ICF construction leverages thermal mass
In creating a LEED Platinum home in Fennville, Michigan, builder Jake Vierzen knew keeping the ICF home’s window-rich walls facing south delivered passive solar warming and cooling in the design of Prickly Pear Sanctuary.
The south side is completely open, “and that allows that solar heat to be in all the living spaces of the home. If we had moved bedroom space and bathrooms to the south side, then only those little spaces would have received any heat from the sun.”
Prickly Pear was a gas free home without propane or natural gas. Normally with a forced air system and electric heat, designs specify use of a heat pump to heat or cool the air. Prickly Pear used radiant heat. “Only a few systems on the market — and they’re all new — will heat and cool water using a heat pump,” Vierzen said. “So that was a big learning curve for everybody involved in it.”
Among the lessons learned, “maybe don’t be the first one to try something that complicated,” Vierzen said. “It was a new manufacturer. If it was somebody like Carrier they’d have a lot of factory support. We kind of got bit by this, with very little support of a Chinese-made product. Newer isn’t always better.”
The homeowner wanted to be gas-free and so specifying a pump system like the one used was the owner’s choice. “We only knew of one product, so there weren’t a lot of options. Now there are four different brands. Hopefully the next one we’ll have better support. It’s successful now that it’s going, but we had to a figure a lot of things out on our own.”
The efforts to close the knowledge gap and meet homeowner needs were noticed. At every stage, the homeowner was excited with how quickly the ICFs went up, the excitement of the pour, the incorporation of various details, the comfort level, and energy performance.
The homeowner was onsite every day, he noted. Normally that would give Vierzen and his tradesmen pause. The homeowner provided genuine help. “It was a real collaborative approach,” Vierzen said. “He was there to clean up on an ongoing basis. He recycled most of the waste and was there to make decisions very quickly. One thing I learned was don’t be afraid of that. It was very helpful and in the long run it saved him money.”
Having a homeowner on the site’s build yielded some scrap innovation, too. The homeowner saw an opportunity to put ICF into even more duty for energy savings. By recycling scraps of the ICF forms, R-Value was able to raise the R value of the garage area from an R9 to an R20.
Another ICF home already has been started not far away as a result of showing off Prickly Pear. “There were many folks from the area who toured this home,” Vierzen said, “They learned concrete homes are beautiful, too.”
A relationship has existed between this builder and the designer for over 10 years, a period when trust was built: a top-quality home and thrilled clients were not only possible, but the expected outcome. This included the designer Hughes working hands-on in a project with Vierzen’s team to gain a deeper understanding of what goes into ICF construction.
The selection of the ICF brand was left to Vierzen, who chose Nudura, a product he’s used successfully many times and is stocked locally.
The home is the first one certified Platinum under the GreenStar program. Predicted energy costs are $409 per year to heat and $60 a year to cool; the photovoltaic panel array produces more than enough to cover these loads.
R-Value is the name of Vierzen’s firm, but he also understands that the energy rating of a house might not be the most important aspect for the owner.
“R value is nice and it’s important, but it’s not the most important aspect when it comes to having a healthy comfortable and efficient home,” he said. “Air ceiling is most important. We focus a lot on the air ceiling to the point where additional insulation in the walls doesn’t make sense. There are guys building stick walls of R 40 to R 60-plus. I don’t see any need for that once the home is tight.”
Vierzen, who’s now a leading resource on the tactical aspects of building with ICFs, said traditional stick homes are in his rear view for good.
“I get calls all the time from people to ask if I build other types of homes. And my answer is that by the time I address all the problems with stick instruction, we’re better off to do ICF. Another way of saying that is ICF kills many birds with one stone.”