Energy & Atmosphere
TARGET: 29.5 POINTS
The buildings we live in consume large quantities of our energy resources. The goal is to reduce the amount of energy required. We have taken a number of steps in that direction:
The ceiling has a minimum of 6 inches of polyurethane foam spray for an R-value of approximately 39. All rim board areas are sprayed to a minimum of 4 inches.
Basement walls are framed with 2 x 4’s sideways on a 2 x 4 sill to allow complete coverage of walls with a minimum of 2” thick spray foam below grade and 3 1/2” on the above grade basement walls.
Above grade 2 x 6 walls (except for the plumbing wall of the master bath) are sprayed with a minimum of 2 inches of foam and then filled in with 3 ½ inch high density R = 15 batt insulation.
The plumbing wall of the master bath is a 2 x 4 outer wall with 3 ½ inch of foam. The inside wall is then furred out with 2 x 4’s in the narrow direction to allow an inside cavity for plumbing.
The complete spray foam shell and careful attention to sealing around openings resulted in an ACH50 blower door test of between of approximately 0.8 ACH. Sealing to this level requires a forced ventilation system.
The largest area of windows is directly south facing with an overhang and solar screen coving the upper windows. The solar screen allows full winter sun while completely blocking the sun during June, July and August. Windows are all metal clad, double glazed, krypton filled with an average U in the 0.3 -0.31 range and a SHGC of about 0.3.
HEATING & COOLING DISTRIBUTION SYSTEM
Although all HVAC ducts and the air handler are locating within the conditioned envelop a Duct Blaster test was conducted and the duct resealed to minimize leakage and improve system performance.
SPACE HEATING & COOLING EQUIPMENT
A Manual J calculation resulted in a winter heating load of slightly more than 40, 000 BTU per hour and a cooling load of approximately 2 tons. A three stage 60,000 BTU furnace (FUE > 95%) was chosen and a 2 stage 3 ton air-conditioning system (SEER > 15) because the system operates more efficiently at lower heating and cooling loads than a smaller 2 stage 40,000 BTU system and single stage 2 ton cooling system. The larger system is also more responsive in retuning to normal temperature levels from low setback temperatures. Four heating/cooling zones are used to improve comfort and improve system efficiency.
The kitchen and master bath are stacked in the house design and the guest bath and powder room are within 20 feet of the hot water heater. A 1-inch diameter manifold system is used with ½ inch diameter hot water lines running directly to each fixture. The manifold and water lines including bends are insulated to an R = 4 level. The water heater is a gas-fired sealed combustion tankless water system with an efficiency of greater than 82%.
Almost all lighting is 5 inch recessed cans. Lights are are more than 80% dimmable CFL or LED light bulbs. All exterior lighting is controlled switches with a photovoltaic override.
High efficiency appliances were selected. The refrigerator, dishwasher, washing machine and ceiling fans in the master bedroom and screen porch are all ENERGY STAR. In addition, a dishwasher that uses less than 6.0 gallons per cycle and a clothes washer with a modified energy factor (MEF) > 2.0 and a water factor (WF) < 5.5 were chosen.
There are 12 Kyocera KD 205 (watt) panels for a total of 2.46 kW were installed on the garage roof. The system is expected to generate 3,045 kW hours per year. The HERS reference home annual electricity demand is 11,423. The percentage of HERS annual reference electric load supplied by renewable energy system is 3,045/11,423 = 26.6%. We expect the house to use less electricity than the HERS prediction so that the PV system will actually supply a higher percentage of the load. Conduit was provided for future solar panels on the roof of the main house.
OFF THE GRID
Madison Gas & Electric offers a buy-back program for the energy we generate. They pay us about $0.25 per kwh generated and they charge us about $0.13 per kwh used. Separate meters keep track of the generated and used power.