Whether retro-fitting a home or choosing insulation when building a new one, spraypolyurethane foam (SPF) insulation is among the best ways to increase energy efficiency andimprove comfort.
What is SPF & How Does it Work?
SPF, a spray-applied cellular plastic, is made by mixing chemicals to create foam. Thosechemicals react very quickly, expanding on contact to create foam that insulates, air seals andprovides a moisture barrier. When properly installed, SPF forms a continuous barrier on walls,around corners and on contoured surfaces. It resists heat transfer very well and is an effectivesolution for reducing unwanted air infiltration through cracks, seams, and joints.
SPF insulation applied by professionals is usually described as either a high- or low-pressurefoam and is available as either open- or closed-cell. Each type has advantages and disadvantagesdepending on the application requirements. The comparison chart below can be helpful inexplaining or understanding which type of SPF insulation is best suited to a specific application.
Closed-Cell vs Open-Cell Foam: A Comparison
| Closed-Cell | Open-Cell |
|---|---|
| Higher R-value (greater than 6.0 per inch) | R-value (approximately 3.5 per inch) |
| High moisture barrier (lower moisture permeability) | Lower moisture barrier (higher moisture permeability) |
| Air barrier | Air barrier at full wall thickness |
| Higher strength and rigidity | Lower strength and rigidity |
| Resists water | Not suggested for applications in direct contact with water |
| Medium density (1.75 — 2.25 lbs./ft3) | Lower density (0.4 — 1.2 lbs./ft3) |
| Absorbs sound | Absorbs sound very well |
More about the Chemicals and How They React
Two liquids combine during a chemical reaction to form SPF. The two liquids come in differentdrums or containers, and professionals generally refer to one container as the “A” side and theother container as the “B” side.
The “A” side of a spray polyurethane system is commonly comprised of methylene diphenyldiisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI). The “B” side istypically a blend of polyols, catalysts, blowing agent, flame retardant and surfactant. Note that the “A” and “B” sides may be reversed outside the U.S.
The polyols are part of the chemical reaction to make foam. The remaining ingredients in the“B” side serve different purposes to help control the creation of the foam bubbles (the “cells”) inan optimal way, and to provide the various characteristics of the finished foam product (flameretardancy, for example).
After the chemicals are mixed and reacted, the foam hardens very rapidly. The time to completereaction depends on the type of SPF insulation and other variables.
Safety Data Sheets (SDS) are available for both “A” and “B”side chemicals. As a SPF professional,it’s important that you understand the information on safety sheets and are able to share thedetails with your customers.
SPF Installation: Educating the customer
Professionals will want and need to give their customers guidance about the process forinstallation and time when they can reenter their home after an interior, two component foaminsulation application.
Part of that guidance will be explaining that interior, two component foam is applied with theprofessional using specific personal protective equipment (high-pressure foam is installed whileusing a respirator, for example). It is encouraged that professionals explain clearly to customersthat this equipment, coupled with certain work and engineering practices, including ventilation,is used to minimize exposures to the chemicals used to make SPF during the job.
Further, professionals will want to share how homeowners can minimize or eliminate theirexposure to the chemicals used to create spray foam by carefully following guidance about notoccupying the home or space during the installation, job completion and cleanup and for anappropriate period after.
