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Insulating a 2nd floor ceiling no roof ventilation?

PLIERS | Posted in General Questions on

So I have a second floor bedroom that is getting hot.  There is no attic space, basically my ceiling is directly under my roof.  During some renovation last year I gutted another bedroom and bathroom on same floor and insulated ceiling with fiber batts.  Those rooms are more comfortable.  I was going to try to retrofit this bedroom I have by shooting cellulose in ceiling.  Contractor came and gave me price but said he looked around and it looks like I have no soffits or any sort of roof ventilation.  He was concerned about moisture.  Said he won’t do job until a contractor fixes that.  Right now I have a chimney that is non structural going straight through center of house.  I was planning on removing it.  Should I ventilate the roof through the existing hole of chimney?  With or without removing chimney is there something wrong with using fiber batts to insulate ceiling?  Should I gut this room like the others, is that just easier to get it insulated?

Joe

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Replies

  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Joe.

    What you are asking about is an insulated cathedral ceiling and they can be done as vented or unvented assemblies.

    You didn't say where your house is located, but your contractor is generally correct. Insulated cathedral ceilings with only fibrous insulation should be vented. Filling the rafter bays with fiberglass insulation may help with comfort in the short term, but may also introduce durability issues down the road. Removing the chimney won't help with venting.

    A vented roof typically has a continuous air space from intakes at the soffit or otherwise near the eaves that extends all the way to an exhaust vent at the ridge in every rafter bay. Here are some articles you may find helpful:

    How to Build an Insulated Cathedral Ceiling
    All About Attic Venting
    Venting a Tricky Old Roof

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