Attic...Ice Dams...Ventilation Issues

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Old 09-29-15, 10:24 AM
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Attic...Ice Dams...Ventilation Issues

This past winter (in New York), I ended up with some rain showers in my kitchen and dining room due to ice dams. My roof is probably around 17 - 20 years old and I decided I would get a new roof once autumn arrived. I'm not sure if there is ice and water shield on the roof and I know some of the flashing is not done correctly.

Form my research on ice dams, I know that the real issue is attic insulation. My house is a small ranch, built in 1955. The roof edge is even with the outer walls, so there are no soffits, hence no soffit vents. There is a gable end vent at each end of the approx 800 sq ft attic. There is batt insulation between the floor joists. I was thinking I should add another layer of insulation, but approx 40% of the attic is covered by a floor (the batts are under the floor boards), plus the air handler for my central A/C is up there as well.

I'm thinking now that my only option is spray foam insulation, but as I researched that, I found a lot of negatives about it. Now I have no idea what to do. Any advice would be greatly appreciated!!!
 
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Old 09-29-15, 10:30 AM
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When the top plate of your wall is only a few inches away from your roof deck, its going to cause a lot of melt and want to ice up. IMO your money would be best spent on some heat cables to create some drainage. You can also rake snow off as needed. But trying to solve it by insulation and ventilation could possibly be an impossible dream... simply because of the way it was built.
 
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Old 09-29-15, 10:47 AM
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If you are going to replace the roof, there are a couple of options for "edge vents". I like the vented drip edge as it extends beyond the current edge providing better exposure from snow and ice.
Attic Ventilation, Attic Moisture, and Ice Dam Solutions
But there are others and easy to have installed when a new roof is going on.

But X is correct that the limited space above your outside wall will limit any attempt to add insulation. The ideal solution would be 4" of rigid foam on top of the roof sheathing with the new shingles and plywood on top of that. The advantage of this approach would be what we call a hot roof where you eliminate all ventilation and include the attic into your conditioned space. That ac unit up there would love you, but your wallet might not.

If you add an edge vent then you need to be sure you have enough high vent area. You can leave the gable vents, but I would add a ridge vent. The combination of high and low venting along with best possible insulation and baffles to allow air flow below the roof sheathing should do a good job of reducing those ice dams. Ice and water shield does help, but you should never allow the ice to accumulate that much in the first place. More on ice dams if needed, I have lots of first hand experience.

Bud
 
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Old 09-29-15, 11:54 AM
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Thanks for the replies!

Xsleeper....Last winter, I did use a roof rake, but it just seemed to move the ice dams further up the roof. I have thought about heat cables, but #1, I don't have anywhere to plug them in, and #2, I've read many conflicting things about how well they work and how safe they are.

Bud....I looked at the link for the vented drip edge, but due to my gutters, that won't work for me. It doesn't appear that I'll be able to add any type of venting to the edge of the roof, which means that a ridge vent most likely wouldn't be of any benefit to me.

My thinking was that spray foaming the underside of the roof would keep any warm air that gets into the attic from warming up the roof sheathing. Am I incorrect in that line of thinking?
 
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Old 09-29-15, 12:56 PM
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Couple of thoughts: When you use a roof rake, you have to remove all the snow from the roof, not just the lower part (not sure if you did that, but). Ice dams are driven by the heat rising from the house melting the snow on the upper part of the roof (heat rises), whereupon the water runs down the roof. The lower edge of the roof is below freezing, so the water freezes. This creates a dam that continues to grow as more snow melt runs down the roof. If you rake only the lower edge of the roof, you can make the ice dam happen faster, because the roof is not exposed to cold air directly without insulating effect of the snow. By removing the snow from the whole roof, you break the cycle.

The idea behind improving ventilation is that if the attic has enough ventilation to carry away the heat rising from below, then the snow won't melt at the upper part of the roof and the cycle is broken.

While good ventilation helps, it is not the total solution since direct warming from the sun can also cause the melting even on a well ventilated attic so ice dams can still occur under the right (wrong)conditions.

If you are going to have the roof replaced, you may consider turning your attic into conditioned space. The idea would be to remove the existing roofing. Then it is insulated with thick foam panels applied to the current sheathing. Over that they apply furring strips to create ventilation on top of the foam and then another layer of sheathing and shingles. This raised the roof several inches, but also give you the opportunity to extend it a little over the walls.

It is possible to insulate the attic with spray foam between the rafters, but this is not as trouble free. First, the rafters themselves aren't insulated. Second, with no ventilation of the roof deck, the roof temperature can get really high in the summer and can deteriorate some roofing materials. Many shingle warranties are void if they are installed over unventilated roofs.

If you don't want to dive into all that, and can't improve ventilation enough, then heat cables like X suggested work well, although they are expensive to operate.
 
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Old 09-29-15, 01:06 PM
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Converting to a hot roof is more involved than just spraying foam under the rood deck. First, you would have to meet code minimum and that would be in excess of 5" of foam and it would also need to cover the rafters or they might be cold enough to pose a condensation issue. You would also need to seal and insulate the gable ends. Technically, you would want to remove the ceiling insulation so the attic could be more like the house. leaving half way inbetween results in cold spots and again condensation.

The drip edge vent I referenced is only one option. BTW, gutters can be a huge part of ice dam issues. Few homes here in Maine use them specifically for that reason.

When you rake the snow off the roof, as you learned, you must go all the way to the top.

A ridge vent with the existing gable vents will be far better than just the gable vents.

When I added 3.5" of rigid foam to my house along with new siding I didn't like losing that much of my soffit area so I extended all of my rafter tails and created new soffits. In your case you could just extend and not build a flat soffit underneath, leave it sloping. That would involve removing the existing fascia board which would also give you access to detail best possible insulation over the top plate.

At a minimum, since much of what I have described is probably not an option at least for this year, add the ridge vent and install baffles in every rafter bay. And then get a longer roof rake .

Bud

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Last edited by Bud9051; 09-29-15 at 01:09 PM. Reason: addition
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Old 09-29-15, 01:41 PM
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Wow. So there is a lot more involved in curing my ice dams than I thought. In regards to the roof raking, my rake and its 3 poles only reach halfway up the roof. I wish I knew a way to get all the snow off without climbing up there and risking a broken neck lol!

Financially, making major changes to the roof or attic just isn't in the cards unfortunately. Even just getting the shingles replaced will be a stretch. I guess I was just looking for the most affordable way of preventing ice dams this year. I spent a good amount of money getting the ceiling repaired so it would be so depressing to see water coming through it again.

Just one other thing I'd like to mention. About 4 years ago, I had new vinyl siding installed on the house. About 3 months after the job was completed, I had gone into the attic and noticed that the installer had installed the new gable end vent grilles (or are they called louvers?) over the existing ones. So I have two grilles on each end. Will this seriously impede air flow through the vents?

Thanks again everyone for your help!!
 
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Old 09-29-15, 02:00 PM
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The double gable vents will cut the air flow approximately in half. More reason to consider adding a ridge vent.

Ice dams can be tricky, just when you think you have it solved a perfect storm of conditions arrives and they are back.

Buying another roof rake with the same poles will give you some extra length. Or a piece of electrical conduit and duct tape. If it gets ahead of you there are people out there you can call, young and brave. But the longer you let it go the worse it gets until the magic thaw arrives and it is all gone.

Bud
 
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Old 09-29-15, 02:20 PM
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Looks like I'll be going back up into the attic to see if I can pry off those inner gable vents so that there is only one on each side. I just assumed they'd remove the old grill rather than putting another one on top of it. Never assume lol!

Maybe for this winter, I'll just have to be more aggressive with my roof raking.

Thanks!!
 
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Old 09-29-15, 04:34 PM
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Are you still going to install the new roof this year?
Google "extending my roof overhang or gable overhang. Lots of articles and YouTube videos. A 12' overhang, which I consider the minimum, helps to keep the rain off of the siding, windows, reduce the splash from run off, move that water a bit away from the foundation, all positives, along with adding soffits and ventilation. Were you going to install the new roof or hire out?

Bud
 
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Old 09-30-15, 09:38 AM
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I was originally thinking about installing the roof this year (hiring a professional) when I thought that might solve my issue with water coming in from the ice dams. I've since learned that the problem is more my ice dams and less my roof, so a new roof certainly won't guarantee that it won't rain in my kitchen this winter. I've also learned from all the great advice that you and the others gave me on this thread that my attic ventilation is the key issue here.

I looked up extending the overhang, but I'm guessing that would be fairly expensive. Any idea what something like that would cost? I know it depends on the size of the roof, and I don't have the measurements now, but it's approx. 1000 sq ft ranch.

Thanks!
 
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Old 09-30-15, 11:05 AM
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Before I forget again, when you replace the shingles the one you select can also help or hurt the ice dam issue. A black roof will absorb more heat from the sun and send that melt water down to the edge where the dam begins.

But anyway, if your attic is 800 ft² then the roof is probably in the 1,200 ft² range. You could get some estimates with and without extending the soffit area. There is some trim work that is necessary when you build a new soffit area, but roofers should be able to quote the whole job as they often have to do related repairs.

Once you have some numbers, with and without, then you have an idea as to what adding soffits would cost.

Can you post a picture of the house?

Bud
 
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Old 10-08-15, 08:20 PM
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Good point about the shingle color, Bud. Luckily, I'm looking to keep the same color, which is a light grey. I have a roofer coming to give me an estimate and I'll ask about extending the soffits.

I don't have any decent pictures of my house and roof, but I'll try to take some and put them on my PC and post them here.

Thanks again!
 
 

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