Door and window weatherstripping: types and mistakes

Weatherstripping or caulking?

Both are used to stop air, but not in the same place. ENERGY STAR and Natural Resources Canada (NRCan) make the same distinction: caulking seals what is fixed, weatherstripping seals what moves.

Caulking closes the joint between the frame and the wall. Weatherstripping closes the gap between the opening part and the frame when the door or window is shut. A well-sealed home needs both. Changing the weatherstripping without looking at the caulking often solves only half the problem.

The two jobs also complement each other over time. Exterior caulking mainly protects against water and wind. Weatherstripping wears with every opening and closing, so it needs a more frequent look.

NRCan adds a useful tip: a window you never open can be caulked instead of weatherstripped. Still, keep at least one opening window per room, for ventilation.

Types of weatherstripping

NRCan compares weatherstripping in its guide Keeping the Heat In. Each type has its strengths and limits. The choice depends on the opening: a door that rubs at the threshold, a sliding window or a hatch you rarely open don't call for the same product.

In practice, we look at three things: the gap to fill, how the opening part moves, and exposure to cold. Weatherstripping that's too thin lets air through. Weatherstripping that's too thick keeps the door or window from closing. Here's what NRCan says:

• Foam: it can crack over time
• Ribbed rubber: very durable
• Tubular gasket: rubber lasts longer than plastic
• V-strip metal: sturdy, but it can bend out of shape and frost up
• Magnetic: less effective in the cold, because of frost
• Threshold: very effective, but it wears out
• Sweep: more durable, but often less effective

Sash windows and doors

For sash windows, which slide up and down, the Government of Quebec recommends V-strip or tubular weatherstripping. They follow the movement of the sash without blocking it. If the window sticks after installation, the weatherstripping is too thick. A window you can no longer open isn't a solution: it must stay usable.

Before changing a door's weatherstripping, the Government of Quebec advises tightening the hinge screws. A sagging door no longer touches the weatherstripping all the way around, even if it's new.

Look at the strike plate too, the metal piece where the lock's latch goes in. If the door doesn't press firmly enough against the weatherstripping when closed, a slight adjustment to the strike plate can be enough to close the gap.

The bottom of the door needs its own attention. You can install weatherstripping on the threshold or on the door itself. If you also have a mouse problem, Health Canada recommends metal weatherstripping under doors, and reminds us that a worn threshold is enough to let them in.

Installing weatherstripping: the steps

Replacing weatherstripping is a job most homeowners can do, as long as it's done from the ground. A few steps make the difference:

• Remove the old weatherstripping and any leftover adhesive
• Clean and dry the surface before installing
• Measure each side of the opening and cut the strip to size
• Install the weatherstripping without stretching it, so it doesn't shrink
• Close the door or window to check that it shuts without forcing
• Check the seal with the candle test described by the Government of Quebec: hold the flame near the weatherstripping and watch whether it flickers

When to replace it

Weatherstripping doesn't last forever. Sun, cold and friction wear it down little by little. According to NRCan, foam can crack over time, and thresholds eventually wear out underfoot.

Check it in the fall, before the cold, and again in the spring. Run your hand along the closed door on a cold day: a stream of air will tell you where to look. It needs replacing when you see one of these signs:

• It's torn, cracked or flattened
• It's coming away from the frame
• You feel a draft with the door closed
• Frost forms on the edge of the door or window

Two common oversights: paint and the attic hatch

The Government of Quebec puts it plainly: never paint weatherstripping. Paint hardens the material. The weatherstripping no longer compresses when you close the door, and air gets through. If you're repainting a door or frame, remove the weatherstripping first, or mask it carefully. If it has already been painted, it's better to replace it.

The attic access hatch is the other oversight. NRCan and ENERGY STAR recommend weatherstripping the hatch frame and fastening the hatch securely. It's a small opening, but it leads straight into the attic.

If the attic is hard to reach, or if the hatch is at the top of a staircase, take the time to set yourself up properly, or ask for help. Don't work off balance.

When we caulk a home, we can replace worn weatherstripping as part of the same job. We look at both during the assessment.