I posted a question last week or so about my neighbor's roof having a wet spot on it. Two days ago, I took a few more pictures. It was below feezing overnight and at 7:30 am the neighbor's roof looked like this:
The main suggestion under the other post were that it is caused by a possible ventilation problem. The bathroom that is right there where this spot is.
Thanks so much for everybody's input! Angie
Certainly looks like condensation. I'd say it is an insulation and/or ventilation problem.
It's hard to tell, but it looks like the "spot" is frozen. If so perhaps it's just frost? Maybe that section of the roof is getting
*better* air flow so it's staying cold longer. Frost on roofs around here is a good sign. ...well not this week (record temps).
Ya, but why would just that spot 'frost' and not the rest of the roof? I doubt the rest of the roof is 'bad' and this one spot with frost is 'good'. Obviously, there is a problem with moisture at that point on the roof. Excess moisture in that spot is causing the frost. In the last round of pics that were posted, it looked like the sheathing was sagging and damaged as well. Could be caused by problems with venting. You really need to have a pro look at this. One who can investigate the cause, and correct it. There could be a boatload of mold up there as well.
The problem will not fix itself or go away, but it will get worse!
Good Luck! J.A. Michel
Are you sure that the entire roof isn't frosting during the night and as soon as the sun comes up it all melts except for that spot? Perhaps that spot has better insulation. Does the house have cathedral ceilings (no attic)? That would typically not be the case in bathrooms so they would still have a space over them.
I'm going to go out on a limb here, and say that's perfectly normal. The frost shows which parts of the space under the roof are properly insulated: every place you see frost, the insulation is good. Where you don't see frost, the insulation is inadequate: so much heat is escaping from the house in those places that the roof is too warm to collect frost.
In a nutshell, the parts with the frost are OK. It's all the parts that
*don't* have frost that have a problem.That's my guess, anyway.
Frost forms when a surface cools to a temperature which is colder than the dewpoint of the air next to the surface. The frosted area of the roof must be cooler than the rest of the roof and has nothing to do with moisture in the roof itself.
but why isn't there frost on the eaves then?
The frost/snow is where it is the coldest. In other words, all of the roof is colder than the are where the frost is. The area where the frost is either the area of best insulation or most ventilation. Your neighbor should wish that all of his roof look like what you call wet spots.
Take another look, the white stuff is frost on the outside of the house, the black areas are where the frost melted. There is no problem, unless you consider all the are that isn't frost covered.
The black areas are there even in 100 degree temperature in the middle of August. I think somebody suggested it could be mold.
Angie
It *is* a wet spot when it's not below feezing. It is obvious that the shingles are wet in this one spot in the morning. They dry durig the day, but the next morning they are wet again.
Angie
That does make sense, but why are the shingles wet when it's not below freezing? That's why I was thinking that it's this wetness that causes the frost.
You all have some very interesting theories! My neighbor hasn't called anybody yet to look at her house because of the holidays, but I hope she will soon. She already had a leak in her roof in another spot last year. She usually calls the guy who built the house, but I would think this is not a good idea. If anything was in fact wrong with the construction of the house, he sure wouldn't admit to it and fix it, he would try to cover it up instead.
Glad it ain't my house! Angie
Perhaps you mean "frostpoint" :-)
Nick
Frost is moisture from the air which condenses on objects which radiate heat to become colder than the surrounding air. The eaves are exposed to the air on both sides and stay warmer than a well insulated area which is exposed on only one side.
SJF
first of all this house is a hip roof that has no ventilation on the hips therefore the middle vented area takes longer to defrost.
2nd this area is over a bathroom that may have poor insulation in the roof allowing moisture to escape and causing condensation to freeze on the roof.
Perhaps that section of roof has better ventilation, so gets colder faster. Perhaps worse so it warms slower. It's hard to tell, but I see such things all the time.
It could easily be that there is no 'good' or 'bad', just 'different'.
No, it's not obvious at all. It certainly isn't moisture coming out of the house freezing on the roof. Shingles aren't intended to breathe.
*VERY* unlikely. The moisture would have to get through the shingles.Didn't see them. If there is a problem, it's venting not moisture coming through the shingles. If the sheathing is damaged (I can't see it) it is a serious moisture problem.
I *highly* doubt it, though anything can happen. I think you're looking for a disaster.
Not if there is no problem.
When the temperature falls below the dew point, moisture (dew) forms. If this temperature is below freezing the moisture sublimates from its gaseous state directly to a solid (frost).
A call to an independent might help, if you can find one who wants to get involved.
ALL houses have issues. :-(
Whether wet or frosted the area in question is cooler than the rest of the roof. When this section gets cooler than the dewpoint then either dew or frost will form. The majority of the roof usually never gets cold enough for frost or dew to form because the majority of the roof is warmed by the escaping heat from the house.
The area in question does no receive as much escaping heat as the majority of the roof. This small section is insulated or sealed from the rest of the house better than the majority of the roof.
Same reason. The only difference between dew and frost is the temperature.
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