Collector


The hard work of framing the solar kiln collector (otherwise known as a roof) was covered in the framing section. Before the polycarbonate sheets could go on, an additional support framework was put in place. Treated 1x4 appearance boards were used. Why treated? It was the most cost effective off-the-shelf solution available at the local hardware giant. All horizontal boards were ripped down to about 2 1/4" while the verticals were left full width. Two intermediate horizontal boards were included to help support the long lengths of polycarbonate.

With the new support framework in place, all of the roof boards including the 2x4 rafters were painted flat black. Anything that would be exposed to sunlight and not get covered by interior sheathing was painted with the cheapest gallon of flat black I could find at the local Habitat for Humanity restore.

Collector support framework in place Collector support framework in place Collector support framework in place
An interior view of the bottom horizontal collector support An interior view of the top horizontal collector support - we'll need some caulk to fill the gap I used a hand plane to trim down the lower support piece flush with the sheathing.  I did this so the trim work would butt up nicely against the polycarbonate.
El cheapo flat black latex paint Painting complete on the collector support framework Painting complete on the collector support framework
Painting complete on the collector support framework

The support framework was complete and ready for the polycarbonate panels. Two rows of "wiggle foam" was installed at the top and bottom horizontal boards while single rows were installed at the two intermediate boards for additional support. The wiggle foam is sold right along with the corrugated polycarbonate. Using some spray adhesive on the backs of the wiggle foam helped hold them in place until the polycarbonate could be installed. Some standard adhesive backed foam weatherstripping was put down on the two vertical boards on the end.

Wiggle foam for horizontal support of the polycarbonate Spray adhesive to hold the wiggle foam in place Basic weatherstripping for the vertical contact points
Wiggle foam and weatherstripping installation complete Wiggle foam and weatherstripping installation complete Wiggle foam and weatherstripping installation complete
Closeup view of the double rows of wiggle foam Closeup view of the vertical weatherstripping installed

Corrugated polycarbonate can be found at just about any hardware store. It is important to purchase the clear panels that are UV resistant. If not, they will begin to become brittle and may only last one or two years. These panels were purchased at Home Depot. They are made by Palram and are branded as Suntuf. The hold down screws with rubber washers were also available right along with the wiggle foam and panels.

On all of the horizontal runs the screws were placed at the corrugated peaks to help minimize any water leaking in. Unfortunately, that wasn't possible on the vertical runs, but hopefully the rubber washers will do their jobs. I predrilled holes at all of the screw locations. The foam weatherstripping on the vertical supports had to have small sections cut out at each screw location before predrilling. If the weatherstripping isn't cut away, the drill bit or even the screw itself will grab the foam and twist it up into a big mess. Obviously this was learned the hard way.

With all of the holes predrilled, installation of the polycarbonate was just a matter of laying a panel on the wiggle foam, screwing it down, then laying the next panel on with some overlap. Each panel was 2' x 12' so there was a substantial amount of overhang. I found that the easiest way to trim the polycarbonate was to first draw where I wanted the cut line with a sharpie. Then I scored the line with a utility knife. If it is scored well then you can easily create a starting cut at the edge of each panel with the utility knife then simply roll the excess polycarbonate. It should separate at the score line as you roll it. If it stops separating, don't force it. Pull out the utility knife and go back over the score line to make sure there were no skips.

Hang on to the excess polycarbonate. You never know when you may find a good use for it.

A ridge cap was needed to finish off the collector panel installation. A polycarbonate ridge cap was available but it was pretty expensive and I didn't see the value of polycarbonate in an area that wouldn't really contribute to the heat gain of the kiln. On the same shelves were some Onduline corrugated panels and ridge caps. The Onduline ridge caps were less expensive so I grabbed a couple of those and topped off the kiln.

Polycarbonate installation started Closeup view of the panel screws in place Polycarbonate panel installation complete
Polycarbonate panel installation complete Polycarbonate panel installation complete Closeup view of a panel edge - 12' kiln length doesn't leave much panel overhand on the ends.  Trimwork may barely fit under the panels.
Rolling off the excess panel Collector panel installation complete Collector panel installation complete
Collector panel installation complete Ridge cap installation complete Closeup view of the ridge cap
Ridge cap installation complete Ridge cap installation complete View of the ridge cap from the north side 
 
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