When purchasing insulation panels of any type the first question should be, “How much R-value do you want or need?”
Just what is R-value?
R-value is a rating used to measure a material’s thermal resistance, better understood as the ability for heat to travel through it. The higher the R-value, the greater the materials insulating effectiveness. This varies, depending on the type of insulating material, its thickness and how dense it is. Simply stated, the harder it is for heat to flow through your walls or roof, the lower your heating and cooling costs.
Most structural insulated panels use various types of foams as insulation, each with its own corresponding R-value. Let’s take a closer look at these different insulation panel foams.
Expanded Polystyrene (EPS)
This is the most common form of foam insulation used in structural insulation panels. We all are familiar with the white foam coffee cups and packaging made up of a thousand tiny beads of foam compressed together. EPS is the most readily available and least expensive foam on the market but it also is one of the lowest in R-value at around 4 per inch, based on the foams density. Because of its low R-value, walls need to be thicker to achieve required insulation values. With a high perm rating, moisture and associated rot and molds can be a real problem. And EPS’s low melting point allows for builders to carve the product with heated cutting tools, but also reduces the product’s resistance to fire.
Extruded Polystyrene (XPS)
Extruded polystyrene foam insulation panels are similar in appearance to EPS insulation panels with the manufacturing process the being the most significant difference. At one time XPS claimed to have a higher R-value than EPS, but with recent environmental changes in materials used for manufacturing, XPS R-values fall slightly below the R-4 of EPS. XPS is stronger than EPS foam, has a lower perm rating and higher melting point which makes it harder to work with but more resistant to fire than EPS. With the availability low, structural insulated panels made with XPS are generally more expensive than EPS SIPs.
Polyurethane (PUR) / Polyisocyanurate (PIR)
Structural insulation panels made with polyurethane and polyisocyanurate are so similar in composition that in the case of manufactured insulation panels, they can be considered the same. Polyurethane panels have the highest insulating R-value of any foam at around 7 per inch. Dense with superior strength and with a much greater R-value per inch, thin walls and roofs are possible while still maintaining an optimum insulation performance. Low perm rates make it highly resistant to moisture and molds. With a high melting point that offers a class-1 fire rating, the foam is easy to work with using standard construction tools. More expensive than the styrene products, polyurethane is a far superior product offering a much greater return for your investment.
RAY-CORE superior insulating structural insulation panels are made with high density closed cell polyurethane foam. Watch for our next post where we will see how structural insulation panel foams compare to other insulation products and methods.
You can learn more now about RAY-CORE’s structural insulated panels SIPs by clicking on the green button on the right of your screen.