Passivhaus Finds a Home in the Bayou State
An architect and university professor applies the standard to the design and construction of a house in Lafayette, Louisiana
Although sustainable materials and energy efficient design have found their way into some post-Katrina residential rebuilds on the Gulf Coast, Louisiana isn’t otherwise known for leading the charge to greener home construction. And that puts the house built by architect Corey Saft at the forefront of green housing in the state.
The home, a 1,200-sq.-ft. three-bedroom, two-bath in the south-central town of Lafayette, is in fact an anomaly in Louisiana, mainly because Saft designed it to qualify not only for LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. Platinum certification but also certification by Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Institute US.
Saft, a professor of architecture at the University of Louisiana, told the Lafayette-based news daily The Advocate that the building’s energy-recovery ventilator – an UltimateAir RecoupAerator, with MERV 12 filters – will deliver exceptional air quality. The home’s overall airtightness and shell insulation, he adds, make it “a little bit of an experiment” for housing in the Louisiana climate.
Insulated and airtight
The house has been variously dubbed “the 204House” or the “LeBois House.” The project features R-28 IcyneneOpen-cell, low-density spray foam insulation that can be used in wall, floor, and roof assemblies. It has an R-value of about 3.6 per inch and a vapor permeability of about 10 perms at 5 inches thick. LD-R-50 walls and an R-55 Icynene LD-R-50 roof, with 2x6 and 2x8 advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope., Saft noted in an email to GBAGreenBuildingAdvisor.com. The exterior walls are wrapped in 1-inch polyisocyanurate, the roof in 2-inch polyiso. Siding consists of pre-painted fiber cement board and white standing seam metal panels. Saft said there is a 1-inch space between the siding and the polyiso to help “shade” the walls and prevent heat and moisture buildup.
R-21 extruded polystyrene (XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation.) was used for the basement/crawlspace walls, and R-16.5 XPS under the slab. Saft also used SeriousWindows’ 501 series vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate).-frame windows, with SeriousGlass 8 double-pane glass.
The one renewable-energy component of the house is a 3.25-kW thin-film photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. system by Houston-based WhirlwindSolar.
- Corey Saft
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