A Habitat for Humanity chapter in Kalamazoo, Michigan, is among six “grand award” winners in a Department of Energy Zero Energy Ready Home competition this year, proving that high performance doesn’t necessarily come with a high price tag.
The annual contest recognizes innovative residential building in five categories, according to the DOE. Habitat Kalamazoo picked up the award for its entry in the Affordable Non-Profit category. Thrive Home Builders of Denver was the top winner in the Affordable For Profit category.
In all, 23 builders from around the country earned innovation awards. The grand winners were announced in San Diego in October. Habitat for Humanity chapters in Venice, Florida, and Hickory, North Carolina, also were recognized.
What separates Kalamazoo’s entry from the other top prize winners is its low cost, according to a post at LinkedIn by Philip Beere. While other winning entries carried price tags ranging from $400,000 to $1.6 million, Kalamazoo Habitat built its three-bedroom, 1,000-square-foot entry for less than $150,000.
The design decisions that guide Kalamazoo’s building program are the work of Tom Tishler, the director of construction operations, who joined the program in 2008. At the time, the houses that the local chapter were building were Energy-Star-certified and had an average HERS Index of 78, meaning they were 22% more efficient that a code-complaint house, Beere writes. Now, Habitat Kalamazoo’s new homes get a HERS score of 50 or better. With certification from the Zero Energy Ready Home program, the houses should be able to hit net-zero performance with the addition of a renewable energy system (for example, a PV array).
A push beyond Energy Star
In a telephone call, Tishler said that the program had been building Energy Star homes until the Zero Energy Ready Home program came along. About the same time, Michigan updated its energy code, and Tishler realized that state codes and Energy Star weren’t all that different, meaning they had to try harder.
“When I read through the Zero Energy Ready checklist, it was like we’re doing all but four things,” he said, “so it was not an easy jump, but it wasn’t a massive quantum leap for us, either. … We’ve always wanted to push a little big. We want to build really, really good homes for our homeowners.”
The chapter built its first Zero Energy Ready home in 2015. Each of the four to six houses it builds each year are now built to that standard. Habitat for Humanity serves people without a lot of money, so low energy bills and high comfort makes an appealing package.
For the prize-winning house, the Habitat crew built its own insulated concrete forms for the perimeter of the foundation with 2-inch thick foam donated by Dow, he said, and also placed 2 inches of foam under the slab.
Walls are framed with staggered 2x4s, 24 inches on-center, on 2×6 top and bottom plates. Corners are reinforced with 1/2-inch CDX plywood, and the house is otherwise sheathed with 2-inch foam. The 5 1/2-inch thick walls cavities are insulated with 2 inches of rigid foam and R-13 fiberglass batts, for a total wall R-value of about 33.
The roof is insulated with 18 inches of blown-in cellulose (the trusses have a 16-inch high energy heel). All penetrations through the ceiling are sealed with spray foam, Tishler said, an approach that has drastically reduced air leakage. A house the program just finished, for example, tested at 1.8 ach50 with a blower door. The house that won the award tested slightly higher than that.
Tishler provided these additional building details:
Windows: Pella 250 series with triple-pane argon-filled glazing (U-factor of 0.21 or 0.22).
Siding: Vinyl attached with 3 1/2-inch long roofing nails driven through the exterior foam. Getting volunteers not to pound the nails too tightly into the foam can be a challenge, Tishler said, but the siding is easy to install and relatively inexpensive.
Whole-house ventilation: A Venmar F8 heat-recovery ventilator provides 80 cubic feet per minute of fresh air. Tishler said that the program is likely to begin using a Broan model with slightly more capacity in the future (Broan has purchased Venmar). Although the Venmar unit provided enough outdoor air to meet ASHRAE recommendations, Tishler said he though the house might still be slightly underventilated.
Domestic hot water: Navien model 150 gas-fired tankless.
Gas-fired furnace over minisplit
The house is heated with a gas-fired furnace made by Dettson, a Canadian company. That may come as a surprise to the many advocates of ductless minisplit heating and cooling systems, but Tishler had good reasons for the choice.
Chief among them is heating capacity, or rather too much heating capacity. The program had been using Amana furnaces, but the smallest one they could find was rated at 30,000 Btu/h (21,000 Btu/h on low-fire), while the heating load at the house was just 13,000 Btu/h at a design temperature of 0° to 4°F.
The “Chinook” model from Dettson modulates down to 5,000 to 6,000 Btu/h and comes with a fan that can run as low as 150 cubic feet per minute. The ductwork consists of an 8-inch round main trunk line that feeds 2 1/2-inch miniducts to individual rooms. The furnace runs almost continuously in winter.
The heating contractor they use recently installed a Dettson system on a for-profit job for between $17,000 and $18,000. Although the furnaces aren’t cheap, Tishler said, the payback is quick, and the systems are very efficient. Last December, for example (the coldest December in Michigan in the last 75 years), a Habitat homeowner spent just $105 for heat and electricity.
Tishler said that the Habitat chapter has used ductless minisplits in the past, with mixed results.
“The big thing is the cost for the homeowner,” he said. “They’re super-efficient, but in the dead of winter the heating bills are outrageous. It’s so cold that those things are running continuously. The dirty little secret of those things is that they go into a defrost cycle. It’s like running a toaster, or a couple of toasters, nonstop 24 hours a day.”
A family might get a heating bill for the month of $300. Summertime electricity use is very low, and a monthly budget plan might even out spikes like that. But when a low-income family gets a heating bill of $300, the result is “catastrophic.”
The other issue with a ductless minisplit is uneven heat distribution, Tishler said. Homeowners complained that the main living area might be a balmy 70°F while bedrooms were a chilly 55°F. The program tried a number of fixes, including transfer grilles and using Panasonic bath fans to distribute warm air around the house. But in the end, switching to the Detttson furnace solved a lot of problems.
Market cost of less than $150,000
Tishler said that they can build a house like the one that won the award for about $80,000. That figure does not include the $10,000 or so in donated materials that come from manufacturers such as Dow and Square D. And it doesn’t include a number for the volunteer labor the program gets, accounting for about 75% of the labor total.
With that in mind, Tishler estimates the house could be built at market rates for under $150,000.
Tishler said that he’s the kind of person who loves tinkering with WUFI software and actively looks for ways to make his houses better. He’s eyed the Passive House building standard, but recognizes that he probably won’t get all the way there on his very tight budget.
The Kalamazoo program has been lowering the HERS scores for the houses it builds. The last house earned a score of 42. But, Tishler added, he’s becoming more focused on putting health, safety, and indoor air quality ahead of playing the “HERS point game.”
“If your HERS rating is 5 points higher but we’re providing extra ventilation or something to help occupants’ health,” he said, “that’s the angle we’re taking now.”