Real world insulation values & cost difference
Qschultz
| Posted in Energy Efficiency and Durability on
Was watching Home Performance’s latest video on YouTube with Spray Jones & they mentioned that Europe uses real world cases to determine U values. I made this chart based on pricing I’m able to get in the US. Does this seam fairly accurate? I used most of my data points from the article at the bottom of the image I attached
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Note that the rest of the world uses metric R-values.
Like DC said, you need to multiply your R-value per inch by 5.678 to get it to US units of R-values. Also, why is polyiso not on your list? And, in what world does fiberglass have a lower R-value than cellulose? They must be assuming a poorly installed Kraft paper batt. That is being way too harsh on fiberglass, you could have a poor quality installation on any of these materials.
Loose-blown fiberglass is less than R-3/in; loose-blown cellulose is around R-3.8/in.
Fiberglass batts are usually around R-3.2/in, though higher-R batts are available in some thicknesses, and normal for 5.5" walls. Dense-packed cellulose is around R-3.6/in.
My wild guess is that field mixed spray foam applied under variable conditions by cowboys does not really have 64% higher R value than foam made under ideal conditions in a factory.
“Real world R values” sound like someone is putting a thumb on the scale in some way to sell a product when you lost in the laboratory. Not uncommon in the spray foam sales game when one must sell the most expensive, riskiest least green product on the market since asbestos was removed. Just guessing the other products were install in wall with no air barrier.
The price for spray foam will vary widely base on the size of the project and travel distance.
One must admire how the spray foam marketing team they have managed to convince so many that it is the perfect product and worth the perineum price they demand.
Walta
I don't think those numbers are accurate at all. Converted R values for spray foam end up putting it up over R6.5 per inch, which I think is overly optimistic. I'd use R6 per inch. The numbers for fiberglass appear to assume low-density material too, rougly equivalent to R11 batts for 2x4 walls. You can get fiberglass batts in 3.5" thickness ranging from R11 (low density), R13 (the current standard), up to R15 (high density). The chart you posted makes no distinction at all about that.
Also, what is "real world" for R values? Whole-wall values using some specified framing fraction? If that was the case, that information should be specified and I don't see it mentioned on the chart.
Construction tends to build one-off houses, unless you're a production builder. That means EVERY HOME is essentially a prototype. There is no "typical". What you want in this case, to be accurate, is an R value for a MATERIAL determined under controlled, standardized, conditions in a laboratory, then information how to convert that to a "real world" value for YOUR specific building assembly. That's what we do in these forums all the time: take published R values for an insulating material, then work out how it will work in our SPECIFIC assembly, using OUR framing fractions, and allowing for a mix of cavity and continuous insulation R values. You end up more accurate this way.
I don't like the idea of a published table of "real world" R vales, especially when the test conditions aren't even defined. I would not rely on that table for any of my own projects.
Bill