Dusty attic smell in one of the bedrooms.

We have lived in this house for 28 years and never experienced this problem. About 2 months ago, you could walk into one of the bedrooms and smell that dusty attic smell. The house was built in the early 70' and has blown insulation in the attic. This is not musty smell, indicating a moisture problem. This is the dusty smell you find in attics with blown insulation where the house is 40+ years old.

My first thought was the air ducts. I can smell the a/c air coming out of the register and it seems to be fine. If it is a duct problem, I should be experiencing this in other rooms, which is not the case. It is only one bedroom that it is happening in. You can walk into the room while the a/c is blowing and notice about 10 degree change in room temperature near the ceiling.

My second thought was poor attic ventilation. There was 3 roof vents on the house when we bought it. Yesterday, I had 4 more installed and it seems to have helped a bit, but not enough. Thinking that the hot air might be entering through light fixtures, I dropped all of them and made sure they were sealed enough to keep the dust out. I looked closely at the sheet rock on the ceiling and it all appears to be solid. Warm air is still coming in from somewhere.


Ok...so the ducts smell ok throughout the house. I reduced the heat in the attic with more vents and sealed around the light fixtures. I put in a hepa air cleaner which helps some. I still cannot get rid of the dusty smell coming from the attic.

Sorry for being so long-winded, but my real problem is that I use that room for home kidney dialysis. When I was told that I would have to start long term dialysis, we renovated the guest room and set it up as an office, bedroom and dialysis room. It is probably about as close as I will ever get to having a 'man cave'. I work and sleep in that room, so I am in there 12-16+ hours a day. We spent several thousand dollars renovating this room for kidney dialysis, so I can't just drag everything into one of the other spare bedrooms.

If anyone has encountered this problem, I would really appreciate knowing how you fixed it.

Thanks,

Tony

 

Tony, is it possible a duct leading to that room alone could have been compromised in the attic? It could be sucking hotter air in and air conditioning your attic You probably wouldn't notice a smell unless the attic was really bad. I think warmer air regardless where it originates will smell odd. Any way to check that?

 

When something new pops up, like you smell this now and didn't over the past 28 years, I look for what has changed. In your case you mention that this room has been renovated for its current purpose. My suspicion is you changed something.

Now, another detail is that the smell seems similar to a hot attic. During the summer when you are running the air conditioning the house is filled with heavy cold air. That air falls and finds ways of leaking out the lower portions of the house. Air leakage is much more significant than most people realize with 1/3 of all of the air in your home escaping every HOUR. When that air leaves, outside air must come in to replace it and often that is the hot attic air. They call this reverse stack effect, although not technically correct the air does flow in the opposite direction of winter stack effect.

So, something you did seems to have provided a path for that replacement air to enter from the attic.
1. Leaky attic ducts when the ac fan isn't running are one possibility.
2. Recessed lights (cans) and ceiling electrical boxes, but you said you did some sealing there.
3. A very strong return register with a limited or closed supply register.
4. Leaks around a return register in the ceiling.

What else did the renovations entail.

You also mentioned adding more roof vents. Attic ventilation requires high and low vents, where are yours?

Bud
And welcome to the forum Tony

 

Thanks Bud9051...

The house was built on a slab and all of the duct work is in it. It is definitely warm air coming in from somewhere, so it looks like the a/c is ok and it smells clean. The return duct is in the ceiling, about 15 ft down the hallway.

The house has always had 3 roof vents near the crown and 2 gable vents. Today, I had 4 more roof vents installed. There have never been any vents in the soffit.

We renovated the room back in October 2014. We pulled old paneling down, patched and textured sheet rock, new moldings, paint, carpet and a ceiling fan...no structural changes. We made the same renovations to the master bedroom 2 years ago and no problem there. There was never a problem in this room when the kids were growing up.

There could be something we did during the renovation that is causing this, but I am baffled at what it could be.

 

Wow, lots of issues for your to-do list. Not to drift, but a quick list for future threads.
1. Attic venting can be improved.
2. I suspect air sealing and insulation need an upgrade.

I've read several articles about ducts in the slab corroding and leaking ground water in and creating a swamp down there. May be part of this problem but in any case i would want a visual inspection.

One return for all the supplies results in an imbalance in pressures. This should be part of that to-do list, but may be contributing to this issue. The question is, what changed. Typically old painted trim has been sealed in place for years with many coats of paint. Removing that trim could have provided multiple leakage paths that are now allowing attic air to leak into that room. Just throwing out comments to see if any stick.

Carpets have in some cases been a source of odors and being on a slab adds to that risk.

I'll be back.

Bud

 

There is another return vent in the great room, so 2 return vents for 2300 sq ft.

We're not smelling any damp, musty, mold type smell. However, having the ducts cleaned and sealed is on our short term 'to-do list'. We moved into this house with the intent of selling it in 5 yrs ...that was 28 yrs ago. Thermal windows are on order.

This was one of our kids bedroom and it changed colors several times over the years. We used Behr, 'one coat' paint... that took 2 coats to cover the dark blue 'sponge paint' look. The old carpet that was replaced had a much denser pile than the new carpet. The trim was also replaced. They recommended not completely compressing the carpet with the trim, so I pushed the trim about 1/2 inch into the carpet as I nailed it down. New trim was the only difference from how we renovated the other rooms.

The room has 2 exterior walls facing the SW. The roof has a really steep pitch to it creating a lot of empty space in the attic. When it was built, for a few thousand $, it would made a decent two story. After losing most of our mature shade trees, on a really hot day, the room does get about 10 degrees warmer than the rest of the house. When we moved in, there were several large, mature trees that helped keep the sunny side of the house much cooler than it is today. Ice storm damage over the years has left us with only one large mature tree that provides shade over the roof. With all of that extra space in the attic to build up heat, should I look at adding more vents to the seven that are already there?

Thanks for your help with this.

 

There are guidelines for determining how much venting you should have and where it should be located. 1 ft² of net free vent area for every 150 ft² of attic floor, divided half high and half down low. Typically we like to see high being a ridge vent and low being soffit vents, but being a tall attic, low roof vents might work with high roof vents and those gable vents. But you need to check how much net free area you have and where.

We may have to get innovative to see what we can determine. If you have any window fans, install them and set them to blowing air out. At the same time, turn on all exhaust fans, bath, kitchen, and even the dryer (just fluff, not heat needed). The idea is to exhaust as much air as possible. The result will be, replacement air will have to leak back in and hopefully your nose can pick up where in that room the smell is entering. Have your av off during this test.

Another test would be to endure several hours with the ac off to see if the smell increases of dissipates. If there is an imbalance in duct pressures bringing that attic air into the room, then with the ac off (fan off) the small should become less.

Bud

Note: before you add more insulation in the attic you should review the air sealing needs, top priority, more so than windows or more insulation, and it is the least expensive fix.
http://www.efficiencyvermont.com/ste...ide_062507.pdf

 

I'll do some measuring over the weekend and see what I come up with. I don't have any window fans, but I do have an 40+ yr old utility fan in the garage that if you put wings on it, it could probably fly. I can strap it to the step ladder going into the attic. It should push quite a bit of air up there.

"Enduring several hours with the a/c off...."

Nope....not happening....Mama don't like to sweat....and when she does, she gets pretty cranky. When mama's not happy ain't nobody happy around our house.


Thanks!