I am looking at replacing my existing garage doors. I prefer to have insulated doors due to extreme heat in summer and extreme cold in the winter. One of the doors I’m looking at has an R-value of 6 and another has an R-value of 9.5. I know that the 9.5 is better insulated door, but I don’t really know how much better than the 6. Is it really 58% better, based upon the differential in the values? Or does the increasing R-value have a diminishing return on ambient temperature retention?
Anyone know more about this?
ETA: There is a price differential in the doors. The higher R-value door is approximately 17% more expensive.
It should make an approximately 58% difference in what makes it* through the door panels*. What difference it makes overall will depend on how tightly the door seals against the frame and floor and how well insulated the rest of the garage is. If the rest of the garage is uninsulated and leaks like a sieve, then it will hardly make any difference. If the rest of the garage is well insulated such that most of your heat loss/gain is through the door, then obviously adding insulation to the door can make a big difference.
The 58% equation based upon the different R-values is how I should be looking at it, assuming the appropriate insulation elsewhere in the garage?
Granted I’m not running heat or air into the garage, so there’s not a real cost savings from lowering my utililty bills, but for an additional 17% in costs, if I can reduce the amount temperature loss through the closed door by 58% (primarily in the summer and winter) that seems like a good trade. (i.e. makes getting into the cars in the winter time and working in the garage at various times a bit more bearable.)
I suspect that, unless you have very good sealing and weatherstripping (in garage-door terms), heat transfer via air infiltration around the door and between its panels will overwhelm the amount of heat transfer through the door. Consider that even an intermittent gap a millimetre wide under a garage door of typical width might add up to a hole the diameter of your wrist with air flowing freely through. Seal first… then insulate. Low-hanging fruit and all…
What are the dimensions of the door? What type of sealing or weatherstripping do you have?
I have a 3 car garage. One door is a double wide (16’) and the other is a single wide (8’). There is existing weather stripping on the sides of the door facing, and the bottom of each door will also include stripping.
