Air Leaks in Home
DEAR TIM: Now that Old Man Winter is here, he's constantly reminding me on windy nights that I've got window air leaks as well as other drafts. Can some of these be remedied now in cold weather, or do I have to wait until spring? Where should I start to look for air leaks? I know to start to see if my door leaks air. What mistakes could I make? What advice do you have in case I'm building a new home? How can you minimize air leaks in new construction? Dawn P., Asheville, NC
DEAR DAWN: I have distinct memories of my childhood home, its air leaks, and the condensation that poured down the single-pane metal casement windows. When one stops to think how many old homes there are in this great nation of ours and you add up the total energy loss, it's got to be astounding.
The good news is you can attend to many of the air leaks in your home, even on the coldest days of the year. You may be a little uncomfortable as you work, but you can have lots of success.
The first place to start looking you're already aware of: doors and windows. These two places can account for a significant amount of air leakage. Be sure the weatherstripping is in good shape and contacting the doors and windows. I have a high-quality exterior French door in my home, but it has a horrible air leak unless the door has the dead bolt lock turned.
If you have wood trim around doors and windows, air could be entering there. It's common for the builder or remodeler to do a poor job of installing insulation between the door/window and the rough opening. Believe it or not, I've seen many doors and windows with no insulation around them. It may pay to carefully remove the wood trim to check to see if the narrow cavity is insulated.
If it's not, you can insulate around windows and doors with expanding foam. If you use this product, be absolutely sure you use one that's made for doors and windows. If you use the wrong one, the foam can expand too much and cause the window or door not to open and close properly.
You can carefully stuff strands of fiberglass insulation around windows and doors. It should not be packed too tightly.
Electrical outlets on exterior walls can be sources of air leaks. In the winter, you can stop some of the air by removing the cover plate. Take a wet-dry vacuum and carefully clean any dust from sides of the box and the plaster and drywall around the box. Usually there is a gap between the electrical box and the wall covering material. Caulk this gap.
Air leaks can happen through electrical boxes, but these can't be sealed easily after a house is built. The entry hole where the electric cable enters the box can be sealed before the house is insulated and the drywall is up, but to do it afterwards is highly problematic.
If you have access up into your attic, go there with a good flashlight. If you're lucky enough to have fiberglass insulation up there, it can tell you where air leaks are. When you see black or dirty insulation, it's acting like an air filter in your furnace. Air is passing through the insulation and dirt is being captured by the fiberglass. Trace the source of the air leak and seal it.
Be sure to turn off any lights in the attic and look for light leaks through the insulation. These light leaks are almost always air leak locations. Be careful around recessed lighting. Older recessed lights are not allowed to be in direct contact with insulation. You have to construct special housings that create an air space around the entire fixture before you insulate around it. Check with your fire prevention officer if in doubt about how to do this.
The building code in most places requires an air gap between chimneys and any wood framing. This gap can be a huge source of air leakage. You can stuff this gap up in the attic with fiberglass batts to stop air from pouring down into your home.
Inspect your basement for air leaks where the wood framing is in contact with the foundation. Air leaks here can be sealed with caulk from the interior during winter months.
When building a new home, air infiltration can be minimized with a comprehensive system and different products. It's not a matter of just using a large air barrier on a roll and wrapping your home like a giant Christmas gift.
You need to think of your house as a boat. Imagine that the air around your house was water and how might it leak into your home. Every crack in the sheathing needs to be taped, the contact between the foundation and the sill plate needs a gasket, the flanges of doors and windows need to be taped to the sheathing or air barrier wrap, the contact points of wall plates and flooring need to be caulked, every hole in a top plate that leads to the attic needs to be sealed, etc.
Sealing a new house is all about attention to detail.