Completed a new house in March where low density spray foam insulation was used for the walls and underside of roof. I have seen houses where the OSB joints telegraphs through the shingles. Roof trusses are 24″ OC. A small leak has developed around the chimney that is being addressed today. However, the roof has telegraphed and some shingles are not completly flat. It is hard to see in normal daylight, but as the sun sets and you see the shadow across, it is disconcerting.
The HVAC system is an air source heat pump with a 6×6 diffuser and a 6×6 return in the attic space. On cool nights, the HVAC may run to circulate air throughout the house with the windows open to bring in outside air.
House is in Pennsylvania.
My question, is there an issue with operating the HVAC system this way with this type of envelope construction?
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If you have joints telegraphing before you've even seen a winter, it probably doesn't have anything to do with the HVAC system. Because you used an open-cell foam you might have some moisture migration from the inside out in cold weather that you would not have with closed-cell foam. But in this case it's probably an outside-in source of moisture, like the chimney leak or it could have happened during construction. OSB swelling is the reason I don't use it, but that doesn't help you much right now.