How to Best Insulate an All-Steel Building

How to Best Insulate an All-Steel Building

I know lots and lots about post frame buildings, however when it comes to all steel buildings (PEMBs – Pre-Engineered Metal Buildings aka Red Iron) I go to an expert.

Today’s expert is John Lyle McInroe aka Mr Bee Happy, he has been in the building industry since 1988. From 1988 to 1996 he built pole Barn structures. In 1996 he built his first steel building and for eight years built both pole Barn and red iron structures. In 2004 he went into red iron full time and has been building red iron structures of all shapes and sizes ever since. If I was looking for a red iron building in John’s service area, with out question he would be my man.

The most effective way to seal your steel building would be to use spray foam. Since the steel sheeting is already screwed down, I would start with getting closure strips for your panels. You take the closure strips and cut the high rib part off the strips and stuff it in all the high ribs of your panels. This would need to be done at the bottom and top of your sidewall panels and on the bottom and top of your roof panels as well. You want to make sure that anywhere you see daylight is sealed up. I would also use silicone to seal these closure strips into place. Also, just for a little extra, I would also use a flashing tape on any spots that you see daylight that isn’t necessarily where high ribs are. Places like gable end walls where roof and wall come together and corners. Simply, just want to make sure its sealed as well as possible. Once everything is sealed, I would have a reputable spray foam company spray two inches of closed cell foam on all walls and roof and make sure all steel is covered with the closed cell foam. This would include all purlins girt and beams. At this point you have sealed the envelope of the building but have a low R value, roughly 14. So what we do is use an open cell foam on top of the closed cell. We do 5.5” in the roof with 3.5” in the walls. At this point you have an R value of over 33 in the roof and 26 in walls and you have sealed the envelope. Now when we use this method on our projects, we make sure our HVAC company knows how to put in proper HVAC system. Main thing is making sure the system has a fresh air intake system. These are the processes and procedures that we use on all of our projects.


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