Let me start this section by stating my vents are clearly over designed and I'm still not convinced they are the best way to get the job done. I attended one of the short courses on solar kilns given by Dr. Brian Bond at Virginia Tech. I recall that he wasn't completely pleased with the off-the-shelf foundation vents they were using on the kiln. Also, most of the other kilns I've seen utilize a top hinged door for the vent covers.

I thought the hinged door covers would be a bit difficult to regulate well so I opted to design my own. Essentially they are two horizontal doors that slide on upper and lower tracks. They are easy to adjust accurately, but their downfall is they don't do a good job if we get a driving rain (which doesn't happen too often), and construction is quite a bit more involved. Future plans for the kiln include an awning made from the leftover polycarbonate above the top vents. This should help keep rain out of the vents and even off the back door cracks and crevices. There are lots of ways to skin this vent cover cat. Pick the method that works best for you.

The vent covers were constructed from leftover treated 1/2" plywood from the interior sheathing and some treated 1x appearance boards. The first step was to put some horizontal boards inside the vent openings to keep the doors from falling into the vents. I could've just as easily made the doors larger than the vents and let them slide against the exterior sheathing, but I already felt the openings were too large so it wouldn't hurt to fill them some. With all of the doors cut, they were used as guides to locate the upper and lower slides made from the same plywood.

Materials for the vent doors Top and bottom boards added The doors before being cut in half were used as spacers to determine the position of the top and bottom slider boards

Once these slides were in place they allowed for the installation of the appearance boards with a little overhang. This overhang serves to hold the doors in place. Basically this was a "built up" rabbet instead of cutting rabbets into each top and bottom trim piece. Unfortunately, in an effort to get a reasonably tight fit on the doors, many wouldn't slide well or at all. The fix was to rabbet the edges of the doors until they slid easily. So, despite my effort to avoid rabbeting a bunch of boards, I ended up doing it anyway.

Installation of the slider boards complete and the door removed Side view of the trim board installed and the resulting slot for the doors A little custom fitting on the doors to make them slide easier

With all of the custom fitting complete, the doors were slid in. The double doors allow an unlimited amount of accurate adjustment. A couple of the tighter fitting doors get tough to move when it rains and they swell, but hopefully the future awning will reduce this.

Doors closed Doors half open or half closed if you're a pessimist Doors full open
All of the vent doors complete
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