Archive for the ‘ventilation’ category

Excessive Moisture in the Attic

January 21st, 2010

In September I added blown cellulose to my attic. I then covered the cellulose with plywood in order to have a usable space for storage. I have a walk-up stairway that does not seal very tightly. When I went in the attic to bring Christmas decorations down, I noticed it was damp. I installed a humidistat, and it read 90% humidity. I have a ridge-vent, and I installed sofit vents before blowing in the insulation, so I am not sure where the humidity is coming from, or why it is staying in there.



Your problem is warm air leaking into the (now) cold attic. In the past, air leaks existed but the attic was warm because of the lack of insulation. When the air is warm it holds a lot of moisture, so the “relative” humidity was low and there was no moisture problem.

The solution is to air-seal between the attic and the heated space below. Seal around the chimney and all penetrations, including the access door. If you stop the air leaks you will solve the problem and save lots of energy.

Check out my article:

Insulate Your Attic – But Don’t Stop There!

Leaky Bathroom Fan – Drip, Drip, Drip

December 30th, 2009


I have a bathroom exhaust fan that is vented into the attic, up to the ridge-vent area. Since the weather had gotten colder, water drips back into the bathroom from the fan after it has been on for a while. Do I need a certain type of material for the vent? Should I insulate it? I’m not sure what the solution is. Thanks for your help.



Your problem is condensation in the cool fan duct. Warm, moist air from the bathroom condenses on the cool duct and runs down the duct to the fan. The duct is now cold because the attic is cold.

The duct should be insulated. Make as short of a run as possible to a vent connector through the roof deck. The fan duct should not be run to the ridge-vent. You can find insulated duct and a vent connectors at a building supply store.

The fan and the vent connector through the roof should also have a damper that closes when the fan is off to limit air movement.


Removing Mold in the Bathroom

December 22nd, 2009


We are a family of six living in a 1,100 square foot single-story home. Our one full bathroom has mold growing on the ceiling. We have used TSP to clean it, and Kilz to paint it. We’ve also installed a new bathroom fan, but the mold keeps coming back. Do you have any other suggestions? Do we need to get a more heavy-duty fan? Do we need to replace the drywall ceiling and start over? By the way, the roof was redone last summer, but the mold problem hasn’t gone away. Do we just keep scrubbing away? Help!



You need to try to reduce the moisture level in the bathroom, and that will be tough with a family of six. I would try these steps:

  1. Run the bath exhaust fan 24/7, or until the bathroom is completely dry. If the fan will not remove the moisture and dry the walls, install a better fan and make sure it has a large, straight exhaust duct that carries the moisture to the outside. Broan is a great resource for bath fans and installation information.
  2. Dry the walls (where the mold is growing) with a towel, and remove the towel from the bathroom.
  3. Clean up the mold with laundry bleach and water. Then, paint the walls with Zinsser Brand Bathroom Wall and Ceiling Paint. This paint will not cause mildew. Follow the label directions.


More Insulation in the Attic?

December 21st, 2009


Where can I find someone who can tell me if I need more insulation in my attic?  I’m afraid that if I go to an insulation company they will say I do, when I really don’t.



Insulation - Thermal Boundary/EnvelopeThe question should really be where can I make energy efficiency improvements that save me the most money. While insulating the attic is often high on the list, what about the furnace, basement sill plate, etc.?

I suggest you have a energy evaluation by a Focus on Energy Consultant (800-762-7077). The consultant will review, test your home, and establish a priority list for improvements. I think it’s a great deal.

As far as the attic, you need about 12 inches of insulation (about R-38). More is better, but may not always provide a payback. See my website article at the Free Articles page titled Insulate Your Attic – But Don’t Stop There. It will explain insulation and air sealing. The air sealing is more important than the insulation.


Housewrap on a Detached Garage?

December 18th, 2009

Hi Tom,

We love your Saturday morning show and listen whenever we can! We are in the middle of building a new detached garage. What is your opinion on installing housewrap like Typar? The garage will be mostly unheated, but in the future I may insulate the walls and use temporary heat occasionally. I was thinking that the Typar may be an extra wind-break, but I am not sure if it is risking a moisture problem since it will mostly be unheated.

Thank you!!

Keith and Rika


Housewrap should be used under the siding to provide a moisture barrier. All siding leaks and you need to keep moisture out of the wall framing. The housewrap will also provide a wind barrier if you ever provide heat in the garage. The housewrap will not be a moisture problem for the garage with or without heat. If you ever do heat the garage on a constant basis, the interior finishes should include a vapor barrier under the first layer of finish on the heated side. This stops interior moisture from penetrating the wall structure.

Condensation on East Windows – Not West?

December 16th, 2009

Saturday I listened to you talk about moisture on windows and looked the article up on your website. I have a question. What if some windows get moisture and some do not? We have a 16-year-old house – two story. The bedroom window on the east side of the house gets moisture (always has), but the bedroom window on the west side of the house does not. After reading the article I learned a lot, but I just have this other question. Thank you so much.



Wind Pushes Air Through a HomeWhen warm, moist air contacts a cold surface, you have condensation (just like moisture on that iced-tea glass in the summer).

I assume you are getting condensation on the storm window. Wind blows at your house, and in the Milwaukee area it often blows from the west to the east. On the west side of your home, cold air is blown in around the storm and leaks into your home. The air blowing in is very dry and there is no condensation.

On the west side of your home warm, moist air is leaking out of the windows and you have condensation on the cold storms. The storms trap the warm air and the storm glass is cold.

For folks that want more information, look at my website article “Fogged Up? Clearing the Air About Window Condensation Problems.”


Dehumidifier During Winter Months?

December 14th, 2009


Hi, I live in a Franklin, WI condo with a finished basement (rec room). During the summer we run a dehumidifier. Is it necessary to run it during the winter months? We have no moisture problems. Thanks.



DehumidifierSorry, but there is no simple answer to this. It depends on the moisture balance in your home and if the lower, finished level is connected to the central heating system.

I would anticipate that with a newer condo and a finished basement, you don’t need to operate a dehumidifier. I assume the space is connected to the forced-air furnace, so basically the moisture level in the lower level will be the same as the upper level. Moisture will move quickly through the forced-air heating system.


Peeling Paint and Mildew in the Bathroom

November 18th, 2009


I have a problem with peeling paint and mildew on the paint in the bathroom. We have a big family and use the exhaust fan, but we still have a problem. What can we do with the paint?


You should try to run the exhaust fan as much as possible. Try to operate it until the shower walls are dry. Consider adding a timer switch so the fan can be set to run for an hour after the bathroom is used.

I have had great luck with a bathroom paint that is guaranteed not to mildew or peel. Sound too good to be true? Well, over the past 5 years in my home, I have found it does not mildew and does not peel.

Try Zinsser brand, Perma-White, Mildew-Proof, Bathroom Paint. You will find it in most paint departments and paint stores. It is self-priming, water based, low odor, and can be tinted.

To use the Perma-White, you do need to kill any mildew with laundry bleach. Water stains or dark stains should be primed with BIN. The surface must be clean and free of loose paint, dirt, grease, and soap film. Apply two coats. The first coat primes and seals the surface. The second coat provides more mildew resistance and scrub-resistance.

Cleaning Lint in the Clothes Dryer Vent Pipe

October 28th, 2009


We have a home that is about five years old and the clothes dryer vent goes through the floor, then travels about 10 feet between the finished floor and ceiling to an outside vent. We have noticed lint collecting near the vent outside. We clean the lint filter with each load of laundry but are concerned lint may collect inside the pipe and be a fire hazard. It is working properly now. Is there some way the vent pipe can be blown clean?


Great Question! Clothes dryer manufacturers normally recommend a smooth metal vent pipe with minimal bends that can be checked and cleaned periodically. Vent pipes that pose the greatest risk are the flexible plastic vent pipes because lint can build up on the rough surface and the bends may not be smooth and uniform. The plastic pipe is also flammable.

If you know the existing vent is make of smooth metal with smooth metal elbows and fittings, you have limited risk. I still think you should try to vacuum out the vent every year through the inlet and discharge. You can use extensions on a shop vacuum. You could also try to blow it out with a shop vacuum. If you don’t have the equipment, contact a furnace duct cleaning company.

If you have a flexible, plastic vent pipe, it should be removed and replaced with a metal vent with smooth metal elbows and fittings.