Porch Plexiglass Storm Windows

This is my first instructable. It is about time I gave back to the community as I have used the site plenty of times for my own projects. So thank you to everyone who has posted!

The purpose of this instructable is to outline the process I used for building plexiglass storm windows for our outside covered patio.....or as we call it the catio. The issue was that our cats love being out here, but living in the midwest, winters can be a bit chilly. As a result, we started looking for ways to seal the windows during the winter. We like the full screen windows in the summer and didn't want to install windows that would block any of the airflow when the weather is nice outside.

First I looked at installing sliding windows and also got a quote from a window installer. The quote was over $6000 so we defenestrated that idea. Next I looked at custom storm inserts. This quote was better but I still didn't want to spend $3000+ for this project. I started looking into material costs for making storm windows myself. At first I was very discouraged. The shipping cost for the plexiglass sheets was going to be much more than the cost of the sheets themselves. Fortunately there was a plastic supplier with a local office (piedmontplastics) who not only cut the sheets for me, but the price came in way under what I was looking to spend. Total the plexiglass ended up costing $360.32 for 9 windows and a door.

Step one is measuring. Measure and document your measurements. Then think about it some more and go back and remeasure. Be sure to take into account the thickness of the wood and the weatherstripping that you are going to install around the frames. I measured with the goal of having the plexiglass sit 1/2" into each side into the wooden frames with 1/4" clearance around the outside that would be filled by the weatherstripping. As you can see I had plenty of help with the measurements.

I ended up buying 5" x 72" x 1" boards and ripping them to 2" x 72" x 1" pieces. I know every woodworker out there is saying you shouldn't do that because it can cause the board to change and you're right! For my project however, the frame was still rigid enough and the strength of the plexiglass ended up fixing any curved pieces. Used my table saw blade to cut a dado for the plexiglass which worked really well as the plexiglass was 1/8" and the table saw blade is the same thickness. I cut this 1/2" into each side of the frame. Then I painted all the pieces of the fame.

I pre-drilled pilot holes for the frames and used a 2.5" screw to attach three parts of the frame. I then slid the plexiglass in from the top and finally attached the top piece with two more 2.5" screws as pictured. Be careful not to screw the screws in too tight because it can crack your frames. The second picture of the frame with no plexiglass was a test frame to make sure it would fit as I envisioned. Not a bad idea to make one and check your measurements before doing the rest! In retrospect I would have gotten two smaller pieces of plexiglass for the door and put a cross-piece of wood in the center. It is still plenty strong, but off all the frames this one had the least structural rigidity.

I bought two hooks for each frame just in case. This would prevent high winds from knocking one of the frames out onto my cats! With the weatherstripping, the fit was so tight I don't know if even need them, but it makes me feel better.

The windows turned out really well. They block the outdoor air even better than I expected. I had two inspectors come out immediately to make sure my project was up to code! Using my multi-meter to measure temperature differences, I was pleasantly surprised. It was a 10 degree C difference between indoors and my porch and a 8 degree difference between the porch and outside. For Fahrenheit reference it was about 74 in my house, 55 on the porch, and 41 outside. This porch to outside ratio has held up pretty well enabling my cats to enjoy being outside on days down to about -1 degrees C.