A window draft in a Calgary January is not a minor comfort issue — at -30°C outside and +21°C inside, the temperature difference driving cold air through every gap is 51 degrees. That same gap that you could ignore in Vancouver's mild winter becomes a serious heat loss problem here. The good news is that most window draft repairs are inexpensive and the energy payback in Calgary's climate is among the fastest in Canada.
Finding window drafts: three reliable methods
The challenge with window drafts is that air infiltration is invisible until it is severe enough to create a noticeable cold zone in the room. To find smaller leaks before they become expensive, use one of these methods:
1. Incense stick test
Light an incense stick and hold it 2–3 cm from the window frame perimeter on a cold, windy day with the furnace running. Work around all four sides of the frame, the corners, and the meeting rail (where upper and lower sash meet on a double-hung window). Smoke deflecting toward you means outdoor air is pushing in; smoke deflecting away from you means indoor air is being pulled out through a gap. Both indicate a sealing problem.
2. Hand test (Calgary winter only)
On a day below -15°C, hold your bare hand 2–3 cm from the sash-to-frame junction while the wind is up. You can feel infiltration as a distinct cold sensation before you can see any smoke movement. Pay particular attention to the bottom corners of the sash and the meeting rail area — these are the two highest-frequency leak locations in Calgary's double-hung windows.
3. Flashlight test (nighttime)
After dark, have someone on the exterior shine a bright LED flashlight along all edges of the window while you observe from inside with the interior lights off. Light visible around the frame or between sash and frame confirms a gap. This works well for large gaps but misses small infiltration that the incense test would catch.
Draft locations and causes in Calgary homes
| Location | Common cause | Fix |
|---|---|---|
| Sash corners (where sash meets frame) | Weatherstripping worn or compressed flat | Replace V-strip or foam tape |
| Meeting rail (double-hung) | Foam rail seal compressed after years of use | Replace foam or add compression strip |
| Bottom of sash at sill | Original sill seal worn; sash dropped out of square | Replace sill sweep or re-square sash |
| Frame-to-rough-opening gap | Original fiberglass insulation compressed; no backer rod | Re-insulate with low-expansion spray foam + backer rod |
| Exterior caulk joint (frame to siding) | Caulk cracked from Calgary thermal cycling | Remove and replace with silicone or polyurethane |
| Interior trim joint (trim to drywall) | Acrylic caulk shrinkage over time | Re-caulk with paintable latex or silicone |
Weatherstripping types: which to use and where
Not all weatherstripping products handle Calgary's conditions equally. The temperature range in a single year can span 75°C, and products that are flexible at room temperature can harden and crack at -35°C.
| Type | Best application | Lifespan in Calgary | Temperature range | Notes |
|---|---|---|---|---|
| V-strip (tension seal), bronze or stainless | Double-hung sash channels, sliding windows | 15–25 years | Handles full range | Best long-term choice; does not compress flat |
| V-strip, vinyl | Double-hung sash channels | 5–8 years | Becomes brittle below -30°C | Cheaper upfront; replace more often |
| EPDM foam tape (closed-cell) | Casement and awning windows (compression seal) | 5–10 years | Good down to -40°C if EPDM; avoid PVC foam | Not for sliding sashes — friction destroys it |
| Rope caulk (removable) | Seasonal seal on sash perimeter | 1 season (remove in spring) | Down to about -20°C before cracking | Quick winter fix; not a permanent solution |
| Door bottom sweep (for window sills) | Bottom of sash at sill on large picture windows | 5–7 years | Good if EPDM brush or wiper type | Not standard window product; custom fitting |
| Foam self-adhesive tape (open-cell) | Avoid on operable windows | 1–2 years | Hardens below -10°C | Compresses flat; loses seal; deteriorates in UV |
The clear winner for Calgary double-hung windows is bronze or stainless V-strip. It installs in the channel that the sash slides in, springs outward to fill the gap, and the sash can still be operated without wearing the seal down. At 15–25 years of service life in Calgary conditions, it is the only weatherstripping that you install once and do not think about again.
V-strip installation on a double-hung window
- Open the window sash fully. Measure the height of the sash run in the channel — this is the V-strip length needed.
- Clean the channel with a dry cloth to remove dust and paint chips that would prevent adhesion of the V-strip flange.
- Cut V-strip to length. For bronze strip, use tin snips; for vinyl, use scissors.
- Insert the V-strip into the channel with the folded spine toward the outside (the open side of the V faces inward to contact the sash).
- Nail (for bronze — comes with nails) or press-to-adhere (for vinyl self-adhesive) along the flange at 6-inch intervals.
- Repeat for the other sash channel on the opposite side of the window.
- For the meeting rail (where upper and lower sash meet), use a flat foam or EPDM compression strip along the top rail of the lower sash.
- For the bottom sill, use a vinyl or EPDM wiper strip along the bottom edge of the lower sash if the original sweep is worn.
- Test operation: sash should slide with slight resistance (the V-strip providing compression) but not bind. If binding occurs, the strip is too tall — trim 1mm at a time.
Caulking: frame perimeter sealing
Weatherstripping addresses the operable sash. The frame itself — the junction between the window unit and the wall — is sealed with caulk. There are three caulk joints on most Calgary windows:
- Exterior frame-to-siding joint: Use 100% silicone caulk rated for -40°C. In Calgary, silicone is mandatory for this location — polyurethane is second choice. Latex and acrylic caulks crack in the first or second winter from thermal movement at this exposed joint.
- Frame-to-rough-opening gap (inside the wall): Often accessible from inside by removing the interior trim. If fiberglass batt is used here, it is compressible and allows air to pass through even when stuffed tight. Low-expansion spray foam is the correct fill — it adheres to both frame and rough framing, creating an air seal. Use low- expansion specifically (standard foam exerts enough force to bow vinyl window frames).
- Interior trim-to-drywall joint: Use paintable acrylic latex caulk. This joint is interior and temperature-controlled, so thermal range is not a concern. The acrylic cleans up with water and takes paint. Any colour; will be painted over.
Energy savings: the Calgary math
Calgary has approximately 5,000 heating degree days per year (base 18°C). For context, Toronto has about 3,500 HDD and Vancouver about 2,900 HDD. The higher the HDD, the higher the energy penalty for every cubic metre of cold air infiltrating your home.
A drafty double-hung window with worn weatherstripping has an effective air leakage rate roughly equivalent to leaving a 1-cm round hole open in the wall. For a home with 10 such windows, that is the equivalent of a baseball-sized hole in the building envelope — constant infiltration during every windy day from October through April.
Natural Resources Canada estimates that air sealing (windows, doors, and other leaks combined) can reduce heating costs by 15–25% in a leaky home. For a Calgary home spending $2,400 per year on natural gas heating, that is $360–$600 in annual savings. A full window weatherstripping job on 10 windows costs $400–$700 — a payback period of roughly one heating season.
Rope caulk: the seasonal quick fix
Rope caulk is a soft, putty-like product sold in rolls that you press into the gap between the sash and frame. It is not adhesive and is meant to be removed in spring. It works well for winter when the gap is large enough that V-strip alone does not fully close it, or as a temporary measure until a proper V-strip installation can be done.
Application: clean the surface, press a length of rope caulk into the gap, and smooth with a wet finger. It can be applied over paint without damage. In spring, it peels out cleanly — do not leave it for a second winter, as sun and heat cause it to bond more firmly and it becomes difficult to remove without leaving residue.
At Calgary temperatures below -20°C, rope caulk becomes stiff and loses some flexibility — it will still seal but may crack if the window is operated. Apply it in the fall before temperatures drop, not mid-winter.
Typical costs in Calgary (2026)
| Service | Typical cost | Notes |
|---|---|---|
| V-strip installation, single double-hung window | $60–$90 | Includes material; 30–45 min per window |
| V-strip, whole house (8–12 windows) | $450–$700 | Efficiency of batching reduces per-window cost |
| Exterior caulk, per window (frame perimeter) | $40–$65 | Includes silicone caulk material |
| Interior trim re-caulk, per room (4–6 windows) | $120–$200 | Often combined with painting prep |
| Full window air sealing (V-strip + exterior caulk + trim), per window | $100–$150 | Most comprehensive single-window treatment |
Frequently asked questions
How do I find window drafts in a Calgary home?
Use an incense stick on a cold windy day — smoke deflecting toward you indicates infiltration. Focus on sash corners, the meeting rail between upper and lower sash, and the bottom of the sash at the sill. These are the three highest-frequency leak locations.
What is the best weatherstripping for Calgary double-hung windows?
Bronze or stainless V-strip (tension seal) is the best choice — it handles Calgary's full temperature range, doesn't compress flat over time, and lasts 15–25 years. Foam tape works only on casement windows that compress the seal on closing, not on sliding sashes.
How much energy does sealing window drafts save in Calgary?
Calgary's 5,000+ heating degree days mean air infiltration carries a larger energy penalty than in most Canadian cities. Proper weatherstripping and caulking can reduce heating costs by 15–25%, typically paying back in one heating season.
Can I use exterior caulk to seal a drafty window in Calgary?
Yes, for the frame-to-siding perimeter and frame-to-rough-opening gap. Use 100% silicone or polyurethane rated for -40°C on the exterior. Latex caulks crack at Calgary temperatures. The moving sash itself must be addressed with weatherstripping, not caulk.
When should I replace a window versus seal it?
Seal if the frame is sound and glass is clear. Replace if the frame is rotted or warped beyond correction, the glass is fogged (failed seal), it's single-pane, or it's a 1980s aluminum-frame window — the thermal loss from those is too high for weatherstripping to meaningfully address.
Feeling drafts around your Calgary windows?
Steve identifies the draft source, installs V-strip weatherstripping, and re-caulks frame perimeters — a whole-house window sealing package that typically pays back in the first winter.
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