Does it really matter which side the facing of fiberglass insulation goes on when installing it in a 1962 construction home without a modern impermeable membrane in New Jersey with cold, wet winters and hot, humid summers?
Asked by Jeremy Hamilton 
4 months ago
Last Updated: July 26, 2024
I’m sure this question has come up before, but I’m a bit confused about which side the facing should go when installing faced fiberglass insulation. I’ve seen conflicting information – some say it should be on the warm side in winter, while others say it doesn’t matter. I’m wondering if it depends on whether your house has a modern impermeable membrane between the exterior plywood and siding, which ours doesn’t.
Just for context, we’re in New Jersey, not near the shore. Winters are usually cold and wet, while summers are hot and humid. It’s been a couple of years since we’ve had a good snowfall, but sideways rain is pretty common.
When installing insulation, ensure that the paper faces the conditioned side to act as a vapor barrier.
I was a bit confused about the purpose of the paper facing on the insulation as well. It acts as a vapor barrier, but it’s important to consider where the humidity might be higher depending on the season. The idea is that during winter, when indoor humidity is higher, the vapor barrier should not get cold enough to cause condensation against the drywall due to the insulation preventing heat transfer effectively.
William M. nelly mentioned that the paper on the insulation has a lip that can be stapled to the 2×4 framing.
Make sure to check if NJ has any specific code requirements for insulation installation. If not, it may not be a big concern. Check here for more details: https://www.energyvanguard.com/blog/in-or-out-where-does-the-paper-facing-of-batt-insulation-go/
Oh yeah, that’s where I came across it when I was googling.
William M. nelly
I’ve found their suggestions to be very accurate for other projects I’ve utilized them for.
Make sure the paper is oriented towards the heated side when placing the insulation.
You know the paper on the insulation is actually larger than the insulation. This is so you can use the excess paper to staple it in place. Whether you refer to it as the paper side, the heated side, or the conditioned side, it should be facing the interior of the house.
Consider the temperature around you. The side more prone to condensation is the best choice. In NJ, it’s recommended to have it facing the interior.