I have a walk-up unfinished attic in an old ranch house in Pennsylvania, where we see summer temperatures over 100F and winter temperatures well below freezing. Because there is planking over the joists the in-joist insulation over most of the living space is realistically limited to R-25.
The attic/roof is ventilated with soffit and ridge vents.
Right now (it's still 100F outside!) I'm thinking of ways to reduce the cooling load on the central HVAC. I wouldn't mind moderating the temperature in the attic itself year-round either.
I have a roll of AtticFoil-like radiant barrier. If I staple that to the exposed roof rafters (without blocking the soffit-to-ridge vent circulation) I understand it will reduce the heat gain on sunny days.
But given that the house also goes through a cold season during which heat gain would be a bonus, should I avoid such radiant barrier insulation in this location and application? (I'm not sure how to balance the seasonality, especially given that there is less sun exposure during the winter due to shorter days and lower sun transit.)