Fixing Leaky Windows
Q: The windows are single-pane and leaky, and the furnace is 15 years old. Which should I fix first?
Last year I bought a 1910 bungalow with a mash-up of original single-pane windows, many without storms, and cheap vinyl ones—most with broken latches. The furnace is 15 years old. Which should I replace first, the furnace or the windows?
—'Bou,' St. Paul, Minn., via TOH message boards
Tom Silva replies: A new furnace would definitely be more efficient than the one you have. But it would simply pump warm air into the house and out through your leaky windows, so I'd focus on the windows first.
I'd fit all the original windows with good quality storm windows. They stop air infiltration about as well as most replacement windows, and at a much lower cost. And they'd protect those valuable originals from the weather. Expect to pay about $150 apiece for exterior storms, not including installation. They should be bedded in butyl or elastomeric caulk at the sides and top, but leave the bottom flange uncaulked to allow condensation to drain. Then weatherstrip the existing windows.
Your vinyl windows present a slightly different problem. Assuming they're double-glazed, the least expensive solution would be to replace the sash locks so that the meeting rails don't leak warm air. These locks will improve your security, too. Also, replace the weatherstripping if it's worn. You may find that your windows are so flimsy that neither fix can be done. In that case, you might want to consider upgrading to wood or fiberglass replacements that go with the house's original windows.
While you're at it, see that your doors are properly weatherstripped, too, seal small gaps around the house with caulk, and fill large gaps with expanding foam sealant. All this, plus the attic insulation, should result in a noticeable improvement in your heating costs and your comfort. By the way, make sure you take advantage of any federal or state stimulus programs that can offset some of your expenditures. Put the savings from your reduced heating costs into a "new furnace" account.