Weatherstripping near you

Natural Resources Canada's materials guide sorts weatherstripping by how it seals: compression strips squeeze shut when the door or window closes, tension strips spring against a sliding or swinging surface, and door bottoms close the gap at the sill.

The bottom of a door is usually where the biggest, most obvious gap is, and there are two ways to close it. NRCan's materials guide compares them directly: a door sweep is easier to install than a threshold and more durable, but often gives a less effective seal, while a threshold gives an excellent seal but is less durable. Its window and door guide adds that a good seal can usually be had with gasketed door-bottom weatherstripping attached to the door, or with full or partial threshold weatherstripping attached to the sill.

In practice the choice depends on the floor and the traffic. A sweep suits a door over tile or hardwood that can't take a raised sill, while an adjustable threshold, raised with screws until it meets the door bottom evenly, suits a door whose sill is already in place. Doors that drag across a mat or an uneven floor wear sweeps out quickly, and frost at a bottom corner in winter usually marks where the seal isn't meeting the sill.

NRCan calls a good-quality V-shaped vinyl strip the easiest and most effective weatherstripping for a door frame, and notes that many combination strips of metal and foam or rubber are screwed to the door stop. Whatever the product, a strip only works if the door closes against it evenly all the way around.

New strips put on without knowing where the air comes in often miss the leak. Besides smoke from incense on a windy day, NRCan describes a rudimentary fan test: close all the windows and doors and turn on the exhaust appliances, such as bathroom and kitchen fans, so outdoor air is pulled in through the gaps. It says to turn off any fuel-fired space and water heaters before starting, to prevent backdrafting of combustion gases.

An attic hatch sits at the top of the house, where warm air pushes out hardest in winter, and it is often a loose panel resting on trim. NRCan's advice is to seal it exactly as you would an exterior door: caulk around the frame and between the casing and the ceiling drywall, weatherstrip the edges of the casing or the panel itself, and fit hooks with eyebolts or a latch that holds the hatch firmly against the weatherstripping. Its attic guide also suggests building a framework around the hatch so the insulation can be filled right to its edge.

Weatherstripping has no fixed replacement date. How long it lasts depends on the material, how often the door or window is used, how much sun it gets and how cold the winters are, and NRCan's comparison shows wide differences between types: ribbed rubber is rated very durable, spring metal can deform permanently, vinyl foam may crack over time, and sweeps outlast thresholds. A check each fall, before the heating season, catches worn strips while they are still easy to change.