If you own a greenhouse, you have probably have learned the benefits of louvered vents for your exhaust fans or a standalone openings for letting fresh air in- or warm air out of the greenhouse. Whether automated, manually-operated, or merely blown open by the air flow from a fan, they are open when needed and closed when not, helping maintain the conditions within.
Unfortunately, those openings also provide an excellent way for insects to enter the greenhouse.
To get around that issue, I built some highly effective, yet inexpensive enclosures – vent screens – that cover the outside without interfering with the louver’s operation.
The parts and tools needed are all available at your local home improvement store:
- Aluminum flashing used to cover the fascia on a building. I suggest 8″ or 9″ width.
- Extruded plastic or aluminum window screen frame material, with corners (here’s a cross section):
- Window screen
- Spline
- Silicone caulk or glue
- Masking tape
- Tin snips or a hack saw
- Spline tool
- Drill
- Pop rivet tool (sheet metal screws may be substituted)
- Tape measure
Fabrication is pretty straightforward, too:
- After measuring the outside dimensions of your louvered vent frame, starting from one end, mark the 1″ lip of the flashing at distances corresponding to the length of the bottom, side, top, and other side of the vent, in that order, then add one more inch.
- Cut the length of the flashing at that last mark, and cut only the lip at the other four marks. All cuts should be perpendicular to the edge – in other words, at 90° angles.
- Using the sharp edge of a table or board, bend the wide part of the flashing 90° at those cut points, with the lip facing inward – you’ll overlap them at the corners. Apply silicone caulk to that extra, one-inch “tab”, and press it against the inside of the first side segment. Use masking tape to hold it temporarily in shape. At this point, you should have an 8″ tall box with a 1″ lip to the inside.
- Measure and cut the window screen frame so it will fit on that lip, with the outer edges matching the walls of the aluminum box.
- Assemble the screen frame with the spline groove to the inside, stretch the screen over it, and affix the screen by pressing the spline material into the groove with the spline tool.
- With the lip side of the aluminum box facing upward, apply a bead of silicone caulk to the center of the lip, and place the assembled screen on top of it.
- Drill holes through the corners of the screen frame and overlapping corners of the aluminum box lip, and affix them with a pop rivet.
- Once the glue has set up, remove the masking tape and slide the open end of the box over your louvered vent frame. Drill a few more holes and affix the box with more pop rivets. Run a bead of silicone caulk at the edge of the box to ensure a seal with the frame, and you’re done!
