Polyurethane Foam Insulation: An Alternative with Big Benefits

Freda Parker • Published • Polyurethane Foam

No stranger

“Polyurethane foam is no stranger to us,” said Monolithic’s President David B. South in a recent discussion of home insulation at MDI headquarters in Italy, Texas. "After all, it’s a major component of the Monolithic Dome building process, he continued.

“But I’m still continually surprised by how little the construction industry and the average American homeowner know about this wonderful product.”

David believes that this information gap is, in large part, due to years of clever advertising and promoting by manufacturers of fiberglass insulation.

“Many people don’t even know that there are other insulating products besides fiberglass – one of which is polyurethane foam,” he said. “But when people understand how insulation works, selling them on the idea of using polyurethane becomes a lot easier.”

How it works

David explained that heat always travels from warm to cool. For example, in cold weather we heat our homes, but that supplied heat continually struggles to get out of the warm room and into cooler space, such as the unheated attic, the attached garage, or the outdoors. It escapes via any opening, regardless of size – a window or door, an electrical outlet or plumbing fixture, even a small nail hole.

In hot weather, the reverse happens; outdoor heat, using the same escape route, strives to penetrate the cooler interior of our homes. Ideally, by insulating a structure, we prevent or significantly diminish this heat transfer process.

“But here’s one problem,” David said. “Insulation is rated with a R-value. The R-value is supposed to indicate that material’s ability to resist heat flow. Much of the literature, including information published by the DOE (Department of Energy) says, ‘The higher the R-value, the greater the insulating effectiveness.’ What’s usually not explained is that R-values are determined in a laboratory, rather than a real-world environment, and how insulation works – its effectiveness – in reality can be very different from how it tests in a lab.”

Other problems

David cited other problems that can mitigate R-value. For instance, a structure usually loses only about 20% of its heat through a conductive, horizontal process. In other words, 20% of the heat escapes by penetrating the outside wall. But that same structure can lose 80% to 90% of its heat through convection, or wind blowing through those walls.

“Then too, heat can be very sneaky,” David said. "It can work itself into wood or metal and actually leave a structure by sneaking around the insulation, through studs and joists.

“Sprayed polyurethane foam or SPF Insulation combats all these heat transfer processes – usually more effectively than other forms of insulation. It has many big “benefits.”":/topics/benefits

Information on various websites maintained by our Department of Energy as well as the SPF industry support David’s views, and some list the benefits of SPF:

  • Application process creates a seamless, water-proof, durable building envelope
  • Eliminates drafts by completely filling seams, crevices and cracks
  • Reduces energy use
  • Provides high R-values
  • Resists water, mildew and fungus
  • Adds structural strength
  • Provides stability – does not shrink or settle
  • Reduces noise

Automatic benefits with a Monolithic Dome

“We automatically get all those benefits when we build Monolithic Domes,” David said. "What most people, even some builders, don’t realize is that SPF can be used with conventional, brick-and-stick construction.

“Experience has taught me that 1.8 to 2 pound density of polyurethane foam sprayed to a thickness of 1 1/4 inch will give the home owner 99% of the insulation that we can expect from the walls of a house. Properly applied, the 1 1/4” replaces the structure’s exterior sheathing and plywood corner bracing. These items are not to be taken lightly as their installation is costly.

“The best insulated brick house you can buy is one where the brick is laid a half inch away from the wood studs with no sheathing,” David said. "You then spray polyurethane two inches thick onto the back side of the brick. The reason that I specify two inches rather than the inch and a quarter is that I want a little more grip on the brick and studs. Polyurethane sprayed in that manner ties the brick to the studs better than any brick ties you can nail to the studs.

“So, the wall literally becomes one piece,” David concluded. “The brick – for the first time, because of the polyurethane – actually becomes its own total weather service. Now that’s a big benefit!”

Editor’s Note: For detailed information on polyurethane foam, please review Urethane Foam: Magic Material and the Best Kept Insulation Secret by David B. South.