Overview
Hold a lit incense stick near windows and doors — smoke movement indicates air leaks.
Step-by-Step Guide
Choose a windy day or create negative pressure
Air leak detection works best on a windy day. Alternatively, close all windows and doors, turn off the HVAC, and turn on all exhaust fans (kitchen, bath, dryer) to create negative pressure that pulls outdoor air through leaks.
Light an incense stick or use a smoke pencil
Hold the incense near the edges of each window and door frame. Watch the smoke trail — if it flutters, blows sideways, or gets sucked toward the frame, you have found an air leak.
Test all four edges of every window
Slowly move the incense along the top, bottom, and both sides of each window sash. Also check the joint where the window frame meets the wall — caulk failures here are common.
Check exterior doors and thresholds
Run the incense along the top and sides of exterior door frames. Then hold it at the bottom — a draft under the door indicates the sweep or threshold needs replacing.
Do the dollar bill test on doors
Close a door on a dollar bill. If the bill slides out easily with no resistance, the weatherstripping is not making good contact and needs replacement.
Inspect and replace weatherstripping
Peel off any cracked, compressed, or missing weatherstripping. Clean the surface with rubbing alcohol, let it dry, and apply new self-adhesive foam or V-strip weatherstripping.
Re-caulk window and door frames
Use a utility knife to remove old, cracked caulk from the exterior of window and door frames. Apply a fresh bead of exterior-grade silicone or polyurethane caulk and smooth it with a wet finger or caulk tool.
Verify the fix
After sealing, repeat the incense test on the areas you repaired. The smoke should now flow smoothly without deflection. Mark any remaining problem areas for follow-up.
What You'll Need
Tools
- - Incense sticks or a smoke pencil
- - Lighter or matches
- - Utility knife
- - Caulk gun
- - Rubbing alcohol and rags (for surface prep)
Materials
- - Self-adhesive foam weatherstripping (various widths)
- - V-strip (tension seal) weatherstripping for double-hung windows
- - Door sweep or replacement threshold seal
- - Exterior-grade silicone or polyurethane caulk
Cost Estimates
DIY Cost
$15 - $40 for weatherstripping, caulk, and incense sticks
Professional Cost
$200 - $450 for a professional energy audit with blower door test
Safety Tips
- Keep the incense stick away from curtains and other flammable materials.
- Open a window briefly after testing to ventilate incense smoke if it bothers you.
- If using spray foam around windows, use minimal-expansion foam (window and door formula) — standard foam can bow the frame and prevent it from opening.
When to Call a Professional
Call a professional for a blower door test if you want a precise measurement of your home's air leakage rate, or if you suspect air leaks in walls and ceilings that you cannot reach.
Pro Tip
On double-hung windows, the meeting rail (where the two sashes overlap in the middle) is the single biggest source of air leaks. Add V-strip weatherstripping along the meeting rail for an immediate improvement.
Common Mistakes to Avoid
- Testing for air leaks with the HVAC running — the system pressure masks leaks. Turn it off first.
- Using standard expanding foam around window frames — it can bow the frame and jam the window. Use low-expansion window and door foam only.
- Applying new caulk over old deteriorated caulk — always remove the old bead first for a proper seal.
- Ignoring the lock mechanism on windows — when locks are engaged, they pull the sash tighter against the weatherstripping for a better seal.
Local Handymans in Clinton Township

Handyman Connection of Ann Arbor
Ann Arbor, MI
(734) 205-9000A2 Handyman
Ann Arbor, MI
(734) 972-4982
Neighborhood Handyman AA
Ann Arbor, MI
(734) 881-5513Founding Member
Premium spot in Clinton Township
Ambassador
Lead the Clinton Township community
Founding Member
Premium spot in Clinton Township
Clinton Township Housing Market
Fair Market Rents — Clinton Township
Studio
$1,009/mo
1 Bedroom
$1,122/mo
2 Bedroom
$1,411/mo
3 Bedroom
$1,724/mo
4 Bedroom
$1,868/mo
Source: HUD FY2026 Fair Market Rents — Detroit-Warren-Livonia, MI HUD Metro FMR Area
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