Spray Foam Insulation for Existing Attics
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Spray Foam Insulation for Existing Attics

Spray foam insulation for an existing attic can provide increased energy savings over the life of the home. This simple project can be accomplished as a DIY project or contracted by a reliable contractor who is in the business of attic insulation work

Spray foam insulation for an existing attic can provide increased energy savings over the life of the home. This weatherization project can be accomplished as a DIY weekend task or contracted out to a reliable contractor who is in the business of attic insulation work

Foam insulation applied to existing attic spaces is a good weekend project for one or two persons to accomplish if they have a reasonable handyman skill level and the correct materials and safety equipment.  Many of the big box home stores or local hardware stores carry the items you need.  If the homeowner prefers to hire a professional to do the job there should be many local area contractors who will inspect a home attic and recommend products and techniques to accomplish the job. 

The video and information below is based on open-cell spray foam insulation applied directly to the underside of a roof over an attic space.  In this instance, you can spray the foam directly on plywood roof underlayment or use purchased baffles to add air space under the plywood decking. The baffles will allow moisture to migrate to the outside of the shingles should any build up between the open-cell foam and the shingle decking occur over time. This moisture could lead to rotting of the shingle underlayment. Note:  Baffle installation is not part of this article.


Here are some facts and suggestions from professionals and do-it-yourselfers to aid you in selecting the correct spray foam type and techniques for your particular home attic situation.

  • Spray foam insulation is a superb product. Foam kits are available for the homeowner and each states the R-value per inch thickness.  independent test results are used by foam manufavturers to  confirm what the R-value is per inch of thickness of a given product. R-value is a measurement of thermal efficiency; it is a measurement of the resistance to heat flow. The higher the R-value number the greater resistance the particular insulation has to the movement of heat. You can expect to get about an R-4 to R-7 from one inch of a foam product (actual values may vary). Some manufacturers state that a 3 inch foam application of closed cell foam equals an R-21 result.  Check product lables.
  • Spray foam kits are available from many companies.  Just look on the web and you will find several in your area. The manufacturers also provide instructional and demo videos to assist you in selecting the correct technique and product for spray foam insulation for attics. Each supplier has technical and installation experts that are a phone call away.  Use them.
  • No matter what insulation is used, roof ventilation is critical. Make sure any excess water vapor can ventilate in the cooler winter months. Large, wind-powered roof turbines do a good job of exhausting air from attics.
  • If you have a shingle warranty you're concerned about, you can use baffles from your local home improvement superstore as mentioned above. They're easy to install, very inexpensive, and help avoid that shingle warranty issue entirely. Just nstall the baffles first and then spray foam against the baffles. The spray foam doesn't touch the roof at all. Another benefit of spraying foam on the baffeling is that if you ever reroof you won't need to re-foam because the baffles serve as a drainage plane.
  •  Be sure you have full body protective gear before embarking on your attic insulation project:  protective suit, head protection or suited hood, full eyes and nose coverage goggles with filtered reather, protective gloves. For added protection use blue painters tape to tape wrists and ankles around garments. Sturdy shoes are a must. 

Steps for spraying:

  1. Start in lower corner attic area and spray in lineal strokes.  Spray foam where wood rafters and joists meet first, then use lines of spray to form rectangles, then fill in with strokes.
  2. Work carefully but quickly as foam will immediately adhere and expand slightly. Do small sections first, then move to adjacent sections.
  3. Finish by checking any possible openings or cracks to outside like bents through roofs.  Do not cover any soffit vents... this is critical to allow attic space to breathe.
  4. When you get to the intersection of the angled rafters and the ceiling joists, cut a one-inch piece of rigid foam board about 12 inches tall  to fit between the ceiling joists and place in space to snugly close the angle opening and to provide a flat surface on which to spray foam. You only need hand-insert the foam board before beginning to spray foam. Spray at top, sides and bottom of the rigid foam board to close cracks.
  5. When in doubt, follow manufacturer recommendations for the foam kit used.
  6. When finished be sure and remove all materials from attic space. Hint:  Use cardboard box to place materials and hoses in while entering and leaving attic work area.

For additional information and resources see:



For video on protective gear suit up seehttp://www.tigerfoam.com/

Additional resources:

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