Inward-Opening Windows: Rain, Wind, Furniture and Egress

An inward-opening window is a hinged window whose sash swings into the room instead of out into the weather. The type includes turn-only inswing casements and tilt and turn windows, where the same sash can also tilt inward at the top. This page covers what the swing direction changes: rain and wind performance, clearance for furniture and curtains, egress, cleaning and screens.

How an inward-opening sash is held shut

When the sash is closed, it sits against a gasket on the frame, and a multi-point lock pulls it against that gasket around its perimeter. Wind pressure from outside pushes the sash toward the frame, in the direction the gasket seals against. For an outward-opening sash, the same pressure acts to lift the sash away from the frame, so the lock and hinge hardware carry that load. This is a design principle, not a measured advantage: the actual air and water performance of either type is established by testing.

Rain and wind

What decides water performance

Swing direction does not by itself decide whether a window leaks. Three things do:

1. The tested rating of the unit. In the North American window standard AAMA/WDMA/CSA 101/I.S.2/A440, the Performance Grade (PG) rating reflects the lowest result among the applicable tests, and a PG 60 product has a 60 psf minimum design pressure and has passed the water penetration test at 9 psf, which is 15 percent of that pressure (FEMA). A higher PG rating means a higher water test pressure.
2. The sill and drainage detail. Water that gets past the gasket must be able to drain out again, which is a function of the profile design and of how the opening is flashed.
3. The installation. Flashing, sill pan and sealant at the rough opening are the installer's and architect's detail, not the window's.

Ask for the PG rating and test report of the exact unit and glazing. Compare them against the design pressure of the project location.

While the window is open

An open inward sash is sheltered from the weather on the room side but is still exposed on the outside glass.

• Tilt position: the sash top leans into the room, so rain falling straight down runs down the outer glass face, which gives some shelter from vertical rain. Wind-driven rain can still reach the opening at the top.
• Turn position: the sash is fully open, and rain can enter like any open window. Occupants close the sash before storms.
• Wind gusts: an inswing sash held open in turn mode can be caught by wind and swing against furniture or the wall. Hardware makers offer retrofittable anti-slam devices that secure the sash in the tilt position. One maker lists an 80 mm (about 3 in) tilt depth for such a device.

Furniture, curtain and wall clearance

The arc of the sash is the planning constraint. A sash swings through floor and wall space about as wide as the sash.

• Furniture and radiators: keep the swing arc clear, or limit the opening with a stop where the use allows.
• Curtains and blinds: drapery in front of the window blocks the swing and must be drawn aside or mounted on a rod that clears the arc. Roller shades and shutters that sit inside the window reveal can collide with a tilted sash.
• Deep sills: a sill that projects into the room reduces the reach to the handle and can block the sash in tilt. Natural Resources Canada also notes that deep sills, closed drapes and blinds, and nearby furniture block air movement at a window and can let cool air pool near it, raising condensation risk on the glass. See window condensation.
• Walls and doors: a sash that swings 90 degrees may hit an adjacent wall, a door leaf or a window beside it. Check the hinge side relative to the nearest wall in the plan.

For heavy sashes, the corner hinge carries the load. One heavy-duty hinge line is rated for up to 440 lb (200 kg) on tilt and turn sashes and 660 lb (300 kg) on turn-only sashes, so sash weight and sash width should be checked together at the specification stage.

Egress

Under the 2021 IRC, every sleeping room and basement needs at least one operable emergency escape and rescue opening. The net clear opening must be at least 5.7 sq ft (5 sq ft at grade floor), at least 24 in high and 20 in wide, with the bottom of the clear opening no higher than 44 in above the floor (R310.2.1 to R310.2.3). The opening must be operable from inside without keys, tools or special knowledge (R310.1.1), and the dimensions are measured as the result of normal operation of the opening.

What this means for an inward-opening window:

• The sash swings into the room, so the usable clear opening is determined by the frame opening less the hinge side and any hardware in the opening, and not by the sash outside it. Measure the result in the fully open position.
• Tilt does not count as the egress position.
• A key-locking handle is a problem on an egress window if the key is needed to operate it from inside.
• Window opening control devices and fall prevention devices that comply with ASTM F2090 are permitted on required egress windows in the 2021 IRC, provided they can be released for full opening.

States and cities amend the IRC and may require more. Confirm with the local building official. See egress window requirements and do European windows meet US code.

Cleaning

An inward sash that turns fully open puts the outside glass within reach from inside. In tilt mode the sash stays in the frame, so reach to the outer glass is limited. Cleaning from inside does not apply to units that are fixed, to outswing casements, or to sashes too heavy or too tall for the occupant to handle.

Screens

The inward swing means the screen cannot occupy the same space as the sash. Insect screens for inswing windows are mounted on the exterior of the frame. One US screen maker states that its fixed exterior screen works only on units where the sash sits outside the frame when closed (offset sash) and not on flush sash and frame designs. This is a frame-profile decision made before ordering. Fixed exterior screens are removed for cleaning or stored for winter, which differs from the operable screens US occupants often expect.

When inward opening is the right choice

• The exterior has no space for an open sash, as on narrow balconies and walkways.
• Cleaning the outside glass from inside matters.
• Weather exposure at hinges and operators should be avoided.

It is a poor fit where the room side is tight, where heavy drapery or built-in furniture sits at the window, or where a room-side screen is mandatory. For the comparison with the common US outswing type, see tilt and turn vs casement, and for how these conventions differ more broadly, European vs American windows.