Order of upgrades
In an older house, is there a particular order in which air sealing and insulating upgrades should be made? I understand every situation is different, so I am looking for general guidelines. I am looking at possibly purchasing a 40 year old house and planned on trying to air seal the attic and rim joists of the crawlspace right away as well as duct sealing. Any big holes like pull-down attic stairs would also be addressed. After completing the most obvious work I’d like to have a blower door test done. I could be wrong, but other than curiosity it seems like the blower door test would be more useful after the major leaks are addressed rather than before. Does air sealing at the ceiling and floor preclude encapsulating the crawlspace and attic (at the roofline) in the future? Ducts are in both the attic and crawlspace. The bigger upgrades would have to be done over time as the budget allows so I am looking for low hanging fruit but I don’t want to regret the work later. When it comes time to encapsulate the crawlspace and/or attic is one preferred before the other?
I don’t have specifics of the existing insulation other than that the attic has fiberglass batts in place (didn’t think to take a ruler or tape measure with me to get the depth).
I am on the line between Zone 3A and Zone 4A if that matters.
I recently found GBA and have been reading to educate myself. I appreciate any insight you could offer.
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Replies
I agree with your first priorities and I don't see any way it would lead to regrets later. The guide to air sealing that Energy Star provides is a good one.
Why do you want to bring the attic in the envelope? Because you have ducts in the attic, perhaps? A good low-hanging-fruit is usually to add lots of cellulose on top of the fiberglass in the attic--that's much easier than sealing and insulating at the roof.
By waiting on the blower door test all you lose is bragging rights about how much you improved it. That might be a real issue if you have a utility program that requires you to start with an audit.
Daniel,
Q. "Does air sealing at the ceiling and floor preclude encapsulating the crawlspace and attic (at the roofline) in the future?"
A. No.
Q. "When it comes time to encapsulate the crawlspace and/or attic is one preferred before the other?"
A. If you have ducts up there, I would do the attic first.
If everything goes through I would also be replacing flooring and painting early on. I planned on caulking and spray foam to air seal at the baseboards. Do I need to caulk at the corners and along the ceiling as well? I thought that this combined with sealing in the attic and crawlspace would provide more air tightness by trying to seal from both sides. Switches and receptacles would also be caulked. Thanks again for the help.
Normally joints between drywall and drywall have been taped and "mudded" for a clean look and that provides air sealing as well, so you shouldn't need to caulk them. An exception would be if there is crown molding and they didn't finish the drywall joint behind it. I'd save that for the blower door test--assume it doesn't leak until the blower door test tells you otherwise.
While the old carpet is up, is there any need to seal the subfloor (as in taping the joints between sheets)? It looks like the roof will likely need to be replaced in the next few years so I would have a chance to add some rigid insulation above the roof deck. Does this provide much benefit if the attic is not sealed at the same time?
Daniel,
Here are links to two articles that might help you:
Air Sealing an Attic
Air Sealing a Basement
If you are installing a new plywood subfloor, it makes sense to install it in an airtight manner. Caulking or taping between the sheets won't hurt (although air sealing isn't necessary for some types of flooring, such as sheet vinyl flooring).
If you want to create an unvented, conditioned attic, the best approach would be to do all the work at once. But you could stage the work if you want to do it gradually. For more information, see Creating a Conditioned Attic.
Anything that impedes "stack effect" air flow is generally a good idea. It's almost impossible to adequately air-seal a floor, but it doesn't hurt to try.
The bigger vertical air leaks are usually the plumbing & flue chases, electrical penetrations, duct chases, duct-boot sealing to the sub-floor, etc. The seams between 4x8' sheets of plywood are pretty small in cross section by comparison, but if you can tape or mastic-seal them (with fiber reinforced duct mastic) before the new finish floor goes down you will have ruled it out as a cumulatively large leak. Even small leaks can move a lot of air if your ducts are imbalanced &/or leaky, since the air handler can impart a real pressure difference between the crawlspace and first floor.
Get an energy audit - in addition to the blower door test, an auditor will (or at least should) give you a list of work with estimated energy savings associated.