Use a lit incense stick to find where air actually moves. Air at the sash is weatherstripping. Air at the trim is an uninsulated perimeter. No air movement but a cold feeling is convection off cold glass. Those are three different problems with three different fixes.
Drafts get blamed on windows more than any other building component, and windows are often not the cause. Replacing them and still feeling a draft is a common and expensive outcome.
Five dollars of incense and twenty minutes will tell you what you actually have.
The diagnosis
Pick a windy day, because pressure difference is what drives infiltration and a still day tells you nothing. Close and lock every window and exterior door. Turn off any exhaust fans. Light an incense stick and hold it a couple of inches from the surfaces you want to test, moving slowly and watching the smoke. Where the smoke bends or streams, air is moving. Work the full perimeter of each window and door: the sash edges, the meeting rail on double hungs, the trim where it meets the wall, the threshold, and the corners. Then do the same at electrical outlets on exterior walls, at the attic hatch, at the basement rim joist, and around any plumbing or wiring penetration. Write down what you find. The results are frequently surprising.
What each finding means
| Where the smoke moves | Cause | Fix | Rough cost |
|---|---|---|---|
| At the sash edge | Failed weatherstripping | Replace weatherstrip | $20 to $60 per window |
| At the meeting rail | Window not latched, or worn rail seal | Latch it, or replace the seal | Free to $40 |
| At the interior trim | Perimeter gap never insulated | Remove trim, foam, reinstall | $20 to $60 per window |
| At the door threshold | Threshold or sweep | Adjust threshold, replace sweep | Free to $40 |
| At an outlet on an exterior wall | Wall cavity connected to outside | Foam gaskets behind the plate | $1 per outlet |
| At the attic hatch | Uninsulated, unsealed hatch | Weatherstrip and insulate the hatch | $30 to $80 |
| At the basement rim joist | Uninsulated band around the house | Foam and insulate | $600 to $1,800 |
| Nowhere, but it feels cold | Convection off cold glass | Better glass, or accept it | Varies |
The balloon framing problem
Many Capital Region homes built before roughly 1930 use balloon framing, where the wall studs run continuously from the foundation sill to the roof rather than stopping at each floor. That creates an uninterrupted vertical air channel inside the wall cavity, from the basement all the way to the attic. Cold basement air rises through those channels and warm air escapes at the top, and the resulting airflow chills the walls and the floors. It is why an old house can feel drafty in rooms where no window is leaking at all. The fix is to block those channels at the top and bottom plates with rigid material and sealant, which is usually done from the attic and from the basement. It is not glamorous and it is one of the highest value interventions available in a pre-1930 house.
Cold glass is not a draft
This is the distinction that determines whether new windows will help. If the incense smoke does not move but the area still feels uncomfortable, there is no air leaking. What you are feeling is convection: air near the cold glass surface cools, becomes denser, and falls, creating a current of cool air moving across the floor away from the window. It feels exactly like a draft and it is not one. The fix for it is warmer glass, meaning a better insulated unit with a low U-factor and a warm-edge spacer, or a storm window over an existing single pane. That is the case where window work genuinely is the answer, and knowing that before you buy is worth the twenty minutes.
Ranges reflect typical Capital Region projects and are for planning only. Every Sundog quote is written, itemized, and free.
Frequently asked questions
How do I find where a draft is coming from?
Light an incense stick on a windy day and hold it a couple of inches from the window and door perimeters, watching where the smoke bends. Movement at the sash means weatherstripping. Movement at the trim means the perimeter was never insulated. Also check outlets on exterior walls, the attic hatch and the basement rim joist.
Will new windows stop my drafts?
Only if the air is actually leaking through the window. If the leak is at the trim where the frame meets the rough opening, a new window installed the same way will leak the same. If there is no air movement at all and the area simply feels cold, that is convection off cold glass and better glass genuinely helps.
What is the cheapest way to stop a draft?
Latch every window, which costs nothing and compresses the sashes against their weatherstripping. Then adjust exterior door thresholds, also free. Then foam gaskets behind outlet covers on exterior walls at about a dollar each. Those three take an afternoon and cost almost nothing.
Why is my old house drafty even with new windows?
Frequently balloon framing, which leaves continuous vertical air channels inside the walls from the basement to the attic. Cold air rises through them and chills the walls regardless of window quality. Blocking those channels at the top and bottom plates is the fix and it is one of the highest value interventions in a pre-1930 house.
Is it worth weatherstripping old windows?
Very much so, as a first step. Air leakage around an unweatherstripped sash is usually a larger heat loss than conduction through the glass. It is cheap, reversible, and it tells you how much of your discomfort was air movement versus cold glass, which is exactly the information you need before deciding on replacement.
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