In the first two posts of this overly wordy series, we saw a few ways to insulate an attic while avoiding some of the worst problems that can lead to moldy, rotten attics and roofs.
If you recall, the big problem is that moisture from the house rises up through the walls and all the little cracks around light fixtures, hatches, wiring, and the moisture condenses on cool surfaces. Over time, this will lead to mold growth and potentially, rotten roofs.
How do you know if you’ve got a problem? I’ll give you a hint – if you have ice forming under your roof like in this picture, you had better do something before you have to replace your roof!
In the first installment on attic insulation, I discussed why it can be dangerous to add insulation to your attic without air sealing the attic floor first. Moisture can slip through tiny cracks in the attic floor and lead to rotten roofs. Given this information, we walked through the process of finding and sealing all those insidious air leaks in your attic, some easy, some difficult. But finally, after fixing all these problems, you could lay more insulation down on your attic floor, more confident that doing so wouldn’t lead to a humid, moldy attic.
But what if there’s an easier way?
Whether you’re building a new house or retrofitting an older one, you can make life much easier on yourself by using professionally applied spray foam insulation that air seals and insulates in one shot. There are two ways of doing this, each with their own benefits and disadvantages. We’re going to review both methods. One is spraying foam on the attic floor, instead of using loose fill or batt insulation. The other is spraying foam under the roof deck. Continue reading →
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.
The winter snow can be your best friend – at least when it comes to finding where your home is losing energy.
Take a look at this house. Half the roof is covered with snow, while on the other half, the snow is all melted. What’s going on here?
There’s a serious problem with heat leaking out of the living space and into the attic. It takes a lot of energy to melt snow, so undoubtedly, these people are spending lots more on their heating bills than they should.
The first thing to do is to go up to the attic and check the insulation. Is it missing in this area or is there some other reason why the heat is leaking out? Maybe there are heating ducts running through the attic and they’re leaking badly. If your ducts are leaking, you’ll often find that the insulation around the ducts has turned black. Once you learn what to look for, it’s pretty easy to find problems. You might also find mold growing on the underside of the roof.
Another big problem that might be happening is there may be a bathroom vent that is blowing into the attic. You never want this because it can rot out your roof! Usually, you’ll find that the roof sheathing is black or discolored. If you see that in your attic, you know you’ve got a big air leak from the house into the attic.
The main thing is this – if you see something strange like this, you know that there’s a problem. Go find it!