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The short answer for older windows
A window air conditioner needs two things from an older window: a firm seat and a slight lean toward the outside. LG's manuals for the LW1022FVSM and the LW1224RSMX both say the unit is designed for a standard single-hung or double-hung window, and that non-window installations are not proper for those models. A storm window frame can change the depth of the opening and can hold the cabinet level, which works against the lean the maker asks for.
So the decision is not wood frame versus vinyl frame. The first question is whether the storm frame leaves room for the cabinet to tilt down and back. If it does not, LG's manuals describe a wood strip on the inner sill to lift the mounting point. Midea's manual for the MAW06R1WWT takes another route, with separate installation sections for wooden windows and vinyl-clad windows and a note about a storm window that blocks the unit. The window types guide covers which openings take a window unit at all.
Why the tilt decides the fit
Midea's window air conditioner FAQ says a unit should be slightly tilted so condensed water from the evaporator flows to the back and is expelled, and it lists water leaking inside the house as a sign the tilt is wrong. LG's manuals say the back should sit slightly lower than the front: about 1/4 inch on the LW1022FVSM and about 1/2 inch on the LW1224RSMX. Both LG manuals also say the bottom of the unit should sit between 30 and 60 inches above the floor.
A storm window frame that props the cabinet up can cancel that lean. That is why the wood strip in the LG guidance is not a cosmetic shim: it restores the angle the drainage depends on. The tilt guide explains the same principle on an ordinary double-hung window, and the leak guide covers what a wrong angle looks like indoors.
What LG's manuals say about storm frames
LG's manual for the LW1022FVSM states that a storm window frame may prevent the air conditioner from tilting down toward the outside, and that for proper drainage a piece of wood is attached to the inner sill, trimmed to a length that fits inside the window frame. The manual's figure shows the top of the wood strip set higher than the top of the storm window frame, at 3/4 inch. The LW1224RSMX manual describes the same idea with a 2 by 2 piece of wood on the inner sill.
Both manuals also warn about the window itself. On vinyl or similarly built windows, the LW1022FVSM manual says to fasten the L bracket with a type A screw, and the LW1224RSMX manual says to fasten the window locking bracket with a type C screw, so the glass and frame are not damaged. The LW1022FVSM manual also includes heatproof foam to be inserted between the upper and lower sash. The support bracket guide covers the bracket side of the job.
| Model | What the manual says about the window |
|---|---|
| LG LW1022FVSM | Standard double-hung window; wood strip on the inner sill when a storm frame blocks the tilt; about 1/4 inch lean to the back |
| LG LW1224RSMX | Standard double-hung window; 2 by 2 wood strip on the inner sill for a storm frame; about 1/2 inch lean to the back |
| Midea MAW06R1WWT | Separate steps for wooden and vinyl-clad windows; pitch to the rear for drainage; storm window drain holes must stay open |
Midea's wooden and vinyl-clad steps
Midea's manual for the MAW06R1WWT does not treat every older window the same way. It has one set of fastening steps for wooden windows and another for vinyl-clad windows, and it notes that a pilot hole keeps a wooden sill from splitting. That split matters on an older sill that has already been drilled for a previous unit.
The manual also gives a pitch figure of 5/16 inch toward the rear, which it calls necessary for proper condensate management and drainage, and it warns that the pitch has to hold even if the side panels are left off. For a wooden window it gives a range of roughly 3/4 inch to 1 inch at the measuring point it shows. Those figures are the maker's, and they are the ones to work from rather than a guess.
Storm window drain holes and the outer frame
Midea's manual addresses the case where a storm window blocks the air conditioner, and the case where the storm window frame has to stay in place. In that second case it says the drain holes or slots in the storm frame must not be caulked or painted shut, because rainwater and condensation have to be able to drain out. That is a check worth making before the unit goes in.
LG's manuals handle the same water in a different way. Both describe a slinger fan that picks up condensed water and throws it against the condenser, and the LW1022FVSM manual says the drain cap should normally stay in place, with removal only for storing the unit for the season. The drain plug guide explains how that differs from a portable unit's tank.
Sealing the sash and the sides
Older windows leak air around the sash even when the unit fits. Midea's FAQ describes the black foam strips that come with the unit as a way to block the window sash, wedged between the front and back window once the unit is installed. LG's LW1022FVSM manual includes heatproof foam cut to length and inserted between the upper and lower sash, and says the foam improves cooling capability.
The side panels matter too. Midea's manual says the accordion panels should sit securely in the frame channel, and LG's manuals warn that the side and top louvers must not be covered or blocked. The side panel guide goes through the sealing points in order.
When the window cannot be adapted
Some storm frames sit too far forward, or the opening is too shallow, or the frame is fixed in a way that will not take a wood strip. LG's manuals are clear that their window units are meant for standard double-hung windows and that other installation methods are not proper for those models. Forcing a fit is not the answer, because the tilt and the bracket are what hold the cabinet in the opening.
In that case the choice is another window in the room, or a portable unit that vents through a window kit instead of sitting in the frame. Portables are ranked on the seasonally adjusted cooling capacity figure, the Department of Energy number for portables, so compare them on that number only. The portable versus window comparison sets out the trade-offs, and the buying checklist lists what to confirm before ordering.
Which to choose
| If you | Look for |
|---|---|
| If you have a storm window frame that holds the cabinet level | Plan for the wood strip LG's manuals describe on the inner sill, sized to the window frame, so the unit can still lean to the back. |
| If the sill is old wood that has been drilled before | Follow Midea's wooden window steps, which include a pilot hole so the sill does not split. |
| If the window has vinyl cladding | Use the vinyl-clad steps: LG's manuals call for a specific bracket screw type, and Midea's manual has its own fastening section for these windows. |
| If the storm frame has to stay in place | Check that its drain holes or slots are open, as Midea's manual requires, before the unit goes in. |
| If the opening is too shallow for any tilt | Look at a portable unit with a window kit instead of a window unit, and compare portables on the seasonally adjusted cooling capacity figure. |
Questions people ask
Does a storm window frame stop a window air conditioner from working?
Not by itself. LG's manuals say a storm frame may prevent the unit from tilting toward the outside, and they describe a wood strip on the inner sill to restore that angle. If the frame cannot be adapted, the unit should go in another window.
How much should the unit lean toward the outside?
LG's manual for the LW1022FVSM gives about 1/4 inch with the back lower than the front, and the LW1224RSMX manual gives about 1/2 inch. Midea's manual for the MAW06R1WWT gives a pitch of 5/16 inch toward the rear for condensate management.
What is different about a vinyl-clad window?
The fastening. LG's LW1022FVSM manual says to attach the L bracket with a type A screw on vinyl or similarly built windows, and the LW1224RSMX manual says to attach the window locking bracket with a type C screw. Midea's manual has a separate vinyl-clad section.
Why do storm window drain holes matter?
Midea's manual says that if the storm window frame must remain, its drain holes or slots must not be caulked or painted shut, because rainwater and condensation need a way out. A blocked slot can leave water sitting against the frame.
Can a portable unit be used instead?
Yes. A portable vents through a window kit rather than sitting in the frame, so the storm window only needs to accept the kit. Compare portables on the seasonally adjusted cooling capacity figure, the Department of Energy number for portables, and not on the listed BTU figure.