I just purchased a cottage where the furnace is in the attic. Above the thin layer of insulation (Foil backed, facing up insulation).
The vents to the rooms, and exhaust vent are all un-insulated.
Well there is water damage to the walls, interior and exterior. Owner, RE agent, neighbors, etc., etc. all say it was due to ice damns in gutters. I am guessing that just as much came from the heat that was lost into the attic causing rain (condensation) in the attic. This then hit the foil backed insulation and ran to the walls.
Does this make sense? The house was set to 55 degrees in winter, no apparent damage to the roof.
Next question, I plan to insulate the vents to the rooms but not sure about the exhaust vent. It appears to be more “industrial strength” – Does this pipe get too hot for the wrap-around insulation that I see in HD and basements?
I figured I would test this approach before I blow in more insulation. No sense getting it all wet if the insulation doesn’t fix it.
appreciate any comments,
jack
Replies
Where is this cottage located?
I have little doubt the damage WAS caused by ice dams, and it has nothing to do with the gutters. All that waste heat in the attic created perfect ice dam conditions every time it snowed and it was freezing cold outside.
The only cure for the disease is to get that heat unit out of the attic. To treat the symptoms, put ice and water membrane under the roofing.
Insulate the ceiling and ducts as much as possible, but I doubt you'll ever seal the unit enough to prevent ice damming.
Al Mollitor, Sharon MA
"I am guessing that just as much came from the heat that was lost into the attic causing rain (condensation) in the attic."
Actually you have it backwards.
You have 2 or 3 potential problem here.
First the head escaping from the furnace and duct work will heat the roof unless there is a very large amount of ventalation. That heat can cause snow on the roof to melt run down to the lower areas where it will ice dam. Then backup under the shingles and come in the attic.
The heat it'self will help reduce any condenstiaon problems.
But those uninsulated ducts are also probably leaky. So they allow more moist air from the house to escape and into the attic and condense on colder parts of the roof.
And if the unit has AC then the ducts are cold in the summer and you can get condensation on the ducts that then drips down into the ceiling.
Bill,
It's in Michigan, so nice and cold.
The problem with taking it out of the attic is that it is a cottage with limited space, not to mention the noise it would create.
Can't i wrap everything, the vents, the furnace itself, everything but the fresh air intake???
i guess i could condition the attic, moving all insulation to the roof...
Thanks. i then don't get why i have water damage to the interior walls. The roof doesn't leak, that i can see.
Also, I thought that the heat escaping vents would cause the same thing you get on your windows, the heat from the house causes the window to sweat (condensation) on the inside of the house, when cold is outside.
more confused now...
"Also, I thought that the heat escaping vents would cause the same thing you get on your windows, the heat from the house causes the window to sweat (condensation) on the inside of the house, when cold is outside."
No "heat" does not cause condensation.
Air can contain a certain amount of moisture in the air. The higher the tempature the more that moisture that it can contain. The ratio between the maixium amount at any one temp and the acutal amount in the air is the relative humidity.
Take a "huck" of air cooling it to a point where the relative humity is 100% then you get condensation. That point is the Dew Point.
Warm that air up, WITHOUT INTRODCUING ANY MOISTURE, and the condensation will stop.
The problem is not with any heat that is coming off the system (except possible ice damming), but rather the mositure that is in the air that is leaking out the system and/or other openings to the house such as electrical boxes and plumbing chases.
For example if you have a relatively dry house, 70 degree, 20% RH then allow that air to escape into a cold attic the dew point is 28 degrees. So any outside temp lower than that and if the attic ventalation is not enough to carry away the moist air and you will get condensation.
Bill,
I think I get it. The $40 question is, what do you recommend I do?
Things I want to avoid...
Heating while I am not using the house. Seems like a waste of $$ as we will probably only use for sporadic daytrips during winter months.
Moving the furnace into the kitchen.
Since moisture came up... the house sits on brick, no concrete pad, and no room to crawl under to put down barrier. I could run the de-humidifier year round...
I really appreciate the help.
Jack
It is a little hard without seeing ALL of the details.
But SEALING the duct work and attic penatration are the first step.
Use the latex duck seal for sealing the duct work. I have seen it at Lowes. You an also use the ALUMINUM METAL foil, but the latex is better for places like transistion from duct to duct. Whatever you do don't use the cloth duct tape.
And use the canned foam, Great Stuff, for sealing any all of the penatrations from house around any light fixture, plumbing or wires into the attic.
Also check what kind of ventalation that you have in the attic.