My attic is encapsulated with open-cell spray foam. High performance? No way! Spray foam isn’t a miracle product They’d be doing the first two of those things anyway if Georgia hadn’t weakened the IECC requirements in those areas.īut come on. Yeah, they’ll have a bit more airtightness, get mechanical ventilation, and have some insulation in the rafters.
Codewatcher code#
If R-20 spray foam attics are that close to the line of barely legal-uh, I mean, code minimum-you’ve gotta really stretch to call that a high-performance home. (The floor plans modeled are 3,200 sf with R-20 insulated roofline, 14.5 SEER air conditioner, 96.1 AFUE furnace, and ducts in the attic.) Those same house plans with an air leakage rate of 4.99 ACH50 miss the threshold by more than 10%. The one that passed came in at 0.3% less than the required threshold. One passed, and one failed at 2.99 ACH50. We modeled two house plans of a local builder. The performance path in the energy code, section 405, may allow some homes to pass, but based on our examination of this method, it’s very close. Here’s what I wrote about that in my letter opposing the amendment: We’ve done some modeling on what it takes to get R-20 spray foam−encapsulated attics to pass the current code, and they just barely make it. Does spray foam in the attic lower the heating and cooling load of ducts in the attic? Probably. Now, not so much.ĭoes spray foam in the attic make the house more airtight? Maybe. Fifteen years ago, I would have agreed with that statement. In talking about the amendment with supporters, I heard people say that encapsulating an attic with R-20 spray foam makes it a high-performance home. Does spray foam equate to high performance?
Codewatcher plus#
Check the four boxes (the three above plus R-20) and you pass. This amendment would make it a prescriptive requirement to put R-20 spray foam insulation on the underside of the roof deck.
Codewatcher install#
To do so, they’ve got an amendment up for adoption that would automatically allow R-20 impermeable insulation ( i.e., spray foam) if they meet three other stipulations:Ĭan Atmospheric Combustion Work in a Spray-Foam-Insulated Attic? Georgia’s R-20 spray foam amendmentįast-forward a couple of years, and now builders want to go back to the simpler days of getting R-20 spray foam−insulated rooflines to pass automatically. In other words, they could get a lower insulation level for the attic to comply by using better-than-code windows, which builders were doing already anyway. They had been getting this lower level of attic insulation approved with a simpler method called the total UA alternative.
Further, because the code also requires better windows, home builders can’t get homes to meet the code with R-20 spray foam insulation on the roof deck without demonstrating compliance through what’s called the performance path (section 405 in the IECC). The new state energy code requires R-38 attic insulation statewide. We did improve the attic insulation, though. Yes, we still allow R-13 2×4 walls in new homes. When we did, we increased the airtightness requirement, but not as much as the International Energy Conservation Code (IECC), and we opted out of better insulated walls.
Codewatcher update#
It took us seven years to update the energy code. Unfortunately, Georgia has fallen behind. Now most states require blower-door tests and the threshold is generally in the 3 to 5 ACH50 range. Perhaps the biggest advance was that it required all new homes to meet a threshold for airtightness (7 ACH50). Ten years ago, Georgia led the United States in adopting a new energy code.