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Old 01-07-2017, 11:13 PM   #1
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Frost in attic nightmare... No Solutions in rural area


So here is the story.

For the last 4 years we have been experiencing frost buildup in the attic after two major things happened. First I did a DIY install of a bathroom exhaust fan, secondly a professionally installed wood burning stove also vented through the attic and through the roof.

I should note, we never checked out the attic before any of these 2 things and have been living here for 6 years. The Previous home owner had blown in insulation sprayed throughout the attic to increase energy efficiency. When both things were installed it was summer time with warm weather.

My wife; which I recently discovered through a search for answers (blow to a man's ego), posted a question in regards to a DIY project that went to hell (picture attached, though I still don't believe is a bathroom vent installation issue). Bathroom Fan Disaster - Attic Frost

No frost is visible in that picture as it was taken in the summer when we had water pouring from the bathroom vent (condensation). The sag has been fixed and has been secured with a plastic sheet of poly to brace so there is no sag in the vent. Also, a new high powered commercial bathroom vent has been installed (It vents vertically as opposed to horizontal which helped kill the U-Turn from the unit to continue back up through the roof vent) . Once this new fan was installed it seemed to be good, no leaks in the bedrooms when the snow and ice was melting on the roof.

All seemed to be good, but then I went into the attic 2 weeks ago to install some wires for a sound system, and noticed that the seal from the insulated vent line had lost contact with the roof vent and there was slight molding in that one section where moist heat had been blowing into the attic instead of through the roof. Yet... No frost in the attic, and the insulation was dry? So I reconnected the venting line and really tightened the clamp so it wouldn't come off (for extra measures I applied gorilla tape around the connection).

Now, the problems start again. It has been minus 35 the last week, and when I got out of the shower last night, the bathroom was completely steamed. The Bathroom fan seemed to be reverse flowing, blowing air back in to the bathroom. I went in the attic to check the connections and all was still connected going through the roof. However all areas of the attic were covered in frost: Insulation, rafters, and underside of roofing. I should also note that only a week ago when the vent was blowing directly into the attic (as it was detached from the roof vent) and there was no frost whatsoever. So this can't be a small leak issue.

What I will say is that I did shovel the roof last week after repairing the exhaust roof vent connection. I cleared off about 12" of snow that was on the roof, leaving the roof with a thin layer of ice/snow between the shingles. We have also, been running the wood stove more frequent since we had a planned power outage and normally run off an electric oil burning furnace (vented out the side of the house). But the wood stove was also running prior to frost in the attic this year. Could this be an issue with clearing the snow from the roof in minus 35 - 40? I noticed in my area no one else seems to be shoveling their roof.

I am at my wits end, I have gone in the attic with a shop vac and sucked up insulation blocking soffits (had to use an 10 ft PVC connector tube to reach) from every side of the attic. You can see sunlight during the day pouring through the soffit holes. Both gable vents are open and clear. I did notice when I was up there tonight it was much much colder than last week before the snow was cleared and the bathroom vent tubing had crunchy ice within in the insulation.

Finally , to add. When I was shoveling the roof I noticed a dark sediment around the base of the smoke stack connecting through the roof from the wood stove. At first I thought it was mold. Upon shoveling around it, I realized it was encrusted in the snow which was more of an ice ring around the stack.

Any thoughts?

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Last edited by gravitysdepth; 01-07-2017 at 11:17 PM.
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Old 01-08-2017, 12:15 AM   #2
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Re: Frost in attic nightmare... No Solutions in rural area


Quote:
Any thoughts?
Yes I have some thoughts. Only thoughts not answers.

My first thought is if I lived where it gets to -35 degrees, I would leave and never come back.

Looking back at the post where you showed the exhaust vent pipe. (I hope that it correct).
Why does the vent piping go so far inside the attic from the ceiling to the roof. Why doesn't it simply go through the roof directly above the ceiling.

My next thought is the size of the piping. It appears to be quite large for an bath exhaust vent. Think about it this way. You are blowing warm moisture air from the bath up through a very cold area. The longer the warm moisture air in in the cold area the more condensation and frost is going to occur. A smaller pipe might reduce the volume of air that is moved but its velocity would be increased. Less time for condensation to occur. This may be a case where bigger is not better.
My suggestion would be to reduce the size of the piping and vent it through the roof directly above the place it comes through the ceiling. Metal piping would be smoother inside and less restrictive to air flow. Heavily insulated.

After going through the roof there should be some kind of hood to prevent snow and rain from entering.

Just my thoughts.
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Old 01-08-2017, 05:18 AM   #3
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Re: Frost in attic nightmare... No Solutions in rural area


Sounds like the wood stove pipe is warming up the attic.
Is it insulated? Did you put your hand on it to see if it was cool to the touch?

My upstairs walls were getting frost on the insides last winter when I was running the furnace with no insulation in the house.
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Old 01-08-2017, 07:12 AM   #4
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Thanks for the reply. It is a 4" venting hose which seemed to be standard for bath vents (but maybe with a shorter run). Reason for the vent being so far away - Silly mistake on my part I cut the hole before getting a bath vent to put in the bathroom amd realised after the fact

My plan was to install a new vent direvtly above but the last few nights it has been minus 45 with wind chill. I don't believe this would be a safe project in the winter as I don't want to crack the shingles.

A huge concern was why there was no frost when it was blowing directly into the attic, then once snow was removed from roof and the vent pipe resecured to go outside all of a sudden there is frost.
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Old 01-08-2017, 07:14 AM   #5
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Thanks for the reply.

Due to its location in the attic I can't crawl that close to it to touch. I will check temp with my ir temp reader today and take some more pictures.
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Old 01-08-2017, 07:21 AM   #6
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Re: Frost in attic nightmare... No Solutions in rural area


First, we can determine the source of your frost, so be patient. There are several issues involved here and here are some questions.

1. You have mentioned soffit vents and gable vents, but have not discussed how much vent area they provide. We need to review the vent area, the size of those vents, and total area. Estimate or measure the size of those gable vents and tell us the size and number of soffit vents.

2. In the other thread your wife mentions "ceiling tile ceiling". They do not provide a good air seal even with a plastic vb above. If they are fastened directly to the ceiling joists without drywall above then they are probably leaking a lot of air into the attic. Tell us more about those ceiling tiles?

3. You have an attic access and that is often a source of air leakage. Is it well air sealed?

4. Since the moisture in the attic is coming from the house you need to take steps to reduce the amount of moisture your activities generate. A humidity meter is a good way to keep track of any progress you make. Are you seeing condensation on your windows?

You asked if shoveling the snow off of the roof could affect the frost problem and the answer is "slightly". As you noted the attic got cooler and being colder reduces the natural ventilation and that is why we need to address #1.

Keep your posts as short as possible, it helps to get more people to read and respond.

My list of related notes is longer than the above but we will get to them a few at a time.

Bud
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Old 01-08-2017, 08:29 AM   #7
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Re: Frost in attic nightmare... No Solutions in rural area


Quote:
The Bathroom fan seemed to be reverse flowing, blowing air back in to the bathroom.
That would imply that there was some kind of blockage, possible ice or snow.


Quote:
So this can't be a small leak issue.
I think I would disagree. With the vent pipe open, a larger amount of warm air would have been put into the attic but it would have been distributed over a larger area because it was under force. With a small leak it would have not been distributed and would be concentrated around the vent pipe.

Quote:
then once snow was removed from roof and the vent pipe resecured to go outside all of a sudden there is frost.
The snow on the roof would have been acting as a blanket of insulation. With the snow removed the attic would be colder.

There is a house on my street up for sale. Of course, it is getting colder here also. Last night it almost got down to freezing.
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Old 01-08-2017, 08:51 AM   #8
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Re: Frost in attic nightmare... No Solutions in rural area


Bud9051,

Thanks for taking the time to read through all of it. So to answer the questions you asked. Will keep as short as possible.

1. The soffit vents are completely across the front side of the house and the back side of the house. The Gable vents are about 2 1/2' x 2 1/2' on both sides. We also have 4 roof vents installed.

2. The ceiling tile seems to be affixed directly to ceiling joists. I know under the tile is a black type of paper and once you pierce through that, shreds of various materials come out, it is almost like a cat littler fibers. Here is a picture of the tile. https://postimg.org/image/ypahqcrw3/

3. The attic access has been sealed with styrofoam,and taped off with a sheet of poly plastic.

4. We were seeing a lot of condensation on the windows, the main window in the front room was collecting puddles of water on the bottom ledge by morning. We put Poly plastic over the windows and taped them off during the winter months.

Last edited by gravitysdepth; 01-08-2017 at 09:07 AM. Reason: Image added
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Old 01-08-2017, 10:17 AM   #9
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Re: Frost in attic nightmare... No Solutions in rural area


#1, sounds good, but had to ask.
#2, I have run air leakage test on ceilings like that and the results were not good. That doesn't say yours is in trouble, but it is high on the list. How much of your ceiling area is covered with the tiles?
#4, the condensation on the windows is telling us you have high humidity in the house. However, your very low temperatures make it difficult to prevent condensation even at a reasonable moisture level. A humidistat to monitor the actual RH is always a good tool. Doesn't have to be expensive. Once you know the RH you can work to change your activities to get that number as low as comfortably possible.

What other air sealing activities have you undertaken? The big leaks are more important, like plumbing vent pipes, around that bath fan, around the chimney (metal flashing) drop ceilings over cabinets, recessed lights, fireplace, and plumbing under sinks, showers, and tubs.

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Old 01-08-2017, 10:42 AM   #10
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Re: Frost in attic nightmare... No Solutions in rural area


Just 2 bedrooms have this type of ceiling. The bedrooms are about 12 x 12 at a guess (at work right now). The rest of the house was refinished with drywal by the previous owner. In the attic there is batt insulation with sprayed insulation added after when he was trying to increase efficiency.

I noted when I went up there last night, the insulation was kind of icy (like it was freezing). This was only above the bedrooms with the tile ceiling. as I went further down by the bathroom fan, the insulation felt a little damp to dry.

We have a dehumidifier and were running it, we have to empty it about twice a day. Even with that on the window was still getting a water (not as much but still some).

The Pot lights have been sealed around, the bathroom vent has been spray foamed around and the exiting duct from the unit to the vent hose has been taped with that metal ducting tape. I also taped any holes or openings on the fan unit in the attic, the insulation does feel warm around the unit but not damp. I was going to go up there today and connect a ABS pipe with plumbing cement to the vent that goes through the roof (as the vent only has a 2" neck after passing through the roof, and it is very hard to attach a clamp and tape a proper seal).

Also, the wood stove was sealed on the roof around the flashing. I don't see any kind of seal around the plate (this could have been done from within the attic when they installed) that connects to the ceiling in the living room to pass through the attic. Other than that there really isn't much else going into the attic.

Is it possible to install a new bathroom vent that is directly above the fan unit on a roof in minus 35 - 40 without damage to the roof? My concern is the caulking used wouldn't take in the temperature causing a broken seal on the roof.
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Old 01-08-2017, 10:57 AM   #11
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Re: Frost in attic nightmare... No Solutions in rural area


Just an added note, I realized after googling. The cat litter type of insulation material above the bedrooms appears to be vermiculite. However, the house was built after aspestos was banned in ontario. The house was also checked by an inspector when we purchased, and when they checked the insulation level in the attic.
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Old 01-08-2017, 11:14 AM   #12
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Re: Frost in attic nightmare... No Solutions in rural area


Sorry error above about details. Just an added note, I realized after googling. The cat litter type of insulation material above the bedrooms appears to be vermiculite. The house was built in 74 but aspestos wasn't banned in ontario until 1980. The house was checked by an inspector when we purchased, and when they checked the insulation level in the attic - Could this have been missed? Could this possibly contain asbestos?
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Old 01-08-2017, 11:28 AM   #13
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Re: Frost in attic nightmare... No Solutions in rural area


The areas of concern for air sealing are where things pass through the ceiling into the attic.

As for installing a new vent for the bath fan, much better to wait until warm weather. You really can't work with asphalt shingled in cold temperatures. However, your bath fan is not directly contributing to the frost in the attic. Its contribution would only be when it fails to properly vent the moisture from the bath area adding to the house humidity. As a note, bath fans leak air past the internal damper and when going through a cold attic that can result in a buildup of ice inside the duct.

You said "I noted when I went up there last night, the insulation was kind of icy (like it was freezing). This was only above the bedrooms with the tile ceiling." That needs some more investigating. If those tile ceiling are leaking like I think they might be, that would amount to a very big leak.

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Old 01-08-2017, 09:53 PM   #14
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Re: Frost in attic nightmare... No Solutions in rural area


Reducing a 4" flex duct to a 2" termination pipe will give some back pressure, as will having that kink in the ducting. SOP when using flex is to run one size larger due to the turbulence all the ridges create- hence requirements to fully stretch it out. There is 2-3 times more surface area for your warm moisture to catch on with flex. Save it to use over some new metal smooth wall pipe as insulation/vapor barrier. Tape all ells and joints, terminating in a hood on the roof, not a smaller pipe that is reduced which adds to restrictive air flow; for dryers- but you get the idea; http://dryerbox.com/ratings/dryerfittingschart.htm

Just lay some plastic sheeting over the insulation at those rooms (use a long stick with nail protruding), no doubt it will show condensation under it next day- giving you source of problems; https://buildingscience.com/document...bout-diffusion

I forgot where you are if this might pertain or not; http://www.smtresearch.ca/resources_...20Climates.pdf

Gary
PS. cover your low density FG insulation with some cellulose or housewrap to stop convective R-value loss- up to 50%, links if needed; https://books.google.com/books?id=_Y...0attic&f=false
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Old 01-09-2017, 07:11 AM   #15
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Re: Frost in attic nightmare... No Solutions in rural area


You have moisture in the attic. If it's cold outside, outside air would be dry. So the moisture is from inside.
1. wood stove - anything burning will throw out a lot of moisture. Pro installed? Need to check the whole system for venting/burning and you need more info on wood stove to account for that variable.
2. attic insulation - done by previous owner. So you need to check the entire attic floor to check for air seal. Cellulose (paper) insulation is supposed to give you better air seal but you have a problem and need to check the whole system yourself.
3. fan vent cap damper will be covered over and/or freeze shut. If your showers are that long, recommend moving it to the wall. Using aluminum duct, sloping it toward the cap and sealing the connections make it naturally draining. keep it close to floor, protect from being stepped on and cover with more insulation.
4. your natural soffit/ridge venting will not work if snow covers it and/or not enough hole and condition of the ridge vent material. As such, your solution may be to abandon the natural vent and install a fan.
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