In browsing various mfg of exterior doors, I don’t seem to see much in the way of R or U value for the door, like the U that is on the sticker for a new window. Does anyone have any info on this, and which mfg offer the best insulating doors?
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ACCA Manual J, Table 4A lists many types of doors, assigning each a U-value.
U-value, as you likely know, can be converted to R-value by dividing the U-value into 1. The lower the U-value, the better the insulation.
Examples:
Metal w/polyurethane core w/storm: 0.17 U-value (R 5.9)
Metal w/polyurethane core, no storm: 0.29 U-value
Solid core wood, w/storm: 0.26 U-value
Solid core wood, no storm: 0.39 U-value
Frame and panel wood: 0.54 U-value
Fiberglass core: 0.60
You are correct if you think you've found a major weakness in the insulation of many homes.
In my own place, I have a steel clad, fiberglass filled door. No matter how you look at it, there's just no way this door is going to perform as well as the 2x4 framed walls.
My place always had quite a draft, and I was convinced that I had a major air leak- I thooght it cane grom the threshold; I was wrong. No amount of sealing the bottom edge of the door made much difference. Only when I addae an inch of foam to the door did the problem mysteriously disappear!
Did it look bad? Not at all. I wrapped the edges of the foam with white duct tape, and covered the exposed face of the door with some carpet.
Nor did the 1" thickness affect the operation og the locks and lever-type doorknob.
If insulated, they should give you an R-value. Most mfgs want to brag about the insulation value when they've gone through the trouble of insulating them. Stanley should have specs listing the R/U values I would think. I've typically found it somewhere. Not sure if they do NFRC testing on doors or not. Probably not required to have the lable on them.