Single Family Residential

Amanda Webb & Omar SweiFeb 04, 2011

CONCRETE SUSTAINABILITY HUB

Major Model Changes

CONCRETE SUSTAINABILITY HUB

Category Aug 2010 Model Jan 2011 Model

Reference Standard ASHRAE Standard 90.2-2007 Building America House Simulation Protocol (based on IECC 2009)

Envelope(small differences)

ICF – R-26Attic Floor –R-60 (Chi)

ICF – R-20Attic Floor – R-40 (Chi)

Internal Gains Single Input Highly Detailed Input(based on BAHSP)

Infiltration & Ventilation

- Infil difference- No nat vent- HVAC Outdoor Air

- No infil difference- Nat vent- No HVAC Outdoor Air

Domestic Hot Water No DHW System Detailed DHW System

Chicago, ICF Chicago, Wood Phoenix, ICF Phoenix, Wood0.00

10.00

20.00

30.00

40.00

50.00

60.00

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

The mass does make a difference…

Peaks reducedWhat if we add more concrete?

What if we expose the concrete inside?

Better in PHXCould get better with more exposed surface area?

Energy Model Conclusions

• Infiltration, R-value, and mass benefits of ICF should be considered separately

• Infiltration highly climate dependent; mass somewhat climate dependent

• Mass makes a small difference

CONCRETE SUSTAINABILITY HUB

Heating-dominated (G) in Chicago vs. Cooling-dominated in Phoenix (E)

Work Through Aug 2011

• 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• Two research questions to contextualize role of

concrete…

CONCRETE SUSTAINABILITY HUB

Work Through Aug 2011

• Q1: How does mass shift the ‘PV Start Point”?– Christensen, et. al., 2004– Consider LCA (embodied energy) –

CONCRETE SUSTAINABILITY HUB

Enough to prove significance,Don’t have to build

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