Window drafts have four common sources, each with its own $10 fix. An hour of sealing usually pays for itself within the season, and none of it needs more than scissors and a caulk gun.
Riley Brand
On a windy day, move a lit candle or incense stick slowly around the window: along the sash edges, the meeting rail, the frame-to-wall joint, and the sill. Wherever the flame dances or smoke streams sideways, that is a leak. Mark each spot with painter's tape.
A damp hand works too, and at night a helper shining a torch around the frame from outside reveals daylight-gaps from within. The mapping matters because the four leak locations take four different fixes - sealing the wrong one is the most common reason 'I weatherstripped and it's still cold'.
Gaps where the moving parts meet - sash against frame, sash against sill - get weatherstripping, because those joints must still open. Self-adhesive options by gap size: V-strip (springy folded plastic) for thin, even gaps in the side channels; EPDM rubber or silicone bead for medium gaps where the sash closes against the frame; foam tape only for the most sheltered, low-wear spots, as it crushes flat within a season or two.
Prep decides whether it lasts: clean the surface with soapy water then alcohol, dry fully, cut with scissors (not torn), and press firmly along the whole run. Apply in above-10C weather or warm the strip indoors first - cold adhesive grips poorly and peels by January. Done right, the window should close with a slight, even resistance: snug, not slamming.
The joint between the window frame and the wall does not move, so it gets caulked shut - interior gaps with a paintable acrylic-latex caulk, exterior with an exterior-rated silicone or hybrid. Rake out any old cracked caulk first with a utility knife, clean and dry the channel, cut the nozzle small, and run a steady bead smoothed with a wet finger.
For sash windows you want sealed all winter but openable in spring, rope caulk is the renter's gem: a putty cord you press into the gaps by hand in seconds and peel away cleanly in April - no tools, no residue, about $5 a window. Drafty single-glazed sashes also leak around loose glazing putty on the glass itself; crumbling putty lines are a re-glazing job worth pricing.
Shrink film - clear plastic taped to the interior trim and tightened drum-flat with a hairdryer - effectively adds a still-air pane to the whole window for about $3-4 each. On old single glazing it makes a startling difference, and applied carefully it is nearly invisible. It seals the window shut for the season, so pick the rooms where that is fine.
Layer the cheap physics on top: floor-length thermal or lined curtains, closed at dusk, cut heat loss through the glass substantially - close-mounted and wider than the window so they seal against the wall. A draft snake on the sill and closed trickle-vent covers (only where the room has other ventilation) finish the job.
Condensation fogging between the panes of a double-glazed unit means the seal inside the unit has failed - no exterior caulk fixes that; the glass unit needs replacing (often possible without replacing the whole frame). Rotten wood sills, frames soft enough to dent with a fingernail, or sashes so warped they cannot meet their stops are likewise past weatherstripping.
A sensible escalation: seal everything for a season and feel the difference. If a window still leaks badly after good weatherstripping and caulk, get a quote for that one window rather than the whole house - replacing the two genuinely failed windows usually delivers most of the comfort at a fraction of the cost of full replacement.
Rope caulk for the gaps, shrink film for the worst windows, and a draft snake on the sill - all fully removable, under $10 a window, and no landlord conversation required.
Silicone and EPDM rubber profiles last years; spring V-strip is close behind. Cheap open-cell foam tape is the shortest-lived - it compresses permanently within a season or two in a window that gets opened. Buy by gap size first, material second.
Seal the drafts, but the house still needs ventilation - especially kitchens, bathrooms, and bedrooms (condensation and mold trade places with drafts). Leave trickle vents functional where they exist, or air rooms briefly daily. The goal is controlled ventilation, not zero air.
Applied carefully - clean trim, double-sided tape, hairdryer shrink until drum-tight - it is barely visible from a metre away. Wrinkles and sag come from skipping the shrink step. It comes down in spring with no marks if you warm the tape as you peel.
