My builder is advising against spray foam insulation in my wall because of high moisture in the framing lumber here in the south and fear of locking in that moisture. Is this a legitimate concern and how can I get around it?
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I’m not familiar with building in the South. I am in the Midwest with extreme summer and extreme winter weather. Foam works great if it is installed correctly and is the right type of foam. Most all of the problems associated with it are b/c it is not installed properly. The science behind it is very important b/c it is not as forgiving for moisture control if installed wrong compared to other types of insulation. If you are one of few people to install it in your area it might be bad for your climate. Give a call to a good local spray foam company as they should be up on the science. There are energy audit type companies as well that can help out as well. Or go to the green building advisor website. There are a bunch of insulation nerds on there that can give you solid advice. Make sure you let them know you are building conventionally and not using advanced construction methods as they’ll make your head spin with all the most cutting edge methods and technology. You need to try to find region specific help, someone like me responding from a totally different climate is not the best source for relevant info. Foam is not great if there are pre existing moisture issues, but those should be taken care of anyway. If your ventilation, heating and cooling are not up to speed that can create moisture problems as well. The big thing with super sealing homes is to make sure that the walls can dry out. You often hear walls should be able to breathe, but that is not accurate, you are not bringing fresh air into the wall, the goal is to allow ventilation systems to draw moisture out of the wall. This involves a good HVAC system ERV etc. There’s a lot to it. If you and/or your contractor are not confident in applying the science stick with the basics.
Get a moisture meter and measure the water in lumber. By the time you dry in your home things should have dried out.
If you are worried about moisture use open cell foam.