Stamping out heat loss in your home
This will be of interest to homeowners. Let's try to keep this as simple as possible. It has to do with saving money on your heating bill first; perhaps on other utility costs as well, since they're often tied together.
Estimates place the portion of your dollar that goes to heating at somewhere around 50 percent if your home is of medium age; 40 percent if it has been built as well as possible within the last 20 years or so. So if you can make changes in your home that affect parts of that percentage, chances are, those are the changes that you should make.
Without a doubt, sealing up the air leaks is at the top of the list. It does very little good if any good at all to blow insulation into an attic if there are air currents sucking air out of your living space -- we'll start calling that the building envelope shortly -- into the attic. It gets up there because wiring needs holes in those framing members to pass in and out and through. Plumbing vents need holes from bottom to top. Heating flues and/or heating pipe itself needs holes. Chimneys, the same. Once one begins to understand just how many holes there are from where you live to the attic where you don't live, it becomes more understandable why they're such a problem.
Because homes are subject to hot air rising, called a "stack" effect, to wind pressures, to exhaust fan pressures, those holes -- bypasses -- have extra pressure on them to send air that exists within the house to the lower pressures that exist in the attic and outside the home. A two-story on a basement, for example, will have a negative pressure (relative to outside) in the basement, a neutral pressure somewhere on the main floor, and a positive pressure upstairs. This one effect pushes heat at the one place in your house likely to be the leakiest. And that's just one of the driving forces stealing your inside air.
Finding those holes is relatively easy, and pretty inexpensive. Find someone to do a blower door test on the house. Blower doors are fans that mount in your entry door and suck air out of your house. That lets you find where it's coming in the fastest. Those are the leaks. Caulk them. Air seal that attic. Find those missing pieces of sheetrock, those holes that exist, fix them. Then the insulation you put into the attic gives you full value.
In this house I live in, I've had all the old insulation that was in the attic, which was vermiculite (bad stuff -- asbestos), rock wool and cellulose removed by a huge vacuum truck, spray foam applied down to the attic floor -- which air sealed the attic -- and insulation blown in on top of it. This is extreme, both in cost, and in savings. The attic is the first place to direct resources toward. It loses the most heat in most homes.
While the blower door is pulling that negative pressure on the house, it's easy to find other leaks, often around entry doors and in through electrical outlets. More easy fixes. You want to know where it comes in the least? Your windows. That's a statement that can sometimes be disproven, but most often, it's true.
I once had an energy auditor say to me, "It's never the windows!" Well, sometimes it is, but not very often. If, for example, 50 percent of your bill is for heating, then usually somewhere around 10 to 13 percent of that is your windows. Now, if you're determined to replace your windows because of other reasons, that's fine, but if you're doing it because you're throwing several thousand dollars at them that you think will pay you back for doing it, uh uh. Your savings comes back to you at 4 or 5 percent (the savings from new windows) of 10 to 13 percent of 50 percent. Unless you live in a castle I don't know about, those savings -- even at inflated energy costs as time goes by -- never happen.
In the order in which heat is lost through most homes, it's the attic first, the walls second, and you guessed it: windows last. Remember that air infiltration can be the worst offender of all of these, and can affect each of them.
So next it's the walls. Whoever does the blower door test will have suggestions about what to do with the walls.
One huge loss of energy happens where the house joins the concrete basement wall. Again, those leaks at that junction are easy to spot with a blower door test, and relatively inexpensive to repair (compared to new windows, for example, which won't fix this spot to begin with).
One cautionary bit of advice: fixing an air leak in one spot puts more pressure on any other spot, so it's important to not just repair some of them.
I'm in a two-week school on building analysis, so you can expect to hear more from me about all this.