If a Door Invites in a Breeze
This Old House general contractor Tom Silva’s preferred method for sealing the bottom of an entry door requires routing a groove in the bottom edge to accept a silicone gasket that remains hidden from view (find various models at Conservation Technology). But he has also used an easier-to-install version, shown above, that works just as well, if you don’t mind seeing the sweep. A visible flange simply screws to the bottom face of the door and keeps vinyl fins pressed tightly against the threshold (U-Shape Door Bottom, $12; Home Depot).
For leaky basement doors, use a draft stopper that holds on to the back of the door, and tight to the floor, by means of clips or magnets. One to try: Evelots Clip On Door Draft Stopper ($18; Amazon).
Pro Tip: As Tom Silva explains the principle behind all door sweeps: “Fill the gaps, so the cold air won’t blow under the door. There’s a lot of options.” One type acts like a series of squeegees that rub against the threshold as the door opens and closes, stopping airflow.
If Your Windows Leak
Get fast relief by squeezing a bead of clear-drying temporary caulk around or between sashes—just be sure to use it in a ventilated area. Later on, when you get ready to fling open the window, pull up a corner of the caulk and it will come off in a single string, leaving the paint intact. $17; Amazon
Diagnose Before You Seal: On the This Old House Arlington project, the crew used a smoke pencil to pinpoint exactly where drafts were sneaking in—and found the worst air infiltration wasn’t at the sash but up by the rope pulleys in the weight pockets. “That’s the worst place we found so far,” the team noted. Before reaching for the caulk, hold a lit incense stick near your window’s edges and pulleys to find the real culprits.
For gaps that are too wide for caulk alone, consider stuffing foam backer rod into any openings ⅛ inch or wider before sealing. As outlined in TOH Magazine’s quick-fix guide, this gives the caulk a solid backing and fills large voids that a bead of sealant can’t bridge on its own. For an even more comprehensive temporary fix, a shrink-wrap window insulation kit—held in place with double-sided tape and tightened with a hair dryer—creates what the magazine calls a “Tupperware-tight, see-through seal.”
Pro Tip: When sealing around storm windows, TOH general contractor Tom Silva warns against caulking across the bottom: “If we caulk across the bottom, we create a dam. Think if the rain gets in there, where’s the water gonna go? You can rot your sill.” Leave the weep holes at the bottom of storm windows open so any moisture that gets behind the glass can drain out.
If You Want to Keep a Window AC Unit Where It Is
Air conditioners in walls or windows leave an open passage for cold air. The first line of defense can be a heavy-duty polyethylene and vinyl cover that you fit around the outside of the unit. We like Frost King’s extra-large Window Air Conditioner Cover ($8.98; Amazon)
If you still feel a draft, try this winter weatherproofing tip- wrap the inside grille and the sides with 2-millimeter-thick plastic sheeting and double-sided tape, or use a shrink-film kit, like M-D Building Products’ Shrink & Seal ($14; Amazon). Then add another layer inside with a quilted cover. Look for one that offers a snug fit with elastic or a drawstring, like CoverMates (from $10; Amazon).
It’s worth the effort: according to TOH’s reporting, roughly 2 to 5 percent of a home’s air infiltration comes from unsealed openings on exterior walls—including around window AC units and even electrical outlets. Those small leaks add up fast when winter winds pick up, so a multi-layer approach to sealing your in-window unit can make a noticeable difference in both comfort and energy bills.
Pro Tip: This Old House general contractor Tom Silva recommends addressing air leaks at every layer. As the TOH team has demonstrated, sealing gaps around window units follows the same principle as weatherproofing any window opening: use caulking cord or weather stripping to fill gaps around the sash area, then add insulating layers to create a stagnant air pocket that acts as a natural insulator. The goal isn’t just to block wind—it’s to create dead-air space that slows heat transfer.
