of the
building every day before the school
opens and after longer periods, when
the school is closed. This will decrease
the gas consumption by 80%. In order
to improve the performance of the
system, the pipe system has to be well
insulated.
The building will need 4.500 KWh/a for
heating.
For the summer situation the split units that exist, will cover the needs of the building. It is proposed to put
these units on the corridors of each Level and the ventilation system will supply the fresh air in all rooms. 20Kw
of air-conditioning power will cover the whole building. The building will need 11.500 KWh/a for cooling.

57
4.5 The overall results of the passive house retrofit
With the implementation of the above described specifications and according to the calculations with the
Passive House Planning Package PHPP ver. 9,1/2015 the new energy balances of the building will be as
following:
4.5.1 The winter situation (monthly method)
Figure 30 : Winter energy balance from PHPP after renovation

58
The losses of the external walls (light blue), the windows (yellow) and the airtightness on the left column are
extremely decreased. The losses are more balanced now. There are no losses to the ground. On the other hand
the solar gains (yellow) on the right column are still not big enough. A further improvement for the solar gains
could be to install horizontal windows on the existing south oriented sloped roof. The heating energy demand is
decreased by 85%.
4.5.2 The summer situation (monthly method)
Figure 31 : Summer energy balance from PHPP after renovation

59
The additional ventilation with the by-pass control and the night ventilation through the windows is very
important for reducing the risk of overheating. The mechanical ventilation should be decreased during the
summer period by 50% and the night ventilation should add 0,50 ACH/h.
Below is the new energy balance of the building according to PHPP calculations:

60
According to these results the building is a Passive House Plus Building. The heating demand is now
4KWh/m2a, decreased by 93% and the cooling demand is 9KWh/m2a,
EnerPHit-Verification
Foto oder Zeichnung Building:
Street:
Postcode / City:
Province/Country
Building type:
Climate data set: ud---02-Athinai-Piraeus
Climate zone: 5: Warm Standorthöhe: 50 m
Home owner / Client:
Street:
Postcode/City:
Province/Country
Architecture: Mechanical system:
Street: Street:
Postcode/City Postcode / City:
Province/Country Province/Country
Energy consultancy: Certification:
Street: Street:
Postcode / City: 15234 Postcode / City:
Province/Country Province/Country
Year of construction: 1987 Interior temperature winter [°C] 20,0 Interior temp. summer [°C] 25,0
No. of dwelling units: 1 Internal heat gains (IHG) heating case [W/m2]: 2,8 IHG cooling case [W/m²]: 2,8
No. of occupants: 260,0 Specific capacity [Wh/K per m² TFA]: 204 Mechanical cooling: x
Specific building demands with reference to the treated floor area
Treated floor area m² 1263,8 Criteria Fullfilled?2
Space heating Heating demand kWh/(m²a) 4 ≤ 15 -
Heating load W/m² 13 ≤ - -
Space cooling Cooling and dehumid. demand kWh/(m²a) 9 ≤ 15 16
Cooling load W/m² 12 ≤ - 11
Frequency of overheating (> 25 °C) % - ≤ - -
Frequency excess humidity (> 12 g/kg) % 0 ≤ 10 ja
Airtightness Pressurization test result n50 1/h 1,0 ≤ 1,0 ja
PE-Demand kWh/(m²a) 76 ≤ - -
PER demand kWh/(m²a) 25 ≤ 45 30
kWh/(m²a) 57 ≥ 60 36
2
EnerPHit Plus? ja
Task Name Surname Signature
1-Projektierer
Ausgestellt am Ort
09/05/15
Non-renewable primary energy
(PE)
Primary Energy
Renewable Generation of renewable
energy
Stefan
I confirm that the values given herein have been determined following the PHPP methodology and based on the
characteristic values of the building.The PHPP calculations are attached to this application.
ja
GR-GriechenlandAttiki
Iraklidon 15B
Chalandri
Attiki
27th Elementary School of Piraeus
Attiki
Municipality of Piraeus
GR-Griechenland
School
Stefanos Pallantzas
ja
ja
Alternative
criteria
GR-Griechenland
Pallantzas
CEPH Designer - Civil Engineer Athens

61
decreased by 82%. These results cover the passive house criteria for our
climatic region (<15 KWh/m2a for heating or cooling).
The loads for heating and cooling are 13W/m2 and 12W/m2, 10
times lower than these of the conventional buildings.
The Primary Energy Demand (PE) is 76KWh/m2a, fulfills the 120KWh/m2a criteria. Also following the new PER
criteria of Primary Renewable Energy the criteria are fulfilled.
Furthermore, if we install a 160m2 Photovoltaic System on the south roofs of the building, the building will
produce on average over 45.000 Kwh of electricity every year, a factor which will make the building a PLUS
passive house, a building that produces the energy it needs.
Name of system System 1 System 2 Anlage 3 Anlage 4 Anlage 5 PV-Referenzanlage
Location: Selection in 'Areas' worksheet 3-SLOPED_ROOF 54-2f_ROOF_SLAB
Size of selected area 126,4 505,9 m²
Deviation from North 180 0 °
Angle of inclination from horizontal 13 0 °
Alternative data input: Deviation from North °
Alternative data input: Angle of inclination from the horizontal °
Information from the module data sheet
Technology 4-Mono-Si 5-Poly-Si 5-Poly-Si 5-Poly-Si 5-Poly-Si 4-Mono-Si
Nominal current IMPP0 7,71 7,71 7,71 A
Nominal voltage UMPP0 30,50 30,50 30,50 V
Nominal power Pn 235 235 0 0 0 235 Wp
Temperature coefficient short-circuit current a 0,040 0,040 0,040 %/K
Temperature coefficient open-circuit voltage b -0,340 -0,340 -0,340 %/K
Module dimensions: Height 1,658 1,658 1,658 m
Module dimensions: Width 0,994 0,994 0,994 m
1,6 Modulfläche [m²]
Further specifications
Number of modules nM 50 50 0,0
Height of module array 1,0 1,0 m
Height of horizon hHori 0,0 0,0 m
Horizontal distance aHori 15,0 15,0 m
Additional reduction factor shading rso
Efficiency of the inverter hWR 95% 195% 95%
Results
Area of module field 82,4 82,4 0,0 0,0 0,0 0,0 m²
Free area on the selected building element 44,0 423,5 m²
Allocation to building element 65% 16%
Annual losses due to shading 0 0 kWh
Summe
Annual electricity yield of the inverter, absolute 15704 29909 45613 kWh/a
Related to ground area 19,5 37,2 57 kWh/m²AGrund*a
Specific PE factor (non-renewable primary energy) 0,30 0,11 kWhprim_ne/kWhEnd
Specific CO2-equivalent emisson value of system 44,5 20,9 g/kWh
CO2 equivalent emissions according to 1-CO2 factors GEMIS 4.6 (Germany) 2104,4 3110,5 5214,9 kg/a

62
5 Comparison of PASSIVE HOUSES Step-by-Step Approach & KENAK
5.1 Step-By-Step Enerphit Renovation actions of the 27th
Elementary
School of Piraeus
In our case we propose a 3-step renovation of the building according to the most efficient and cost effective
way:
5.1.1 1st
step: Insulation of the building envelope
Our calculations with the PHPP show that the main losses of the building, especially during winter are from the
external walls and the roof. By putting 100mm of external insulation. for example EPS insulation 035 on every
external wall and by adding 100mm of additional insulation on the flat roof and the erker slabs, we have the
following results in energy consumption :
The heating demand will decrease from 56 to 29KWh/m2a, the cooling demand will decrease from 49 to 40
KWh/m2a and the Primary Energy Demand will decrease from 192 to 133 KWh/m2a.
This means :
 48% decrease of heating demand during winter.
 18% decrease of ccooling demand during the summer days.
 30% decrease of primary energy demand during the whole year.
The total cost of this 1st
step is estimated to be 95.000 euros (1853 m2 of external surface * 50euros/m2).

63
5.1.2 2nd
step: New windows and doors, Additional Shading, Night
Ventilation schedule
The second step of the renovation has to be the replacement of all the windows and doors of the building, the
design of better shading to the south, the increase of the air tightness of the building and a new night
ventilation plan.
The results after these steps are:
KWh/m2a and the Primary Energy Demand will decrease from 133 to 76 KWh/m2a.
This means :
 45% decrease of heating demand during winter from 1st
step and 71% from existing building
 55% decrease of cooling demand during the summer days from 1st
 43% decrease of primary energy demand during the whole year from 1st
step and 60% from existing
building
The total cost of this 2nd
step is estimated to be 85.000 euros for the windows and doors. (335 m2 of surface *
250 euros/m2, together with increase of airtightness).
The new shading system to the south is estimated to cost 25.000 euros. No costs are for the night ventilation.
Space coolingCooling and dehumidification demand kWh/(m²a) 19 ≤ 15 16
Airtightness Pressurization test result n50 1/h 3,0 ≤ 1,0 nein
PE-Demand kWh/(m²a) 76 ≤ 123,970558 ja
PER demand kWh/(m²a) 51 ≤ - -
kWh/(m²a) 0 ≥ - -
2
(PE)
Primary Energy
energy
-
nein
nein
Alternative
criteria

64
5.1.3 3rd
step: Mechanical Ventilation with heat recovery and PV panels
on the roof
The final step of the renovation will cover the building systems and the use of Renewable Sources. The
mechanical ventilation with heat recovery and ground heat exchanger, as described in our primary study will be
installed.
Two PV systems , one on the sloped roof and one on the flat roof will produce over 45.000 Kwh every year. This
means 57KWh/m2a of RES will cover nearly 70% of the needs of the school. This system can be increased in the
future in order to make the school energy-neutral.
Finally the airtightness of the building will be reduced to 1ACH, by closing all possible gaps in the building
envelope and creating a continuous airtight layer on the inside surface of the building.

65
The results after these steps are:
KWh/m2a and the Primary Energy Demand (nonrenewable) will decrease from 76 to 25 KWh/m2a.
This means:
 75% decrease of heating demand during winter from 2nd
 50% decrease of cooling demand during the summer days from 2nd
 67% decrease of primary energy demand during the whole year from 2nd
step and 87% from existing
building.
The costs of the ventilation system are estimated as follows:
 The Ventilation unit with preheating and summer-bypass and regulation 30.000 euros
 The ground heat exchanger 15.000 euros
 The Duct system 20.000 euros.
 The cost of the PV system is estimated 20.000 Euros.
 The costs of the finalization of the airtightness layer is estimated 15.000 euros.
Space coolingCooling and dehumidification demand kWh/(m²a) 9 ≤ 15 16
Airtightness Pressurization test result n50 1/h 1,0 ≤ 1,0 ja
PE-Demand kWh/(m²a) 76 ≤ - -
PER demand kWh/(m²a) 25 ≤ 45 30
kWh/(m²a) 57 ≥ 60 36
2
ja
ja
Alternative
criteria
ja
(PE)
Primary Energy
energy

66
5.2 Economics of Step-by-step approach by ENERPHIT
5.2.1 Economy and financing of efficiency according to the EnerPHit
standard
The economic assessment of buildings has to be based on life cycle costs. From the beginning this was the
concept of the Passive House, and the concept of cost optimality (“cost optimal level”) based on life cycle costs
has become a major issue in the Energy Performance of Buildings Directive (EPBD) of the European Union.
There are many methodological frameworks that fit more or less in this scheme: not all methods though fulfill
the requirement of reflecting the whole economic picture. Furthermore, boundary conditions are as important
as the method. Inadequate methods, different assumptions or boundary conditions are the most important
cause of extremely different results of empiric studies. The main sources of major distortions are assignment of
costs that are not related to energy efficiency, underestimation of life expectancy, failure to consider residual
values at the end of the calculation period, unrealistic assumptions on energy price increases, unreliable design
and quality of measures, inadequate expectations on return and related discount rates, and lock-in effects. The
net effect of these influences is usually that estimated economic energy savings result much lower than they
are, which turns out to be a strong barrier for the implementation of energy efficiency.
Economic Assessment of Energy Efficiency
The overall longevity of buildings implies that short payback periods cannot be expected; they are not good
indicators since they are neither related to the investment period length, nor to the relevance of the measures.
Instead, the whole life cycle as well as the interests must be regarded. This view is implemented in dynamical
methods based on present values. In theory, economic activities aim at profits which can only be evaluated in
comparison with alternatives. The alternative to an energy efficiency investment is the investment in other
assets or a bank deposit which yields interests. Another option would be to avoid the loan, thus saving interests
on debt.
Costs
Expenditures are made to achieve benefits. However, these investments have follow-up operational costs, e.g.
for maintenance and energy. The end of the building useful life in most cases is not planned as it will happen in
the far future. It is not even known whether costs or revenues will occur at demolition. Therefore, life cycle
costs of buildings mostly include the investment cost and estimated running costs, referring to the same point in
time. Life cycle costs are the total costs over the building life time, discounted according to the year when they
occur.

67
Investment theory
Benefits become market goods, and investments are made to achieve revenues from benefits sold on the
market. The goal of the investor is to achieve an economic advantage: an investment should be at least as
attractive as its alternatives that are available on the capital market. Surpluses are gains, when they are higher
than those for an alternative, economically comparable, capital asset. The benchmark is the return for
comparable assets (classification: risk; a subjective assessment can involve non-economic factors too). In a
perfect capital market there is only one interest rate (= price of capital). Investments should be profitable on the
long run.
Figure 32: Cash value (or present value) of periodic revenues depending on number of periods and interest
rates. High interest rates depreciate the value of the revenues and thus the market capitalisation.
The present value of revenue (or any cash flow) is the amount needed now to yield the same revenue from the
bank, including interests. The present value of a payment is the amount you need ‘now’ to pay ‘later’, when the
expenditure occurs. Since present values refer to the same point in time, all receipts and expenditures become
comparable, but the result depends on the discount rate. Discount rates are crucial: High expected rates of
return depreciate later revenues, thus the upfront investments. Therefore, the choice of an adequate interest
rate is important. For effective economic assessments, it is useful to do the calculation based on real prices and
interest rates, while inflation - which does not affect the economic result - is taken out from the calculation.

68
The net present value (NPV) is the sum of all present values: costs (or payments, e.g. the investment) are
negative, and revenues are positive. The NPV is the total gain of the investment, when all lifetime costs and
revenues are taken into account. Therefore, a positive or non-negative NPV means that the investment is
economic. As long as capital (incl. debt) is available, it is economically profitable to make any investment up to a
NPV of 0.
Besides the net present value, other target values and methods are used. While our main focus is on the
investment’s object, investors may have a different point of view (equity perspective). Instruments like the
Discounted Cash Flow (DCF) (based on the same discounting principle of the present value method) or the
Visualization of Financial Impli-cations (VoFI's) methods are used to optimise financing (equity or debt capital) or
taxation aspects. In VoFI's all in- and out-payments (i.e. original payments that are not discounted) imputable to
an investment are reported for individual periods. This includes all funding as well as interests and tax
payments; the method is especially used for liquidity planning.
Methods, boundary conditions, possible distortions
As long as boundary conditions and perspectives are the same, the above mentioned dynamical methods lead to
the same economic result. But it turns out that this result is very sensitive to the assumptions about boundary
conditions. Therefore, it is very important to survey boundary data very carefully. Special attention has to be
paid to all estimations of future data, in case of doubt sensitivity analyses shed light on the possible range of
results. Otherwise, the economic assessment may be severely distorted. In particular, it is necessary to verify:
Figure 33 : Residual values for calculation period of 20 years

69
Figure 34 : The economical effect of bringing forward the exchange of windows (2013)with Passive House
windows
Figure 35: Medium quality is a barrier to future energy efficiency investments. Here: Wall insulation, profit
depending on insulation thickness equivalent before refurbishment

70
• Proper attribution of investment costs: only (additional) investments that are imputable to energy
efficiency may be accounted for in the economic analysis. Although this seems obvious, the calculation including
all the measures’ costs which are often many times higher than the additional investment costs for energy
efficiency, is very often the reason for a wrong economic assessment result.
• Life cycle of the measures: make sure that revenues (e.g. saved energy’s costs) yielded after the end of
the pay back time are not forgotten. Total life cycle results are what counts.
• When calculation periods are longer than the life cycle of the measure or the component, replacement
costs must be considered. However, when they are shorter (which is often the case for buildings), residual
values must be regarded at the end of the calculation period – instead they are often forgotten. Depending on
the lifetime span, the calculation period and the discount rate, residual values can easily be up to 30% or more
of the original investment.
• Interest (discount) rates: often the expected rates of return are inadequately high (see next chapter)
• Future energy prices and price increase: Assumptions on constant rate of growth may lead to
unrealistically high energy prices for long calculation periods.
• Point in time of the measure: does the measure fit within the normal renewal cycle, or is there a
residual depreciation of the component? In the latter case, the residual value of the basic investment has to be
added to the extra energy efficiency investment. This proves that undertaking retrofit based on potential energy
savings is not an effective strategy
• The starting point of energy efficiency interventions: medium quality reduces energy demand, but also
possible energy savings later, thus the potential revenues of an energy efficiency investment. Future
amendments to improve their quality are very improbable because they will not pay back, thus impeding future
sustainable developments. Therefore, “when you do it, do it right”.
Risk and return
One of the most prominent distortions results from the frequent expectation of high returns. The expected
rates of return are the calculatory interest rates (or discount rates) in the dynamic economic assessment. We
have seen that the present value of future payments decreases with high interest rates and depreciates the
investment. But high interest rates are coupled with high risks. On the capital market, it is not possible to earn
high interests with risk free investments. However, energy saving investments are risk free or even risk reducing
- as long as the building they belong to are not in question. Which buildings should be kept in the stock and
upgraded is a decision concerning the real estate portfolio management. However, once the decision to proceed
with the retrofit has been made, it is always advantageous to include the energy efficiency investment, reducing
the risk of higher energy prices that might affect the market. Since risky investments with the chance of higher
ROI's are not comparable with energy efficiency investments, they are not eligible alternative assets to measure

71
the economic success. For low risk investments, however, a “risk premium” cannot be expected. They can be
financed by credits though, and they should when equity is expected to yield high rates of return.
Figure 36: Risk and return. Risk premium on the capital market is the additional expected rate of return
attributed to the risk.
Cost optimality
The European EPBD aims at the implementation of “nearly zero energy buildings”. The economic criterion
beyond the directive is the reference to life cycle costs for both new and retrofitted buildings. Economy is
assessed solely on the basis of life cycle costs. The minimum requirements to be defined by the member states
have to meet the 'cost optimal level' which is supposed to move in the direction of higher efficiency after the
effects of learning and scale; member states are expected to support this development. It has been shown that
Passive House components allow achieving profitable levels and given PH low energy demand, the basis for the
supply with renewables from nearby. This is the background of “Passive House Regions” [PassREg].

72
Figure 37: Life cycle costs for external insulation (refurbishment) depending on insulation thickness. The cost
optimal range is in the range of EnerPHit Standard
It is important to tap the full potential of profit -at least up to the cost optimal level. Otherwise it would become
very difficult to mobilise the rest of the potential, as measures’ minimum costs would be too high to be paid
back within the life time. The cost optimality curves are usually very flat; therefore very low additional efficiency
investments fall within the uncertainty range with respect to cost optimality. Never the-less they are a risk
reducing and cheap insurance against energy shortage and price rises. It is important to note that, as discussed
before, the rate of return is an interest rate for risk free investments, and, obviously, is not the target value for
optimisation.
Even Passive House components for renovation projects are economically optimal, when evaluated on the basis
of correct life cycle costs (see ). For such renovations, PHI has established the “EnerPHit” label. Depending
mainly on the building conditions before refurbishment, there might be a high economic gain leading to an
extremely good rate of return with a low risk investment. It is hard to find anything that could provide a similar
economic advantage.

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