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The author with the solar thermal panels that heat his workshop's floor.

My wife Rebekah and I decided to move from California to rural Maine for many reasons—mostly to live an affordable rural lifestyle in a beautiful environment. Having survived the California "energy crisis," we became even more energy conscious. Rebekah even started to refer to me as an energy nazi!

Using solar energy is something I have always wanted to do, ever since reading the Whole Earth Catalog in the late '60s. We were fortunate enough to make a significant profit on the sale of our suburban house in California, and used some of the proceeds for solar energy equipment and energy reduction in our new home in Maine.

We replaced all the incandescent lamps in the house with low wattage fluorescent lights, and purchased a Staber clothes washer. We plan to install a grid-intertied, solar-electric system for the house this year. Rebekah drives a 2001 Honda Insight and loves it! She gets an average of 61.2 mpg on most trips.

We both work at home, and wanted to be sure to have warm, comfortable, and well-lit work spaces. Rebekah's basement knitting studio is heated by a woodstove that heats most of the house. A propane backup heater fills in at night so we don't have to get up and stoke the stove. Our property includes a recently constructed barn that is perfect for my needs.

I make furniture and design electronics for a living. So I need two distinct work spaces. The barn has a full second floor for my electronics lab. That dish antenna you can see above the solar collectors is for a StarBand satellite modem. For my engineering work, I absolutely require high bandwidth. Due to our rural location, a satellite modem is the only viable high-bandwidth option. As soon as cable internet service is available, I will switch, since I find the slow speeds and long delays of the satellite to be much worse than advertised. Bad weather can knock it out entirely!

I suffer from migraine headaches that are triggered by cold temperatures, so heating in the Maine winters is crucial for my well-being. I decided to use a radiant heated floor, which is known for comfort. A particularly nice feature is that the heat rises up from the floor to warm my large, floor-mounted power tools. I had no intention of freezing my hands off in the Maine winters! The radiant floor is heated primarily by two, 4 by 8 foot (1.2 x 2.4 m) SunEarth Empire series solar collectors, augmented by an AquaStar (AQ125-BLP-S) propane on-demand water heater.

Sometimes the Maine winter is relentless—an AquaStar tankless water heater fills in when the sun doesn't shine.

The heating system begins with the two SunEarth solar collectors that are connected in parallel. A PV powered pump circulates the heated glycol mixture through a heat exchanger. A second PV powered pump circulates heated water into the 80 gallon (300 l) storage tank. A thermostat controls the AC pump that feeds the two, 300 foot (90 m) loops of tubing in the concrete floor.

System Design

My first step was to have a heat load analysis done by Peter Talmage of Solar Market in Arundel, Maine. This helped to define my heating system design goals and insulation requirements. The barn was bare stud walls on a concrete foundation and rough concrete floor when we acquired it. It had been built to store the previous owner's lobster boat.

The floor plan is 24 by 28 feet (7 x 8.5 m), with a 10 foot (3 m) high ceiling on the ground floor and a full second floor. The ground floor is framed with 2 by 6 lumber, and the 45 degree roof (unfortunately facing east and west) is framed with 2 by 8 rafters. The barn had seven original windows, and I installed two, standard, well-insulated exterior doors.

Guy's barn was oriented the wrong way to put his solar panels on the roof. The shed Guy built on the south end has a 45 degree roof pitch— perfect for the two, 4 by 8 foot solar hot water panels.

Guy's barn was oriented the wrong way to put his solar panels on the roof. The shed Guy built on the south end has a 45 degree roof pitch— perfect for the two, 4 by 8 foot solar hot water panels.

Corbond spray-on foam insulation has an R-value of about 7.3 per inch.


The first task of any solar heating design is to get the best possible insulation for the walls, ceiling, and floors, and thoroughly seal any openings that would allow unwanted cold air into the building. I insulated the windows with removable Windo-Therm interior plastic double glazing that will be used only in the cold season (five months in Maine).

I insulated behind the original sliding barn doors by adding two in-swinging doors, which fit within the doorway when closed. Resembling hinged wall sections, the auxiliary doors are framed with 2 by 6s, filled with fiberglass, and finished with 3/s inch (10 mm) exterior plywood. They are thoroughly weather-stripped. These are huge (4 x 9 foot; 1.2 x 2.7 m) and imposing to open—I call them the "Doors of Doom!"

I contracted the installation of Corbond—a sprayed-in polyurethane foam insulation—throughout the structure. Corbond has an approximate R-value of 7.3 per inch. I had 3 inches (7.6 cm) installed in the walls on the ground floor, and 4 inches (10 cm) in the walls upstairs. A significant advantage of the foam is that it forms an airtight seal throughout the building. I left the building to air out all the urethane fumes for over four weeks before completing the interior work.

The exterior walls of my barn were 1 by 10 inch shiplap barn boards installed vertically over 1 by 2 inch horizontal battens. A layer of Tyvek housewrap is in between the battens and shiplap. As such, it was far from airtight. I added fiberglass inside (over the Corbond) to increase the R-value to about R-30 downstairs and about R-40 upstairs, and installed drywall over that. I estimate that I have approximately R-37 in the roof.

Radiant Floor

For the radiant floor, my first job was to install 1 inch (2.5 cm) polystyrene high density construction insulation over the existing concrete floor. I then laid 6 inch (15 cm) steel grid (commonly referred to as road wire) over that for securing the radiant tubing, using nylon cable ties. I laid out two loops of 300 feet (90 m) each of the tubing, which I connected to a manifold in the utility room.

A local contractor did a great job of pouring 3 inches (7.6 cm) of concrete over the tubing. I asked him to use a 4,000 psi fiberglass mix to give me a strong workshop floor. Naoto Inoue at Solar Market sourced the materials for this job and specified the details. He originally suggested 2 inches (5 cm) of concrete to create a very responsive system.

Laying 1 inch polystyrene insulation board over the old floor insulates the heated slab from the earth.

Laying 1 inch polystyrene insulation board over the old floor insulates the heated slab from the earth.

The 600 feet of hydronic tubing is held in place by road wire.Three inches of concrete will make the final layer.

Hydronic Loop Layout

Large Doors

Utility R

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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