The document discusses methods for estimating the heat demand in buildings. It covers topics such as the energy situation in buildings, physical principles of heat and moisture transfer, energy balances, and calculation methods. Specifically, it provides information on the energy consumption and fuels used for space heating in Germany. It also discusses categories of buildings based on their heat demand and regulations in Germany that establish limits on energy demand and methods for calculating a building's energy demand.
2. CONTENTS
• INTRODUCTION
– ENERGY SITUATION IN BUILDING SECTOR
• PHYSICAL PRINCIPLES
– HEAT TRANSFER
– MOISTURE TRANSFER
• ENERGY BALANCES
– STEADY STATE BEHAVIOR
– DYNAMIC BEHAVIOR - THERMAL INERTIA
• CALCULATION METHODS
– MONTHLY METHOD
– SIMPLIFIED METHOD
05.05.2011 SS 10/11 2
3. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY SITUATION
• ENERGY CONSUMPTION IN
GERMANY Lighting,
Domestic 5%
Energy consumption by sectors (Germany) hot water
demand,
13%
Industry, 27%
Space
heating,
81%
Households,
Transport, 28% 45% Source: VDEW-Materialien: Endenergieverbrauch in Deutschland, 2002
05.05.2011 SS 10/11 3
4. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY SITUATION
• FUELS USED IN GERMANY TO SUPPLY THE SPACE HEATING
DEMAND
Electricity 4%
Others 8%
Renewables are
here!
Distric heating 7%
Natural gas 43%
Carbon 2%
Gasoil 36%
Source: VDEW-Materialien: Endenergieverbrauch in Deutschland, 2002
05.05.2011 SS 10/11 4
5. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY SITUATION
IN GERMANY EnEV - “Energie-einsparverordnung”:
– Limits the maximal energy demand for buildings according
to their constructive details
– Establishes a calculation method for the energy demand of
a building -> basis for comparison
– Defines different building “categories” according to their
energy consumption
05.05.2011 SS 10/11 5
6. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY SITUATION
05.05.2011 SS 10/11 6
8. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY SITUATION
RENEWABLE ENERGY HEAT STANDARD
“EEWärmegesetz”:
– Approved July08 ->
Jan 09
– Application to new
buildings
• Biogas 30%
• Solar: 15%, 0.03-0.04m2coll/m2living area
• Others (biofuels, wood, geothermal or environmental heat) 50%
05.05.2011 SS 10/11 8
9. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
GENERAL BALANCES
ENERGY BALANCE IN A TYPICAL BUILDING
100%
Transmission Biggest energy saving
Internal gains potential!!!
losses 80%
Ventilation
losses 60%
40%
20%
Solar heat Heat supplied
gains by heating 0%
system Cold bridges %
Ventilation losses %
Transmission losses %
05.05.2011 SS 10/11 9
10. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
GENERAL BALANCES
• BUILDING ENVELOPE: Heat losses can amount up to 75%
of total heat losses
External walls
20% Roof 19% Moving to energy
efficient buildings…
Floor to crawl
space 9%
BASIC USED
SOLUTION: Reduction
of the major heat losses
Windows
52% using better materials in
Percentage of heat losses through different the building envelope
constructive parts of the envelope
05.05.2011 SS 10/11 10
11. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
• CONDUCTION
Tin
d layer [m2K/W]
Rlayer =
λlayerl Tout
Rwall = ∑ Rlayer [m2K/W]
λmaterial [W/mK]
1 1 dmaterial [m]
U wall = = [W/m2K]
dlayer
Rwall
∑λ T
layer
QT , wall = U wall ⋅ Awall ⋅ (Tin − Tout )
05.05.2011 SS 10/11 11
12. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
TRANSMISSION LOSSES: Conduction + convection
1 1
U wall = = [W/m2K]
Rwall 1 d layer 1
+∑ +
hi λlayer he Superficial heat transmission coefficient: [0 -
100 W/m2K]
T
• Floor to unheated basement • Roof under winter conditions!
• Roof in summer conditions
05.05.2011 SS 10/11 12
13. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
THERMAL BRIDGES
• DEFINITION: Places on the envelope where, during the heating
period, higher heat flows and lower inner surface temperatures
occur.
• CAUSES:
Material caused thermal bridge Geometric thermal bridge
Source: Maas
05.05.2011 SS 10/11 13
14. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
THERMAL BRIDGES
• CHARACTERISATION: Ψ = Coefficient of losses through
thermal bridge, [W/mK]
f = (superficial) Temperature factor , [-]
Θsi= surface temperature inside wall
Source: Maas Θe = exterior temperature
Θi = indoor temperature
f=0 -> exterior temperature
f=1 -> indoor air temperature
05.05.2011 SS 10/11 14
15. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
THERMAL BRIDGES
Source: Maas
05.05.2011 SS 10/11 15
16. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
THERMAL BRIDGES
Source: Maas
05.05.2011 SS 10/11 16
17. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
VENTILATION (CONVECTION) LOSSES
05.05.2011 SS 10/11 17
18. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
VENTILATION LOSSES
• Definition: Energy losses due to the exchange of an air flow
between the building and the surroundings
• Characterization: measured in h-1 = represents the portion of
the total (heated) building volume exchanged in one hour
• Causes:
– Air leakages in the building envelope: constructive
problem / solution
– Health and Safety reasons: necessary to allow pollutants
leave the living space
According to building typology (residential, office buildings,
hospitals…) minimum air exchange rates have to be assured
05.05.2011 SS 10/11 18
19. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
VENTILATION LOSSES
Air exchange
Tight envelope (n50<3h-1)
Untight envelope (n50> 5h-1)
Regulable Ventilation units
Window open up without cross ventilation
Window open up with cross ventilation
Window open without cross ventilation
Window open with cross ventilation
Source: Recknagel
05.05.2011 SS 10/11 19
20. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
HEAT TRANSFER
VENTILATION LOSSES
TYPICAL VALUES for a non efficient old building: 1,5 – 2 h-1 or even
higher (through air leakages in envelope)
According to EnEV (Energieeinsparverordnung) in Germany:
Non efficient Efficient (proven tight) Efficient building
building building without with mechanical
mechanical ventilation ventilation system
system
Values allowed Air leakages: 0,7 Air leakages: 0,6 Mech.vent.: 0,4
in EnEV, h-1 Air leakages: 0,2
05.05.2011 SS 10/11 20
21. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
1 - 2 liters/day person
• Transport mechanisms:
2 people house: – DIFFUSION
ca. 2liters/day – CONVECTION
person
(ventilation)
– (SORPTION)
4 people house:
ca. 4liters/day
person
Source: Maas
05.05.2011 SS 10/11 21
22. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
Maximal water content in air MOISTURE TRANSFER
10°C
9.4g
7.9g
Air temperature
Source: Maas
05.05.2011 SS 10/11 22
23. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
CARRIER (MOLIERE) DIAGRAM
05.05.2011 SS 10/11 23
24. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
CARRIER (MOLIERE) DIAGRAM
1.- 100%RH, 20°C,14.5g/kg
2.- 100%RH, 10°C,7.5g/kg
3.- 70%RH, 20°C, 7g/kg
4.- 85%RH,17°C, 7g/kg
Air density ≈ 1.2kg/m3
Dew point temperature
05.05.2011 SS 10/11 24
25. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
Rel. humidity
Air temperature
Dew point temperature
Dew point temperature
Rel. humidity
Source: Maas Air temperature
05.05.2011 SS 10/11 25
26. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
SUPERFICIAL TEMPERATURE
THERMAL BRIDGES
Outdoor air temp. -15°C
Surface
temperatures
Max. relative
humidity
Indoor air temp. 20°C
70%RH
External wall - corner
05.05.2011 SS 10/11 26
27. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
MOLD GROWTH
05.05.2011 SS 10/11 27
28. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
MOLD GROWTH
HUMIDITY TEMPERATURE
Probability of growth
Probability of growth
Relative humidity, % Surf. temperature, °C
Source: Maas
05.05.2011 SS 10/11 28
29. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
WATER CONDENSATION
Rel.
Humidity
MOLD GROWTH
Source: Maas
05.05.2011 SS 10/11 29
30. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
EXAMPLE
Mold growth is more restrictive condition Rel.
Humidity
Source: Maas
05.05.2011 SS 10/11 30
31. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
DIFFUSION
Source: Maas
Description Unit Description Unit
Temperature Partial vapor pressure
Heat transm. Coeff. Material transm. Coeff.
Heat conductivity Vapor diffusivity
Thermal resistance Resistance to vapor
diffusion
Heat flow Vapor diffussion flow
05.05.2011 SS 10/11 31
32. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
DIFFUSION
Air Bitumen
Metal
Insulation
d air
Concrete
Z air δ air δ air
μ= = =
Z material d material δ material
[-] δmaterial
dmaterial=dair Source: Maas
05.05.2011 SS 10/11 32
33. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
g
DIFFUSION - EXAMPLE
Material μ
Concrete 70-150
1086
Insulation g = 0.421 g/m2h
Kork 5-10
PU foams 30-100
Alu-foil Tight
472
(100000000) 281
Wood 40 (50/400)
Source: Maas
[m h Pa / kg]
05.05.2011 SS 10/11 33
34. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
CONVECTION - EXAMPLE
Source: Maas
05.05.2011 SS 10/11 34
35. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
CONVECTION - EXAMPLE
Vh,buil=50m3 ; n=0.8 h-1 Ps = 1170 Pa
Vvent=40m3/h (=Vh,buil*n) R = 462 J/kgK
Ti=20°C, RH=50% Ps = 139 Pa
Te=-10°C, RH=80%
and
-10°C and 1.15
263.15
1.15 304.3
Source: Maas
05.05.2011 SS 10/11 35
36. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
COMPARISON
CONVECTION - DIFFUSION
g
Aint,walls=22.5 m2 g = 0.421 g/m2h
n = 0.8 h-1
Outside: 80% RH, -10°C
304.3 g/h 9.47 g/h
Inside: 50% RH, 20°C
Source: Maas
05.05.2011 SS 10/11 36
37. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MOISTURE TRANSFER
CONVECTION:
Air exchange
Required air exchange Rel. humidity
Humidity production
Source: Maas
05.05.2011 SS 10/11 37
38. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY BALANCES
STEADY STATE
Transmission Internal gains
losses
Ventilation
QT losses
Qv
Solar heat In order to keep
gains Heat supplied
by heating the room temperature
system
at a constant acceptable value
Energy Supplied = Heat Losses - Energy Gains
“Active gains” “Passive gains”
05.05.2011 SS 10/11 38
39. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
THERMAL LOSSES
TRANSMISSION LOSSES env,i = walls, floor, roof,
windows
QT ,env = ΣU env,i ⋅ Aenv,i ⋅ (Tin − Tout ) [W]
(separately for each of them)
– INCLUDING THERMAL BRIDGES
H T ,building = ΣU env ,i ⋅ Aenv ,i + ΔU tb ⋅ Aenvelope [W/K]
– TOTAL TRANSMISSION LOSSES
QT ,buil = (ΣU env,i ⋅ Aenv,i + ΔU tb ⋅ Aenv ) ⋅ (Tin − Tout ) [W]
05.05.2011 SS 10/11 39
40. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
THERMAL LOSSES
VENTILATION LOSSES
n = air exchange rate [h-1]
H V = Vh,buil ⋅ 0.34 ⋅ n [W/K]
HEATED Heat
volume of the capacity of
air [Wh/m3K]
building [m3]
QV = H V ⋅ (Tin − Tout )
According to the German regulation EnEV, can
be simplified:
Vh ,buil = Vbrutto ⋅ 0.76
05.05.2011 SS 10/11 40
41. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
THERMAL LOSSES
TOTAL LOSSES (TRANSMISSION+VENTILATION)
– Transmission Losses
QT ,buil = (ΣU env,i ⋅ Aenv,i + ΔU tb ⋅ Aenv ) ⋅ (Tin − Tout ) =HT ⋅ (Tin − Tout ) [W]
– Ventilation Losses
QV = H V ⋅ (Tin − Tout ) [W]
– Total Losses
Qlosses = ( H T + H V ) ⋅ (Tin − Tout ) [W]
05.05.2011 SS 10/11 41
42. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
THERMAL LOSSES + GAINS
WINDOWS
– Upane = 3 – 0.6 [W/m2K]
-> great influence on heat
demand
– SHGC, g = 0.5 – 0.8 [-]
-> great influence on
cooling demand
– ε = 0.84
– εlow = 0.2 !!!
05.05.2011 SS 10/11 42
43. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
ENERGY - DYNAMIC
ENERGY BALANCE - DYNAMIC BEHAVIOR
Transmission Internal gains
losses
Ventilation
QT losses
Qv
Solar heat
gains Heat supplied
by heating
system
Energy Supplied = Heat Losses - Energy Gains +- Energy Stored
05.05.2011 SS 10/11 43
44. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
5000
4000
Specific heat capacity ENERGY - DYNAMIC
THERMAL MASS
c [J/kgK]
3000
2000
1000
0
Aluminium
Foam glass
Glass
Brick
Wood
Sand
Concrete
Water
insulation
Mineral
3000
density
2500
2000
rho [kg/m3]
Csto = ci ⋅ ρ i ⋅ Ai ⋅ d i 1500
1000
500
0
Aluminium
Glass
Brick
Sand
Concrete
Foam glass
Wood
Water
insulation
Mineral
Source: Wikipedia
05.05.2011 SS 10/11 44
45. lambda [W/mK]
0
1
2
3
4
5
Wood
Glass
05.05.2011
INTRODUCTION
Source: Wikipedia
Mineral
insulation
Foam glass
THERMAL MASS
Sand
Brick
PHYS. PPLES.
237
Aluminium
c [J/kgK]
Concrete
0
1000
2000
3000
4000
5000
rho [kg/m3]
Water
0
500
1000
1500
2000
2500
3000
Wood
SS 10/11
Wood
Glass
Glass
Mineral
insulation
Mineral
insulation
Foam glass
ENERGY BALANCES
Foam glass
Sand
Sand
Brick
Brick
Aluminium
Aluminium
Concrete Concrete
45
THERMAL MASS
Water Water
CALC. METHODS
46. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
Specific heat capacity ENERGY - DYNAMIC
THERMAL MASS
Concrete Insulation
Temperature
Temperature
Thickness
05.05.2011 SS 10/11 46
Source: Maas
47. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
Specific heat capacity ENERGY - DYNAMIC
U-Value Mass THERMAL MASS
[W/m2K] [kg/m2]
6cm
Outdoor Temperature
40cm
Energy flow
43.5cm
Solar radiation
26cm
Time of day
Outdoor Temperature
radiation
Solar
05.05.2011 SS 10/11 47
Source: Maas
48. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
TOTAL LOSSES (TRANSMISSION+VENTILATION)
– Transmission Losses
QT ,buil = (ΣU env,i ⋅ Aenv,i + ΔU tb ⋅ Aenv ) ⋅ (Tin − Tout ) =H T ⋅ (Tin − Tout ) [W]
– Ventilation Losses
QV = H V ⋅ (Tin − Tout ) [W] For which time-step
Depends on the
data we have for the
do we apply this
equation?
outdoor
– Total Losses temperature…
Qlosses = ( H T + H V ) ⋅ (Tin − Tout ) [W]
Tin is the indoor desired temperature: regarded as a CONSTANT value,
typically set between 19 and 21°C for the heating period.
05.05.2011 SS 10/11 48
49. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MONTHLY METHOD
TOTAL LOSSES
Q losses = Σ ( H T + H V ) ⋅ (Tin − Tout ) ⋅ t M ⋅ 24 [Wh/a]
months
• Tout represents MONTHLY mean values
• tM represents the number of days of the month considered
05.05.2011 SS 10/11 49
50. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MONTHLY METHOD
SOLAR HEAT GAINS
QSolar , windows = Σ Awindows ⋅ g i ⋅ FF ⋅ Fs ⋅ Gwindow [Wh/a]
months
• gi represents the energy
transmissivity of the window glass;
typically is around 0.6
• FF represents the % of glass against frame in the window
area; typically is around 0.7
• Fs represents the % of shadowing over the glass
• Gwindow represents the incident solar radiation onto the
window, in Wh/m2
05.05.2011 SS 10/11 50
51. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
THERMAL LOSSES + GAINS
WINDOWS, 52% of total losses:
Does not require
1. Avoid heat losses -> Better insulation materials:
much more planning
- Uw= 3 - 0.6 W/m2K
Three pane window
Single or two
effort.
filled with Ar/Kr
pane window
Typ. In efficient houses
2. Increase solar heat gains -> Orientation
- Highest solar irradiation on the south façade,
Requires integral planning of
high potential for solar heat gains -> maximize
glazed surface facing south
the building integrated into
- North façade receives very few solar
its environment for solar gains and
irradiation, low potential
high heat losses through windows -> minimize
Typ. Approach passive houses
glazed surfaces Yearly variation of solar
path in the sky
05.05.2011 SS 10/11 51
52. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MONTHLY METHOD
INTERNAL HEAT GAINS
• Internal heat gains depend on the use pattern of the building:
office, hospital, residential…
• For residential buildings: constant hourly value of 5 W/m2, per m2
useful area in the building
Qint_ gains = Σ 5 ⋅ AN ⋅ 24 ⋅ tM [Wh/a]
months
05.05.2011 SS 10/11 52
53. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MONTHLY METHOD
ENERGY DEMAND
– Simplification:
Qh = Qlosses − QSolar , windows − Qint_ gains [Wh/a]
– Actually, not all energy gains can be “used”:
Qh = Qlosses − η (QSolar , windows + Qint_ gains ) [Wh/a]
• η depends on the heat storage capacity of the building structure
and its materials, which is a function of ρ [kg/m3], c [Wh/kgK], d [m],
A [m2] of the material:
Csto = ci ⋅ ρ i ⋅ Ai ⋅ d i [W/K]
05.05.2011 SS 10/11 53
54. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MONTHLY METHOD
ENERGY DEMAND
– Types of building constructions according to its heat
capacity
• LIGHT
– Csto/A < 50 Wh/m2K
• HEAVY
– Csto/A > 130 Wh/m2K
Qh = Qlosses − η (QSolar , windows + Qint_ gains ) [Wh/a]
– η = 0.9 for light buildings [-]
– η = 0.95 for heavy buildings [-]
05.05.2011 SS 10/11 54
55. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
MONTHLY METHOD
ENERGY DEMAND
– BUILDING WITH ZONES AT DIFFERENT
TEMPERATURES:
• German Norm: gives correction factors, Fx, that have to be applied
to obtain the HT corrected of the building
Building part Fx [-]
Outside wall, window, roof, floor 1
H T = ΣU wall ⋅ Awall + ΔU tb ⋅ Aenvelope Walls and roofs to unheated rooms 0.5
- Floor to ground 0.6
- Walls and floor to unheated crawl
space
H T = ΣU wall ⋅ Awall ⋅ Fx + ΔU tb ⋅ Aenvelope
05.05.2011 SS 10/11 55
56. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
DEGREE-DAYS METHOD
TOTAL HEATING DEMAND
DEGREE-DAYS
z
[Kd/a]
Gt 20 /15 = ∑ (Tin − Tout )
1 [°Cd/a]
• Tout represents mean DAILY values
• Sets up a “heating limit” (15°C), above which no space heating is
required. For this conditions (Tin-Tout)=0
• Below the “heating limit”, (Tin-Tout) is calculated and added up to
give a value of the “degrees-day”
05.05.2011 SS 10/11 56
57. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
DEGREE-DAYS METHOD
TOTAL HEATING DEMAND
[Wh/a] Qlosses = Σ ( H T + H V ) ⋅ Gt Q losses = Σ ( H T + H V ) ⋅ (Tin − Tout ) ⋅ t M
months
days
[Wh/a] QSolar , windows = orientation Awindows ⋅ g i ⋅ FF ⋅ Fs ⋅ Gwindow
Σ
QSolar , windows = Σ Awindows ⋅ g i ⋅ FF ⋅ Fs ⋅ Gwindow
months
[kWh/a] Qint_ gains = 22 ⋅ AN
Qint_ gains = Σ 5 ⋅ AN ⋅ 24 ⋅ tM
months
[Wh/a] Qlosses = Qh − η (Qsolar − Qint ernal ) Qh = Qlosses − η (Qsolar , windows − Qint ernal )
05.05.2011 SS 10/11 57
58. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
DYNAMIC TOOLS
– The equations for steady state conditions are not valid
here!!!-> Energy stored in the building structure plays a
role
– FREEware available (Hourly simulations):DOE2, eQUEST,
ePLUS (http://www.doe2.com/ )
Much more accurate results
× Require the description of the HVAC system as INPUT
× Time demanding to learn how to work with them: weather
data for Stüdl Hütte, etc… may not be in database
05.05.2011 SS 10/11 58
59. INTRODUCTION PHYS. PPLES. ENERGY BALANCES CALC. METHODS
STATIONARY METHODS
• STATIC (simplified) METHODS & SOFTWARE:
– Based on the steady-state simple equation -> quite simple
calculations
Depends only on (rough) CLIMATIC data and the
BUILDING ENVELOPE -> Does not require the description
of the HVAC system as INPUT
× Much more rough results
– Examples: “DEGREE-DAY Method” and Monthly
simplified method in EnEV http://www.uni-
kassel.de/fb6/bpy/de/index.html
05.05.2011 SS 10/11 59
60. THANK YOU FOR YOUR
THANKS FOR YOUR
ATTENTION!!!
ATTENTION!!!!!!
05.05.2011 SS 10/11 60
61. EXAMPLE 3.0m
• AN = 147m2 ; Vbrutto = 580 m3 3.0m
10m
• Awalls = 209.34 m2; Afloor = 88.2 m2; Aroof = 88.2
m2 7.35m
• Awindows: S 15 m2; E/W 10m2; N 5.5 m2
• Uwalls = 0.45 W/m2K (walls); • G19/10 = 2750 °Cd/a (Hamburg)
Ufloor-roof = 0.3 W/m2K (floor and roof);
Orientation
Solar
radiation
Uwindows = 1.4 W/m 2K (windows) [j] [kWh/m²]
Nord 136
• Utb = 0.1 W/m 2K
Süd 349
• n =0.6 h-1 Ost 220
West 220
• Windows: Ff= 0.7; Fs=0.9;g=0.58;
• Heavy building
05.05.2011 SS 10/11 61
T 19°C