Taking window screens off before winter: what to check while the glass is bare

Window screens hold moisture, pollen and grit against the frame all summer, and they cover the parts of a window that most need looking at before heating season. Taking them out in September, while it is still dry and warm enough to work outside, costs about fifteen minutes for a whole house and turns a chore into an inspection. This is what to check while the glass is bare, what tends to break during removal, and how to store screens so they still fit the openings in May.

Why screens come off before winter

Nothing obliges you to remove them. Two practical arguments do. A screen cuts light and solar gain through the glass at the time of year you want both, and it keeps a film of water and debris against the sash and the sill — the part of a wood or clad frame that fails first. Natural Resources Canada's window chapter puts rot, mould and/or staining on or around the window at the top of the list of things to check on a window, and a screen keeps exactly that area damp and out of sight.

It also matters more than it looks. NRCan puts windows, doors and skylights at up to 35 percent of total house heat loss, so the condition of the frames and the weatherstripping is worth ten minutes before the furnace starts running every day.

• The outside of the glass becomes washable. Through a screen you cannot clean the exterior surface at all.
• The sill and the bottom rail become visible and can dry out properly.
• The weep slots along the bottom of the frame become reachable.
• On a house with seasonal storm windows, the storm sash can go on.
• Winter wind stops driving grit into a mesh you will have to wash in spring anyway.

Which side you work from depends on the window

A casement or awning sash — the ones with a crank — swings outward, so its screen has to sit on the inside. A slider or a double-hung sash moves inside its own frame, so the screen sits outside. That single difference decides whether an upstairs window is a two-minute indoor job or a ladder job, and it is worth walking the house and sorting the windows into those two groups before you start.

There is a mechanical reason to do this in September rather than November. Cold makes plastic corner keys and hardened spline brittle, so every failure listed below gets likelier as the temperature drops.

What actually breaks when a screen comes out

The five-minute check while the glass is bare

This is the part of the afternoon worth more than the screens. NRCan's own list for taking stock of a window is short: check each window for rot, mould or staining on or around it, the condition of the glass, putty and paint, the weatherstripping, and the operation and condition of the hardware — then check for air leakage around the frame and at all movable joints. With the screen out, all of it is at arm's length.

1. 1Press the sill and the bottom railWood that gives under a thumb is soft under the paint, and paint over soft wood is the normal way this stays hidden for a season. Note the window and deal with it while it is still dry outside.
2. 2Look above and beside the opening, not just at itStaining on the wall or trim around a window is a water path, and it usually starts higher than the mark it leaves. NRCan lists staining around the window alongside rot as a first-order signal.
3. 3Run a finger along the weatherstrippingCompression and magnetic seals are what make casement, awning and hopper windows airtight. Flattened, torn or missing stripping is the cheapest repair on this list and the one that shows up on the heating bill.
4. 4Work every piece of hardwareCrank the casements fully open and closed, throw every latch, and check that a double-hung sash stays where you leave it. Hardware that no longer pulls the sash tight against its seal is an air leak, whatever the weatherstripping looks like.
5. 5Find and clear the weep slotsThe small openings along the bottom outer edge of a frame let water out. Blocked with grit and spider web, they hold water in the frame through every freeze and thaw.
6. 6Look at the glass itself, from outside and inNote anything foggy, and which layer it is on. That distinction is the whole next section, and it decides whether you have a cleaning job, an air-sealing job or a glass job.

Condensation: three kinds of fog, three different answers

Fog on a window means different things depending on which surface it is on, and NRCan gives a different remedy for each.

• On the inside surface, in the room. This is interior surface condensation, and it is about the humidity in the house meeting a cold surface. Worth knowing before you spend: NRCan notes that some homeowners buy new windows only to find the problem gets worse, because the old leaky windows had been helping to reduce indoor humidity.
• Between the panes of a storm window or a non-sealed unit. Moist house air has leaked past the inner pane and condensed on the outer one. NRCan says this is common on second storeys, where the stack effect pushes more air out through the window. The fix is to weatherstrip the inner sash to stop the leak, and to make sure the weep holes on the storm window are open to the outside.
• Inside a sealed double-glazed unit. The seal has failed. NRCan's answer is to replace the glazing unit, and to check first whether the window is still under warranty.

If the house has storm windows

Where storm windows are still in service, the numbers explain why they were worth the trouble: NRCan puts single-glazed windows at 10 to 20 times the heat loss of the same area of properly insulated wall, and says storm windows or double-glazed sealed units cut that by almost half. Seasonal units should be inspected each year before they go on, for the condition of the glazing, putty and weatherstripping. The guide is equally plain about the cost — the labour of putting them up and taking them down every year, and the space to store them.

There is one rule that decides whether they help or rot the frame: seal the inside window more tightly than the outside one. If the interior window leaks more, moist household air gets between the two, is trapped there, and condenses on the cold outer pane, which NRCan says causes deterioration of the sash and frame. Permanent exterior storm windows usually have a built-in screen and a sliding sash, so on those the seasonal job is closing the sash rather than removing anything.

The window not to seal shut

Sealing up a window that never opens is legitimate, and NRCan says so: windows that do not have to be opened and do not serve as emergency exits can be locked and caulked. The guide attaches a technical note to that permission: building codes require every bedroom to have at least one window that opens from the inside to allow escape in an emergency. Confirm which window that is in each bedroom before any of them gets caulked or screwed shut for the season.

The order matters too. Caulking on the outside of a window should be done only after the interior sealing is finished. Caulk the exterior first and you can trap warm, moist air inside the wall, which over time damages it. Interior caulk also has to be a product meant for indoor use — exterior caulking does not belong inside.

Storing screens so they still fit in May

Two things go wrong in storage: the frames bow, and the screens lose track of which opening they came from. Screens from the same house are rarely interchangeable, because each was cut to its own opening even when two windows look identical. Both problems are solved in the ten minutes right after removal, and neither can be solved in the spring.

1. Label every screen as it comes out — room and position, on masking tape on the frame, in pencil or marker. Not on the mesh.
2. Wash and dry them before they go away. A soft brush and plain water is enough; mesh stored dirty holds moisture against the frame all winter.
3. Stand them on edge against a wall, never flat in a stack. A flat stack puts the weight of every screen above onto the frames below, and that is how a frame bows.
4. Keep the bottom edges off bare concrete. A length of scrap wood or a strip of rigid foam underneath is enough to stop them wicking up floor moisture.
5. Put them somewhere nothing gets leaned against them — not behind a car door's swing, not where a bike or a ladder ends up.
6. Bag any clips, screws or plungers that came out with them, label the bag, and tape it to the first screen in the row.

Where a wrecked screen goes

Torn mesh in a frame that is still square can be re-meshed rather than replaced. Mesh and spline are ordinary hardware-store material, and the job needs a spline roller, a flat surface and about twenty minutes per screen. A bent frame or a snapped corner is scrap metal, and both regions here have a route for it.

In Peel — Mississauga, Brampton and Caledon — Peel Region says scrap metal can be dropped at any Community Recycling Centre free of charge, up to a maximum of 2.4 m (8 ft.) in length, or taken to a scrap metal dealer. In Halton — Oakville, Burlington, Milton and Halton Hills — the Region publishes a Metal and Appliance Collection page under Recycling and Waste; check it for what qualifies and how the collection is booked before putting anything at the curb.

When this is a job to do yourself, and when it is not

Every casement and awning screen in the house, and every ground-floor slider, is a do-it-yourself job that needs no tools and no ladder. There is no reason to pay anyone for those. What changes the job is an upper-floor slider or double-hung window, where the screen sits on the outside: removing it means climbing with both hands occupied and coming back down holding a light panel that catches wind. That is the same calculation as washing the outside of a two-storey window, and it deserves the same honest answer about reach.

If someone is coming with a ladder anyway, sequence the autumn exterior work into one visit rather than three. Screens out first, then the exterior glass while it is bare, then the eavestroughs once the leaves are down — and the same weekend logic applies to decks and fences before winter. On the window cleaning page, screen removal and re-installation is listed as an add-on to a cleaning visit, which is the version of this that costs you nothing extra in ladder time.