Re: adding more insulation…. There are diminishing returns when adding more R-value.
This article a good information source
For lighting, I’ve used Costco’s led shop lights. Whatever was cheap at the time.
From a theoretical academic standpoint he uses just one equation for a side wall to base all his economic conclusions, but not one word about the temperature difference expectations across the various insulation thicknesses, [nor the fact that heat loss is mostly vertical, nor the effects of direct sunlight on a metal garage door.]
Seems to me that’s what really matters—if its 95 outside and you want to be 75 inside, then that 20 degrees has to come from either thick insulation or running the AC, which costs more?
Same with heating in the winter, if its 20 outside and you want your wife to be happy, then you need to make up the 55 degree difference, either with extra insulation or running the heater.
I will tell you what else matters. If that temperature differential between periods of time is close enough and substantial, the plastic containers of liquids that you store high will eject liquids, even unopened.
Not fun with brake fluid.
Yes One thing leads to another—now i have a dozen plastic bins to put on the shelves to hold the cans of unopened liquids prone to self destruct and leak. Learned that the hard way too. 
Kennybobby is on point about insulation vs AC. I sized my mini-split to what I could best guess as far as the non-insulated doors and highest indoor temps reached (120F+). If I can find an old temp log, I’ll POST it.
After talking to the AC guys - they were at first thinking 1.5 Ton. We went for a 2 ton unit.
The thing is a variable speed compressor, so it will ramp down if max cooling is not needed.
Had a few super hot days and with the thermostat set for 68F. I wanted to see if the thing could hold that temp during peak heat time. It almost could do it. Inside temp just went up a few degrees. This would give me a good idea of what temp settings would be most beneficial Temp vs run time wise.
Also turns out I didn’t have the settings optimized. RTFM!, so maybe it might have done a bit better. But don’t think I was off by much.
With the new doors, I haven’t had a super hot day for testing. But best guessing, I think the max inside temp with the AC off would end up in the mid to high 80s - maybe low 90s when it’s really cooking outside.
The AC should have no problems keeping up with that. No matter where I set it.
Now as far as energy vs $$. You can buy a heck of a lot of KWH of angry pixies for what a new set of doors costs. Payout will not be in my lifetime (old fart here).
But I needed new doors and openers - the old doors were getting way cranky. This happened not long after I got the new AC installed.
So I felt it was worth the extra bucks to get the best I could reasonable afford.
I’m glad I did. The quality is way nicer than the single ply doors and the added quiet operation and exterior noise reduction is much appreciated.
I’d make the same choice without reservation if given the same conditions.
I’m looking forward to not having stuff in the garage die premature deaths do to super high temps (including me!).
All the Best,
Jeff
It’s funny how often you hear folks talking about insulation…
” i put R-30 in the attic, but i wish i had only put in R-16”
or
“i sure miss paying a higher bill for my utilities”
Haha, so right. I actually can’t think of an example of someone saying they installed too much insulation. Jeff’s approach, using data, is a great way to not overspend.
I used R-Matte-Plus R5 3/4” thick rigid foam insulation to insulate my single wall metal double garage door. The door faces about 335 degrees, so gets hot in summer in Alabama. I cut the foam to just fit in between the supports on each horizontal panel, then taped small scrap pieces to the inside of the door panels to create an air space between the door and the insulation panel. Tyvek tape worked very well to attach the panels & seal most of the gaps. Light enough that I didn’t need to adjust the door springs and relatively inexpensive. Very noticeable reduction in temperature in summer, which was my goal. The real payoff was a surprise - the garage now stays significantly warmer in winter!
If you want high CRI lighting Waveform Lighting has some of the better off the shelf options at the moment. Here are the shop lights.
it may never pay for itself, if that is what ‘worth it’ means, and depending on what you would do for energy either way
i doubt garage temps are going to affect house temps much, so if that is what you are looking it, probably not worth it
if you would spend money on AC or heat for the garage itself, then maybe - depends on how often you turn that extra AC or heat on and for how long
otherwise ’ worth it ’, is just an opinion
wle
I do believe that extra insulation in any part of a garage that is attached to a heated or cooled habitable space will affect the rate of heat gain or loss of the habitable space. How one measures the worth of that has many variables, not just the actual dollars that may be saved on heating or cooling the habitable space.
We built our home in 1985 and it has the typical attached 2 car garage. Not so typical for its time are the 2x6 wall framing (instead of 2x4) and blown in place cellulose insulation. The garage walls were insulated and the ceiling was drywalled like the house and R36 insulation in both the garage and house ceilings/attic space. The steel overhead door was only a steel panel when installed. I fitted the panels with foam insulation panels cut to fit. That helped slow the cooling off and the heating up some. But, in winter for example one could feel the cold radiating off the steel panels parts that were folded over to the inside.
The garage is my workshop and a stand-alone 2 car garage was built later to park vehicles in.
So we are now into cold weather so let’s look at what I have noticed so far. The garage was never as cold as the exterior temperatures in winter. If I did not heat the garage it was still warmer than the outside temperatures, though it could get quite chilly. Heat has been via wood stove with a kerosene heater used when it was not so cold outside; spring, fall.
With the new R18.8 garage door I have yet to see the temperature in the garage drop below 55 F. That is with night temperatures frequently in the 25 F to 28 F range. I can get that temperature up into the high 60’s almost too easily. I have to relearn how big a fire to make in the wood stove. I have grossly overheated several times. I am learning. I think I might be able to heat the garage/workshop with a small heat pump instead. I have an excess of solar electric energy from the changes made to more efficient appliances heating and cooling for the home, as well as led’s instead of incandescents. Our actual KWh used is now less than it was when the house was built. And now it is our power, not the power company’s.
The garage with the new door does not cool off as fast. It does not get as cold as the outside air.
I believe we all know that insulation slows the movement of heat. We should know that heat also always moves from the warm side to the cool side.
Not recognized by many is the fact that heat moves, or transfers, at a greater rate when the differential between the hot side and the cool side is greater. So a warmer garage slows the rate of the house cooling.
So, #1, the new garage door keeps the heat inside the garage better. #2, with the garage being warmer the rate of heat loss from the house is slowed down.
Whether or not I would get a cash payback on the cost of the new door is going to be hard to measure dollarwise in our situation. But I have a workplace with a more stable temperature, I will not have to cut wood, split it, haul it, make and keep a fire going, and then haul and dispose of ashes, etc.
I know that the time, effort and money spent starting a decade ago to replace windows and increase the house insulation has paid off in comfort.
They would not be worth it to me. My garage is not insulated at all.
No inside walls either, just studs.
No ceiling, open attic to roof.
Thanks Don that is an interesting story and makes a lot of sense to me.
i feel like an uninsulated metal garage door is only slightly better than having the door open all the time.