Window Condensation Problems

I had a past client call the other day with a question about their windows. This summer they had some more work done on their home in Bath,

including new siding and more new windows.  Recently, as the temperatures outside got lower, they had been getting condensation inside the new windows. They’d never had condensation on either the original windows or the larger triple pane ones they had installed as part of our project together, so they wondered if the new windows were faulty.

I told them the problem probably isn’t with the windows, but with the humidity level in the house.  The triple pane windows didn’t have condensation because their interior surface stays warmer than the glass of the double pane windows they just installed.  The 1950’s windows they had just replaced didn’t get condensation as easily because they let more fresh air into the house through their leaky construction and installation.  I’m guessing they had more air sealing done as part of the siding work too.  So now the moisture from showers, cooking, houseplants, and everyday activities stays in the house longer; driving up the relative humidity and creating condensation on those nice new windows.

Two catch phrases in building science are “build tight, ventilate right”, and “the house is a system”.  My clients had made a lot of progress on getting their home more air tight, and I’m sure their energy bills will be lower this winter.  But since they had changed the part of the system of their house that brought in fresh air (even though it was brought in by accident through leaks, without any way of controlling it), they need to change their behavior to take out the extra moist air from showers and cooking. I expect running the bath fans and range hood longer than they used to will help.  If a house is tight enough, it may be necessary to have a dedicated ventilation strategy such as a heat recovery ventilator (HRV or ERV), a fresh air intake at the furnace, or an exhaust fan that runs on a timer.  Ventilating right also means not having a super-sized kitchen hood without providing make up air, because that has been known to cause dangerous back drafting at the furnace.

Most of us can’t upgrade everything in our homes all at once, so doing one project at a time is the most practical way to improve our efficiency.  Just remember that a change to one thing can affect a number of others.  So check in with a home performance professional or your architect to learn more about how the pieces fit together.

The Energy Audit Saga Continues

In my last newsletter, I wrote about the two energy audits I had done recently: one through Dominion East Ohio’s GoodCents program, the other through a company specializing in audits. If you missed that article and would like to read a comparison of the two audits, just click below: Battle of the Energy Audits. Well, after getting all that information on where my house is losing energy, you might wonder what I’m doing about it.

I’m pretty passionate about the importance of insulation and air sealing, so I would have liked to have done the deluxe package recommended by the one company, pulling back all the existing insulation in the attic and getting thorough air sealing around all of the openings there. However, since I’d had the worst of the holes closed up before insulating 10 years ago, I thought the payback on that would be minimal. So I’m moving forward with adding more cellulose insulation in the attic (for a total of 14” deep), putting air tight boxes around the can lights in the attic, sealing leaks in the basement ducts, and sealing the rim joists around the top of my basement walls. I’m especially excited about the rim joists, because having this done should make it more comfortable in my walk-out basement office. The rim joists have fiberglass batts in them now, but I know that they provide almost no insulation value without a good air barrier. Here are two details of ways to insulate the rim joist.  The one on the upper left is what I had done.  If you want to do it yourself, using rigid foam as shown on the right is a good way to go.

The next question was who to have do the work. While the other company was very knowledgeable and professional, they just couldn’t compete with the rebates available through the Dominion program. By getting the audit done and then having the recommended work done by one of their participating contractors, I’ll get a rebate of 22% of the cost of the work! I’m looking forward to a more comfortable house next winter, with lower heating bills. How about you? I’ve heard that the GoodCents program may be discontinued in the near future, so if you’d like to take advantage of the Dominion rebates, now is the time! For details on the program click on: Dominion East Ohio

First published May 1, 2012