Owner Builder Projects
A Super-Insulated Home
My wife and I wanted a compact, low maintenance house for our retirement years (whether we retired or not), and we particularly wanted to make a statement of energy efficiency and cost effectiveness
For several years we made calculations around solar designs, and concluded that a passive design was the route to go on new construction. We choose pre-stressed concrete beams (Flexicore) for the floor to provide thermal mass. By calculation this mass was not enough to avoid overheating on sunny winter days, so we put 10 runs of 4 inch plastic pipe under the basement slab in 10 runs, a total of 400 feet, underneath the shaded areas in the south basement family room and all the floor area in the utility room and work room. There is 1 inch of blue board under the ducts and slab.
This system takes air from the clerestory and injects it under the slab and is thermostatically controlled. This was a fortunate decision because the early model catalytic wood stove we purchased tends to generate a lot of heat early in its fuel cycle. The heat storage capacity of the basement slab is sufficient to take care of the excess. Stove air intake is through the foundation drainage tile.
Our hot water bills are so low we could not justify the cost of a solar hot water heater; we use 100 therms of natural gas annually for hot water heating for a cost of about $65.The tankless water heater (a Paloma unit) doubles as backup furnace. Its input of 89,000 Btu per hour is more than adequate to handle our calculated hourly losses of 30,000 Btu per hour at minus 30 degrees F of 30,000 Btu. Or first winter, with 7407 degree days, confirmed our calculations within 10%. We burned 3273 lbs. of wood (1 1/8 cords) and 6o therms of gas for heating. Insulation of R54 in the ceiling and R30 in the walls along with a remarkably low infiltration rate plus 65% of our heat from the sun explains our low fuel consumption. Test by Wisconsin Power and Light Co. showed total leaks of 0.46 square feet, 1.97 air exchanges per hour in a 30 mph wind, and 0.09 air exchanges per hour in still air. We do have a homemade air to air heat exchanger.
Cathedral ceilings are a problem in our cold, humid climate, but such a ceiling was essential for our clerestory design. Our solution was Cubic Structures of McFarlane, WI. Their system consisting of notched bead board blocks that fill the spaces between the 10” rafters and meet 2” above them. Sheathing is applied with pole-barn nails through the 2” projection. We applied rolled roofing over the sheathing, the treated 2x2 furring strips (notched for drainage and ventilated horizontally), and finally metal roofing. Thanks to very careful application of the Visqueen vapor barrier there has been no moisture problem. Our carpenter-builder even taped the staple lines in the Visqueen on the rafters and taped plastic bags enclosing the electric boxes on the ceiling and outside walls.
The walls are plaster, sheet rock, 1” Thermax, 2x4 studs, 2” blueboard, then the Insulcrete system for an outside finish. The south windows are double glazed; the large ones are patio door replacement panels, which saved us some money. These south windows have thermostatically controlled window quilts which open and close quite appropriately in cold weather when we are not at home (Window Showcase from Appropriate Technology, Brattleboro, VT). All other windows in the house have manually operated quilts or Thermax panels. The clerestory panels are ganged and operated simultaneously from one loop of cord in the living room.
Pella low-emissivity slim shades on the east have been a good low maintenance substitute for awnings. In summer our 2 foot south overhang is expanded to 4 feet by swinging a slatted 2 foot portion out from under the soffit and holding it with telescoping, spring loaded aluminum struts. Summer indoor temperatures reach 80 degrees F after a week of 90 degree outdoor temperatures.
Louvered vents high in the clerestory provide a good stack effect for night time ventilation. We have no north windows, but the north rooms have abundant light and winter mid-day sun from the clerestory through large tempered glass windows in the upper portions of interior walls.
An unusual landscape feature is scarcely visible corduroy parking strips in the front yard among ground cover of Aguga.
Our cost was $105,000, which does not include the work of the owners, namely all the inside plumbing, inside wiring, masonry behind the stove, ceramic tiling totaling 2500 8x8” tiles, and most of the wood trim finishing inside and out. The cost does include a 24’x25’ garage of pole barn construction, sided with locally sawn vertical oak boards and battens. The boards are nailed on one edge only and the battens screwed through the girts from the inside, holding the unnailed board edge and preventing splitting due to shrinkage.
We have no major dissatisfactions and feel a great deal of gratitude to architects John Schaffer and Dennis Ostdyke. We also developed respect for the many helpful local craftsmen. Jeff Lardy, our carpenter-builder, was essential to the entire project, from planning to finishing and all stages in between. His skill and experience as a master carpenter was combined with enthusiastic interest in our sometimes radical innovations. His unflappable good nature kept us all working harmoniously together through the inevitable rough spots, and our friendship has survived and thrived. As fairly elderly first time owner-builders (we were both in our 60s) we are gratified at our accomplishment, but do not intend to repeat the experience. I am especially grateful to my wife for her trust in my inventions and designs. The book, Low Cost Energy Efficient Shelter (Eugene Eccli, ed., Rodale Press, 1975) was especially useful.
Possible suggestions I would make to someone following our plans include considering argon-filled low emissivity glazing to see if it would be cost effective in the context of really good moveable window insulation. If used with such insulation, I doubt that it would solve the problem of condensation on the cold glass when the insulation is first removed on a cold morning. Also, in areas of high radon levels, the basement slab would probably need to be modified.
Published in Designer’s Circle, winter 1987