Spray Foam Insulation vs. Fiberglass
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Published 2014-01-23
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!
All Comments (21)
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I think combining air sealing with pink batts and cellulose in spots where needed is probably the best while keeping future home improvement projects in mind
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In a vaulted ceiling you DO NOT want fiberglass batts touching all four surrounding wood surfaces in most northern climates. You need airflow (1" minimum) above the insulation layer to remove vapor that would otherwise condense and rot wood framing. One problem with spray foam is that it actually makes construction "too tight". Wood framing needs to breathe. Water vapor does pour through construction assemblies (particularly from bathrooms toward a cold exterior) and foam is impermeable - meaning that the wood studs are the route. There are some reported problems with spray foam involving chemical sensitivity / smell for some people.
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Many have commented on the air space in the roof - that is because we are doing an unvented roof here. If we made a vented assembly and used fiberglass batts, the batts are subject to wind-washing and the R value is lowered. As I stated in the video, R values are in a closed cavity. A vented rafter bay is not a closed cavity.
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An alternative to spray foam people might want to consider is stone wool insulation like Roxul that is very stiff and holds it's shape better than fiberglass, up to 90 percent recycled wool fiber, also it is less flammable than fiberglass. Rigid foam board is less toxic than spray foam and still is a foam insulation. It can be cut to fit between studs.
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I am happy with my foam job. Built in 2009. Nice and warm and easy to heat. I put almost all of my plumbing into interior walls except for maybe 15ft of an ABS sewer pipe and a 1" water line, I have no reason to expect I will need to see them again. I have never had anyone smell anything like a chemical smell in my house, I did use a vapor barrier on the inside, call me old fashioned, but that is easy to do on a new build than after the interior finish is done.
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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.
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your videos are all great. would you mind if I post one or two on my spray foam websight?
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Mix it wrong and these guys have destroyed your home.
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I took a course in alternate energy back in the 70's. One thing I remember that has bothered me to this day is what happens to the R value of foams (installed properly) over the years. In other words, how much do they outgas - and "poof" there goes your R value?
Can you direct me to reliable tests that have been done on the long-term effects of R value for the various types of foams? -
If installed correctly fiberglass is very efficient, the problem is you get unskilled installers that don't understand the concept of heat flow. There's a high turnover in the insulation industry. Lets face it there isn't exactly a line of people willing to do this kind of work
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If the incorrect ratio is mixed during the install, then you the homeowner are at a significant risk. (out-gassing of hazardous organics will mess your health up) Make sure the company has a written policy on removing poorly installed spray foam insulation.
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Most of these people being negative about spray foam have never even walked into a construction site- they only went to a YouTube channel and watched a video on the apparent dangers of spray foam! How embarrassing. It's a rare case that the job is done poorly enough where it has to be ripped out. In that regard, never hire anybody without a good reputation, a contractor license, and insurance. Nuff said
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It seems most people commenting here have no understanding of insulation or foam insulation for that matter...
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What a great sales pitch . properly installed glass has been around for years with no stink . new Zealand can be cold and batts have been great . What chemicals Are in fish foam
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can you talk about the risk and the chemical inside spray foam that potentially can get your company in trouble thru law suite if any?
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I had my new home spray foamed in 2006 best decision I have made but you want to have plumbing and electrical where you want it electric bill is easy on pocket book also makes home more structured solid went thru A couple hurricanes in Houston area
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what do you do with the encapsulated wires if you ever needed to do work on those?
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Stone wool insulation is fireproof, cuts with a bread knife and is a handy alternative to either fibreglass or foam
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I have a basement that’s going to be on an independent HVAC system. Wood floors upstairs. How is foam at reducing the noise from a square dance (kids) being held upstairs?
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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.
