Can blowing in insulation resolve the condensation issue caused by a damaged bathroom exhaust fan in the middle of an insulation project?
Hey, just a heads up about my not-so-great drywall cut from way back when that I still haven’t gotten around to fixing. And, not really looking for a lecture on codes right now. I’m knee-deep in an insulation/attic ventilation project at the moment. The insulation in this part of the house was basically non-existent before, so I just wrapped up air sealing the knee wall. But now, I’ve noticed some condensation forming in the bathroom exhaust fan. I can see the damper outside opening and blowing when the fan is on. The light on the fan is already busted, so I’ll need to replace that once I’ve sorted out the leveling and installation. It’s a Utilitech 100 cfm fan, by the way. Do you think once I add in the insulation, the condensation issue will go away? Thanks for any advice.
Condensation is usually the result of warm, moist air coming into contact with colder air and forming liquid on cold surfaces. Nick suggested ensuring that you have a properly insulated duct in the attic. If possible, check the inlet and outlet temperatures to see the difference. It would be even better if you have access to IR imaging for an accurate assessment. In the absence of that data, here are a few things to consider:
1. Confirm that the duct seams are sealed properly (hopefully done before insulation installation)
2. Ensure that the duct insulation is fitted correctly without any gaps
3. Make sure the fan housing is insulated according to the manufacturer’s guidelines. You can use rigid foam and expanding foam to create a protective barrier.
4. Check if you have selected the appropriate insulation for your climate
5. Verify that the damper is not stuck open at the vent cap
6. If applicable, ensure that the fan damper is not stuck open
‘s house is insulated. There was definitely some air leakage before, but it might take a bit longer before I can get the cellulose blown in. Do you think I could just wrap it with some batts for now?
You could purchase an insulated flex duct for this, or there’s a sleeve that can be placed over the pipe. If you’re already up there, consider wrapping insulation around it, but it might be better to just replace the pipe. Try to do it before winter ends and it gets really hot out.
The duct is already insulated with what you mentioned. I was specifically asking about adding temporary insulation around the fan housing in the attic. Sorry for the confusion.
I’m not entirely sure about that. Have you thought about placing an insulated box over the housing? It’s possible that the condensation is coming from that area, as the moist hot air meets the cold housing. In my house, I sealed the perimeter of the attic fan with expanding foam. I still get condensation, but not as much as before.
It all began when I decided to spray foam the fan in the attic, haha. Sometimes luck just isn’t on my side, haha.
Wondering about the details of the insulation plan? So you mentioned blown in insulation – does that mean you have soffit and ridge venting? Or are you actually blowing in insulation into the wall cavities? Just a heads up, blown in insulation can create quite a mess in the living area. Have you thought about using bat insulation instead?
Did some insulation work in the attic. The blow in the wall cavities is a concern due to the age and construction of the home. I fixed some mistakes to ensure that the flex duct is properly installed and insulated now. Currently, the metal fan housing is fully exposed in the attic. I’m debating whether to purchase a new fan and redo the installation or just swap out the damaged parts. I need to figure out if insulating the fan housing will solve the issue or if there’s another problem to address.
I agree, putting batts in the attic won’t work with the irregular joist spacing, which ranges from 17-18 inches apart in some areas.
I hear you, seems like the lack of insulation in the housing was causing the problem.
Has been trouble-free in the 7 years the fan has been installed. But, when you try to improve things, sometimes more problems come up haha.
Suggested that bats up to 24″ wide can be used and cut and spliced as needed. It may require more work, but it will prevent a constant stream of dust from the attic. They mentioned blown-in insulation as a common problem and shared their parents’ experience with sealing the attic.
Pointed out that if there was an exposed fan housing for a long time without any issues, then it’s probably not the cause. They suggest checking the dampers.
Mentioned that the attic was exposed, with gaps that weren’t sealed. There was no attic ventilation until recently when shingles were replaced and vents were added.
Even after that, we didn’t have any condensation until recently, after we had the attic spray foamed.
Oh I see, that’s why it wasn’t a problem earlier haha. Your electric bills must have been crazy during the summer.
We never went over $500 in a month, at least not yet, got close though haha. Same as the previous month. I’m hoping it goes down once everything is finished.
Having an attic with no passive or active ventilation (and probably no insulation on the rafters) is going to be really inefficient when it’s hot. I got a new roof 2 years ago with a new ridge vent, and it still gets up to 120°F up there on really hot days. I can only imagine how much worse it would be with no way for the air to escape. It’s basically like an oven. Depending on the size of your house and the climate, $500 may not be too bad. We reach around that amount in the middle of summer, but we have a 3,900 square foot house in the Philadelphia suburbs with 3 separate HVAC units. One of those units is just for a 600 square foot sunroom, which is very inefficient by design. Regardless, you should see a decrease in your bills if you went from having no ventilation to having passive ventilation.
It’s a house that’s less than 1500 square feet in Georgia. Upstairs, there are 2 knee wall rooms where we’ve had to run window units 24/7 to keep them cool. We don’t have HVAC, just propane logs in the old fireplace. There’s been no ventilation and very little insulation in the attic until recently. It’s been a long, slow process, trying to do what I can. Thankfully, we’re almost done with properly prepping one of the knee wall attics for insulation, aside from this bathroom fan issue.
Yeah that sounds really high for under 1500 square feet. I’m guessing you don’t have vaulted ceilings or anything like that, right? Those can be very inefficient, but I doubt a 1500 square foot house would have them. Georgia gets pretty hot, as we know. So the best thing you can do is make sure your attic stays cool in the summer. Just make sure the soffit vents don’t get blocked by insulation. I’m not sure about the specific R value you need for your area, but I’d say you probably need insulation on the joists that’s at least a foot thick. The more insulation, the better. And if you do insulate the joists, make sure you DON’T insulate the rafters. Some people make that mistake. It should be one or the other, never both. And with the passive venting you have now, stick to insulating the joists only.
Hey , I wanted to say thank you for the advice, I really do appreciate it. Right now, my plan is to use 14 inches of cellulose insulation. My house doesn’t have vaulted ceilings. I have a Harbor Freight IR Camera that I’ve used to check for heat from the bathroom side, but I haven’t gone into the attic with it since I started having condensation issues. The camera isn’t the best quality, so I might sell it and get a new one instead.
Flir makes this cool phone mounted IR camera that uses your phone screen and camera to show the results. It’s not bad, especially for the price range of $200-300. The quality of the IR camera isn’t top-notch, but it’s similar to my handheld Flir IR camera that I paid $600 for. The phone camera overlay feature is really handy.
Is the duct that leads outside properly insulated? Warm, moist air from the bathroom can lead to condensation in the cold attic.
Thanks for your advice. I’m thinking about trying it out, but I’m not sure if it will make a difference while I wait to insulate the attic.
You could cover it with blow insulation and make sure there’s natural ventilation circulating air in the attic.
I’ve installed the correct ventilation now, there wasn’t any before.
I think your exhaust hood may not be closing all the way outside, letting cold air in the pipe that ends up condensing in your bathroom. Adding a damper or fixing the exterior should do the trick, or maybe both.
Is closing. This has never been a problem until I had spray foam applied around the fan.
It sounds like your fan might not be properly air sealed or tied into the vapor barrier as required by code. It’s important to follow the code correctly to avoid issues like this. Maybe it’s time to shift your approach towards doing things right by following the code.
Mentioned that the house, constructed in the 50s, lacks insulation or a vapor barrier. There are no specific codes I need to adhere to.
It’s interesting how you’re here complaining about issues that can be resolved by adhering to building codes. Ever wonder why those codes exist? Whenever you make changes, you should always follow the latest building practices. Best of luck, individuals like you ensure folks like me stay in business $$
Good to hear from you. I never mentioned ignoring updated building practices. I intend to exceed the insulation code requirements. I just want to understand why there’s condensation occurring and how to fix it without having to add a vapor barrier to the entire 70-year-old house. I’m seeking advice on why condensation appeared after air sealing that part of the attic and what steps I can take to resolve the issue beyond just adding insulation where it was lacking for the past 40 years.
To prevent condensation, make sure to insulate the area and exhaust vent properly. Running the fan for an additional 20 or 30 minutes after a shower can also help.
We had a similar issue with water leaking back into the bathroom due to condensation. Proper insulation made a big difference.
Thanks for sharing your insights and experience. The insulation will be top-notch once I complete this project. It seems like I’ll have to manage until then.
Hey there, sounds like you have the same issue. Let me help you out!
Try replacing the duct that connects the fan to the roof vent with a highly insulated duct with the highest R-value you can find. Make sure to add a slight dip right before it reaches the fan to catch any condensation and prevent it from dripping into the fan.
In your attic, start by sealing all the holes that are allowing heat and humidity to enter, like the one that’s been there for 7 years around the fan. Check your rooms for ceiling holes that could be letting heat up there – remember, heat leads to condensation in the attic.
Next, locate your soffit vents. If you don’t have any, you’ll need to install some. Take a look at the eaves, you might have siding covering them. You’ll need to see inside, so carefully remove the siding, clean out any blockages like animal nests or insulation, and then cover the hole with a vent. I did this on two sides and my problem improved.
Lastly, consider installing a ridge vent. It’s a simple process with a few tools and a kit that will cost you a fraction of what a professional installation would.
With soffit and ridge vents in place, you’ll have a proper attic ventilation system that should solve your issues, as long as your roof is well-constructed and the attic floor has enough insulation. A weather barrier between the ceiling drywall and rafters is also a good idea. Alternatively, you can insulate the attic floor to keep it cold like the outside.
🙂
That seven-year-old hole is no big deal, man. Invest in some top-notch pre-mixed patch mud. This stuff is more durable than the plasterboard. Spread it into the cracks with a spatula – don’t worry if it sticks out a little, you can sand it down smoothly. Then, use a putty knife to cover up where you tore the paper off. Get a small block sander and gently sand it down until it’s mostly flat. You can leave it like this until you’re ready to paint to save some money.
Ridge was installed in July during the roof replacement, and the eaves were boxed in at that time. Soffit vents have been recently added to one side of the house, with plans to add them to the other side soon. The vent terminates on the outside wall with about 15 feet of insulated flex duct. There is an approximate 90 degree bend immediately at the fan, so I’m going to get an adjustable elbow to correct that. Everything in the knee wall attic space has been sealed with foam, which is when the condensation issue started. I currently have some temporary batt insulation covering the fan, but I will probably make some changes when I add the elbow. The bathroom is 72 square feet, and the fan is 100 cfm.
Flex duct is not the best option, so it’s great that you’re changing out the 90-degree bend for something more solid. Make sure your exhaust port is in good condition to allow for a smooth flow of 100 cfm, which should be sufficient for the space. You may need to run the fan for longer periods initially, but replacing the elbow and insulating the duct could also improve the situation.
Thank you for letting me know. The duct is insulated, but the rest of the attic still needs to be done. Hopefully, that will happen soon.
Yes, you definitely need to install those soffit vents as soon as possible. The ridge vent is currently blocked, consider contacting the power company for an energy audit as they can assist with insulation.
The knee wall space with soffit vents is finished. Dealing with my health concerns, unreliable contractors, and a family friend’s health issues while working on our project has made this whole situation a complete nightmare.
Make sure there’s proper intake, pay attention to the windward wall because it’s like the south wall that will help clear away condensation. I only needed to address two walls to fix the issue.
Mentioned that he had a discussion with a representative from the power company before commencing the project. Although the rep didn’t visit the site, Jim reviewed his plans with him. The rep approved most of the ideas and provided some advice over the phone.