From Event to Action: Accelerate Your Decision Making with Real-Time Automation
Gulf Coast Green 2012 Joe Webb
1. Water
Greenroofs
Resilience
Independence
Gulf Coast Green – Houston – May 2012
2. to save energy
to sustain our and our children’s lifestyles
to inflict less damage on our environment
to rid our inhabited realm of chemicals, additives and
supplements that harm
to improve our living environments
to conserve the most valuable asset on the planet –
water
Better known as – save the planet!
3. Evaporation – accounts for the movement of water to
the air from sources such as the soil, canopy
interception and water bodies.
Transpiration – accounts for the movement of water
within a plant and the subsequent loss of water as vapor
through stomata in its leaves.
Evapotranspiration – a key element or part of the water
cycle – describes the sum of evaporation and plant
transpiration from the Earth’s land surface to the
atmosphere.
4. Acre-foot – a unit of measure denoting one acre of
ground (a chain x a furlong – 60’ x 660’) x one foot
depth of water. 325,851.4 gallons. Historically
visualized as the amount of water a suburban family
household will use in a year.
1 kWh = 3413 btu
Evaporation – 1 gm of H2O = 580 calories
1 btu = 252 calories – 1 ton = 72,576,000 calories
1 gallon = 3783 grams
1 cf = 7.4805 gallons
5. 75% of the surface is water
25% of the surface is land
Of that 25%, 50% is habitable
Of that 50%, 50% is arable
98% of the water is in the oceans
2% of the water is fresh but 1.6% is locked in polar ice
caps and glaciers and .36% is underground in aquifers
and wells
0.036% is actually found in rivers and lakes
Water is in a constant cycle – we never lose it
6. Two (2%) percent of the surface of the earth is
comprised of cities
Fifty-three (53%) of the population of the Earth lives in
cities
Sidenote: thirty-five (35%) of those residents live in
slums with minimal or no services – e.g. no running
water, sewage conveyance or storm water controls
7. Five intensive green roofs constructed
Roughly 1.40 acres (.6 hectare)
Design/build approach
Anticipated - Energy Star and LEED certification
So far – three Platinum certifications
Goals
◦ Minimum 50% less energy usage
◦ Unique identity within the community
◦ Control long term costs
◦ Radically lessen impacts by and to water
8. Firstly
reduce stormwater run-off
improve water quality
decrease overall water use
reduce the heat island effect
conserve energy
reduce sound reflection
create wildlife habitat
improve the aesthetics of the roof
9. Long term investment
Long term maintenance and operations are crucial
components dwarfing the initial cost of the facility
Long term utility requirements and energy needs
present a serious case for understanding and pursuing
sustainable design and building
Greatest water impact opportunities
10. First, third and fourth buildings – composite framing
Second building – pre-engineered steel frame + bar joists
with concrete deck
Fifth building – steel frame + bar joists with concrete deck
Composite system – reinforced concrete slab diaphragm
with steel girders + shear connectors
Unanticipated benefit – 24 tons less steel at roof with
composite system at roof
Our loads – 50 psf live load + 30 psf (saturated) soil mixture
+ 25 psf dead load (the structure)
All roofs - intensive
11. Average depth – 9 to 10 inches; maximum depth 12”
Repeated floor system at roof = minimal cost impact
Composite system inherently rigid
Intensive – less complicated wind resistance
Extensive – wind uplift issues; complicated anchorage
Intensive – more robust plantings
Extensive – smaller scale plantings
12. o 15,741 sf green roof (based on Bush rainfall rate)
o 8” soil depth results in run-off of 133,085 gallons
o 8” soil depth results in retention of 329,985 gallons
o 15,741 sf green roof (based on Hobby rainfall rate)
o 8” soil depth results in run-off of 182,355 gallons
o 8” soil depth results in retention of 360,035 gallons
o Bush retention equates to 44,113 cf = 1.013 ac-ft
o Hobby retention equates to 48,130 cf = 1.105 ac-ft
o These quantities never impact the storm system
13. Texas Water Development Board
Texas Manual on Rainwater Harvesting
Texas Rainwater Calculator, Version 2
Garden Roof Storm Water Run-off/Detention Estimator
Run-off and Irrigation worksheet
Innovative Water Technologies
14.
15. Evaporative cooling off-setting solar radiation
based on month of June
Average direct solar radiation – 1443 btu/sf/day
Equates to 363,550 calories/sf/day
Equates to 626.81 grams/sf/day
Equates to 2607 gallons/day on total roof
Resultant required evaporation = 6.7477mm
Equivalent tons of ac avoided = 78.85
Power saved = 6655 kWh
Cost savings at $0.12/kWh = $798.60
16. Evaporative cooling based on average Eto
(inches/month) again using June (6.57”)
Equates to 0.219 inches/day
Equates to 2,149 gallons/day over entire roof
Equivalent tons of ac avoided = 65.001
Power saved = 5,486 kWh
Cost savings at $0.12/kWh = $658.34
Resultant kBtu/sf (of building/day) = 13.215
Average resultant kBtu/sf = 8.93
Resultant cost savings/sf = $0.11
17. Evapotranspiration data
ITC – Texas ET Network found at texaset.tamu.edu
Rainmaster.com – provides evapotranspiration data by
zip code
18. Roof top retention
Underground cistern approach
Above ground cistern approach
Side benefits – detention system and opportunity to
retain stormwater + reclaim
Capture condensate
Filter out/settle out suspended particles and phosphates
19.
20. Absorb storm events
Hold 2.52 – 2 year storm events before discharge
Gulf Freeway cistern system holds 395,000 gallons
Gulf Freeway facility – 1.0127 acre-feet never leave
the site or enter the storm system thanks to the green
roof
Total site holds 2.2238 acre-feet (725,000 gallons)
before any impact on storm system
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24. • Net Zero Water: One hundred percent of occupant’s
water use must come from captured precipitation or
closed loop water systems that account for downstream
ecosystem impacts and that are appropriately purified
without the use of chemicals.
25. Ecological Water Flow: One hundred percent of storm
water and building water discharge must be managed
onsite to feed the project’s internal water demands or
released onto adjacent sites for management through
acceptable natural time-scale surface flow, groundwater
recharge, agricultural use or adjacent building needs.
26. The gaps between our current building design and the
Living Building requirements include the processing of
water for potable use onsite for a true closed-loop
system and some potential minor additional capacity
during dry seasons.
27. Recreational rooftop garden – 20%
Productive rooftop garden – 7%
View onto a green roof – 4.5%
Adjacent properties – range of 2 to 7%
Source: Monetary Value of the Soft Benefits of Green
Roofs – Canadian Mortgage and Housing Corporation
28. Particulate matter removed from atmosphere – 1 square
meter (10.76 sf) absorbs .2kg/year (644#’s)
Oxygen production – 1.5 square meters (16.15 sf)
produces enough oxygen for 1 person per year. A
person uses 6 pounds of oxygen per day (975 people)
Sound attenuation – dependent upon roof assembly
reductions can range from 10 db to 40 db.
