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Old 02-19-2010, 08:20 PM   #46
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Damn Ice dam -damn!


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Originally Posted by piste View Post
So if I understand correctly....you put up these panels between the rafters in a way that created a gap between the panel and the roof and then blew the cellulose into that gap??

You are touching on a thought that I had...which is...Even though my attic floor is pretty well insulated and I have decent ventilation....I COULD put some insulation in the roof too...to keep any heat in the attic from dissipating to the roof alternatively letting it vent out through the venting. Being as I have a furnace in my attic there is no amount of floor insulation that will eliminate attic heat in winter. Now all that being said....insulating the roof in addition to the floor (of course without blocking the venting) is not only expensive but in a way pointless because....at SOME point the snow WILL melt. doing all of the above will just slow the process down and not sure what degree of a "Fix" it would be for the ice damming and icicle issue anyway.
With your furnace in the attic, which is quite common, I spoke to a neighbor today who has extreme icicicle issues who said that she's resorted to keeping the thermostat @ 60F and not doing laundry during the night time.

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Old 02-21-2010, 11:32 AM   #47
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Damn Ice dam -damn!


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From what I have read in this discussion, ventilation is a waste of effort!
We cannot stop heat loss into the attic, all we can do is minimize it! So, if eaves and soffits are problem, why not quit using them!
Venting is a must, especially attic spaces.

http://www.buildingscience.com/docum...rent-this-time
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Old 02-21-2010, 10:20 PM   #48
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Damn Ice dam -damn!


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Originally Posted by MJW View Post
Venting is a must, especially attic spaces.

http://www.buildingscience.com/docum...rent-this-time
You may have missed my post #24, where I included a link to a CMHA article!


http://www.cmhc-schl.gc.ca/en/co/mah...gemare_001.cfm

A quote from this article! "If you have properly sealed the attic you should not need more attic ventilation. Attic ventilation is overrated. In winter, the cold outside air cannot hold much humidity or carry moisture away from the attic. In summer, attic temperatures are more affected by the sun and shingle colour than by the amount of ventilation"

This article touts that leakage into the attic from the inside of the house is the culprit and our efforts to correct this is more relevant, over trying to vent it with cold air.
If the air cannot absorb the moisture, it will just condense against cold surfaces and cause problems.
Ventilation has been a 'sacred cow' and now the scientists at CMHA refute its value!
The roofers won't like this as it would mean a major loss of income to them!
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Old 02-22-2010, 09:19 AM   #49
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Damn Ice dam -damn!


Wildie - You must have skipped over post #25 where Grumpy told you that the CMHA article goes against every other reputable resource.

Your article states that if you have properly sealed the attic you dont need any more ventilation. Majority of homes dont have a properly sealed attic. Also, the article indicates that you still must have some sort of proper attic ventilation. I dont know how this will be a major loss of income for roofers when it is not even a big source of income in the first place.

Ventilation is a funny thing. It is not even the roofers responsibility but all too often we are the ones who have to address the problem and offer the appropriate solution. It is almost like the Heating Ventilation Air Conditioning guys just sort of want to get rid of the V and just be known as HAC.
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Old 02-22-2010, 12:12 PM   #50
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Damn Ice dam -damn!


I'm surprised by CMHC's claim that ventilation doesn't matter. The prevailing view in my area is that it's not something you should overlook.

In response to Handy Man's question -- right now I have gable vents and a couple of those mushroom vents (not sure what the proper name for them is).

I've gone over the entire attic floor and done my best to seal all air leaks there, and based on observations thus far, I've managed to reduce a fair bit of heat loss, and the resulting ice dams. A building inspector looked at my house and said that the heat loss may be attributed to skylights, and the best way of dealing with it would be to stop air leaks (done), insulate the skylight tunnels (done), and then install a ridge vent to allow attic heat to escape. Despite all the insulating I've done, the attic temps are still warmer than outdoor temperatures, and I am still getting some ice buildup on the shingles.

Last edited by longshanks; 02-22-2010 at 12:18 PM.
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Old 02-22-2010, 12:18 PM   #51
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Damn Ice dam -damn!


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Originally Posted by BamBamm5144 View Post
Wildie - You must have skipped over post #25 where Grumpy told you that the CMHA article goes against every other reputable resource.

No, I did read it and the very point of my posts is to bring attention to the fact that we may be misinformed about the value of ventilation. Makes me wonder how reputable, the reputable sources are?


Your article states that if you have properly sealed the attic you dont need any more ventilation. Majority of homes dont have a properly sealed attic. Also, the article indicates that you still must have some sort of proper attic ventilation. I dont know how this will be a major loss of income for roofers when it is not even a big source of income in the first place.

I agree that most homes are not properly sealed and I would suggest that this is where we should be concentrating our efforts, along with increased amounts of insulation. Its warm, moisture laden air, coming from inside the home that causes attic problems, rather than lack of ventilation.

For the roofers, like contractors in general, its the extras that puts the icing on the cake, so to speak!
I recently purchased a 1948 home and had the roof redone. The contractor claimed that I had insufficient ventilation and offered to improve it for an additional price!
it seemed like a good idea to me, at the time, so I went along with it. Now, after reading the CMHC article, I wonder if the extra expense, was worth it!



Ventilation is a funny thing. It is not even the roofers responsibility but all too often we are the ones who have to address the problem and offer the appropriate solution. It is almost like the Heating Ventilation Air Conditioning guys just sort of want to get rid of the V and just be known as HAC.
In my area, its the roofing and siding contractors that look after the attic ventilation. The HVAC guys don'y seem to like climbing ladders!
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Old 02-22-2010, 01:03 PM   #52
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Damn Ice dam -damn!


Wildie - Who knows if any sources are truly credible on anything. I keep hearing about Global warming but we have been having record amount of snowfalls here in the states. Every few years there seems to be a new thing so I do agree with you there.

However, I have worked on many homes that were improperly ventilated and had ice damming problems. After correcting the problems, they no longer have the same problems as they used to. If your home was purchased in 1948, your roofer may have very well been right. My home is from 1979 and although it at least met or succeeded all minumum building standards at the time, it would be unacceptable if this same house was built now.

Did you have ice problems before the roof was redone? If so, did re-doing the roof and ventilation help to reduce or completely eliminate any ice problems?

One more point here. Shingle Manufacturers try do everything possible to not hold any liability if their product fails. One thing that voids any warranty is improper ventilation and each manufacturer has their guidelines to the appropriate amount.
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Old 02-22-2010, 06:09 PM   #53
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Damn Ice dam -damn!


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Originally Posted by BamBamm5144 View Post
Wildie - Who knows if any sources are truly credible on anything. I keep hearing about Global warming but we have been having record amount of snowfalls here in the states. Every few years there seems to be a new thing so I do agree with you there.

However, I have worked on many homes that were improperly ventilated and had ice damming problems. After correcting the problems, they no longer have the same problems as they used to. If your home was purchased in 1948, your roofer may have very well been right. My home is from 1979 and although it at least met or succeeded all minumum building standards at the time, it would be unacceptable if this same house was built now.

Did you have ice problems before the roof was redone? If so, did re-doing the roof and ventilation help to reduce or completely eliminate any ice problems?

One more point here. Shingle Manufacturers try do everything possible to not hold any liability if their product fails. One thing that voids any warranty is improper ventilation and each manufacturer has their guidelines to the appropriate amount.
This global warming thing is a farce generated by those who hope to cash in the Energy Credit scam. ( another subject).
Where I live ,we have been having an easier winter, but this has been preceded by harsh winters for ten years.

I never have had any ice problems, although in conjunction with the new roof, I installed anothe R20 over the existing insulation. The total insulation must be approaching R40. I made an effort to seal off any infiltration into the attic also!

Roofing warranty's are questionable, under the best of circumstances. Roof's are not like something mechanical that fails completely!
Roof's deteriorate over the course of time and any argument would be, if it failed sooner, rather than later.
I have never ever heard of anybody, ever making a warranty claim that was accepted.
You buy a 20 year roof and 10 years you have a problem. Who's going to go to bat for you! Where I live roofing contractors come and go with wind! So, you can't count him for help!
It may be possible to hire somebody who has credentials that would make him a credible witness. But would it be worth the bother.
A 20 year roof that cost $5000, that has failed after 10 years may be elligable $2500 in compensation. However, your expert counsel may cost you that much, so whats the point!
In my mind, I don't place much value in roofing waranty's.
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Old 02-22-2010, 08:08 PM   #54
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Damn Ice dam -damn!


R38 is code with the IRC in ceilings, although any house without energy trusses will not get anywhere close to R38 on top of the walls in the attic.

With the net anyone can find a "study" that proves their point.

We used to seal crawl spaces, roofs, walls, etc.... in the past, didn't work. They used to seal and heat roofs in the 60's, it just didn't work. The new system with venting and insulating works.

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