Insulating Attic.

[Clarence Martinn]

Had MAJOR work done on the house. New metal roof over the older Rubber roof. New boiler installed. etc.

This year, we had a leak in the same spot in the 1st floor bathroom , when there was just the rubber roof. Heat was only set at 56 degrees.. 14 inches of blown in insulation in the attic and the attic hatch is insulated with 2 one inch thick pieces of insulation board. Got the heat in the upstairs separate unit now turned down to 49 degrees. When it was leaking at 56 degrees, they knocked off 1 foot thick ice dam, that was from the edge of the roof, and went back about 2 or 3 feet.

Question ; Since the 14 inches of blown in insulation is not doing the job, and the eve vents are working, would spray foaming the attic ceiling stop the ice dams ? Attic is closed off unheated and unfinished. Front part of the roof is shingles and has 5 roof vents. They are working fine.

[Steve Demuth]

I don't know that I can fully visualize what you're describing, but I can say that I have two houses with spayed in high density foam in the rafters, and have had zero roof melting issues. The roofs are absolutely "cold" and snow melts off them only when the entire roof is warmed from the outside. So no ice dams.

Mind, these are very well insulated roofs - 10" foam in one case, 8" in the other. They are also entirely unvented, being over cathedral ceilings.

[Doug Dawson]

Had MAJOR work done on the house. New metal roof over the older Rubber roof. New boiler installed. etc.

This year, we had a leak in the same spot in the 1st floor bathroom , when there was just the rubber roof. Heat was only set at 56 degrees.. 14 inches of blown in insulation in the attic and the attic hatch is insulated with 2 one inch thick pieces of insulation board. Got the heat in the upstairs separate unit now turned down to 49 degrees. When it was leaking at 56 degrees, they knocked off 1 foot thick ice dam, that was from the edge of the roof, and went back about 2 or 3 feet.

Question ; Since the 14 inches of blown in insulation is not doing the job, and the eve vents are working, would spray foaming the attic ceiling stop the ice dams ? Attic is closed off unheated and unfinished. Front part of the roof is shingles and has 5 roof vents. They are working fine.
It would be helpful for you to say where you were located. I’m in South Texas and the situation recently has been rather surreal and I don’t know how that applies to what you are going through, so I don’t know whose burro to kick back at.

[Lee Schierer]

It sounds like your attic isn't vented or not properly vented. That's what eave vents and peak or ridge vents are for. No matter how much insulation you put in the ceiling, some heat will escape and without proper attic venting ice dams will result.

[Bill Dufour]

Is 14" of insulation enough for your climate? It is marginal here. Do you have air chutes in each rafter bay. Are they clear, not closed off by insulation. I assume this is blown in insulation is it air washing at the eaves? If the air chutes do not go high enough it will blow around leaving the edges under insulated, causing ice dams.
Bill D

[roger wiegand]

Assuming properly sized and unblocked soffit and ridge vents, I'd look at air sealing between the house and attic as the culprit-- warm air is getting up there somehow. Sealing all penetrations through the ceiling, especially big ones around chimneys and plumbing stacks is essential, as well as electrical boxes. If your local utility offers an energy audit service take advantage of it. In MA we can get an inspection and up to $2K/year of insulation and sealing work done by the utilities.

If that fails then spray foam at the rafters will almost certainly work. We had HVAC equipment in the attic, so it made a lot of sense to bring that space into the conditioned envelope of the house. Eight years on it has worked perfectly, even in weather where 8 in 10 houses in our area were having severe ice dams.

[Lisa Starr]

Ventilation is the issue. We've stopped icing issues completely in several homes by installing a hybrid package on the underside of the roof. It is easy to do and moderately affordable to DIY. Remove all existing Proper Vents etc, they are useless in most cases, because they are collapsed when the insulation is pushed against them. The gist of it is to install 3/4" x 3/4" blocking to the sides of the roof rafters against the roof sheeting. Then cut 1-1/2" thick ISO board insulation to fit between the roof rafters (it can be sloppy) and fasten it to the blocking. This creates a 3/4" x 13" venting space from eaves to peak. Then use the cans of spray foam to seal the ISO board to the rafters. You can then go head and insulate the remaining cavity space with traditional fiberglass insulation. This system works, provided you have well vented soffits and a continuous ridge vent.

[Warren Lake]

thats ineresting what you said there, never heard that before. Read stukff in the past likely Fine homebuilding and others and its different every time I read. Meantioned to a carpenter he said its a moving target. Id watch one pro then the next one who was just about saying what I had already watched was wrong

Years a good craftsman friend brought one of hius friends to my shop. Before he even said hello to me that I did not have enough roof vents. When I did get to ask him what he did, he had been building custom homes from 12 years old. His father was a home builder and that is when he started. I wish he was still around awesome man.

Ive changed stuff in an attic where the last owner plugged very rafter tail so the home could not breath, his view was that he was keeping all the heat in. Everything he touched in that home was crap quality work. Mike Holmes would have a field day.

What you are talking about Lisa is that printed out somewhere. I understand what you are saying I think it would have to start and rest on the top plate or some how terminate there. ill let that settle in, sounds pretty interesting, lot of time and materials to do that and sure cost but also would pay off in some savings.

[Bill Dufour]

I think Lisa's plan can be done with the cheapest plywood or even to aluminum scrim used for radiant barrier. it only needs to come up 16" or so above the attic floor. Her method adds insulation but it is cheaper to insulate the floor and just vent the entire attic interior. Search for "air chutes".
Bil lD.

[Warren Lake]

thanks, think I did see that but but cant remember if it went all the way up. I thought that would be costly then there is insulation value but I dont know enough about it. One friend said its a moving target. I heard a builder on one day and he put the pink stuff inside his home ceilings before drywall and then did purple spray other side then I think blown in on top of that. He said it was amazing and I cant remember the pink thickness maybe it was 1" might have saved it and 2" of purple blow in. I rebuilt this whole roof and facia and eves all fresh then cut under the soffit continuous at the front and put a ridge vent think Shingle vent 2. Not sure how much I like or don't like it. i've seen it covered in a foot of snow, they say it still can breath. Maybe I should make a snorkel for it or several. More to learn. I often look at roofs to see how the snow is melting. You have me thinking about again which is good, will look up the air chutes.

[Warren Lake]

saw more of the pink slip in things than going all the way up. Would it not make more sense to go on the bottom or mid way on the rafters for a larger air space?. Agree it makes sense to focus on the ceiling area. The idea with the baffle is what to keep the underside of the roof cooler for less melt

[Lee Schierer]

When I added additional insulation to our house, I noticed that the added insulation was blocking the air flow from the perforated soffet into the attic. Since the area was almost impossible to get to to add the foam vent panels, I came up with another solution. I purchased 10 foot lengths of the thin wall S&D pipe from the local home center. I cut those pipes into short sections which I pushed across the top of the newly installed insulation to provide air flow from the soffets. I did this in every single rafter bay. Air flow was restored. The only problems we have now is when we get 6 or more inches of wet snow that covers the ridge vent, making it ineffective.

[Bill Dufour]

Those air chutes only need to be in rafter bays that have a soffit vent to the outside air. In theory every rafter bay should be vented to reduce ice dams and rot. Adding an air chute to a unvented rafter bay makes the problem worse. They make 2" diameter vent covers to retrofit venting under eaves.
Or drill the holes from outside and staple window screen over the holes from inside.
Bil lD

[Lisa Starr]

The Air Chutes are only half the battle. The ISO board with spray foam, though more expensive than scrim, allows for a complete air barrier between the roof and the insulation. That is an integral part of this system. If the warm air from you home can't flow to your roof it will greatly reduce ice. Without that complete barrier, you will get warm air reaching your roof and thus ice dams.

[Warren Lake]

Lisa do you find your shingles last longer then as they are kept cooler and not warmed from the bottom? in this home the shingles were trash in 10 years as former owner plugged all the rafter tails. I didnt have it long then had water leak through the roof where shingles had failed and had put nothing under them. I used Grace ice and water and other stuff metal flashing grace under and over, wrapped down over the top of the facia and all as best as I could. Do know attic insulation has to be done. Small home but decent. I find myself thinking about making cathedral ceilings out of what is there so it feels larger.

[Lisa Starr]

I can't speak to shingle life, as the homes we've done have had alternative roofing materials. 2 had metal roofing and 1 had synthetic slate (plastic). That said, all three had ice dam issues. 2 of the homes were cape style so even where the only insulation space is the remainder of the rafter cavities we found the system resolved all icing issues so I think it would work great with cathedral style ceilings.

[Warren Lake]

I can understand aspects of this say for the winter. How is this any better in the summer or not worse. The small air space on the underside of the roof. Would it not be alot hotter and increase shingle temp than unless it was open to the whole attic area?

[Jim Koepke]

Often the problem can be seen from the outside. Parts of the roof without snow accumulation is where the in house heat is getting through to the roof and melting the snow. The melted snow flows down the roof and refreezes, creating ice dams.

jtk

[Lisa Starr]

Warren,

I can't really tell you about summer. I do know that when we were working on one home is was 95 F outside and you could feel the air rushing up the cavities we had finished to the peak. The NFA (Net Free Area of the 3/4 x 13-1/2" space is 10 sq inches. Most Proper Vent type things, if not crushed by insulation, have around 9-10 NFA for 16" cavities and 18-19 for 24" cavities NFA. Additionally, the ventilation is spread over the whole cavity instead of only the center portion.

I'm not saying this system is the answer to every problem or the "perfect" vent system. Simply, my experiences show that the system will stop icing problems and creates good eave to peak flow under the roof decking. With a traditional attic space, insulating the first maybe 4' from the eaves to above the attic floor and associated insulation in the fashion I described may well be the best of both worlds. It would keep the air moving up past any restrictions due to insulation and provide a greater air space.

[Warren Lake]

I think my thoiught was a good thought, I can easiliy see that styro way being better in the winter but switch arount to when attic hit Some peak of maybe 150-170 F under dark shingles and I cant see it helping. Now when there is only 3/4 of air space between the styro and the roof I dont see the pull of air up from the soffit being enough to cool that. Just what came to mind

[Bill Dufour]

I can tell you that a 14" diameter hole in the roof on a calm spring day has plenty of thermal airflow. All the saw dust comes up into your face if you need to trim the hole a bit bigger. So I think the air chutes will have good thermal draft flow in summer when it gets hotter. But not enough to stop a screw from falling.
Bill D.