This week the Pole Barn Guru answers reader questions about likely condensation challenges with a closed envelope in coastal South Carolina, an addition of a 16′ wide garage door to an existing building, and if the Guru knows any pole barn movers in central Illinois.
DEAR POLE BARN GURU: I want to keep my building a closed envelope, for conditioned attic space. 40x60x12. My plan is to use closed cell foam 2″ on walls and 3″ on roof deck applying directly to the metal. Do you foresee any moisture issues? Environment is coastal South Carolina, Georgetown county. Hot and humid, very rare to see sub-freezing temps. Also what kind of HVAC do you recommend? RON in GEORGETOWN
DEAR RON: Unless you are going to mechanically dehumidify, expect to see condensation challenges.
Your site is in Climate Zone 3A, where the 2021 IECC (International Energy Conservation Code) specifies minimums as R-15 continuous for walls and R-49 for ceilings. You could achieve this by just over 2″ of closed cell on your walls, however you would need to add another R-28 to your roof. This could be done by adding unfaced Rockwool (Rockwool is not affected by moisture) batts between roof purlins. Specify 2×10 roof purlins 24 inches on center, then use just over 2-1/2″ of closed cell plus 23″ wide x 7-1/4″ Rockwool batts.
Your HVAC provider can recommend a system most practical for keeping humidity at manageable levels.
DEAR POLE BARN GURU: Can you add a 16 ft wide garage door to an existing pole barn? It would be on a gable end of a 30×50 building. ALEC in TOLEDO
DEAR ALEC: Probably, however it should only be done with a structural review from a Registered Professional Engineer as you would be dramatically reducing shear capacity of your endwall.
DEAR POLE BARN GURU: Do you know any pole barn movers in central Illinois? Have a 52×100 we would like to move about 15 miles, ambitious I am sure. MELANNE in DAWSON
DEAR MELANNE: If I had to take an educated guess, I would say it will cost more to move that it would to build new from scratch. At 52′ feet wide, it would take every road being at least four wide lanes between start and end of trip. You can Google “house movers near me” to see if there is anyone in your area.
