Hi. my question is this: i built a new 24x24 garage this summer. And this
is the first winter it saw. i have a wood burner in the corner of the
garage and i noticed that there is frost on the back wall and when the
garage is heated up to 70 degrees it turns to water. of course this in not
good. but i don't know why it does it! i don't have any leaks in the roof.
and it is only on the back wall and at the bottom of the wall. i sheeted
the outside walls with 7/16 (osb)then applied vynal siding and have no
insullation in the inside of the walls (just studs).
so if you may offer some advice it would be greatly appreciated.
thank you and God bless
Frost in Attic
Summary:
Frost inside an attic is a sign that something is terribly wrong. Water vapor is condensing on the cold roof surfaces and then freezing. The source of the water must be found and stopped. Wood rot and mold are a reality if the frost continues to form.
DEAR TIM: In my Cape Cod style house, the upstairs is unfinished with no insulation. I had a 23,000 BTU kerosene heater up there for two days hoping to dry this space out after heavy rains. When it rains, the attic can get a little damp around the chimney and a couple of other places. I checked the heater today and the roof sheathing and rafters had a very significant accumulation of frost. I assume this came from the heater. Does kerosene combustion create water? What's the best way to get rid of the frost now that it's cold up there and not likely to melt or evaporate soon? Gina P., Gales Ferry, CT
DEAR GINA: The frost buildup can be traced to three possible sources, but the kerosene heater would be the first thing I would blame. The combustion of any fossil fuel such as oil, gasoline, natural gas, propane, kerosene, coal, etc. produces water as a by-product. On a cold winter day, the white cloud you see streaming from a car's exhaust is primarily water vapor. The same is true for the exhaust you see streaming up from house's chimney, as a furnace or water heater burns fuel.
The frost could also be caused from regular water vapor that is seeping from your heated living space up into your attic. Once this vapor contacts a cold surface, it turns into liquid water. If the wood surfaces are cold enough, the water freezes and turns into frost.
The water leaking into the attic from the chimney can also be evaporating and turning into water vapor inside the attic.
There is little you can do at this point. Perhaps the best thing to do would be to operate an oscillating fan in the attic space to get air moving about. If you have good ventilation, the frost will sublimate and the water vapor will escape to the outdoor atmosphere.
In the spring, I would absolutely apply a silane / siloxane water repellent to the chimney to minimize water infiltration into the masonry. You may have to apply a clear brush-on masonry sealer to the mortar joints and the chimney crown to stop all of the water.
I would also try to locate any and all roof leaks that are allowing water to enter the attic. You must do whatever is necessary to stop any and all water from entering the attic.
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shawn 08 Dec 2007, 16:05
AsktheBuilder 08 Dec 2007, 16:43
Shawn,
I think the water is coming from the wood. One byproduct of burning wood is water vapor. It is condensing on the cold OSB.
Vincent 12 Dec 2007, 16:15
I need attic insulation advice please.
1840's farmhouse in New York state (70 miles north of New York City). 2 story + walk up attic (unfinished/uninsulated). Exterior is vinyl siding over wood clapboard. Baseboard heating up to the 2nd floor. The attic floor is wide plank with handmade nails - so, I'm a little sensitive to preserving the floor! The attic has 2 windows at each end and they get iced up. I've noticed some condensation on the ceiling (the wooden underside of the peaked roof. I also notice some droplets of water on the nailheads that were used to attach the roofing shingles - these sometimes go through and are visible when in the attic. My Plan: 1) Attic door - put adhesive-backed foam rubber weather-stripping around the inner door frame. Also attach insulation batt against the door (inside the attic side)? Moisture barrier? Touching the door or facing the attic space? 2) The attic floor: 2a) Interim Solution: buy insulation batts (for between floor joists or for rafters) and without cutting it, lay it down on the floor, creating an insulating 'blanket'. Does this type of insulation require a vapor barrier? If so, does it face/touch the attic floor or face the attic ceiling? 2b) Longterm Solution: remove floorboards and insert insulation batts. Moisture barrier facing down or up? Rvalue? 2c) Longterm Solution: blow in loose insulation in between floor joists. 2d) Can spray foam insulation be used I any part of the attic? 2e) Is it a problem if I leave the roof rafters uninsulated? Thanks very much, Vincent
AsktheBuilder 15 Dec 2007, 08:14
Vincent,
This is a ventilation issue and possibly a vapor barrier issue as well. Please read all of my Ventilation columns as well as those about Condensation and Indoor Humidity.
Brian 19 Jan 2008, 10:19
I live in Wisconsin where we are having a sub-zero cold spell. I have an
attached non-heated garage built 7 years ago. The entire garage is dry
walled. For the first time this year, I have noticed a a very light frost
on the finished ceiling of the garage. The only thing that seems to be
different from past years is that we painted the ceiling last summer. Also
wehave had a lot of snow this winter and several thaw cycles, but i have
not noticed any ice dams.
AsktheBuilder 19 Jan 2008, 10:27
Brian,
What do you think is happening to all of the water vapor that is generated from the water that is created when the snow melts from your cars?????? Read my past columns in my Condensation Category.
Courtney 30 Jan 2008, 16:41
Hi Brian,
We have been living in our new construction home for the past 10 months. We live in Wisconsin and have an extreme cold spell right now. I noticed frost in the corners of our bathroom and bedroom (which the walls are facing the backside of the house). People are telling me is has something to do with the insulation? What are your suggestions? Is this a big issue? I'm concerned because we dealt with rebound mold when we first moved in, now this!
AsktheBuilder 30 Jan 2008, 16:46
Courtney,
I don't know a Brian.... You need to read all of my Condensation columns. Your solution is there. Bottom Line: You are pumping too much moisture into the air in your home.
Courtney 30 Jan 2008, 16:51
Sorry, thanks for your help. Didn't mean to call you Brian by the way.
Good day, Courtney
Chris 05 Feb 2008, 19:59
I Live in Michigans Upper Peninsula and am having the following problem
with condensation. I live in a bi-level home and am in the process of
finishing the lower level. I noticed that there was a large amount of
condensation on the walls behind the fiberglass insulation. The outter
walls have been wrapped with Tyvek wrap and then sided with vinyl siding. I
am planning on putting up sheetrock. Any suggestions as to how to get rid
of this condensation on the inside of this wall.
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