One of the most critical parts of the construction process was running a blower-door test before drywall so we could seal any leaks we found. Our energy model had assumed 600 cfm50, and that’s what we achieved.
Overall cost. The cost of the house, not including the land, was $196 per square foot — about the same as comparable custom homes in this area. That includes the cost of the ground-source heat pump and radiant slabs ($28,000), but not the cost of the wind turbine ($27,000). Superinsulating the shell added around 6 percent to the cost, while keeping the shape simple helped keep costs down. We did, however, choose custom cabinetry and higher-cost fixtures, so the overall cost of the home has as much to do with our finish choices as it does with energy efficiency or “green” design.
Heat-pump cost. Ground-source heat pumps have the reputation of being very expensive. For one thing, they are most efficient at heating when used with a low temperature emitter like a radiant slab, which adds to overall expense. In our case, the addition of the GFX and the variable frequency drive on the well pump also added expense, as did some extra controls, gauges, and shut-offs in the hydronic system. Compared with conventional forced-air heating or hot-water baseboard, a ground-source system is costlier, but then so are systems that include radiant heating and condensing boilers. When installed where there’s already a standing column well (or one has to be drilled anyway), a ground-source heat pump may turn out to be only slightly more expensive than radiant heat with a condensing boiler, and it allows for the use of renewable energy to power it.