Venting a portable AC hose through a basement window can be done by making some modifications. An air conditioner allows you to cool and dehumidify the basement, but the windows are usually too small for a window unit. A portable air conditioning unit uses a vent hose to remove its heat and moisture from the room. You can use a clear acrylic, rigid foam board or a plywood panel for a customized vent hose installation.
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Vent Hose Considerations
A portable air conditioner needs a venting system made for its specifications. Unfortunately they do not offer venting kits for basement or casement windows. You must devise a safe way to do this yourself.
Do not vent a portable air conditioner out of a basement window in a dryer vent opening. The average dryer vent is 4 inches and the average air conditioning vent is 5 or more inches in diameter so it will not fit. Even though the vent hose is flexible, scrunching it into the dryer vent opening will not allow the venting system to work as it should.
The air conditioning air flow is not as strong as a dryer's air stream, so it will not open any hatches that a dryer's air pushes open during operation. This would not allow the air conditioner to vent, possibly overheating and damaging the unit.
Clear Acrylic for Light
Vent your hose through a piece of clear acrylic that you have installed in your window. Simply take the measurements of the glass in your basement window and get a piece of acrylic cut to size at a local hardware or glass store, or cut the acrylic yourself. Cut a hole for your air conditioner's vent hose off to one side of the panel. Bring the vent hose with you to guard against any mistakes in cutting the correct size hole.
It is not recommended the venting hose be extended for a portable air conditioner, in fact it may void out your warranty if you do so. For this reason you will need to bring the unit close to the window, which may mean preparing a pedestal of some type to lift the unit so the venting hose will reach the window. Keep all this in mind before picking out the place for the hole to be drilled in the panel. Even a few inches one way or another can make it too far away for the hose to reach, so do the preplanning of where everything will be placed before having a hole drilled.
Rigid Foam Board for Insulation
Use rigid foam insulation board as a replacement for your window glass if cutting off the outside light and view is not an issue. Foam board is very flexible and less expensive than acrylic. It is also easy to cut. Foam insulation board also helps keep the cooler air inside your basement.
Remove your basement window glass and cut a piece of foam board to the exact size of the glass panel. Cut the hole for the vent by tracing the vent hose opening on the material first. Put a few beads of window caulking along the sides of the foam board and wedge it into the window opening. Put your vent hose through the hole, you can always shave a little extra off if the hose does not fit, so it is better for it to be cut on the smaller side rather than larger.
Basement windows that open by pushing out from the bottom can be fitted for the vent while in the open position. Use a piece 2-inch-thick rigid insulation board with the vent hose opening already cut and wedge it at an angle between the bottom of the open window and the window sill. Seal the edges or use weatherstripping to prevent water intrusion from sprinklers or rainstorms.
Security and Venting
When security is an issue, consider combining a window vent kit with window locks. There are a variety of readily available products manufactured for use with air conditioner vent hoses and windows.
Alternately, cut a piece of plywood or siding to size, add the vent hose hole and paint to match the exterior. Screw the panel to the wall or insert into the window track. However, don't block the only window exit from the basement; in an emergency, you must be able to get out of the house safely.