I looked everywhere on Google, and all I can find is the R-value of insulated garage doors (which I didn't even know existed!). What is the R-value of a traditional garage door, made of a simple sheet of steel?
It would be roughly the same as sheet steel, very poor. Glass, single pane is .9 aluminum siding is .61 with no insulation. Plain steel is little more than a windbreak. You can glue on foam board though.
This shows steel siding
Our garage door is double-wall with Styrofoam between, but I don't recall what the claimed R-value is. I don't think I've seen uninsulated garage doors for a long time.
Perce
Easy to find them on Google (I found them while trying to find what mine was), on sites for manufacturers trying to sell you them, they range from 6 to 18.
I've seen plastic garage doors on new houses, but never examined how thick they are. I assumed they were just cheaper than steel ones. I thought I was unusual in having a heated garage, so nobody bothered insulating them. My house was built in 1979, as was my next door neighbour's. Both have non-insulated garage doors. I guess you live in a newer house.
Do they also build garages with cavity walls now? Mine is just single brick (or it was until I modified it), and my neighbour's is 1 inch thick concrete panels!
I've removed it and built a brick wall with a double glazed window, and am installing polystyrene sheet insulation before wood cladding inside. No, the car doesn't live in there :-)
I think the R value of my old steel Stanley garage door is about -1.
Impossible. That's like having a resistor of -1 ohms. That would be a battery. Or in the case of a garage door, it's sucking heat out of the garage - what you've got there is a fridge that uses no electricity. Patent it immediately!
My bilevel home with built in 2 car garage was built in 1988. It came with thin, uninsulated wood garage doors. Each door panel was less than 1/4 inch thick. I paid extra to have the garage walls insulated, otherwise the builder would have only insulated the ceiling, which doubles as the bedroom floor.
I replaced the doors with r19 metal/foam sandwich units with double pain windows. It makes a significant positive difference during both heating and cooling seasons.
Steve
Check the websites of some of the major garage door manufactures (e.g., Clopay) or a local garage door dealer/installer. If you call them, they could probably tell you.
Clopay do make the old non-insulated doors (first company I've seen that does), but they don't quote R for them (maybe it would be embarrassing, and not important to someone not buying an insulated door anyway), they just quote R for the insulated ones: "Insulated door R-values from 6.3 to 18.4."
Mind you, it would be a good selling point for their insulated doors if they quoted a heat loss of 1000 times less than a steel door.
On 04/04/2016 8:14 AM, Mr Macaw wrote: ...
Well there are still fully-detached garages for which it really doesn't matter...have three here on the farm place. The double car garage uses the lightweight fiberglass from Raynor I think; the old truck garage that serves as a shop now has wood.
My garage is attached ot the house, but I don't see the need for an insulated door as I don't use the garage for anything but to put the cars in. The walls around the garage that meet the house are insulated.
Well, the advantage there would depend entirely on the details of the construction but it would in many traditional constructions still be of benefit by reducing the loss on the various dividing wall(s), floor/ceilings, etc. as often the amount of insulation is far less than optimum. Of course, the severity of the climate matters as well as far as what would be a payback period...
You'd be better spending that time and effort insulating the wall between the house and the garage more.
On 04/04/2016 9:36 AM, Mr Macaw wrote: ...
Again, that'd depend on the details of the construction...
I assume you mean if it's difficult to insulate the house wall?
Of course...what I said in the beginning.
Insulating the garage side of the wall between the two should be easy enough surely? And would have far more effect than letting the heat into the garage then trying to insulate that.
Take it or leave it; I'm not inclined to argue the point.
What you mean to say is you have no basis for your opinion.
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