First determine whether it is actually an air leak

Homeowners often use “draft” for any cold sensation near an exterior door. There are at least three different conditions:

• Air leakage: outdoor air is moving through or around the installed assembly.
• Cold surface discomfort: a person feels chilled near cold glass or a cold slab even without noticeable air movement.
• Convection: indoor air cools near a cold surface and drops, creating movement that can feel like an exterior leak.

Use a thin tissue, smoke pencil designed for building diagnostics or thermal imaging under suitable conditions. Avoid open flames around curtains, finishes and weatherstripping. Record outdoor temperature, wind direction and HVAC operation because conditions affect what the inspection reveals.

Draft location and likely cause

Contractor diagnostic checklist

1. Inspect the weatherstripping

Look for missing sections, paint, tears, compression set, brittleness and shrinkage. Close the door slowly and watch whether the slab meets the weatherstrip at the top, middle and bottom. If contact changes along the jamb, the frame or slab may need alignment before replacement weatherstrip can work.

2. Check latch and strike adjustment

With the door latched, push and pull gently at the handle. Excessive in-and-out movement can reduce weatherstrip compression. Therma-Tru’s troubleshooting guidance recommends adjusting the strike for a tighter fit when the slab is loose in the frame. Do not over-tighten the fit until the door becomes difficult to latch.

3. Inspect the door-bottom sweep

Check for torn fins, wrinkled bulbs, loose attachment and uneven wear. A sweep that seals at one end but not the other may be revealing a sill or alignment problem. Replace a damaged component only after confirming that the threshold is straight and within the sweep’s working range.

4. Test the adjustable sill

Where the system has an adjustable cap, inspect and tune it according to the manufacturer’s instructions. Therma-Tru describes a dollar-bill test: with the door closed, the bill should pull out with resistance but without tearing. Test at every adjustment point rather than only at the center.

5. Verify the corner seal pads

On applicable inswing systems, small pads help close the transition where vertical weatherstrip, sill and sweep meet. Missing, misplaced or crushed pads can create a focused leak at the lower corners. Use the correct replacement parts and placement for the system.

6. Check for slab sag

Compare the head margin from hinge side to lock side. A narrowing gap at the top lock corner can indicate sag. Inspect hinge screws, hinge wear and jamb attachment. Therma-Tru installation guidance calls for long top-hinge screws that pass through the jamb into framing to help prevent sagging.

7. Check frame geometry

Use a long level and diagonal measurements. Check both jambs for plumb, the sill and head for level, and the frame for twist. A lock jamb that is bowed or out of plane may touch the weatherstrip at the top and bottom while leaking through the middle.

8. Inspect the perimeter installation gap

Air around the casing may bypass every door component. Remove a small, appropriate section of trim when authorized and inspect for missing, compressed or discontinuous insulation and air sealing. Also check penetrations for wires or hardware.

9. Evaluate glass and lite-frame conditions

Determine whether the complaint is moving air, low glass temperature or a failed glass unit. Look for condensation between panes, cracked glass, loose frames or damaged seals. Follow current manufacturer instructions rather than applying unapproved sealant broadly around the lite.

10. Examine double doors and astragals

Double doors add an active-to-inactive-panel joint, astragal, head and sill bolt conditions and additional seals. Verify that the inactive panel is fully secured, the meeting stiles align and the weatherstrip compresses continuously.

A simple pressure test for weatherstrip contact

A strip of paper can help compare seal pressure. Close and latch the door on the paper at multiple points around the perimeter, then pull. The resistance should feel reasonably consistent. A loose point identifies a local contact problem; an entire loose edge suggests alignment, strike or weatherstrip issues.

This is a diagnostic comparison, not a substitute for manufacturer specifications or professional air-leakage testing.

Why Quad Cities winters expose small defects

Cold temperatures, strong winds and large indoor-outdoor pressure differences can make small gaps obvious. Stack effect in a multi-story home may pull cold air through lower-level openings, while exhaust fans and fireplaces can increase negative pressure.

Record the conditions during the complaint. A door that leaks only during a northwest wind may have an exposure-sensitive exterior seal or pressure issue that is difficult to reproduce on a calm day. That does not make the complaint imaginary; it means the inspection needs context.

Repair, adjust or replace?

A new slab inside a failed frame rarely solves the whole problem. Review when contractors should replace the exterior door frame before choosing the smallest visible repair.

Do not confuse rating problems with installation problems

An NFRC rating describes the tested performance of a specific product configuration. It does not measure a gap around casing, a missing corner pad or a bowed jamb in the field. Likewise, replacing an older door with a lower U-factor will not cure a rough opening that remains unsealed.

For the product side of the comparison, read how to interpret Therma-Tru U-factor and ENERGY STAR information.

Aesthetics matter during draft repairs

Functional repairs can leave visual damage when trim is removed carelessly or sealant is applied as a wide exposed bead. Plan how casing, paint, stain and exterior joints will be restored before opening the assembly.

• Photograph trim profiles and corner joints before removal.
• Use compatible replacement weatherstrip with a clean, consistent appearance.
• Avoid painting flexible seals unless the manufacturer directs it.
• Keep visible sealant joints narrow, properly tooled and compatible with adjacent finishes.
• Match fastener and touch-up locations to the existing finish.

Common diagnostic mistakes

• Replacing weatherstrip before checking alignment. New material cannot correct a twisted frame.
• Raising the sill until the door is hard to close. Excess compression can damage parts and frustrate the homeowner.
• Caulking every visible joint. Unplanned sealant can trap water or conceal the real defect.
• Assuming cold glass is leaking air. Confirm movement before prescribing an air-sealing repair.
• Ignoring building pressure. Exhaust equipment and stack effect can amplify leakage.
• Quoting replacement before diagnosis. A small service repair may solve the issue; a failed frame may require more than a new slab.

The bottom line

A drafty front door is a symptom, not a diagnosis. Find the air path, identify whether the defect is a part, adjustment, alignment or installation condition, and then make the smallest repair that solves the complete problem.

The ruthless rule is simple: do not sell a new door to solve a missing seal, and do not sell a seal to disguise a failed opening.

Frequently asked questions