This week the Pole Barn Guru answers reader questions about insulating a building that already has reflective foil radian barrier, if one needs vents or exhaust fan in the gable ends of the roof with the high heat/humidity of Alabama, and requirements for frost wall or slab for frost heave.
DEAR POLE BARN GURU: I recently moved into a house with a 40×30 pole barn (wood post and wood trusses) with a metal exterior. The building has a reflective foil radiant barrier between the metal and wood structure. It is extremely hot in the summer and cold in the winter. I want to insulate and cannot afford spray foam. I also don’t have the ability to remove the walls to remove the foil barrier that way. I do have some Silvercote insulation that has an attached vapor barrier. It is just a fiberglass roll insulation that has an attached vapor barrier to it. It is sold around here for use as insulation in metal buildings. I was given enough to insulate the whole shop from someone that had left overs. I would like to install this insulation to help with temps in the shop. I have tried to research to get an answer on the best way to go about this. The shop builder said just put it up but I feel that would create a double vapor barrier. Is my best route to cut the foil radiant barrier out and then install the fiberglass insulation with vapor barrier facing the interior of the building? This would basically take the foil barrier out and install the fiberglass against the metal with the attached face vapor barrier to the inside of the building. I want to make sure I do it right. Thank you. DAVID in OKLAHOMA CITY
DEAR DAVID: If you are dead set on using this Silvercote insulation then you should cut out any foil radiant barrier. You never want to have a double vapor barrier situation as any trapped moisture will have no method of escaping. Downside of this is you do not have a Weather Resistant Barrier (aka housewrap) between framing and siding. An option to consider would be to resell your metal building insulation, then use unfaced Rockwool batt insulation, as it is unaffected by moisture.
DEAR POLE BARN GURU: I plan to build a 28×48 metal pole barn, concrete floor, 12′ eave with 8/12 pitch. Barn will have 6 3×4 windows, and two 10×10 roll doors, one roll door on each gable end. For now, the roof will be insulated with 3in closed cell foam. I plan to insulate the walls down the road with rigid foam board. The building will not have A/C. Question: Do I need vents or exhaust fan in the gable ends of the roof with the high heat/humidity of Alabama? There will be no ridge vent or soffit vents. I may not have the building open every day, either. Thank you. JASON in MONTGOMERY
DEAR JASON: While placing permanent vents might alleviate your possible mold/mildew/condensation issues, they will defeat your insulation investment. In reality, you should look to a qualified local HVAC provider to provide mechanical dehumidification, else you will have regrets forever. Make sure to have a vapor barrier under your concrete floor, to help reduce interior moisture gain.
DEAR POLE BARN GURU: FROST HEAVE, 44′ deep by 64 long pole barn 20 ceiling height, Tenant build, will be insulated but NO HVAC initially. However, is some type of concrete frost wall (downturn?) via monolithic slab required? Dimensions? MIKE in CINCINNATI
DEAR MIKE: Your slab on grade can be poured to a consistent thickness throughout and all you need to do is properly insulate your slab edge to meet IECC (International Energy Conservation Code) requirements.
