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  1. #1
    Join Date
    May 2008
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    Default Traditional versus open cell foam insulation

    I need advice. We have recently returned to Oklahoma after 13 years away and have purchased a home here. The home is roughly 16 years old and my dilemma is over insulation in the attic. Given the increase focus on conserving energy, my wife and I feel the need to insulate the attic to help make our home more energy efficient. The issue is whether to go with traditional insulation or open cell foam insulation.
    The open cell foam insulation representative informed us that once the rafter bays are sprayed they would then cover up the soffit vents and any other openings in the attic including an exhaust fan in the roof. That concept is very contradictory to the lessons that I have learned growing up in New Jersey. I even remember installing baffles in between the rafters before I added the traditional insulation insuring there was a way for air to circulate from the soffit vents to the ridge vents. So the concept they are recommending is counter to what I have grown up with.
    Beside my desire to make our house more energy efficient Iím also concerned about the roof shingles. Since they were just replaced (Dec í07) as a condition of sale of the house I would not want to do anything that would damage our new roof.
    Your advice/insight in this matter would be greatly appreciated.

  2. #2
    Join Date
    Aug 2007
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    The Great White North
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    Default Re: Traditional versus open cell foam insulation

    tquick .....interesting timing for your post .... I've been doing plenty of reading and researching this particular topic .

    You're correct .... the method proposed is contrary to conventional thinking.

    It sounds like the insulating contractor is one that is up on new ideas and the recent discussions in the building sciences.

    What they are describing is a recognition that attic ventilation is over rated.

    Here's the short of the long......

    This way of thinking is to make the attic a conditioned space by insulating the under side of the roof as well the gable walls.... preventing cold and heat infiltration into the attic space as well stabilizing the temperature so that condensation won't form on the underside of the roof .... also this insulating method will prevent ice damns from forming.

    This also means to close off all openings into the attic .... preventing the outside elements from entering the space.

    This thinking is not far from the idea of insulating the exterior walls in the home.

    I'm following this topic with interest since I also believe it's a good way of doing things and will likely be doing this to my own home.

    This method of thinking is very benifical for those that have HVAC equipment located in attics as well.

    However .... there is some contraversey regarding an air space directly under the roof sheathing for relief from heat build up for the exterior shingles ..... that debate continues.

    Now ... the method the insulation contractor suggested would be a good system ... but .... at this time ...... with a slight modification.

    A continious sealed baffle from the soffit directly to a ridge vent.... allowing outside air to freely flow without infiltrating the conditioned space of the attic.

    This could be accomplished by attaching a nailer to each rafter to attach a rigid material ( plywood , rigid foam , etc. ) with a 1 1/2 - 2 inch air space below the underside of the roof sheathing.... and the insulation applied to this baffle filling the rafter bay.
    This would allow the nesscessary heat relief for the shingles yet still providing the insulation performance.

    Hope this makes sense and helps.
    Last edited by canuk; 05-30-2008 at 08:28 PM.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    May 2008
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    3

    Smile Re: Traditional versus open cell foam insulation

    Canuk, Copy the no fun aloud part. Thank you for the response. Just So I understand...the contractors plan is about 85%. You are suggesting that for every soffit vent that I have I should run a continuious baffle from the soffit vent to the ridge and then let him spray the roof rafters with the open cell insulation is that correct?
    I'll have to wait on the ridge vents for a little while as the temps are already too warm here in OK (90+). I would not want to damage the new roof while attempting to install ridge ventshe. Again, I appreciate the advice and I'll see were we can install the ridge vents as we have many angles to the roof versus an A frame. Would probably have to install them on two hips on each side of the house. Kind of like a pyramid.

    Tquick

  4. #4
    Join Date
    Aug 2007
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    The Great White North
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    Default Re: Traditional versus open cell foam insulation

    You are suggesting that for every soffit vent that I have I should run a continuious baffle from the soffit vent to the ridge
    You would need the continuous baffle and a soffit vent for each and every rafter bay.

    If you refer to the attachment you notice where I've darkened the area starting with the vertical damn at the soffit and the baffle would extend all the way continuously to the peak ( ignore the knee wall reference ).

    The vertical damn will allow insulation to cover the most problematic and important area .... the wall top plate ... still allowing venting.


    Keep in mind the reason for doing this is for the recently installed shingles .... you don't want any problems with warranty if the need arises. If there were any problems with your roof down the road ...... you can bet if there wasn't any air space underneath that would be an easy out for the shingle manufacturer to deny your claim.

    Unless of course the shingle manufacturer sanctions that method then all this would be a moot point.

    If there wasn't this air space from the insulation being applied directly to the underside of the roof ... and perhaps down the road there was a warranty issue for the shingles .... how likely would the insulation contractor stand up and do battle for your cause?


    Just a thought.
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    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
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    May 2008
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    Smile Re: Traditional versus open cell foam insulation

    Canuk, Thanks that clears it up

  6. #6
    Join Date
    Jun 2008
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    11

    Default Re: Traditional versus open cell foam insulation

    Okay, my house is a Cape Cod and I do have the knee wall setup you see in the attachment. I also have the batt insulation in the attic floor. The paper/vapor barrier is facing down to my first floor. Because I have the vapor barrier in the attic floor, will I have problems with moisture in the conditioned attic if I have the roof deck spray foamed with open cell Icynene? I have come across quite a few building codes that say it is not allowed.

    My biggest concern is with heat buildup during the summer. Will an open cell foam that is considered an air barrier trap heat in my upstairs bedrooms?

  7. #7
    Join Date
    Sep 2008
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    2

    Default Re: Traditional versus open cell foam insulation

    The vented attic for the sake of the shingles is old school; many manufacturers are recognizing the sealed attic concept and will honor their warranties for the spray foam system of attic insulation. I would follow up with the shingle manufacturer to be sure; however, your shingles will suffer very little with a foamed-in attic.

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