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Todd-Beaulieu 09-04-2009 06:13 PM

Shoudl the attic roof be insulated?
We have section of the house that get serious ice dams. The roof in that attic is not insulated. There's also no vents. I created some vents this week at the soffit (half dozen 2" holes) that go into the attic.

There's a single window near the apex, but no vents. And there are no soffit vents on the other side.

I'm thinking of venting the other side.

But ... what else? Do I run styro channels all the way up the roof and "over" to the new vent? Do I then pack insulation on top of the channels?

Or, so I just need to ensure that the 2" holes can flow freely into the room and then install a new vent over the window and then also install insulation on the roof?

I have no ridge vent.

I'm looking forward to your input! Thanks!

glennjanie 09-04-2009 11:24 PM

Welcome Todd:
Your ventilation is headed in the right direction. A 2" hole in each rafter space, on each side of the house would do a good job when combined with a louver in place of the window for a relief. The ridge vent would be the perfect combination with the holes though.
The attic floor should have the insulation rather than the roof, unless you are using the attic for living space.

Todd-Beaulieu 09-05-2009 05:39 AM

4 Attachment(s)
Thanks for the help! I was expecting you to say I have to insulate the roof. I'm surprised. Don't get me wrong, I don't necessarily want to spend the extra time and money.

I'm including three pictures:

1. The new vent holes that I drilled.
2. The inside view, showing the beams "in the way".
3. A real problem in my mind: the roof over this vent gets HUGE ice dams in the winter.
4. The attic window.

So, do these vent holes look ok? There are 8 of them, I think. The attic isn't that big - maybe 10' x 10' x 8' (center). I've seen writeups about using foam channels to allow the vents to get through insulation. I don't seem to have that problem, since the holes are above the insulation. But ... I have these huge beams in the way. Is that a problem? Will the air just flow into the room and out the new vent above the window?

Also, we get really bad ice dams on the other side, above the vent from the stove. There is a small sheetrocked wall there, presumably stuffed with insualtion. I'd say it's not working! Do you think this indicates heat from the vent pipe (kitchen stove) melts the snow on the roof? What can I do to improve this?

Thank you again. I really appreciate the help. As a new home owner, it's a bit overwhelming, and having a house built in 1734 presents special challenges and situations!

glennjanie 09-05-2009 02:03 PM

Hello Todd:
The holes look great! I would put a pop-in round aluminum vent in each hole to keep insects and birds out of the attic. You can find them at Home Depot or Lowe's. The beam is no problem at all, the air will still travel under it. I would still put something at or near the peak of the attic to allow relief for the holes along the side.

The icing can be stopped by installing heat tape on the roof. There is a type of heat tape that comes in 50' or 250' rolls and you put a small cord on the end to plug it in. One place I know of that sells that heat tape in your area is United Refrigeration.


Todd-Beaulieu 09-05-2009 05:23 PM

The picture is before I put up the fascia, so the vent strips shown are the screen for the holes.

I'm going to research installing a ridge vent to see if I want to do that much work. Otherwise, I'll look into something for over the window.

We have heat wires on a nearby section of the roof and it feels like such a hack. I'd like to solve the problems the right way. But ... tonight I discovered that the bad section is actually above the bathroom, which is why that vent pipe goes the length of the attic. It's an interesting, but funky layout and I'm still discovering what's on the other side of any given wall!

GBR 09-05-2009 11:44 PM

The styro baffles are to keep an air way open when you insulate blow-in loose fill. Do not stuff insulation in them. The insulation goes on the attic floor, whatever is recommended for your location. The vapor retarder (paper face) goes towards the heated area (down) not up as in the picture. Measure the attic area for square footage, not height, and divide by 150. 10' wide x 30' long = 300' / 150 = 2 square feet of vent required / 2 = 1 square foot of intake, 1 square foot of exhaust. Ridge vent net free vent area (NFVA) varies per manu. 1 sq. ft. x 144" = 144" / 9 = 16' of vent required. eg. The fan duct should go straight up from the fan, be insulated and vapor barrier, through the roof. Because it is uninsulated and running across the attic, the heat is lost to the attic roof above it, before it exits the roof. The heat melts the snow near the roofing to refreeze causing the ice dams.
You really need three 2" holes in each rafter bay, for 14.4 sq. in. of vent per foot, not 3.14" per foot. The gable vents would create wind-washing (not good) as per article. Air Vent: Continuous Soffit Vents Specifications
Audel Complete Building Construction - Google Books -Attic Ventilation Problems Ridge vent with baffles: ESB: Research Exposes Attic Ventilation Myth
Be safe, G

Todd-Beaulieu 09-06-2009 05:50 AM

What a great post. Thank you very much!

My insulation is in backwards, huh? I hadn't noticed that. I'll flip 'em all.

Ok, so my holes aren't big enough. Ugh. I did the math, and for 11' x 14' (154 sq ft) I need 1 sq ft total, and .5 sq ft for the soffit vents. As I only have one side to work with, like you said, I'd need 3 holes per "rafter".

Sadly, I already installed the fascia and new gutter. It's not really possible to drill from the inside, and even if I could, it would make a mess in the soffit. I'll have to let this sink in and I'll figure out a course of action when the depression passes...

handyguys 09-08-2009 01:05 PM

Todd - The bottom line is you want the attic to be the same temperature as the outside. Adding insulation to the FLOOR and keeping it from reaching the underside of the roof is what you want. You get ice dams because the snow is melting on the roof above the living space and freezing on the overhangs. Everything you can do to prevent the snow from melting unevenly is your goal. I'm not a fan of the heat tapes. They are a band-aid solution. vent the attic and insulate the living space and you should be golden.

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