Short answer: For shed, barn, and playhouse windows up to about 24 × 36 in., 1/8 in. clear acrylic is a good replacement for glass: it's half the weight, much harder to break, and it won't fall out in sharp shards. Use 3/16 or 1/4 in. for larger panes, and choose polycarbonate instead where balls, kids, or livestock will hit the window.
Where acrylic makes a good window
Acrylic is a smart replacement anywhere glass is a nuisance or a hazard: outbuildings, garden sheds, barn stalls, greenhouses, workshop doors, playhouses, and camper or trailer windows. It lets through about 92% of visible light (as much as or more than glass), stays clear outdoors for years, and is anywhere from 2 to 20 times more impact resistant than ordinary glass of the same thickness, depending on maker and test. When it does break, it cracks into a few large, dull-edged pieces instead of a shower of shards.
It's not right for every opening. Acrylic scratches more easily than glass, and for windows in a house, door glazing, or anywhere near a floor, codes often call for specific safety glazing. Check your local code or ask your inspector before using any plastic in an occupied building.
Acrylic or polycarbonate?
This is the real decision. Be honest about what the window will face:
| Situation | Better choice |
|---|---|
| Shed or barn window that just needs to let light in | Acrylic: clearer, stiffer, lower cost |
| Playhouse or treehouse where kids climb and hit things | Polycarbonate |
| Next to a basketball hoop, ball field, or driving range | Polycarbonate |
| Horse stall or livestock pen where animals kick or lean | Polycarbonate |
| RV or camper side window with a frame and seal | Acrylic, often tinted |
| Greenhouse glazing | Either; see the greenhouse guide |
Polycarbonate is roughly 30 times tougher than acrylic and practically unbreakable, but it scratches more easily, yellows sooner outdoors, and costs more. More detail in acrylic vs polycarbonate.
What thickness to choose
- 1/8 in. for panes up to about 24 × 36 in. in a frame with stops on all sides.
- 3/16 in. for panes up to about 36 × 48 in., or smaller panes in windy spots.
- 1/4 in. for larger panes, panels held only by screws, and camper windows that see road vibration.
Match the thickness of the old glass if the frame has a fixed channel. Single-strength glass is about 3/32 in. and double-strength about 1/8 in., so 1/8 in. acrylic drops into most old frames.
Colors for outbuildings and campers
Clear is the default. Gray and bronze tint (1/8 to 3/8 in.) cut glare and heat in campers and south-facing sheds. Frosted gives privacy in a bathroom outbuilding or a barn tack room while still letting light in. For campers specifically, see acrylic for boat and RV windows.
Installing it so it lasts outdoors
Outdoors, the main thing to plan for is movement. Acrylic expands and contracts with temperature more than wood or glass, about 0.2 in. over 48 in. in a 100 °F swing.
- Cut the pane 1/8 in. smaller than the opening in each direction so it can grow on a hot day.
- If you screw through it, ask us to drill the holes oversize (about 1/8 in. bigger than the screw) and use washers. Snug the screws, don't crank them. The thermal expansion calculator gives exact hole sizes.
- Seal with a neutral-cure silicone or glazing tape, not solvent-based caulk, which can craze acrylic.
- Never drill acrylic yourself with a standard wood bit; it grabs and cracks the sheet. We drill holes for you on request.
Measure the opening, then order it cut to size. If the shape isn't a rectangle, upload a drawing.
Questions
How long does acrylic last as an outdoor window?
Acrylic is one of the most weather-resistant clear plastics and typically stays clear for decades in full sun; clear sheet from major makers such as Acrylite and Plexiglas carries a 30-year non-yellowing warranty. Scratches from cleaning are more likely to age it than the weather; see can acrylic be used outdoors.
Can I cut a replacement window myself?
Thin sheet can be scored and snapped, but edges chip easily and holes crack if drilled wrong. Ordering it cut and drilled saves a ruined sheet.