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For many decades, the material of choice to insulate homes has been fiberglass. Blown fiberglass is used for the attic whereas fiberglass batts are used for wall cavities, ceilings, and pretty much everything else. Today, it is still a very popular insulation material, and is still used in new construction — it is inexpensive and most builders and insulation contractors are used to it.
Yet, there are several insulation materials available today that far outperform fiberglass insulation in many levels, and in the #61 episode of On the Job Larry Janesky, owner and founder of Dr. Energy Saver, will show us how spray foam insulation outperforms fiberglass batts when it comes to wall cavity insulation in new construction.
Larry begins by reminding us that modern houses aren’t built as rectangles with gabled roofs anymore. Most new homes have architectural features such as cantilevers, multi level areas, enclosures and fixtures that create irregular wall cavities and many challenges in terms of insulation.
The house showcased in this video is one example of this type of modern construction.
Fiberglass has an R-Value of 3 per inch while spray foam has a R- Value of 7 per inch. R-Value is a measure of resistance to heat flow, and a lower R-Value per inch means that you need a thicker layer of fiberglass than you would of spray foam to insulate the same area and achieve the same ideal R-Value.
The problem is that the fiberglass R-Value is rated only when the material is fully fluffed, not when it is compressed and touching all the surfaces in the cavity, without edge gaps. A small 4% edge gap will cause a 30% decrease in the R-Value of fiberglass insulation.
Add to that the fact that fiberglass has no air sealing capabilities, and air flows right through the material and you will begin to understand how it can be easily outperformed by other insulation materials, especially spray foam insulation.
Larry walks us through the many architectural and framing features of the building that would create several opportunities for insulation failure if fiberglass were the chosen material — and he shows us just how easily closed spray foam can be applied to the exact same problem areas. Spray foam insulation expands and effectively fills even the smallest spaces and gaps, leaving no holes in the insulation blanket and air seals the walls as well!

At Dr. Energy Saver, we are always looking for ways to make homes more comfortable and reduce the cost of homeownership by improving energy performance. If you would like to make your home more comfortable, visit our website to locate a dealer in your area.

Watch our other On the Job Videos for more information on energy saving home improvements and subscribe to our YouTube Channel to get the latest updates!


  • Dr. Energy Saver January 23, 2014 at 3:51 pm
  • Lawrence Bibi January 26, 2014 at 3:15 pm

    I have heard that spray foam installation is not a breathable material and
    easily forms mold.

  • Michael M March 11, 2014 at 4:24 pm

    Lawrence, Spray foam doesn’t form mold, water creates mold. However, spray
    foam is a great product to use because it blocks air movement (air leaks).
    It also does a wonderful job by filling in small cracks and holes to stop
    those air leaks, and bugs from getting into your house.

  • yacrafter March 14, 2014 at 1:08 pm

    Sir, being in the trades myself, I wish you would have included some of the
    drawbacks of spray foam vs. fiberglass. Just to be fair, could you explain
    residual off gassing and explain the effects of removing spray foam when
    installed improperly? Maybe mention what to look for when the insulation
    job is complete. Thank You.

  • Ted Kidd April 5, 2014 at 6:18 pm

    Ok, we get it, fiberglass is a really crappy insulation material. Any
    doubts, check out this video:

  • IamFreeRu April 26, 2014 at 1:29 pm

    Very informative. Never knew about spray foam insulation. Great video.

  • Mark Williford June 22, 2014 at 5:39 am

    Is spray foam better than the radiant barrier?

  • Bashaar Khan June 30, 2014 at 7:31 am

    foam is proven to cause damp, fiberglass doesn’t 

  • Pete Linster September 11, 2014 at 5:11 pm

    So I live in Fla. and have an existing slab home. What can I do to save
    energy dollars.
    Will it work for me?

  • Tom Ferrell September 18, 2014 at 4:32 am

    your videos are all great. would you mind if I post one or two on my spray
    foam websight?

  • Energyefficienthomes.ie October 5, 2014 at 7:46 pm

    Great Vid

  • Lifetime Insulaion October 7, 2014 at 9:36 pm

    Definitely spray foam hands down.

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