Effects and Alternatives


For many years, fibrous glass or fiberglass, has been the standard material for thermal and acoustic insulation in air conditioning systems. As the health hazards of asbestos became more broadly known and the use of it was phased out from the late 60’s to early 80’s, fiberglass became the “default” insulation to be used in almost every phase of construction including air conditioning.

It has proven to be an effective insulating material, but has not been without concerns regarding health and safety. A famous study conducted by Dr. Mearl F. Stanton of the National Cancer Institute between 1969 and 1977, showed that particles of fiberglass were carcinogenic to animals. For reasons not entirely clear, those studies were not continued or pursued to determine the exact short or long term health effects on humans. To this day, there is considerable discussion about this, but there are no definitive studies showing any connection between fiberglass and cancer in humans. Dead Rat

While the U.S. Department of Health and Human Services issued a report in 1994 stating that fiberglass is “reasonably anticipated to be a carcinogen,” they issued a disclaimer that this did not apply to general consumer exposure. The disclaimer did not go on to explain whether a “general consumer” is a different species of human or not, but the inference is that a general consumer has different exposure levels than one working in the industry.

OSHA standards states the following:

“Health Effects There is insufficient evidence that synthetic mineral fibers cause respiratory disease in humans. Results from animal experiments have led to conservative classifications of certain synthetic mineral fibers as possible human carcinogens. Specifically, insulation glass wool, continuous glass filament, rock (stone) wool, and slag wool are not classifiable as to their carcinogenicity to humans.”

It is, however, interesting to note that currently, the largest manufacturers of fiberglass building and insulation materials are the very same companies who were previously the largest manufacturers of asbestos products and who for decades asserted that asbestos posed no health hazards. They have each since filed bankruptcy and restructured to form a special “personal injury trust” to handle the hundreds of thousands of lawsuits resulting in billions of dollars of settlements and judgments.

As noted above, whether fiberglass is “safe” or not is still a question that hasn’t been fully answered. However, there are things we DO know. The only generally agreed upon fact is that fiberglass is an irritant, something that anyone who has worked with or around that pink fiberglass insulation in their attics has personally experienced. Contact with fiberglass can cause skin irritation, as well as irritation to the eyes and upper respiratory system.

The point of this article, however, is not to debate the health implications of fiberglass insulation.

The point is that there is obvious concern amongst consumers, contractors and health professionals as well as air conditioning manufacturers regarding the use of fiberglass. And from our observation, these same people are looking to use other materials than fiberglass to provide insulation.

Since 1995, Machado has been re-insulating fiberglass lined ductwork and air handling units with non-fiberglass insulation, most commonly Astrofoil or Reflectix, reflective bubble wrap insulation products which contain no fibrous insulation.

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Regardless of what is said, fiberglass insulation DOES deteriorate and come apart and get into the air stream. It gets wet and along with years of accumulated dirt and moisture, it will provide an environment ideal for growing mold and other microbial contamination. As we are in the indoor air quality business, it didn’t make sense to replace the insulation with the same that will result in a similar condition in a short number of years down the road.
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There is no way the above examples (which are all too typical of what we encounter when evaluating a system) could be considered healthful. The air that is supplied to occupied spaces passes over this loose, contaminated fiberglass.
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For many years, Astrofoil and Reflectix have been the go-to proven viable alternative for internal fiberglass insulation. It is clean, lightweight, and hey, it looks great!

Astrofoil and Reflectix, the good:

  • Reflective insulation is a foil covered bubble wrap insulation which is lightweight and easy to work with.
  • It is impervious to moisture and water.
  • It will not provide an environment that will grow mold.
  • It is easy to clean later on. (And it takes a LONG time to get dirty!) Sometimes simply wiping it down is sufficient.
  • It is UV resistant. We conducted a test about a decade ago which was not a “white-paper” test, but nonetheless was conducted by a firm to determine the effects of UV light. After the accelerated equivalent of 10 years of exposure, the astrofoil showed no ill effects.
  • It is DURABLE.
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This astrofoil had been installed 11 years prior to this photograph and looks practically new. Any foil reflective insulation will hold up well if properly installed.

  • The acoustic values, while not the same as fiberous, porous insulation, are usually sufficient for normal office situations.
  • It looks great!

There are few downsides to using reflective non-fiberglass liner, but here they are - the not so good:

  • The R-value of the reflective insulation is NOT equivalent to the normal 1” fiberglass. However, what we recommend is to use the existing fiberglass if it is not totally deteriorated or contaminated and cover it with a new layer of Reflectix. Where the existing fiberglass is in such poor condition it is not salvageable, we strip it out and replace it with a new layer of fiberglass covered with Reflectix. This gives far more insulation than astrofoil alone and improves the R-value of the fiberglass in addition to preventing future deterioration of the fiberglass.
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  • Unless it is properly installed, Astrofoil or Reflectix will come loose and tear apart:
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Machado was called in to repair and properly secure astrofoil sloppily installed by another contractor. Apparently, this astrofoil had been installed just a couple of years ago.
  • Astrofoil and Reflectix are much thinner than 1” fiberglass so if the thickness is an important part of the engineering, this must be taken into consideration when installing it. Often cleaning the existing fiberglass liner and covering it with Reflectix will handle this problem.
  • The reverse can be true as well. Sometimes adding a layer of Reflectix over top of existing 1” fiberglass can often make things “too tight” making it impossible to close an access hatch. In this case, the insulation needs to be trimmed so everything fits.

In addition to Astrofoil and Reflectix, there are other alternative insulating materials, some of which we have done some tests on and others we have yet to check out.

These would include Bonded Logic Natural Fiber Duct Liner, which is actually made out of old blue jeans, treated and remanufactured into HVAC duct liner and is becoming quite the rage in sustainable and environmental circles. Stay tuned - we have gotten some samples and are going to be testing it out. If the surface proves to be as rugged as it appears, then this may be able to be installed without the astrofoil on top of it thereby saving money and time.

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Bonded Logic also manufactures wall insulation which is a very popular alternative to fiberglass particularly in sound studios due to its acoustic properties and the fact that it is not made of fiberglass.

To conclude, there are alternatives to fiberglass insulation for air conditioning systems.

Other alternatives:

Armaflex is a closed-cell elastomeric foam material designed specifically for use as a duct liner. We have little experience with Armaflex so cannot judge its longevity or UV resistance. It is a product which is non-toxic and resistant to microbial growth. It is more expensive than fiberglass or Reflectix.

K-flex Duct liner is another closed cell duct liner with similar properties to Armaflex.

There are numerous other products, from man-made fibrous material that is not fiberglass, styrofoam-type insulation, cotton based, treated paper. Some have been short lived, some are difficult to come by or very difficult to work with.

We continue to look into alternatives that are more healthful, more easily accessible, less expensive and as we lead the way, we’ll let you know!

Tom Pula