St. Peter’s
Net-Zero Affordable Housing
LIFE CYCLE ASSESSMENT: ST. PETER RESIDENTIAL (SBP) NET ZERO AND LOW EMBODIED CARBON EMISSIONS ON A BUDGET
Exceeds ZEROCODE and Architecture 2030 goals. Designed for net zero operation with battery back up. Low embodied carbon (upfront emissions) wood-frame construction. Multi-Family Residential (50 units; one + two bedrooms) 100% New Construction on redeveloped urban site 45,000 Square Feet, 3 stories New Orleans, Louisiana Construction Cost: $164/SF
WHOLE-BUILDING CARBON EMISSIONS INTENSITY BY 2030 embodied emissions 150
100
50 25
operational emissions
e rd a nd ) sta I 43 (EU
qu
le iva
nt
Architecture2030+ZEROCODE this project (net zero)
0 lbsCO2eq. per sf 2020 (construction complete)
2025 year
2030
ST. PETER RESIDENTIAL CASE STUDY
STEPS TO NET-ZERO OPERATIONAL ENERGY
1
Tight Envelope: • Continuous insulation.
•
Field-verified airtightness.
2
HVAC & Water Heating:
•
SEER 17 AC heat pumps.
•
Heat pump water heaters.
3
Efficient Appliances:
•
5x upfront
EnergySTAR rated appliances.
National Average - EUI 32 EnergySTAR 250 tons/year | $50k/year EUI 32| $50k/yr 250 tons CO2e.
4x upfront
Grid-Powered SBP - EUI Power 17 SBP - Grid 130 tons/year | $27k/year EUI 17 | $27k/yr 130 tons CO2e.
3x upfront
2x upfront
1x upfront
2020 Upfront - 2020
2030
SBP - Net Zero Solar-Powered SBP - EUI 17 0 tons/year | Array $0k/year Solar | $0/yr solar upfront cost | $5/sf Upfront Carbon 0 CO2e. 520tons tons | $153/sf 520 Tons Upfront
2030
Carbon Emissions Intensity
CO 2 FOOTPRINT & SOLAR POWER For electricity supplied by utilities, 1.09 lbsCO2eq./kWh is emitted from the Louisiana grid. The national average is 1.13 lbsCO2eq./kWh. Based on the low EUI of 17, SBP would emit 130 tonsCO2eq. each year (200 tons less than the national average multi-family building) for its power use. Designed energy efficiency steps make 100% on-site solar power feasible. 178kW of solar modules on the roof can produce the energy required to power SBP on an annual basis, making its operations net zero. Installation and construction cost of the solar array is paid back in energy bill savings in less than 8 years.
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OPERATIONAL CARBON STRATEGIES CASE STUDY
ANNUAL ENERGY
$1.10/SF EUI 32: EnergyStar certified building operational utility cost.
$ .58/SF EUI 17: Building as designed operational utility cost.
$ .00/SF Net Zero: Operational cost of 100% solarpowered building. (Plus fee to be grid connected.) St. Peter’s Residential from the street. All available roof area is covered in solar panels.
PV PANEL PAYBACK OVER TIME 2.5 2
solar energy CO2eq. produced embodied energy
1.5 lbsCO2e. per sf
SOLAR POWER
1
0.5 0 1
2
3
4
5
PV embodied carbon offsets its upfront carbon emissions in clean energy produced in about 3 years.
years
2
ST. PETER RESIDENTIAL CASE STUDY
EMBODIED CARBON
lbsCO2eq./SF 33
Solar MEP Interior Envelope Structure
16
8
SBP
35 30 lbsCO2eq./SF
54% 23
SBP-including sequestration
avg
50
SBP
average-1-6 stories
87
average-low rise residential
Compared to the CLF database average for lowrise (<5 stories), multifamily residential, SBP achieves a 54% reduction in embodied carbon, meeting the Architecture 2030 40% reduction goal for new construction in 2020.
25 20 15 10 5 150 0
avg
SBP
lbsCO2eq./sf
3
STRUCTURE:60% ENVELOPE: 17%
INTERIOR: 21%
•
Timber Piles
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Zipwall Sheathing
•
•
Concrete Foundation
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Insulation type
Gypsum wall finishes with paint
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Wood-framed envelope and interior
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Glazing and mullions
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Gypsum ceilings
•
•
Wood Joists
Wooden Doors, (hardware excluded)
EMBODIED CARBON STRATEGIES CASE STUDY
BUDGET AS DRIVER
$153/SF $158/SF $164/SF
Base building (exceeds EnergyStar) construction cost.
CARBON STORAGE WOOD
IN
Construction cost with solar panel system. Construction cost with solar panels and battery back up.
Wood is made of carbon. Trees grow from absorbing CO2 and that same CO2 stays in the wood whether in tree form or lumber products. This storage is called carbon sequestration. In LCA, carbon sequestration is seen as an outside benefit, assuming the carbon in wood products stays “locked away” in the building for as long as the building exists. For this study, carbon sequestration is compared to LCA values not including this benefit. Emissions avoided (~15lbsCO2eq./ sf) are separately reported. Including this value in the LCA, SBP upfront carbon is 8lbsCO2eq./sf., an 80% reduction from average.
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ST. PETER RESIDENTIAL CASE STUDY
Battery storage shed near community area in foreground with apartments beyond.
WING TITLE
BONUS: BATTERIES FOR RESILIENCE
,500 kWh/year
I
48
K/YR IN ENERGY COSTS
The non-profit organization acting as developer of this affordable housing project specializes in helping communities recover after disasters. Since power outages commonly accompany such disasters, this client was interested in adding battery backup to the project. Proposed efficiency upgrades lower peak demand and extend battery life during outages. Adding in on site solar PV generation (178kW) - 401,000 kWh/year +245,500 kWh/year to the battery installation (125kW / 371kWh capacity) allowed the developer to 245,500 kWh/year access tax incentives for thisSOLAR combined system. The battery system’s capacity is equal to 15 hours of average consumption. A local utility donated $1M to the BATTERY upgrades solar, and battery systems and will project budget to cover efficiency IN ENERGY $19K/YR IN ENERGY study$19K/YR how these facilities can act as ‘grid citizens.’ COSTS SAVINGS
16 +
NET ZERO
5 NILLA APARTMENT” VS ST PETER | NET ZERO
ENTERGY | SOLAR PANELS + BATTERY BANK
LIFE CYCLE ANALYSIS CASE STUDY
SIMPLE, ATTAINABLE STRATEGIES AT A LOW COST The study of SBP illustrates an affordable, simple construction method with low embodied carbon impacts available in the industry for implementation and execution now. Uncertainties in comparison reveal a need for absolute benchmarks to be established in order to further progress Architecture 2030 goals, but reporting this study helps to expand the dataset on embodied carbon of construction. Funding programs and partnerships helped to make on site solar power accessible. Better than code energy requirements by EnergySTAR certification set the project up to be highly energy-efficient, further facilitating implementation of net zero. Operational energy emissions were drastically reduced, then eliminated through clean power generation on site. Embodied carbon was also quite low for the construction of SBP. This was accomplished through simple building techniques (wood-framed construction), and careful, minimal use of high upfront carbon materials, like glazing. Tally was used for embodied carbon calculations, and those totals are verified against material take offs coupled with ICE (Inventory of Carbon and Energy) to calculate the GWP of this building. The ICE database has values to include carbon storage in wood products, and values that do not account for this benefit. Both methods result in a value of ~23lbsCO2eq./sf. To gain an understanding of carbon storage capabilities, Tally analysis including biogenic carbon and ICE values accounting for carbon storage were calculated and reported separately (~15lbsCO2eq./sf). If this value were included, SBP would report 8lbsCO2eq./sf in upfront emissions.
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