Notes from Windward: #68
Roofing Gray Box
As we edge ever closer to our goal of creating working models of sustainable sytems, the projects we undertake are intended to serve more than one purpose--Gray Box's new roof is a good example.
Sustainable systems have to be flexible in order to respond to changing conditions--since nature is about constant change, we need to be able to respond accordingly. One way we've chosen to insure flexibility involves using shipping containers to create systems which can be moved and reconfigured with relative ease as illustrated by our use of one of our 20' containers to set up the PowerLab where we're doing our research into generating electricity using solar-thermal systems.
Annie replacing some sun-warped deck boards
Vermadise was created using twenty-foot wide pre-bent arches made from galvanized steel tubing. It's a common greenhouse design that we decided to use to create an unusual space by mounting the arches along the inside edges of two 40' shipping containers set 20' apart--Gray Box to the west and Red Box to the east.
The idea was that this would create a 20'x40' work area with a ceiling high enough that we could use it to work on our larger pieces of equipment during the dead of winter. When the snow's too deep to do useful work, that's a great time to be doing maintenance and repair so that these key tools will be ready to go come the spring.
The idea worked well enough for a first-time try, but the primary problem we found was that the rain that fell on the plastic cover ran down the inside surfaces of the containers creating something more akin to an ice-skating rink than a work area. It was clear from that experience that we needed to put some sort of roof on the tops of the containers to catch the runoff from the plastic, and channel the water into a gutter system that captured the rainwater for later use.
In early April, our ground is too damp and wet to do much in the garden, so we're using this window of time to finish up some infrastructure projects such as installing the first of the container roofs designed to catch the runoff from the plastic roof and channel the rainwater into holding tanks. Ground water has dissolved minerals that would foul the inside of a boiler tube, so we'll store and use rainwater to feed the solar steam boiler that will eventually drive our steam-powered generators.
Roofing Gray Box was a project that we'd gotten started on, and then gotten side-tracked onto something else before it was finished. A couple of summers later, some of the deck boards were sun-warped and so the first step was to cut out the warped boards and replace them with boards cut on our saw mill. The warped boards where cut up and sent uphill as kindling for the kitchen woodstove.
Once the deck was repaired, the next step was to insulate the container with six inch thick fiberglass batts. The design we're using is called a cold roof since the insulation in placed on the roof of the interior space rather than against the roof. That creates an air gap between the insulation and the roofing, thereby preventing heat from being conducted from the roof to the container. As heat passes through the metal roof, it heats the air underneath it, the heated air rises along with the slope of the roof and is exhausted thereby routing the heat away from the inside of the container.
The next step, screwing down the metal roofing, is mostly a matter of paying attention to detail to insure that each sheet lines up with the end of the joists and the previous sheet. The key reason we use metal roofing is that here at the edge of the Cascadian wilderness, there's always a risk that summer will bring a forest fire. We've worked to lessen our forest's fuel load, but when a fire comes through, embers can rain down over long distances--and at that point, a metal roof is the best fire insurance you could hope for.
Notes From Windward - Index - Vol. 68