Asked on May 6, 2013

How best to insulate attic?

Euroshield-RoofingWoodbridge Environmental Tiptophouse.comJoe H


I am about to put on a new roof, and I am putting in a subfloor in the attic to use it for storage ( for now). I would like to insulate the attic, but am unsure of the "best" way to do so. One alternative is to "seal" the attic off using spray foam insulation, and the other alternative I am considering is to use a radiant barrier or reflective insulation. the radiant barrier (with a ridge vent) will be significantly cheaper, easier to install, and a lot less messy, but will it be as effective as using the spray foam insulation? Also, if I do seal off the attic with the spray foam, do I have to worry about problems with condensation from regular house air in a cold winter? Also, some time in the future I may want to finish all or part of the attic, and I would like for the insulation to be adequate so that I can reasonably heat and cool the space. I live in North Carolina, wher the summers are hot and humid and the winters do have occasional bursts of fairly cold weather. Any advice would be much appreciated.
5 answers
  • Do not waste your money with reflective films. They are worthless. Forget about all the fancy light demos they use to sell you how well this works etc. How you determine what to do is dependent upon the location of the cooling and or heating system. If you have any ducts located in the attic space you want to foam the roof. This brings in the duct system within the building envelop of the home. When foaming you seal off all ventilation. Soffits, gable ridge and any fans that may be used to ventilate the attic. A closed cell system is required for at least two inches against the roof sheathing. Then switch over to open cell and build up to at least six inches or more. Closed cell does not offer as much of an R value as open cell does, but should the roof ever develop a leak the water will run down the backside of the foam until it leaves the house. Open cell will allow moisture to be absorbed into the foam causing leaks eventually into the home. Be sure to use fire rated foam or spray it with protective coating. Properly done you will have around a R-42 on the roof. You also will need to do the end walls that are exposed to the outside. If its done right your attic should be only around 10 degrees warmer in the summer then the inside living areas. You can remove any old insulation if desired or simply leave it in place. If your cooling or heating system is not located in the attic, simply air seal the attic floor to prevent moisture and air from leaving the house causing mold and higher energy loss. To properly air seal you need to pull back all insulation located above all walls including exterior walls exposing the top plates of the walls. Using spray foam in a can you then fill any spaces between the exposed drywall on ceiling and along all pipes and wire openings. If you have recessed light fixtures you need to construct boxes out of one inch foam boards that will cover over the fixture leaving space of a few inches clearance from box to fixture. Spray foam the box into place. Around the chimney you will use metal sheets to fill in spaces around the chimney to prevent air from flowing up around it within the chase way. If there are any drop ceilings close them off using foam board and spray foam to seal tight. Once your sure all openings are closed up and all spaces between the exposed top plate and the drywall ceilings you can replace the insulation to at least a R-30 or better. Crisscross the insulation over the floor joists so the joists do not prevent energy loss if the insulation poorly fits. Along the soffit areas use foam W shaped boards and staple them to the roof. This will allow air to flow around the top of the insulation and be sure to have enough ventilation along the top or on the gable ends. Steer clear of power vent fans. If done properly there is no need for them. If your planning to use the attic for storage, I suggest you spend the money on the foam. Its much more then the pink stuff but the payback is much better overall. Check locally and state wide for special programs that may be available in your area. In NJ homeowners get up to $5000 in rebates and $10,000 in 0% financing. Often it costs more than available, but combined lended money and monthly heating and cooling bills end up to be less than what they were spending just on energy alone before they even did anything. Paybacks can vary from 5 to 7 years depending upon the rebate programs that your state offers.

  • Miles Enterprises Inc.
    on May 7, 2013

    use the sprat foam it has the highest r value per inch and it also has an increased r value because of the air sealing quality of foam. do not subtract from the air sealing aspect by ventilating the attic

  • Joe H
    on May 13, 2013

    Thank you for the great advice. I will go with the foam. It is more expensive in the short term, but should save long term and make the space much more usable.

  • Joe, if the insulation in the home using foam is done correctly and you upgrade your current HVAC equipment to high efficiency, you should expect to see somewhere in the upper 25-30% range in savings overall. Not to mention greater comfort year round. Depending upon your states energy star program your monthly savings should be more then it would cost you to finance the project combined with the new energy bills. In other words done correctly with the rebate programs, your combined finance loan with the new utility bills should be less then what your currently paying now for your energy use without doing any of the work. Paybacks can be as little as 7 years. This is what folks in my area have been experiencing with the work I do.

  • Euroshield-Roofing
    on May 30, 2013

    check on tax credits and energy rebates in your state. These can help offset costs

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