pur vs. pir | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

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Paul Diaz de Rivera Posted: May 14, 2008 08:45 PM	pur vs. pir Hi Mason, Which do you think performs better, PUR or the PIR? We have been using the PUR for quite some time now and one of my client keeps on insisting that we use PIR because it has better properties. Please give some links to where I can find a good head to head comparison. Thanks, foam75
mason Posted: May 14, 2008 09:09 PM	Not familiar with the terms pur and pir.
Paul Diaz de Rivera Posted: May 15, 2008 01:51 AM	Hi Mason, PUR and PIR stands for Polyurethane and Polyisocyanurate respectively. Thanks again, f0am 75
mason Posted: May 15, 2008 09:25 AM	OK, those are fairly dated terms. I have not seen them used in more than 20 years. You don't see much polyurethane foam board stock anymore, it is most polyisocyanurate (known commmonly as polyiso). Polyurethane foam typically is slightly more flexible and less friable than polyiso board. Compressive strength per density are very similar. For example a 2 lb polyurethane and polyiso board will average around 20 psi compressive strength. R values are pretty similar as well around 6.0 per inch on average. Polyiso foam can achieve better smoke developed ratings than polyurethane foam. Typically a polyurethane foam can achieve less than 25 flame spread and a smoke developed rating around 150 to 350. While polyiso foam can achieve less than 25 flame spread and smoked developed rating less than 50. Polyiso boards are usually manufactured as a board with facers of various types. While polyurethane foam is typically poured or sprayed in place. So most polyurethane foam applications will tend to reduce air infiltration better and provide better moisture control that using a board type insulation. I believe a great wall assembly is to use polyiso sheathing on the outside of building, then spray foam to the inside of the wall cavity. In this way, you eliminated a lot of thermal bridging with the polyiso board while eliminating a lot of unwanted air infiltration with the sprayfoam. Hope this helps. Hope this helps.

Author

Comments

Paul Diaz de Rivera

Posted: May 14, 2008 08:45 PM

pur vs. pir

Hi Mason,
Which do you think performs better, PUR or the PIR?
We have been using the PUR for quite some time now and one of my client keeps on insisting that we use PIR because it has better properties.
Please give some links to where I can find a good head to head comparison.
Thanks,
foam75

mason

Posted: May 14, 2008 09:09 PM

Not familiar with the terms pur and pir.

Paul Diaz de Rivera

Posted: May 15, 2008 01:51 AM

Hi Mason,
PUR and PIR stands for Polyurethane and Polyisocyanurate respectively.

Thanks again,
f0am 75

mason

Posted: May 15, 2008 09:25 AM

OK, those are fairly dated terms. I have not seen them used in more than 20 years. You don't see much polyurethane foam board stock anymore, it is most polyisocyanurate (known commmonly as polyiso).

Polyurethane foam typically is slightly more flexible and less friable than polyiso board. Compressive strength per density are very similar. For example a 2 lb polyurethane and polyiso board will average around 20 psi compressive strength. R values are pretty similar as well around 6.0 per inch on average.

Polyiso foam can achieve better smoke developed ratings than polyurethane foam. Typically a polyurethane foam can achieve less than 25 flame spread and a smoke developed rating around 150 to 350. While polyiso foam can achieve less than 25 flame spread and smoked developed rating less than 50.

Polyiso boards are usually manufactured as a board with facers of various types. While polyurethane foam is typically poured or sprayed in place. So most polyurethane foam applications will tend to reduce air infiltration better and provide better moisture control that using a board type insulation.

I believe a great wall assembly is to use polyiso sheathing on the outside of building, then spray foam to the inside of the wall cavity. In this way, you eliminated a lot of thermal bridging with the polyiso board while eliminating a lot of unwanted air infiltration with the sprayfoam.

Hope this helps.

Hope this helps.

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