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  1. #1
    Join Date
    Apr 2008
    Location
    Upstate NY
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    2

    Question Insulation with semi-cathedral ceiling

    I've been trying to find a solution for insulating my attic, and have so far received all kinds of different answers. I have a 1950's or 60's home with original batt insulation in the attic that has settled down and is basically useless. I live in upstate NY, and have had very significant problems with ice damming - all the snow melts from the peak of the roof down, freezing in huge sheets along the eaves. I am planning to install blown-in cellulose to R50, but am unsure what to do about the inaccessible areas above the "semi-cathedral" ceilings on the second floor (see attached sketch). There are existing baffles, but I'm unsure what, if any, insulation is down between the rafters (it does seem to stay cooler along the bottom of the roof). The house has soffit vents, ridge vents, and gable vents. I am having a new roof installed this spring.

    Any advice? For some reason nobody seems to have seen a house like mine in this area.
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  2. #2
    Join Date
    Nov 2007
    Location
    Sand Springs, OK
    Posts
    467

    Default Re: Insulation with semi-cathedral ceiling

    Here's the problem I see with your blown cellulose insulation. Eventually it's going to settle like the fiber glass bats have and you're going to have the same problem you do now.

    I'm not sure that all those vents are necessary. I could see sofit vents in conjunction with ridge or gable vents but not both. Since you have such an ice damming problem I think I would have them remove the ridge vents all together. There seems to be a higher probability that water would infiltrate the ridge vents with the ice damming.

    I think I would explore another less water permeable insulation since Ice damming is so common on your home.


    Here's another problem I see, hot air floats so your cathedral is harboring all your warm air. If your intentions with mega insulation is to keep that room warm I would investigate warming solutions for the floor as well as adding the insulation.
    Debby in Oklahoma

  3. #3
    Join Date
    Feb 2008
    Posts
    59

    Default Re: Insulation with semi-cathedral ceiling

    if your getting a new roof here's a new option spray foam pull up plywood sheets spray the foam put the plywood back down its supposely does not shrink
    JUST ANOTHER OPTION

  4. #4
    Join Date
    Jan 2008
    Location
    Lakeland ,MN
    Posts
    356

    Default Re: Insulation with semi-cathedral ceiling

    I agree with Pomer. to pull up the plywood when you are replacing the roof would be a good time to have a Insulation contractor give you some good advice. Both venting and insulation options. Most estimates are free. then either do it yourself or hire him. Just becareful if it is to tight you can cause mold. That is why I suggest a pro for advise.

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Insulation with semi-cathedral ceiling

    Quote Originally Posted by Architecture_Chick View Post
    I've been trying to find a solution for insulating my attic, and have so far received all kinds of different answers. I have a 1950's or 60's home with original batt insulation in the attic that has settled down and is basically useless. I live in upstate NY, and have had very significant problems with ice damming - all the snow melts from the peak of the roof down, freezing in huge sheets along the eaves. I am planning to install blown-in cellulose to R50, but am unsure what to do about the inaccessible areas above the "semi-cathedral" ceilings on the second floor (see attached sketch). There are existing baffles, but I'm unsure what, if any, insulation is down between the rafters (it does seem to stay cooler along the bottom of the roof). The house has soffit vents, ridge vents, and gable vents. I am having a new roof installed this spring.

    Any advice? For some reason nobody seems to have seen a house like mine in this area.
    I'll toss hat my in on this ....

    First thing that I'm confused with ...... all the vents.

    The soffit vents should have some channel of flow into the attic area where the gable and ridge vents are located. If they don't .... they aren't doing much.

    The ridge and gable vents could actually be hindering good ventilation. Being so close together .... up high on the roof peak .... they can be causing a short circuit of air flow. In other words the air flow would just occur near the peak of the roof and not further down into the attic space.

    Adding an R50 value of blown in cellulose is a very good thing.

    There is some misconception as to "settling" decreases the performance for this type of insulation. There is a slight amount of " settling" however this doesn't decrease the insulation value ..... or at least extremely little. In a horizontal application any settling wouldn't be an issue.


    Areas that will cause the ice damns would be heat from the living space is radiating and warm air leaking into the area below the roof sheathing and warming it enough to start melting the lower layer of snow on the outside of the roof.
    Taking the step of adding the R 50 will improve this issue greatly by preventing the heat from the living space to transfer through.

    Another step that is just as important as adding insulation is preventing warm air leaking into the attic space. There should be some effort to move back the existing insulation and seal all the penetrations .... plumbing pipes , electrical boxes and holes , etc..
    Too many people rely on the insulation and overlook this sealing .... these two work together.

    It's unclear as to the construction of the second levels sloped ceiling ..... are they 2x4 or larger rafters ? This will determine as to what value of insulation would be available to be installed into these areas.
    One thing to consider are the rooms where the ceiling is located immediately beneath the roof. There is only the depth of the rafter .... so for a 2x4 there is only 3 1/2 inches roughly separating the ceiling of the room and the roof.

    The lumber for the rafter itself is really not a good insulator. If you have ever seen a dark colored roof on frosty morning you may have noticed vertical lines showing where each rafter is located. This is because of heat loss transferring through the rafters which melts the frost or snow. So insulating the spaces between those rafters helps .... but the rafters themselves can be a large part of heat loss.

    Two methods to help over come some of those shortcomings are to apply sheets of rigid foam insulation on either the interior wall and ceiling surfaces or the top side of the roof. This will increase the insulation performance by providing a continuous thermo break.


    For what it's worth ... hope it helps.

  6. #6
    Join Date
    Apr 2008
    Location
    Upstate NY
    Posts
    2

    Default Re: Insulation with semi-cathedral ceiling

    Thanks for your feedback everyone! This is most likely going to be a DIY job for a couple reasons...first, we need to get the insulation installed before the roof will be done because the only access to the attic is through the nursery we're currently renovating...and, second, the insulation contractors I've received quotes from are exhorbitant, to say the least. One quoted me over $3,000 for blown-in cellulose for an approx. 450 s.f. space.

    Canuk, to answer your question, our roof is constructed of rafters, not trusses. I'm not sure of the rafter sizing. We unexpectedly had to delve into one of our walls over the weekend and found some original batt insulation in them, so I'm guessing there is existing insulation between the rafters as well...not that it's doing much! The upstairs consists of 3 bedrooms and 1 bathroom. Everyone seems to say that it's odd having gable vents and ridge vents... I'm not sure if the ridge vents were there originally or not, but there has been plenty of other evidence that the original builder didn't necessarily know what he was doing!

    My current thought is to install baffles between all the rafters, unfaced batt insulation stuffed along the edges of the flat portion (to prevent cellulose from getting down into the sloped areas and sealing off the vents), then blowing in the cellulose to 15 inches thick. The upper portion of the ceiling seems to be where all the heat gathers, so I'm not sure fussing with the sloped areas (that are probably already insulated in some manner) is worth our trouble. Our problem was with all the snow melting from the top down, and freezing along the bottom of the roof, so I think taking care of the upper portion would probably work. Any feedback appreciated!

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