Why Attic Insulation is a Big Deal

A properly insulated attic is supposed to have about R-40 insulation everywhere. This means that the insulation reduces heat loss by a factor of 40 – pretty simple eh? That also means, R-20 roughly equals twice the heat loss as R-40. R-10 is four times the heat loss and so on.

So what’s the R-value of an area of ceiling with no insulation? As it turns out, bare sheetrock on the ceiling has an R-value of about R-1. This means that every square foot of uninsulated ceiling loses about forty times as much energy as a square foot of properly insulated ceiling! 

Put another way, if you have one square foot of uninsulated ceiling, it’s losing as much energy as forty square feet of normally insulated ceiling. So what happens when you have a hundred square feet that are uninsulated, like in this photo? Well, the energy loss from this section of attic are about what the energy loss of a 4,000 SF attic would be!

The take home message is – details matter! Every square inch of your attic should be fully insulated. And if you’re an electrician, take the time to put insulation back carefully after you’re done running wires in the attic. If you don’t you’re basically robbing your customers.