Polyiso VS Blueboad (XPS) Test

[Typhoon]

Good day all.

Here is the test I promised , took a little longer then I expected as I did the test a few times to make sure my data was correct.

I wanted to do this test just to confirm to myself that the Internet information about Polyiso (Polyisocyanurate) losing its R value as it gets colder , as seen in this test.

https://buildingscience.com/document...endent-r-value

This is not a scientific test so don't take it as the holly grail , this is just me doing a little test for my own and who ever would like to read it, information .

Basically what I did was take two outdoor RF temperature sensors , the same things you can buy at any hardware store, encapsulate them in one inch of Polyiso and one inch of XPS or blueboard and through them in a deep freeze and log every 5 minutes the temperature changes. They were the only things in the freezer and spaced equally from the walls .

I removed the foil from the middle layers of the Polyiso so not to get any thermal bridging through the foil but left it on the outside .


And of course the results.

As you can see these two insulation materials are very similar in there performance with neither one being a clear winner . The Polyiso gives it up a bit to the XPS right at the 50 degree mark , similar to other test I have found on the net , but the warm up test made me scratch my head a bit . No clear winner on warm up . As you can see I stopped measuring on the warm up past refrigeration temperatures .

So my recommendation still stands , One inch of XPS on the cold side followed up by Polyiso for the remainder of the insulation lay up schedule inside a box.

Please have a look at my results and chime in.

Regards John.

[SV THIRD DAY]

Great info John...I always like seeing confirming data. Makes me think I'm less crazy.

The mistake I would warn against is using all Blue Board XPS, bases on the temp data. If you looked at the 2" or 3" data you would not see the extream lower temps and thus the increases R value in poly over the low temp degrade becomes more important.

[Typhoon]

Hey Rich .

I was surprised how well the blue board did . Some folks don't have access to Polyiso . I may do a multi layer test measuring temperatures between the layers at deep freeze temperatures to actually see what the insulation is exposed to. Maybe two inches before the polyiso would yield even better results .

Regards John

[SV THIRD DAY]

That's true, in Mexico for example there is only Blue Board or Pink Board on the shelves and I've never seen Polyiso for sale.

[Typhoon]

Yes , people at the show where split in the availability of the Polyiso in there areas,

Did you get to your destination Rich ?

Regards John.

[rbk]

The problem with most foil faced polyiso is the stated R values also reflect the thermal reflective properties of the foil face (bit of good marketing)in order to get those beneficial gains you need to leave a 1 inch air space on the warm side, layering it tight you lose all benefits of the foil. The ongoing off gassing of he blowing agent pentane (contributes to the lose in R value at colder temps) is something to consider when keeping near food (more so exposed fruits and veggies). A good alternative is type 2 eps hs40 at r5/inch highly compressible and performs better the colder it gets. The 5/inch is confirmed by third party testers and is not ‘marketing hype’ the polyiso seems to be. The only draw back is you would want a waterproof liner as hs40 is fairly permeable at 1.5 perms (if I remember correctly). Ideally if wanting to use a ff poly a single exterior layer with a good airspace will reflect most of the heat away, but does not reflect cold back into the ice box.

[Typhoon]

That may explain why the XPS did as well as it did against the Polyiso. It should be 30% better in performance , as rated , but I didn't really see that . If they are calculating the R value with the effect of the foil then really in our application the foil becomes a moot point inside a multilayer insulation installation, ( try saying that a couple of times ) .

Regards John

[rbk]

Ya when dealing with construction insulation the temps involved are more to the extreme. I believe the hs40 start performing better below -15’c then better agin below -25’c. Most of these companies know the general public look at r value and the higher the number must mean better so they tend to sway the numbers in their favour. Personally having built in the north (N of 60’) the only place for ff polyiso is inside the building in cold climates or on the exterior in hot climates. IMO ff polyiso would do exceptionally well deterring heat.

[foufou]

I have read somewhere long ago that polyiso loses R value with time. I know the stuff does absorb moisture. Does any one have confirmation of the loss of R value with age? Thanks for all the research.

[rbk]

Yes to some extent. Off gassing does reduce the R value in polyiso over time but it doesn’t keep going down to zero. Building science Center BSC does a lot of testing of construction products. There’s a lot of technical lingo to wade through but they have a lot of great free info if you’re willing to read 2-3 hundred page tech reports. Another good one is green building advisor but hey do charge a membership fee these days.

[Typhoon]

Originally Posted by foufou

I have read somewhere long ago that polyiso loses R value with time. I know the stuff does absorb moisture. Does any one have confirmation of the loss of R value with age? Thanks for all the research.

This is why we recommend to always seal the cut edges of polyiso with vapour barrier tape . Also any holes in the foil facing should be sealed up as well . This will stop the moisture from attacking your insulation .

Regards John

[SailRedemption]

John,

Any more info on your testing?

At some point before summer we will need to redo our insulation for the 2.5th time. We're thinking, based on reading, is to do two inches of polyiso on the outer foil facing out and 3 inches of blue board on the inside facing the box liner. We'll attempt 6" where we can for freezer side. But we have a large Cool Blue holding plate we have to accommodate for.

Just wanted to see how testing was going.

[SV THIRD DAY]

What we found in our testing was the best scenario was one inch of the blue board and the rest polyiso that gave you enough separation from the extreme cold and then you gained from the increase insulation R-value of the polyiso for the rest.

I'm on the 8th day of standing in the Seattle boat show booth at least I have a demo fridge with cold beer in it that's the only reason I'm surviving.

[Typhoon]

Originally Posted by SailRedemption

John,

Any more info on your testing?

At some point before summer we will need to redo our insulation for the 2.5th time. We're thinking, based on reading, is to do two inches of polyiso on the outer foil facing out and 3 inches of blue board on the inside facing the box liner. We'll attempt 6" where we can for freezer side. But we have a large Cool Blue holding plate we have to accommodate for.

Just wanted to see how testing was going.

Hi Sailredemption .

Presently we are in the middle of testing a MicroPlate setup and the insulation testing has been put aside for another week or so .
From what I have found so far and from the boxes I have built over the years I think you are going the right way with the blueboard backed up on the warm side with the polyiso . The next test will involve a much larger block with an Rvalue of 20 . If this test does not yield a larger gap in performance then I will continue to recommend this technique for box building .
I will post when the testing starts . Usually takes a week to get the results .

Regards John

[SailRedemption]

Originally Posted by SV THIRD DAY

What we found in our testing was the best scenario was one inch of the blue board and the rest polyiso that gave you enough separation from the extreme cold and then you gained from the increase insulation R-value of the polyiso for the rest.

I'm on the 8th day of standing in the Seattle boat show booth at least I have a demo fridge with cold beer in it that's the only reason I'm surviving.

Thanks Rich, that's what we were thinking. Good luck at the boat shows!