Over in the “What’s the Weather Like” thread there were some BLFs who had insulated garage doors installed. Though I’d share my experience.
I just had R18 doors installed. Three car garage with a double door and a single door.
I have a temp data logger running in the garage to see what was going on temp wise during a 24 hour period.
The doors get full afternoon and evening sun.
With the old single ply metal doors, the inside temp in the early evening often exceeded the outside air temp.
I picked two days for comparison that had very similar daytime highs.
Take a look at the difference.
The Blue trace is the inside temp with the old single ply metal doors installed.
The Red trace is the inside temp with the R18 doors installed. Along with exterior weather flaps and much better bottom weather stripping.
Heck of a difference!
Over 100F inside with the old doors.
Less than 80F inside with the new doors.
It would do even better if I insulate the non-insulated exterior walls and ceiling.
And I’ve got a 2 ton mini-split in there now too. No more death sweats while working in the garage for me. No more frozen finger in the “winters” in Texas.
One always needs to be careful of alien signals. And Black helicopters…
I need to investigate ways to get insulation behind drywall in the exterior walls. One gets full sun all afternoon and evening.
When the sun gets covered by clouds, it’s amazing how quickly the temp drops in the radiated areas.
All the Best,
Jeff
My Garage Doors are both the 2 1/4” insulated and double sided finished on the inside —the walls and ceiling are all insulated as well —- with the temp outside hitting mid 90s and the inside temp set around 74 the garage will stay around 78-80 degrees ——the crazy part is —this is a house that I call my camp and when I’m not there I set the AC on 78 — when I get there the garage is still 80-81 degrees —— but lookout when you open one of those doors — it’s like a vacuum sucking in the heat and humidity
I find they sound so much smoother going up and down also — they seem to dampen the noise a bit in the garage also
Definitely worth it! Mine is only R-3, but even that makes a huge difference. My garage walls and ceiling are R-19. Which is pathetic for Colorado (the rest of my ceiling is R-90). But I can heat the garage up to a steady 50-60 F when it’s –5F outside using a 220v 4800 watt radiant baseboard. 50-60 F is still a tad chilly. But it’s long-sleeve weather instead of parka-n-ski pants weather.
I have been watching building science evolve since the 70s. Generally more insulation is better. Vapor barriers are where it gets tricky. Depending on your climate it can be on the outside or the inside. Usually on the warmer side. Don’t want rot forming in your walls. The latest code is calling for extremely tight building envelopes. Mechanical ventilation is required to get fresh air in. The book is still out on a lot of this.
I have a small garage, usually i leave doors open in summer to avoid car engines heating air that then leaks into the house.
In winter i will close doors to keep cold air away from house doors and car engines.
They are not insulated.
The garage is too small for me to ever use it as a work space, so I do not need to heat and cool it.
One thing to remember about R values in these doors is that an R12 is not twice as much as an R6.
I found this chart. Not for doors, but at least gives some comparison.
That shows relative amounts of heat reduction.
A single ply metal door has an R value of 0 according to one source I found.
So any insulation will make a big difference.
One of the unexpected benefits is how much quieter it is inside with the doors closed. A pleasant surprise.
I went with the belt type openers instead of the chain. Much quieter too.
I need to add lighting. Any of you have some suggestions as far as shop lights for a garage?
Another thing that really helps is the newer Weather Strips with the rubber that seals against the door —- Plus a good bottom Rubber that’s not all shrunk up several inches on each end— But I would advise if you keep vehicles — anything that makes carbon monoxide — Have a good Sensor located in the garage — you don’t want to wake up dead
The R value of insulation is the Resistance to thermal energy transfer (mainly conduction). It is additive in that 2 layers of R-6 will give you an R-12 rating.
For example with a given amount of heat or thermal intensity such as from the sun hitting a metal garage door skin, if an R-6 layer will provide a 6 degree temperature difference, then an R-12 will have a 12 degree difference for that same heat flux. Same sized door, same sunlight, same amount of time exposed.
It is similar to electrical circuits where the temperature is ~ voltage, the R-value is the resistor, and the heat flux is the current flow. Double the resistor and current is halved, etc.
You can see my cheap lighting solution. I would not recommend it as is.
Cheap as can be, I just wired in new bulb bases off a ground fault outlet, then used cheapo Y sockets to put 4 or more bulbs in every one. They seem stable now, but when I first did it, a few of the Y adapters made a crackling sound in use and looked like they were arcing on the contact points. Dangerous.
If I were to do it again I’d still use bulb bases (cheap upfront, easy replacement), but instead of 4 rows of 3, I would double at least double the number of bases.
LED shop lights would be nicer, but at the time they were a lot more money for same lumens. I also get to try different bulbs or easily upgrade (already went from 60w to 100w equiv and moved 60W to basement).
Very cool! Well, cooler than before for certain. 
