Vented drip edges

PaulF · 01-06-2009, 05:44 PM

Like many this winter, I have ice dams in on the dormer. The roof design has no sofit space, the dormer has new ice & water shield theentire length & width. The contractor is suggesting the vented drip edge. A portion of the dormer area (with the two skylights) is valted. I've had ice dams on an off for years. It's time to fix this once and for all. I'm incline to install a metal roof.

Any advice?

Baron · 01-06-2009, 06:07 PM

Or heat tape that is on a switch, that may be less expensive.

**Ed the Roofer** · 01-06-2009, 07:17 PM

The "Vented Drip Edge" product sold by Air Vent, is one of their few products that I do not encourage customers to consider.

They recently came out with a Shingle Over Style Eave Edge Intake Vent product.

Now, theres has been out for a little less than one year, but they typically make 1st class ventilation products in addition to teaching users of any ventilation products the most advisable mwthods of providing proper ventilation.

The brand of Shingle Over Eave Edge Intake Vent that I have successfully used for the past 7 years now, is called, "Smart Vent, by DCI Products, Inc."

Both materials would either require a new roof to be getting done, or, if the existing shingles are still pliable and a current batch of the same colors and style can be purchased, then you could remove the bottom 7-8 rows of shingles and install the Intake Vent product and then reshingle over the top of it.

Remember though, that the R-Value of your existing insulation is also a critical factor. Plus, you need to ensure that you have a minimum of a 1 1/2" continuous unimpeded air flow from the eave to the Ridge Vent for the air flowage to be properly balanced. (You Do or Plan On Having a Ridge Vent to corresond with the eave vents, right?)

Also, please be advised, that no matter what preventative measures anyone takes, their is No Guarantee against Nature still providing the right conditions to promote the development of new ice dams in the future on occassion.

Ed

PaulF · 01-07-2009, 07:22 AM

I do have a ridge vent. My concern is the portion of the roof that is getting ice damage is valted. The valted area is closed off from the rest of the attic area thus breathing (a vented drip edge) is not possible (or is it?) with lots of re-work.

Wouldn't a metal roof on the dormer be most likely to solve the ice dam issues (i.e. water backing up and coming in the house) than messing around with the thermodynamics of an old attic?

The roofer wants to "Try" the vented ridge vent first. I need a solution not another winter of trial & errors.... why the metal snow roof is not a clear cut solution is what I'm not understanding.

Tom Struble · 01-07-2009, 09:05 AM

metal roofs are also subject to ice damming with the right conditions.
single ply is maybe less so

Baron · 01-07-2009, 05:16 PM

Ice dams occur due to the sheathing and roof getting warmed from underneath and the snow melting and refreezes at the edges building a dam. Metal roofs can be subject to them as well as any other roof. Due to the small overlay that a metal roof has where the seams are, the conditions can still present themselves and cause some trouble. I think that is why your builder wants to try some edge venting first.

It is important to vent a channel along the underside of roof sheathing to allow exterior air to cool the sheathing and exhaust what moisture develops there. So like stated above insulation R value is important as is the vented space.

With a vaulted ceiling you may have lost too much space to insulate correctly and will have to consider a more affective roofing solution or heat tapes.

Tom Struble · 01-08-2009, 01:23 PM

theres a product called cool vent it 4x8 insulation with 5/4 spacer block then osb top layer we used it on a log cabin cathedral ceiling no insulation at all.Seems like a good product to use on any cathedral

**Ed the Roofer** · 01-08-2009, 05:21 PM

Quote:

Originally Posted by strublesiding@optonline.n

theres a product called cool vent it 4x8 insulation with 5/4 spacer block then osb top layer we used it on a log cabin cathedral ceiling no insulation at all.Seems like a good product to use on any cathedral

Atlas has an insulation board laminated to OSB decking with ventilation gaps in the insulation called Cross-Vent also, if memory serves me correctly.

Ed

DrFrog · 04-03-2009, 05:42 PM

I’m not a regular reader of this site but googling for my ice dam issue turn up this thread.
My issue first and then my question:
My house is located in New England built in the mid 80’s . A contemporary design with cathedral ceilings throughout. We’ve had moderate trouble with ice dams since we purchased in the late 90’s but ice/water was always contained to the outside showing up as ice/water leaking out from behind the siding. That was until last year… (winter 2007-2008). We had major issues on both the front and back of the house with water running the ceilings and interior walls.
As part of the repair process to all the damage we decided to replace the aging roof which was a builder “special”. The new roof was put on after stripping the old roof adding ice and water barrier up 6 feet but the existing vented drip age was left in place.
Along came the winter of 2008-2009 here in New England and my new roof shows as much ice/water seepage as our old roof which had NO ice and water barrier.
Admittedly the cathedral ceilings with all the recessed lighting contribute a lot to the icing condition. But according to our roofing contractor now the issue is the vented drip edge. Supposedly the ice builds up in the gutters and then backs-up into the vents of drip edge and then into the soffit and then behind the siding and then out.
The Questions:
· Does experience show this to be true?
· The roofing contractor is recommending stripping bottom 3 feet of new roof; replacing vented with non-vented drip edge; and installing soffit vents (continuous). Sound like a reasonable remedy? Am I just putting another Band-Aid on? Or replacing one issue for another.

Thanks,
dB

adelaide11 · 04-03-2009, 11:50 PM

I do not think that metal roof will solve this issue and you will be able to rest. What is your contractor is saying about this. If possible took the opinion of two to three contractors with their price. In this manner you will be able to get clear idea and good suggestion as well.

It will be much better if you will attach photos.

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