What R value actually does
R value is resistance to heat flow. A non insulated steel door is a single sheet of metal, close to R 0. A polystyrene insulated door is R 6 to R 9. A polyurethane injected steel back door is R 12 to R 18. In a Boise winter the difference between R 0 and R 16 on an attached garage is the difference between a garage at 25 degrees and a garage at 45.
The bonus room problem
Half the two story homes built in Meridian, Kuna and Eagle in the last twenty years have a room over the garage. If the garage door is uninsulated, the floor of that room sits over a space that is nearly outside temperature. The room is cold in winter and hot in summer no matter what the furnace does. An insulated door is the cheapest fix and it is often enough.
Plumbing, the water heater and the opener
Water heaters and the softener are usually in the garage here. A garage that drops below freezing risks a frozen line, and a water heater in a cold garage runs more. The opener runs easier too; a warm garage keeps the lubricant moving and the door lighter to lift.
What it adds to the price
Roughly $300 to $600 on a single door and $500 to $1,000 on a double, compared with the non insulated version of the same style. The insulated door is also quieter and stiffer, which means fewer dents and less rattle. Most Boise homeowners who replace a door on an attached garage choose R 12 or better.
When to skip it
A detached garage or shop you do not heat, a carport style enclosure, or a door you plan to replace again when you remodel. In those cases the money is better spent on a good opener and nylon rollers.
If you are past the easy answers, the techs we refer handle garage door installation in Boise the same day in most cases. For the background on this topic, see ENERGY STAR.
Frequently asked questions
What R value should I get in Boise?
R 12 to R 18 for an attached garage, higher if there is a room above. R 6 to R 9 is a fair middle ground on a budget.
Does an insulated door need bigger springs?
Yes, it is heavier. Springs are sized to the door on every install the techs we refer do.
Will it lower my heating bill?
Somewhat, mostly through the room above the garage and the water heater. The bigger benefit is comfort and protecting the plumbing.
Is polystyrene or polyurethane better?
Polyurethane. It is injected, bonds to the steel, and gives a higher R value in the same thickness.
Can I insulate my existing door instead?
Kits exist and they help a little, but they add weight the springs were not sized for. A tune up and spring check should follow.
Does an insulated door look different?
No. Every style, from carriage to modern flush, comes in insulated versions.
