There is an old saying in construction: a house needs a good hat and dry feet.
As Environmental Studies professor Debbie Kasper recently shared, the TREE House’s feet were anything but dry (somehow I do not think those cracks in the foundation were meant to be a source of ventilation). This foundation clearly needed some serious work, so the TREE House team decided to rebuild the whole thing and do it in a way that got them way more than just “dry feet.”
Last February, the TREE House had an energy audit, complete with blower door and thermal imaging tests. These measured the air flow in the TREE House. The results showed an air flow rate of more than 6,000 CFM (cubic feet per minute) and 22ACH50 (the number of times in one hour that the inside air volume is replaced with outside air at a house pressure difference of 50 Pascals...just in case you are interested). These numbers are pretty bad (see the table below for comparison). The goals, respectively, are 1100 CFM and 4ACH50. In order to get there, the TREE House needs to really be tightened up.
Starting from the ground up, they decided to build an ICF (InsulatedConcrete Forms) foundation. Actually, George Clapp (of Gemac Excavating) and Dominic Gualtieri (of Gualtieri Construction) and their crews built the walls. I talked with George and Dominic last week to discover more about the advantages of ICFs and how they work.
George described how these forms of Styrofoam insulation are easily stackable (“like Legos”) and that concrete is pumped into the cavity to create strong and highly insulating walls. He says that the “Arxx Steel waffle grid that we are using will give us an R-value of about 50." Compare that to an R-value of 0 to 5 for poured concrete or masonry block walls. In fact, according to their website, structures built with Arxx “average 44% less energy to heat and 32% less energy to cool” than conventionally built structures.
Through my interview with Dominic and George, I have learned about some of the benefits of ICF’s:
- Energy and money savings
- A more comfortable, quiet, strong, and green home
- Great fire-resistance
- Improved indoor air quality
- Mold and mildew resistance
- Increased resale value
I also learned from George that ICF’s can last “1,000 years, like glass; it is tight and the concrete keeps curing as it gets older.”
What about the downsides? Well, ICFs cost more: about $75 per linear foot, on average, than poured concrete (about $15 to $26 per foot installed). To re-build your entire foundation would be not only more costly, but also disruptive if you were still living in the house. If you are not up for that, there are other products available for insulating your basement floor and walls from the inside. But if you're starting from scratch, ICFs are a good choice—a new generation of a better building block.
If you want to know more about the energy efficiency of your own home, you have a few different options. There are a number of professionals in the region who offer energy auditing services (usually around $500 for a package deal, less for individual services). Find a qualified professional near you here. Dominion has a program through which its customers can get a full home energy audit for $50. There are also plenty of ways to do a basic self-audit, and you can even purchase tools for home-use, like an infrared thermometer that also checks for air leaks, at some home improvement stores.
Hiram students will be offering a workshop on doing a household energy self-assessment, so stay tuned!
Acknowledgements: I'd like to thank Debbie Kasper, as co-author of this post.