This week they put up the joists and the first floor sheathing so we now have a kind of underground cave.  If all goes well this coming week then this will be the last post before real walls are up and frantic work begins.  So I figured I’d loop back to an old topic and explain the main reason we fell so far behind schedule over the summer.

As I mentioned in the post about our long trials in getting permit approval, we had been looking at doing a special foundation design using a product from Thermomass. This turned out to be a painful and unproductive detour, but I’ll document the saga here for future generations.

Because our design includes exterior insulation and brick veneer, we have a dilemma at the foundation wall. Modern energy code compliance and good green building standards require some form of insulation of the basement (foundation) wall. The two obvious ways to do this are to put insulation either on the inside or the outside. Both have their pros and cons, as excellently and exhaustively discussed by the incomparable greenbuildingadvisor. If you follow that link and look at image 4, you’ll see the problem with exterior insulation and a brick veneer. The brick must rest on the foundation wall, and the above-grade wall insulation is behind the brick. In the dead of winter you have a fat wall of brick hanging out in air that might be 2 degrees, and its connected all the way around the entire length of the perimeter to the foundation wall which is inside your house. Heat rises, and so the warm(ish) air in your basement will warm the foundation wall which will then siphon that heat straight up into the brick and radiate it out with great efficiency. This will make for very cold basement walls, a cold basement, and ultimately cold floors.

And then I found Thermomass. For those familiar with an ICF wall where there is styrofoam on both sides with concrete in the middle, Thermomass is the reverse of that. They float several inches of sturdy XPS foam in the middle of the concrete forms and then pour concrete down either side, creating a delectable sandwich of concrete and insulation. This is super durable, waterproof, highly insulating, and most importantly would let us line up the insulation straight from the footing to the rafters:

What a dream it was…

Unfortunately, such a design is not yet covered by the International Residential Code.  Our very helpful Inspector K even went and dug in the 2018 IRC which our community has not yet adopted, just to see if it was outlined there.  He thought we were probably 1-2 revisions away from this being standard.  But for now, we’d need a structural engineer to certify the wall design to meet the local building requirements.

Running down an engineer proved to be quite a merry chase.  We called in our architect and he called his friends.  We talked to anyone we could find who would know someone and then called all those people.  Many wouldn’t touch a little residential job like this.  Others wouldn’t spend the time on a job they didn’t design from scratch.  Too small a gig with too much risk.  Just when I was about to give up, we got a hit.  An independent fellow who contracts for a lot of multi-family dwellings was willing to do this on the side.  David Gaskins, you’re my hero!

David confirmed what had seemed intuitive to me (but intuitive is not in the codebook).  Namely that if one side of the concrete sandwich was sufficiently thick to support the wall, and the other part was sufficient to hold up the brick, then it was very hard to imagine how the combined wall could somehow be insufficient.  Still, he read up on code sections he didn’t use regularly and did the engineering to prove that it would meet the wind and structural load standards.

Thermomass was of no help throughout.  Our excellent and well-experienced foundation contractor was initially interested in doing this foundation to see about adding a new product to his repertoire, but after contacting both their distributor (whom he declared “useless”) and then the company itself in Iowa, he had second thoughts.  He was stunned that they could not be bothered to send anyone down here to help with any of the design, engineering, clearing the city permits, or instructing his crew on installation.  In his experience any company wanting to enter a new market would do these common things, but they offered no support.

Still, we got it engineered and approved by the city without their help!  And in the end, this would allow future homeowners and developers to reference our precedent.  After 10 weeks of delay it seemed like we’d finally taste the thrill of victory.

And then when we finally went to place the order Thermomass raised their price to nearly twice the original estimate.  Their material cost alone was well beyond the original price per square foot they had estimated, and that was supposed to include the additional labor for installation.  Now mind you they would never give any pricing information to us, only to our foundation contractor.  They expected him to put a 10% markup on top of their product and didn’t want to admit this to us.  Our contractor laughed at them and said with those prices he’d have to take a loss to sell it, let alone try to add profit.

So all that hard work and delay, ultimately ending in defeat.  As good a fit as this solution would be for our specific design, it isn’t worth $16K more than a traditional foundation.  The economic payback on that thermal efficiency would be measured in centuries.   Maybe we are just 5-7 years ahead of the curve.  May future adventurers have better luck.