Best exterior insulation for CMU remodel
I’m in zone 4/5 B (Albuquerque) with a 1950’s CMU bungalow. I’m trying to decide which insulation product to go with. I’ve contacted several contractors and none are inspiring much confidence. With the foam board insulation they had very little to no knowledge of Polyiso. The EIFS guy had only worked with EPS, but was willing to try Polyiso. One was not willing to sheath the exterior chimney. Others were unwilling to do more than 2 inches of insulation. With polyurethane spray foam one says that 2 inches is the max he can apply due to code the other says he had not heard that code and gave me a quote for 4 inches. If I take the rule of thumb HDD(4400) divided by 180 I’m looking for an R value of 24. My question is: What system people think is best? Foam board with mechanical attachment(nails) w/ restucco, EIFS(Dryvit or STO) with glue attachment, or spray foam w/restucco? Is Polyiso practical to work with stucco or EIFS home applications?
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The NM Code does allow installing up to 2” of rigid foam when installing 2 & 3-coat stucco w/o an engineer stamp. Over 2” you are required to get an engineer stamp. It has to do with the stucco weight and mechanical attachments of the lath. If there are any changes at the local level (which I’m not aware of), you should call the ABQ Bldg Dept. to be sure. Polyiso is a great product for it, plus it has some of the highest rigid insulation R values. With EIFS things may be different. Call Dave Schmitz, tech. advisor at El Rey stucco, and ask for his installation instruccions for their EIFS application on CMU.
I contacted Dave Schmitz and he said they have not tested for EIFS over SPF or Polyiso foam board. Seems that 2" of EPS with EIFS or lath/stucco is common, but Polyiso, SPF or 2+" of exterior insulation is on the more exotic side and difficult to find contractors that regularly work with it.