How to Solve Window Condensation
LESLIE: Now we’re going to talk to Ashley in Delaware who listens to us on WDEL.
Welcome, Ashley, how can we help?
ASHLEY: Hi, thank you. My husband and I recently purchased a house that is at least 120 years old; we’re researching it.
ASHLEY: And we’re going to put it on the National Register of Historic Properties. And we’re restoring the windows that are actually 120 years old, too.
LESLIE: So they’re seeded glass.
ASHLEY: Yes. And we’ve pulled all the windows out and re-puttied them and taken them down to bare wood and done everything necessary to improve them to the best of our ability. And we also bought storm windows because, you know, you can’t replace these old windows. But the problem that we’re having is that after we installed the storm windows, they’re sweating. There’s condensation that’s getting between …
LESLIE: The two panes of glass?
ASHLEY: Yeah, the two – yeah. It’s actually getting on the storm window and the interior window.
TOM: Right. So is the interior window getting wet?
ASHLEY: Yes. They both are.
TOM: Yeah. Well, you have a lot of humidity in your house. That’s why that’s happening. Do you have a hot water heating system?
ASHLEY: Yes, I do; radiator.
TOM: Yeah. Well, it’s a much moister system and you probably have some moisture sources inside the house. And as you know, the windows are not that well insulated, being old windows. You’re cutting down on drafts by having the storm windows on there but, basically, you have the force of condensation working against you there. The warm, moist air inside your house is striking the colder windows, it’s condensing, and then it’s dripping. And there’s a lot of water in moist air and that’s what you’re seeing.
TOM: So what you’re going to need to do is try to reduce the humidity inside the house. Do you happen to also have a hot air – excuse me, a forced-air air conditioning system?
ASHLEY: No, we don’t have air conditioning, presently.
TOM: Hmm. OK.
ASHLEY: Because of it …
TOM: I was going to suggest a whole-home dehumidifier but that would require a duct system to use.
ASHLEY: Right, we don’t have a duct system.
TOM: Alright, well let’s kind of start at the beginning.
Leslie, I think we ought to talk about grading to start, don’t you agree?
LESLIE: Yeah, there are a couple of things that you can work on, on the outside of the your house, which will reduce moisture coming into the basement or anything that’s sub-grade in your house. You want to make sure that all of the grading on the exterior of your house is going away from the house, sloping away, so that if you have any water that does hit that ground, it’s not rolling towards the house but going away. And a good rule of thumb is to go about 6 inches on a grade over 4 feet.
Then you also want to check your gutters. Make sure that they’re always clean. If you have to, get a product like a GutterBrush that might keep those leaves out permanently, which will cut down your work a lot. And make sure that your downspouts are depositing the water at least 3 feet away from the foundation of the house because if the downspouts are just hitting right next to the foundation, it’s depositing the water right back into that foundation.
So those are a couple of things that will take the moisture out of the sub-grade levels.
TOM: And Ashley, even if you don’t have a flooded basement, you have a lot of moisture that collects against the foundation walls that wicks its way through and that becomes moist air inside the house.
The other things I would look at would be your attic ventilation. Typically, in an older house you don’t have enough of it. But you might want to think about increasing the attic ventilation by adding ridge vents or soffit vents so that you take that moist air out of the attic because it will move all the way from that basement space through the interior walls and floors and up into the attic.
And then, mechanically, you might want to look to make sure that, for example, your dryer vent is properly exhausting out. If you have vents for cooking – you know, your exhaust hood over your kitchen – that that’s exhausting out.
LESLIE: And even your bathroom vents. We get calls from people whose bathrooms are venting into the attic, which is putting all that moist air still back into the house.
TOM: Yeah. And finally, in the real, damp, moist periods, you might just have to use a dehumidifier. So all of those things will help you manage that interior moisture.
So congratulations for spending all the time and attention and love it takes to make those windows the way they once were. But the truth is that now our homes are a lot tighter than they were in 1886 or whenever your home was built and, as a result, you have to manage the indoor humidity as well if you want to be able to use these successfully.
ASHLEY: Well, I have noticed any time that we have to go behind a wall, they have the blown-in insulation throughout the entire house and they have it – we have a third floor and then there’s an attic above the third floor – it’s kind of more like a crawlspace – and there’s about 8 inches of it up there. So do you think all that is contributing to the moisture also?
TOM: No, I think the insulation is helping keep the heat in your house but insulation should not be confused with ventilation.
TOM: You know, when you get to the attic, you need to let the air out and you keep the insulation between the attic floor and the ceiling, for example. But above that, it should be ambient temperature. It should be the same temperature as the outside, if it’s properly designed.
ASHLEY: OK. OK.
TOM: OK, Ashley?
ASHLEY: Well, thank you so much. I really appreciate that.
LESLIE: Congratulations on the new house.
ASHLEY: Oh, thank you and I wrote everything down you said so I don’t forget anything.
ASHLEY: OK, thank you.
TOM: You’re welcome. Thanks so much for calling us at 1-888-MONEY-PIT, 888-666-3974. Another happy Money Pit customer.