In Action: Does Foil Insulation Really Work? A video experiment.

Published on: May 21 2013 by


Ice with reflective insulation after 75 minutes in direct sunlight, 91°F.

I hear the following question a lot: “Does foil insulation really work?” To answer this question I conducted an experiment to find out for myself. What I found is that it does work, and it works very well in fact. I started with two buckets (9 ¼” x 10 ¼” with lids) and two 5lb bags of ice. I completely lined the inside of one bucket and its lid with EcoFoil double bubble reflective insulation, leaving a ½” gap between the insulation and the outside of the bucket. We will call this “Bucket #1”, and the un-lined will be “Bucket #2”. I poured one bag of ice in each bucket and then made a reference mark at the height of the ice. Next I securely attached the lids and placed them outdoors in direct sunlight. The experiment began at 2:00pm CST and the ambient air temperature was 91 degrees Fahrenheit.

After 30 minutes I braved the heat to record my observations. In bucket #2 I found that the ice was showing some signs of melting and the level had dropped by about 1” from the mark. The benefits of reflective insulation in Bucket #1 were obvious because it had no visible signs of melting and the ice remained at the reference mark.


Ice with out insulation after 75 minutes in direct sunlight, 91°F.

After 1 hour and 15 minutes I returned to the buckets and found that there was very significant melting in bucket #2. The individual pieces of ice were noticeably smaller and transparent, there was a moderate amount of water, and the level had dropped 2 ½” below the reference mark. Bucket #1, lined with bubble insulation, showed minimal signs of melting, the pieces of ice were white and had a frosty appearance, and the level had dropped only ½” The most significant and surprising observation was that the outside of the bucket with reflective insulation was actually warm and dry while bucket #2 was cold and covered in condensation. This is an example of how installing bubble insulation in a pole barn can prevent condensation.

After making my observations I left the ice in the containers overnight to see what I would find when I returned the next morning. I was surprised to find that bucket #1 still had an 8 ¾” x 2 ½” block of ice. In bucket #2 I found that all of the ice had melted completely.

“Does foil insulation work?” The answer is YES! The reflective insulation kept the ice from heating up under the sun’s powerful rays and high ambient temperature of the surrounding air. The un-insulated bucket allowed all of the radiant heat in and therefore the ice melted at a much higher rate.
Your attic is like that un-insulated bucket. The hot sun beats down on it all day causing the roofing materials and insulation to absorb, retain, and emit radiant heat long after the sun has gone down. You can prevent this by installing a radiant barrier which reflects 97% of radiant heat back to its source. This experiment clearly shows how effective reflective insulation and radiant barriers are at keeping heat out of your home. Installing radiant barrier products in your home, pole building, or workshop will keep them cool and increase their energy efficiency.

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