How to close gaps around doors and vents?

Every part of a house's exterior has some potential gaps, but doors and vents are disproportionately important for a simple reason: they're openings by design, not accidents of construction, and they're often the largest reliably-open routes on a house. A worn door sweep leaves a continuous strip of daylight at floor level running the full width of a door — far larger than a single crack in siding. An unscreened attic or soffit vent is an opening built for airflow, which also means it's built for insects.

University of Kentucky Entomology puts a hard number on the insect threshold: a gap of 1/16 inch or less already admits insects and spiders, and 1/4 inch admits mice. Almost every exterior door on an older or moderately-worn home exceeds that threshold at the bottom corners even when it looks reasonably tight.

Start with the daylight test: from inside, in a dark room, look at the bottom of an exterior door on a sunny day. Any visible light is an entry route. A rubber or brush door sweep, installed with a screwdriver in a matter of minutes, closes that gap. If the threshold itself is worn or the door has settled unevenly, an adjustable threshold may be needed alongside the sweep.

For the sides and top of the frame, compression or V-strip weatherstrip closes the gap where the door meets the jamb. Garage doors get their own rubber bottom seal, and sliding-door tracks take a foam insert. None of this is specialized work — these are standard products sold at any hardware store, designed for a homeowner to install without tools beyond a screwdriver and a tape measure.

Vents present a different challenge than doors, because you generally don't want to seal them shut — a house needs attic and crawlspace ventilation to manage moisture. The fix instead is fine insect screening, at least 16-mesh, installed over the vent opening so air still moves but insects can't pass through. Where the existing screen is torn or missing, patch or replace it; where hardware cloth is already present for larger wildlife, note that its 1/4-inch openings are far too large to stop insects and needs a finer mesh layered behind or over it.

Higher soffit and gable vents may need a ladder or, on a complex roofline, a contractor — this is the one part of this job where 'homeowner project' shifts to 'homeowner with a ladder' or beyond, depending on your house.

For the overwhelming majority of single-family homes, closing gaps at doors and ground-level or easily-accessed vents is a do-it-yourself project — a screwdriver, a staple gun, and an afternoon cover it. There's no reason to pay for a service call to fix a gappy door or patch a torn vent screen you can reach yourself.

The straightforward exception is access: vents on a steep or high roofline, or a soffit system that requires scaffolding to reach safely, are where a contractor really earns their keep — not because the fix itself is complicated, but because the access is. A pest-control service adds value in a narrower lane still: a timed exterior perimeter application as a supplement to your sealing work, not a substitute for the sweep and screen you can install yourself.