Do I need to reconsider open foam vrs fiberglass insulation since I don't run an air conditioner all the time?


Do I need to reconsider open foam vrs fiberglass insulation since I don't run an air conditioner all the time?

Asked by Len Lyle

I have a 16 X 28 work shop with a metal roof installed over felt and OSB Sheating with silver radiant barrier on the underside. I live in South Texas where it gets extremely hot and when building, I added soffits and a ridge vent to help the air flow but it still gets hot inside and it is time to insulate. I have been convinced that open foam insulation is what I should use and the installer said he has to close off all the venting to make the building and insulation work right. After reading your article about needing fresh air I became concerned. I have a small window air conditioner (12,000 BTUs) but I don't leave it running all the time and sometimes I am gone for 5-6 weeks during the hot summer. Will this cause problems? Am I making the right choice to go with the blown in open foam insulation vrs fiberglass batting? Am I creating a hazard by not having an air system?

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Scott Grieves, CPM, CEA's picture

Yes it's possible you could be making the environment in your work-shop conducive to mold/ growth depending on your climate. If you ask any building science professional you will get two sides to the coin--- one will say it's best to make everything tight and the other one will say it's best to allow the space to breath. With that being said, we also sometimes generate humidity or heat inside our spaces such as a refrigerator running or cooking so if that's the case you might consider running the HVAC to just to help control humidity. EPA recommends between 40%-60% relative humidity however its best around 50%, things start to grow above 60% humidity. If you wanting to "seal it tight and insulate it right" and never develop a problem or reduce the risk of mold/ growth. I would recommend consult a licensed insulation contractor or a HVAC contractor in your area and ask the opinion what would be best for your work-shop. FYI: I did radiant heat barrier and open faced fiberglass in my shop 14 X 24 shop and a large fan blower to move air. YES its vented, no foam... The large maple tree above my work shop helps keep it cool in the summer. A/C unit would be nice however I like the space open with a lot of air movement when I'm working on things.