Could the lack of a moisture barrier and plywood, along with low insulation, be causing the moisture issues in your home despite the new windows?
Asked by Mathéo Fernandez 
3 months ago
Last Updated: September 26, 2024
So, I bought this house a little over a year ago, and let me tell you, it’s been quite the adventure. The house was built back in the 90s, and last winter we had some seriously leaky windows that would ice up like crazy. Well, we finally got around to getting some new Anderson windows installed, and now there’s even more moisture inside! I don’t think the seal is broken, so what gives? Turns out, when they were putting in the new windows, we discovered that there’s no moisture barrier or plywood in our house, just drywall and framework with minimal insulation before the siding. Could that be the reason for all this moisture?
It’s tough to pinpoint exactly. I’m assuming the new windows have double pane insulated glass? If they do, you shouldn’t see condensation on the glass under normal circumstances. What’s the humidity like inside your house? That could be a factor. Also, are all the windows experiencing condensation? Or just a few? You might want to try lowering the humidity in the house to see if that helps.
During winter, the issue becomes more apparent when the heat is on. Think of it this way: in summer, when it’s hot outside, you put ice water in a glass and it starts to sweat. The inside of the glass represents the cold outdoors, while the warm air inside your home is like the warm outside of the glass. A few things to consider: poor insulation and lack of a vapor barrier, as well as air leaks around your home. This allows moist air to condense, especially on smooth surfaces like windows on exterior walls. The cold outside combined with the increased indoor heat due to comfort only worsens this sweating effect. Even high-quality windows won’t solve the issue if the home is not properly sealed. You’ve already taken steps to improve energy efficiency and comfort in your home, but there is more that can be done to address condensation issues.
The dew point forms on cold glass due to high humidity levels inside the house. To address this, you need to identify and reduce sources of humidity indoors. This includes adjusting humidifiers, using exhaust fans when cooking, ensuring proper ventilation in laundry rooms, bathrooms, and more.
Having worked in the energy industry for over 30 years, I think your response is spot on. One thing to consider is the location of the house. If they believe they are running the fans long enough, they should also check the air flow of the fans. I once inspected a new house with a similar issue where the problem turned out to be a painted exhaust grille outside the house that was blocking air flow through the bath fan. This just shows that the problem can be tricky to pinpoint, but it’s important to investigate all moisture-related issues. Ensuring proper moisture removal is crucial even with the best fans in place.
I completely agree with everything you mentioned. The first step should be checking if there is a humidistat on your furnace set to high.
Maybe he should consider getting a dehumidifier and setting the dehumidistat to low instead of high.
It should be mentioned that it is set too high
Try running a dehumidifier, that should help. Also, make sure to keep the moisture on the windows and sills under control to reduce the risk of mold.
What type of heat source are you using? Hydronic systems often face this issue. Your insulation is a problem, along with the lack of a vapor barrier. Another person mentioned that moisture is getting inside and causing humidity.
Make sure to monitor the indoor humidity levels
You should consider getting a dehumidifier as soon as possible!
Not quite sure what to do, but our house had this issue back when we were in North Dakota and I always wondered about it.
Baseboard heating is common in the northeast, especially on cold nights. Heavy curtains in front of windows can block the airflow needed to prevent cold air from causing dew to accumulate inside.
Hey , you should also check what’s causing humidity in your home. Is there something producing excess humidity? Do you have efficient exhaust systems where needed? Make sure they’re the right size and working properly. Are they running for long enough? Baseboard heating, whether electric or hot water, can often be very drying. Consider what’s contributing to humidity levels and promoting air exchange. Sometimes, tightly sealed modern homes lack proper air exchange. Whole home ventilation systems can be helpful, as they remove indoor pollutants and excess humidity. Humidifiers and dehumidifiers might not always be the solution. Some air changes are necessary for a healthy indoor environment. Maybe can provide more insights.
So, let me make sure I understand correctly – you’re saying that there shouldn’t be any outside sheeting or vapor barrier? Just drywall, studs with insulation, and siding nailed directly to the studs? I always thought the correct order was siding, house wrap/barrier, wall sheeting, studs with insulation, vapor barrier, and then drywall. Am I mistaken?
Yes, you interpreted that correctly 🙁
May I ask what kind of siding you have? And what is it connected to?
Our addition was constructed in that manner and we haven’t experienced any condensation on the windows inside. (Planning to have it reconstructed next year)
We had the same issue in our new barndominium, but using a dehumidifier solved the problem. Now the windows are clear and everything is working well. Good luck!🙂
Most people attribute window sweating to humidity.
But even with humidity levels below 30%, I still encounter this problem in my home and I honestly prefer not to sleep in a bedroom that dry.
In simpler terms, the condensation is forming due to the glass surface temperature and warm indoor air. It’s important for air to flow across the window surface.
Having many plants or cooking on the stove, especially when boiling, steaming, or sautéing, can increase humidity levels in your home. Keeping curtains or blinds closed on the windows can also contribute to the issue. The number of people in your home and your preferred indoor temperature can impact window condensation. Finding the right balance can be tricky at times.
I found that installing ceiling fans made a significant difference. I used to have a skylight in a high kitchen ceiling that would sweat a lot, according to the previous owners. After installing a ceiling fan that runs on low constantly, I haven’t experienced any condensation issues in 6 years, despite having plants and cooking frequently! Additionally, running bathroom fans while showering and for 15-30 minutes afterward can help.
There’s too much humidity in your house. When it’s really cold, aim for around 20 to 25 percent humidity. Try placing a fan by the window and make sure your floor vent is open. Ceiling fans can also be helpful if they’re blowing or drawing air upwards.
Just an FYI……moisture in the air from showers, humidifiers, washing dishes, etc. will reappear as water at the coldest spot in the house….usually at the intersection of the roof and top wall on exterior walls. Yours is due to a leak from the coldest window. Big issue. Will damage materials and lead to mold.
We put in new Pella windows and we experienced the same issue! It scared me at first but then I realized how bad my old windows actually were because we never had condensation inside. Just goes to show how well the heat is trapped now!
Best explanation and solution I’ve come across.
https://youtu.be/02wFM0JgrcQ
So this guy does a great job explaining why condensation forms. But he barely touches on the best solution: keeping exhaust fans on longer. I’ve been in the glass/window industry since the late ’70s and never heard of this “CR” … condensation rating factor … ??? And it’s pretty obvious this video is just a window sales pitch!! While it appears to be an unbiased look at condensation science …. it’s really just a sneaky way to sell that company’s products/services. The best solution overall is …. keep those exhaust fans running longer to help manage/reduce humidity levels in your home. If you’ve already replaced the windows … that should be your last resort!
‘ explanation and suggestions really helped me. I used to think it was a window issue until I heard him out. What worked for me was keeping my curtains fully open or adjusted to allow for airflow. I have a mix of aluminum and vinyl windows, and now there’s no more condensation on the aluminum. I didn’t need to make any extra effort with exhaust fans in my case.
If your furnace has a humidifier, should it be set to high?
That’s a perfect response!