Students Get an Inside Look at Passivhaus
A Wisconsin technical college builds the first of three Passivhaus structures — a project that connects students in five related disciplines with outside pros
Students enrolled in an unusual collaborative program at Western Technical College can expect a lot more than classroom lectures and an occasional pop quiz as they study high-performance residential construction. Working alongside design and construction professionals, they're learning about the special challenges of Passivhaus construction by helping to build Passivhaus houses.
The students are future architectural techs, landscapers, carpenters, building system specialists, and HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. installers. And now they have at least one thing in common: a 2,597-square-foot, three-bedroom house in LaCrosse, Wisconsin, which they helped design and build. Two other houses are on the boards.
The five technical disciplines, grouped administratively in the Center for Building Innovations on the campus of 12,000 students, is wrapping up work on the first of three "SwiPHt" homes (Structures With Integrated 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. Technology). All three are being built on the re-zoned site of a dismantled greenhouse in LaCrosse's 24th Street neighborhood.
The academic end of the SwiPHt program is overseen by Joshua VandeBerg, a 41-year-old instructor who spent years in the residential remodeling business. He later worked in a program in LaCrosse that combined building with helping high school dropouts earn their GEDs. Two years ago, he joined Western Technical to head its building systems technology program.
The college had been talking for a decade about building a net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. building, VandeBerg said by telephone recently, and because the college values both sustainable building principles and community engagement, SwiPHt seemed like a good first step. "It was an interesting way to tackle both of these values in a pretty meaningful way," he said.
A mix of student and professional effort
Rather than throw students into a Passivhaus project and hope for the best, the college brought in both a professional designer and a general contractor for the brunt of the work on the first house. They included Tim Eian of Intep and Fowler and Hammer, a local general contractor with a lot of commercial experience. (Readers may know Eian through a blog he writes and his Passive House in the Woods project.) VandeBerg was certified as a Passive House consultant last year.
Hillview donated its ailing greenhouse, which students took apart, and gave what amounted to five city lots to the college. With the property rezoned for residential use, the college and a number of other private and public partners came up with the funds to build the first house.
As many as 150 students participated through workshops in planning the house, but only 10% to 15% of the job site work was done by students, VandeBerg said. On the second house, the plan is to have students provide about 50% of the on-site work; and on the third house as much as 75%. The second and third houses will include prospective homeowners as well as students and the college.
"That's going to be a soupy mess in some ways," VandeBerg said, "but it's going to give us a great opportunity with our students to get in and feel what it's like. I think it's really a good thing. There's a ton of things we're going to be able to work through as an institution with our students. That's really valuable real world experience."
More than that: VandeBerg expects the project to win certification through the Passivhaus Institut as well as a regional sustainable building program called Green Star.
The first SwiPHt house is two stories with a full basement and a configuration that could be three or four bedrooms. There are three full baths.
Exterior walls, with a total R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of 58, consist of a structural 2x6 wall insulated with fiberglass batts, then a 14-inch, non-structural outer wall built with I-joists and insulated with dense-packed cellulose. The air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both. is provided by a 3/4-inch-thick layer of oriented strand board between the 2x6 and the balloon-framed I-joist walls that has been taped and sealed. The I-joist outer wall is sheathed with 1/2-inch fiberboard.
The basement slab is poured over 9 inches of extruded polystyrene insulation and two sheets of polyethylene sheeting for moisture control. On the outside of the concrete foundation is an 9-inch layer of extruded polystyrene (R-39).
The raised-heel truss roof is insulated with blown cellulose to R-89.
- Domestic hot water: Solar thermal.
- Whole house ventilation: Zehnder heat-recovery ventilator(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. .
- Heating and cooling: A Fujitsu ducted minisplit with one evaporator/fan coil unit on each floor and a total capacity of 24,000 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. /hour.
- Windows: Optiwin Alphawin triple-glazed units with a solar heat gain coefficient(SHGC) The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. of 0.55 and a whole-unit U-value of 0.129.
- Airtightness:: 0.47 air changes per hour at 50 pascals.
There are currently no 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. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) panels, but VandeBerg says the house is PV-ready.
A mix of building goals
Western Technical College has done more than talk about sustainable building. VandeBerg says any new buildings on campus now must meet 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. requirements.
"We're trying, any time we touch a project, to have sustainability at the forefront of what we're doing," he said. "The hope is that we find that our students who complete the program now are the leaders in the industry 10 years down the road. We're hoping to expose them to the things that will be at the forefront."
In fact, VandeBerg says, students in the program will have a good deal of practical experience by the time they graduate.
"My first graduates tested 16 different buildings," he said. "When they complete their program sometimes they've tested buildings that our local HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5. rater hasn't even touched. And so it's a pretty powerful thing, I think, to have this on their resumé when they complete school. [People will think,] 'Wow, you know how to air-seal and insulate and meet the Passivhaus standard,' and that's pretty awesome."
VandeBerg said the college is still adding up construction costs. They're likely to be inflated slightly by features such as electronic monitoring equipment, a weather station and automatic blinds — "all the bells and whistles," as VandeBerg put it.
The house will be used as a demonstration project for the next couple of years. When the third house in the series is complete, all of them will be sold.
- Western Technical College