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Rapid Fire
Thermal Mass
CONCRETE SUSTAINABILITY HUB
Mass in ICF separate from infiltration, R-value benefits
High heat capacity leads to thermal lag
Mass lag reduces peaks
Carbon, cost, energy, equipment sizing benefits
Key: Optimize use of mass in building envelope and interior
Afternoon Presentation
Residential BuildingsSingle Family & Multifamily
Amanda WebbFeb 17, 2011
CONCRETE SUSTAINABILITY HUB
Major Model Changes
CONCRETE SUSTAINABILITY HUB
Category Single Family Multifamily
Reference Standard Building America House Simulation Protocol*(IECC 2009 equiv.)
DOE Benchmark Midrise Apartment
Envelope ICF – R-26 -> R-20Attic Floor –R-60 -> R-40 (Chi)
ICF with concrete interior -> ICF with wood/gyp interior
Internal Gains Detailed Input No Change
Infiltration & Ventilation - No infiltration difference**- Nat vent- No HVAC Outdoor Air
No Change
Domestic Hot Water Detailed DHW System No Change
= Most significant changes
*From DOE’s National Renewable Energy Laboratory
**Focus in this analysis on mass benefits of ICF
Infil rates same – focus on mass, insul. benefitsR-values different
Mass portion of ICF does make a difference
Peaks reducedWhat if we add more concrete?
What if we expose the concrete inside?
Better in PHXCould be better with optimized use of interior mass
Infiltration sensitivity dependent on climate
Operational energy dominates for benchmark building
Embodied energy matters more in very low energy building
Energy Model/LCA Conclusions
• Very solid model specifications• Better contextualize our work – NREL, etc. • Infiltration, R-value, and mass benefits of ICF
should be considered separately• Infiltration highly climate dependent; mass
somewhat climate dependent• Look at optimized use of mass – balance
changes for low energy buildings
CONCRETE SUSTAINABILITY HUB
Work Through Aug 2011
• How do we optimize the mass benefits of concrete in single family houses?
• What is the role of concrete in very low energy houses? – Trend in housing research (Bldg. America, BEOpt)– Trend in legislation (Greening the Codes, CA AB32)
• Two targets: Net Zero Energy, Passivhaus
CONCRETE SUSTAINABILITY HUB
Work Through Aug 2011
• Q1: How does mass shift the ‘PV Start Point”?– Christensen, et. al., 2004
CONCRETE SUSTAINABILITY HUB
Work Through Aug 2011
• Q2: Does mass make a difference in a Passivhaus? – Suggestion that thermal behavior is different– Combine Q1 & Q2: Is there a “curve” that describes
the optimal use of mass?• Overall: Industry able to make intelligent
decisions about how to promote use of concrete in very low energy houses.
CONCRETE SUSTAINABILITY HUB
Alternate Slides
Chicago, ICF Chicago, Wood Phoenix, ICF Phoenix, Wood0.00
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Total Annual Operational Energy kBTU per SF
Total HVAC
Total Non-HVAC
CHICAGO ICF – tight ELA, Wood – average ELA
PHOENIXICF tight ELA, Wood average ELA
Chicago- 28.8%
Phoenix- 5.6%
Greater savings in Phoenix than Chicago
PREVIOUS RESULTS [AUG 2010 MODEL]
Updated model shows this is b/c of infiltration
Infil Rates SameR-values Different
Heating-dominated (G) in Chicago vs. Cooling-dominated in Phoenix (E)
