Overview: Passive Solar Garden Habitat Domes -

I am starting a new phase of my business to build prefab Garden Dome Kits for delivery within the New England area. I will seek out local sources of materials and keep shipping to a minimum. Domes will come in two sizes - 18 ft and 29 ft as these are best for creating the least amount of raw material waste during construction. The passive solar part is a large solar mass in the form of a 1000 gal water tank for the 18 and a 1500 gal water tank for the 29. The heat stored in the tank from the sun on a sunny day helps to heat at night and on cloudy days. The tank is located on the north side of the dome and the dome above and behind the tank is covered with a reflective material that helps direct low winter sun to the tank and shades the tank from the summer high sun.

The dome is a standard 3 frequency geodesic with 3/8 of a sphere sitting on a 2 ft base wall and consists of 5 full hexagons, 6 full pentagons (one at top), and 5 top half hexagons. An example of calculating space for a dome like this is located here.

Details For 29 Foot Habitat (18' specs are a bit smaller):

Base Panels are approx 6 ft wide and are made of 2x6 Pressure Treated bottom sills, 2x6 Fir Studs, and 2x6 Fir top sill. Panels are divided into three sections, each filled with two sheets of 2" Dow Blue Styrofoam outdoor rated at R20. The inner foam sheet on each end is not installed until the panels are bolted together. Panels are bolted together with two 1/2"x4" galvanized bolts at each end. Exterior is finished with either Fir T-111 or Pine T&G. Other exterior finishes can be used depending on cost and personal preference. Panels are numbered 1-14 clockwise from North with the Door Panel at location 15. Inner panel walls are finished with either galvanized sheet metal where raised beds go.

Hubs are powder coated steel cylinders with welded tabs at the appropriate angles. There are 6 Pentagon Hubs, 5 Hexagon Hubs, 20 Corner Hubs, 5 Hexagon Base Hubs, 5 Left Hand Base Hubs, and 5 Right Hand Base Hubs for a total of 46. Each tab has two holes to allow for 2-1/4" Stainless Steel Bolts to attach each Strut. Struts are 2x4 Fir and are color coded for Pentagon Spokes, Hexagon Spokes, and Perimeters as they are different lengths. Struts are dipped in Waterproofing Sealant to protect from moisture.

Glazing consists of 75 triangles: 45 for Hexagons and 30 for Pentagons made of double walled 10mm (3/8") Polycarbonate with an R value of 2 and 80% light emission (by Macrolux). Panel seams are covered with 3M 8672 Acrylic Tape. Two top Panels are fitted with Bayliss auto vent openers.

Passive Solar heating is mainly accomplished by storing collected solar gain in a large water tank. For the 29' Habitat an 9 ft diameter tank 4 ft high is used with an EDPM rubber liner holding approx 1500 gallons. The Tank wall is galvanized sheet metal painted flat black to absorb solar radiation. The dome above and behind the tank is covered in a foil-bubble-foil material that aids in insulation and also reflects the low winter sun onto the tank as well as shades the tank during high summer sun.

Progress:

Component pieces are complete and actual assembly of my demo/prototype will not start until the ground has thawed (sometime in March) as a 30 ft diameter area needs to be leveled and prepared for the dome base. Base panels are completed and struts are cut. All insulation is cut to size. Polycarb sheets waiting for final dimensions and cutting (not until dome frame is up). A 3/8 dome does not sit completely flat at the half hexagons so some adjustments have to be made to get a flat profile to sit on the base. I added 11 degrees to the bottom of all struts that sit on the base which allows the bottom frame to now sit flat. See pictures for my test build where I made some engineering changes to cuts to get dome to sit flat on base. First assembly to make sure all angles and strut lengths are correct and test hub angles. Everything fits but tolerences are very tight so some pushing and pulling is required during assembly but everything ends up being very tight even before a final tightening of all nuts and bolts. Some unevenness along base but test build area is not perfectly flat and level so that affects the angles of the frame. Final build site that is flat and level should line up all sections evenly.

Pricing: My 29 Foot Model is available for $9950 with free delivery within 100 miles of New Durham, NH. My 18 Foot Model will be $7950. These include:

• 15 Prefab Base Panels 2'x6' with 4" rigid foam R-20 insulation in 2x6 frame
• 120 Prefab 2x4 Struts cut to length, predrilled, and color coded, waterseal treated
• 46 Custom Hubs 4" with tabs fabricated steel welded, drilled, and powder coated
• 75 Prefab Polycarbonate triangular Panels 10mm (3/8") double walled R-2 plus galvanized screws
• 5 Rolls 3M 8672 Poly Tape 2" for Polycarbonate Panel Seam sealing
• 2 Bayliss MK7 Heavy Duty Auto Vent Openers for 2 Hexagon upper panels to act as vents
• 80'x2' Galvanized sheet metal for base panel inner wall/perimeter raised bed lining
• Galvanized sheet metal 28'x4', 20'x20' EDPM rubber lining, rigid foam insulation for Water Tank
• Complete Stainless and Galvanized Nuts and Bolts for dome frame and base panel assembly
• Your choice of either Standard Pine T&G Boards or Fir T-111 for base panel outer covering
• Dow rigid Styrofoam outdoor rated R-10 2" insulation for under perimeter raised beds and outside base panel wall to provide frost barrier - all 30 pieces precut (same material in base panels)
• Entry Door is NOT included (too many options) rough opening for 36" wide door provided