Answer
Aug 04, 2020 - 08:12 AM
I'm doing a roofing job for my house: what should I be doing to minimize energy loss? Can I add insulation when reroofing? Are there incentives for that? Can I improve air sealing from above during replacement? What about adding solar panels? Unfortunately, your roofing has relatively little to do with your home's energy use. In most cases, the thermal boundary of your home, where insulation makes sense, is the floor of the attic/ceiling. In this case, changing your roofing doesn't have any implications for insulation or air sealing, and the time when your shingles are off isn't a particularly good time for getting access to improve your energy performance. It is great that you are thinking about this, and you should check out information about attic air sealing and blown-in insulation. If your attic is part of your home's living space in terms of insulation (in technical language, your home's thermal envelope runs up against the roof). Or, if you want to make the attic a living space or make it a conditioned space to run ducts, etc. (in technical language, to bring your attic inside the thermal boundary), then a roofing job provides an opportunity. In most such cases, insulation (such as spray foam) would be added to the inside (bottom) of the roof sheathing. The main implication to be aware of when reroofing is to do the roofing first so that you don't have to tear your old shingles off new insulation. If you are very ambitious and want to pursue a so-called "deep energy retrofit," you can explore adding insulation between your existing roof sheathing and a new roof. In this case, you'd add several inches of rigid foam above your current roofline and then build a new roof on top. This expensive approach makes the most sense when you have a simple roofline (no dormers) so that the geometry and carpentry are simpler. You'd need to do some good carpentry around the edges of the roof to get the new higher roof to look good with your existing walls. Note that just after you get a new roof is also a great time to think about solar PV, since the solar system will last as long as a new roof, and you can avoid the complication of replacing a roof during the lifetime of the solar panels. If you think ahead, the roofing project is an excellent time to move sewer vent pipes, bath exhausts, and other things that cut through your roof so that you can fit more solar panels. Your plumber can move a sewer vent pipe to another nearby part of your roof that is out of the way of a future solar installation (e.g. on a north-side slope), usually just by moving pipes within your attic. The plumber will leave a patch where the old pipe went through your roof, and your roofer can lay the new roof over the old hole and around the new pipe. (If you're electrifying your home or your chimney is no longer in use, you can even remove your chimney and roof over that hole - and fit a few more panels on.) |
