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The Polyurethane Foam Book

Chapter Two: Spray-in-place Polyurethane Foam

by David B. South
Illustrations by Merrisa Carter

Spray-in-place polyurethane foam is at least twice as insulating as the next best insulation. It also completely seals the structure. When sprayed in place, urethane foam expands thirty times, then sets in about three seconds and fills every nook and cranny. It is virtually waterproof and forms its own vapor barrier. (Relatively low perm rating at room temperatures.) It is also structurally strong.

The two components that make up urethane are kept in separate drums. When applied, they are pumped from the drums, through a proportioning unit on a one-to-one ratio. The chemicals are heated and kept hot through the system at a temperature of about 140 degrees F. The materials mix at the nozzle and are then sprayed onto the selected surface.

Spray-in-place urethane foam has an almost infinite lifespan. The Corp of Engineers has shown "no measurable degradation in the urethane foam properly placed and protected." This includes foam buried in the earth. I tell people that there is nothing you can hold in your hand that will hurt urethane foam but a match --- and sunshine. Only high-powered solvents will break down urethane foam and then only poorly.

But sunshine will break down the cross linking of the molecules and the dust particles will blow away. If a urethane roof is left exposed to the sun, it will disappear at a rate of about 1/4 inch per year. The cells self-destruct under sunshine.

Starting a new venture -- Spraying urethane foam

Within three months of moving back to Idaho from Chicago, I convinced a local company -- MONROC, a large, ready-mix concrete company -- that it needed a plastics division that I should head. As part of MONROC, I bought an early model FF Gusmer Foam Machine. I mounted it in a van, on the back of a two-ton truck and used a generator and air compressor to drive the foam machine. I hired a two-man crew to help and proceeded to GO FOR IT.

Case study

Note: At different points in this book, I use case histories to illustrate a point; much can be learned from them.

In 1970, as one of my first major foam projects, I sold a foam roof on a 20,000 square-foot, food processing plant. The plant was in a metal building, that had problems with condensation. It continually dripped into the process area and threatened contamination. So, like a White Knight, I stepped into the breach and told the owner that I could spray an inch of urethane foam on his roof and eliminate the condensation. He agreed to the price, and I had my first "big" roof project.

At that time, one aluminum asphalt coating company was really pushing its product for use over spray-in-place urethane foam. It was a big company with a great track record for coatings over asphalt roofs, and its sales pitch seemed reasonable. So I dutifully sprayed one inch of urethane foam on the roof and immediately coated over the foam with the asphalt aluminum coating.

This asphalt aluminum coating is still being sold today to cover metal roofs, but you will not find anybody selling it for use over a foam roof. I learned why -- the hard way.

About five months after I applied the roof, I received a call from the owner. He said that the roof had worked wonderfully -- there was no more condensation. The inspectors were happy, he was happy, everybody was happy. But, instead of having that nice silver colored roof, he now had a kind of funny looking, orange roof. Why?

I could not imagine what he was talking about so I drove out to see for myself. From about a mile away, I could see exposed foam over the entire roof. Upon closer inspection, I found that 99.9 percent of it was gone. I learned a very valuable lesson.

Urethane foam is the world's best insulation. But whatever you coat it with has to be able to take the heat. The sun bearing down on coated foam will literally fry most coatings. The problem we had with the asphalt base coating was simple -- the oils boiled out of it. It became a powder and blew away.

Many miles of roof were sprayed with asphalt coatings. I see some neophytes today still trying it. The lesson is very simple: whatever goes on over urethane foam has to be able to take the heat. If it can't take the heat, you better leave it in the bucket.

Within three months of moving back to Idaho from Chicago I convinced a local company -- MONROC, a large ready mix concrete company -- they needed a plastics division and that I should head it up. As part of MONROC, I bought an early model FF Gusmer Foam Machine. I mounted it in a van on the back of a two-ton truck. To drive the foam machine I had a generator and air compressor. I hired a two man crew to help and proceeded to GO FOR IT.

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