Now that we’ve had a month of high temps, I wanted to add a few pics to my workshop blog and report on the design. I’m very pleased with the passive cooling ideas and am happy to report success at achieving comfort (relative, of course) with one 8000 btu window unit.
I chose to build the workshop with wood framing so that I could incorporate several desirables into the shop. I wanted several windows and needed /wanted four doors. I also chose not to insulate the walls/per se and simply painted the inside of the sheathing white for brightness in the shop.
The few pictures following will show some of the design ideas that are working well for me. Although there is practically no R-value in “bubble foil”, it does repel radiant heat. I wrapped the entire building in it and maintained the required air space using 1.5” thick “nailers”. You’ll notice that I furred out for window and door openings and placed the stripping much closer together where the 12” wide cement siding was applied vertically. The two sides that have sheet metal exterior did not need the same level of support as it is much lighter per square foot.
On the roof, I used the radiant barrier foil as well as galvanized sheet metal which will be shiny and repel radiant heat well for the first few years. When the metal roofing dulls, the bright foil will remain.
There’s a large shade tree to the east of the shop, giving morning shade, but I also used wide overhang for one third of the east wall, then a porch to help shade the many windows and east wall. Though insulated, the windows do rob me of btus and interior wall space. This is, however, too pretty a place to not enjoy the view.
With the building on a concrete slab, the earth helps to temper the building and I was pleased last summer to notice that the shop stayed reasonably cool until 1 or 2 pm. In December, I took great pleasure in having someone else do the work and had a metal carport built on the west side of the shop. In designing the carport, my goals were simple, keep the sun off the camper it is designed for and shade the workshop from the afternoon sun. There’s generous air flow with large openings at the front and rear of the carport, as well as the top and bottom of the west wall. I believe on key feature is the air gap at the top of the east facing clerestory wall. As the hot air rises, it is allowed to escape out the top. The carport “breathes”, not trapping heated air and at the same time has reduced wind resistance to storms compared to solid walls. We had 100 mph winds here during Hurricane Katrina, something I hope not see again.
I can comfortably work in the shop on a sunny afternoon, temps in the low 90s, and not break a sweat with only the 8000 btu a/c running. I generally start the a/c a couple of hours before spending time out there. The floor covers about 750 sq ft and there’s room overhead ranging from 9 ft to 13 ft. My one goal for improvement is to find some quilts or comforters to attach to the inside of the two roll up doors that are not being opened during this hot season. Should I want to unload material through the large front door, I’ll simply remove the 8 or so spring clamps holding the quilts in place.
I strongly recommend shade, either natural or man-made. I’ve used agricultural shade cloth on several occasions over swimming pools, decks, etc. and that’s an easy and cheap way to go. I’d thought I might use it to shade the west wall of the carport, but that seems superfluous at this point. Good luck at keeping your cool this summer, fellow LJs!
-- Like Guy Clark sez - "Sometimes I use my head, Sometimes I get a bigger hammer"