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  1. #1
    Join Date
    Apr 2013

    Default Cape Cod insulation and attic venting

    Getting ready for retirement and have down sized to a 900 sqft Cape Cod in Central Penna. 1st floor with no finished living space in attic. Moved in last June and am getting ready to have the roof replaced. Attic area shows no signs moisture/mildew and heating and cooling costs are very low, but I am concerned with the ventilation, there is no soffit to vent so what I have are two 10"x12" gable vents one of which has a 16" fan fastened to it. The fan is next to useless with the small vents so my plan to install 14x14 vents with a 14" fan on one, since the attic shown no sign of moisture I'm assuming that this will be sufficient ventilation. Now on to the insulation, there is only about 8" of fiberglass and I want to add to that and seal any ceiling penetrations. My question is since there are no soffit vent can I run the insulation between the rafter up against the roof deck because there should be no need for baffles for air flow. Any tips or ideas to make sure I have propper insulation and ventilation would be appreciated.


  2. #2
    Join Date
    Aug 2008

    Default Re: Cape Cod insulation and attic venting

    You note in your post you will be replacing the roof shingles; if you will be hiring a contractor for this, nearly all roofing contractors also do attic venting and sometimes attic insulation; why not get an estimate from your prospective roofer?

    If you will be doing the venting as a diy project, ALWAYS WEAR A DUST MASK when you go up in the attic, especially if you in any way disturb the existing insulation, or add any new insulation---lung problems can result if you don't; many local roofing supply dealers (usually wholesale, but will often sell to the homeowner) have a good supply of attic fans & aluminum vents at a reasonable price.

    Consult the videos by Iris Communications (Pt.2 & Pt.1) to get an understanding of the many attic vent options that they mention and the 1 to 150 and the 1 to 300 rules to calculate how many net free vent area square feet are needed for your particular attic---to view Pt.1, Google "how to calculate and install attic ventilation Pt.1"; the free Adobe reader may be needed to view the video links.

    Do you want to use the attic fan(s) to vent also the living space on cooler days to save on AC costs, or are you only interested in cooling the attic?---attic fans burn electricity & there are solar attic fans that can do the job just as well, as noted in Tom Silva's video; however, some homeowners also use an attic fan with a thermostatic switch on cooler days & nites (solar fans don't work at nite) to also cool the living quarters, especially to bring in the cool nite air thru the open attic hatch/door; or you may be able to install enough passive vents according to the Iris Communications formula to avoid powered fans.

    Powered fans can be the cause of an attic fire as they age and have been in service for some time; always install or have installed a solar model or electric attic fan model that has a resettable fusible link (thermal switch) safety switch on the motor (these are required by code in many areas) that will shut down the fan if it overheats; there are many cheap import fans in the local home improvement stores that don't have this simple safety device.

    Last edited by von_steuben; 04-19-2013 at 07:43 AM.

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