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detailedEye 09-05-2008 10:14 AM

Melted Snow - No Permit
The bi-level house we bought last fall had a lot of snow melt on the roof above the exhaust vent for the furnace. The vent is about 4 feet from the eve and snow melted all the way to the ridge. Since we had just moved I didn't have time to do much last year, but now I would like to fix the issue to prevent ice dams from happening again.

I've taken a look around and it appears that the vent is all single wall vent as opposed to double wall, house was built in '73. I've also learned that the person (an HVAC friend of the old owner) who installed the new furnace (Heil 80+) never pulled a nothing was inspected:no:.

Is the single wall vent likely causing the excess heat in the attic? Or is there something else I should look for?

Do I have any recourse with the installer for not pulling a permit?

Any other suggestions would be appreciated. Thanks!

Termite 09-05-2008 11:35 AM

The furnace flue can certainly pump out some heat, or at least enough to melt the snow in the immediate vicinity of the vent. I'd be shocked if it were able to melt snow 4' away however. I guess it is a possibility. How high is the underside of your vent termination above the uphill side of the vent's penetration through the roof, and what pitch is your roof?

Provided the vent's wall is not closer than 1" to combustible products in your roof and attic, is terminated high enough above the roof, and is properly flashed, there isn't much that the inspector could have done for you.

You don't have much recourse for an installer not pulling a permit. You'd spend more in court fighting them than you would replacing the entire installation. Plus, code is a minimum standard. You'd have to illustrate that they didn't do a compliant installation. Whether or not you have recourse as far as making him pull a permit and get an inspection is up to the local municipality. In many cities, the homeowner is equally liable to ensure that permits are pulled for their contractors' work, and bear the ultimate financial responsibility of obtaining a permit and any fines that might be assessed.

concretemasonry 09-05-2008 02:58 PM

Melted Snow - No Permit
I can certainlt believe that snow on the roof directly above the vent could melt with a single wall set-up. See it many times, by just driving down the street.

In the cold weather the furnace runs much more and there is usually not much wind in Minnesota with the very cold days. The heat from the vent pipe can just wander up and warm the inderside of the roof (usually between 2 trusses/rafters. - Not as likely in the warmer winter days when you might have more wind.

detailedEye 09-05-2008 03:23 PM

concretemasonry - This is happening just as you described. The snow melts all the way to the ridge from the vent. The vent is about 3-4 feet from the eve and there is another 8-10 feet to the ridge, it's this 8-10 feet where the snow melts.

I'll post a picture when I get home, b/c this is a bit difficult to visualize, but the question remains...will a double-wall vent eliminate or at least help this problem?

thekctermite - to my knowledge single wall vent is supposed to be 6" away from combustibles, in Minnesota anyway. Someone correct me if I'm wrong. After 35 years I would be surprised if there is a 6" or 1" clearance in my attic.:)

1610 CUB 09-05-2008 03:56 PM

There is no way on gods green earth a 4" flue vent 25ft above the furnace can melt that much snow. Its an 80% furnace! And I cant believe the HVAC guy used single wall pipe throughout.
I really think a trip to the attic to check out whats going on!

8 Ball 09-05-2008 05:39 PM

On a horizontal plane, from the top of the vent to where the plane touches the roof, there should be 10ft. min.. Single wall pipe clearance to combustibles is greater than 1in. I was thinking 12in., but it really doesnt matter. Now that you know, its your responsibility to fix it.

If you can prove the previous owner knew, and didnt disclose before closing, you may have a case. Dont hold your breath.

Replace the vent with double wall, or "B" vent,maintain the proper clearances, do a new flash, collar and cap, live happily ever after.

detailedEye 09-05-2008 06:20 PM

Thanks for the rosey image 8 Ball.:)

I've uploaded a picture to the 'My Photos' link on my profile. My distance estimates might be off slightly but you get the idea. This is the original vent that was put in when the house was built. Also, it's not a 4" vent but a 5" or 6".

I know the vent is single wall above the roof and is single in the furnace room, so I would be highly surprised to see b-vent somewhere in between. I've been in the attic and haven't seen any obvious issues with missing insulation etc, I just haven't crawled over to where the vent is b/c it's not an enjoyable journey with blown-in insulation.

8 Ball 09-05-2008 07:33 PM

Sorry, I was a little grumpy. Forget about the horizontal thing, you dont have any issues there, but the single wall thing is something you want to get fixed.

I can see where you would have snow melt problems.

concretemasonry 09-05-2008 09:02 PM

One thing that people is other climates to not realize how snow can dissapear (not just melt). - It evaporates or sublimates!

With a warm sun, even at minus zero, the sun can decresae the snow thickness drastically, since you never get cold weather without clear skies. Between the heat from a single wall vent (even if not much) heat of the sun and sublimation (change from solid/ice to vapor without melting) you can decrease the snow cover and snow can melt and run down to where it can freeze and form an ice dam where the roof temperature is just below freezing. The darker areas even with some snow cover do warm up from the sun and a small heat leak inide will show up. All it takes is some warmer weather, clouds and precipitation to really cause big ice dams later.

It gets a little strange to see freeways and roads becoming clear and dry in cold weather after some plowing. The clear skies on cold days do remove ice without the overloading of salt that is necessary when it is cloudy elsewhere in the country. Part of it is due to the proverbial "dry cold" that increases the evaporization/ sublimation of snow is some areas, especially when you get a little help from below.

1610 CUB 09-06-2008 11:32 AM

After seeing the photo (and zooming in on it) it is as you said, a single wall pipe. Sorry, I just didn't want to through the installer under the buss, but after seeing the photo. The pipe looks to have angle iron rings just above the roof, and it looks to be a home made top. It reminds me of a wood stove type install.

coolmen 09-06-2008 02:59 PM

the heat may be rising from under the roof(inside attic) and heating that joist all the way to the top. no insulation possibly

Termite 09-07-2008 10:27 PM

You shouldn't have single wall up there, and yes it would need a lot of clearance to be safe. I'd concentrate on getting some type B vent installed in its place.

I have a hard time believing that the attic portion of the vent of what I assume is a lower level or basement furnace would get hot enough to radiate heat through a roof structure and roof materials and melt snow to any great extent.

detailedEye 09-07-2008 10:27 PM

I've already thrown the installer under the bus since he didn't bother to pull a permit. I've also spoken with him several times trying to obtain an invoice from the install in case I should need any warranty work done (not from him). He has been less than helpful and I believe it is b/c he didn't pull a permit. I'm still working on the invoice...:furious:

It's not angle iron, but part of the collar or flashing. The "witch's hat" cap is fairly common in my neigborhood with houses that haven't had any updates. I know the cap is no longer approved.

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