To push the sustainable building envelope further, we are performing a total gut rehab of a condex at 19-21 Judson Street, Haverhill, MA. We recently constructed two new Energy Star homes at 7 67th Street and 10 68th Street on Plum Island, but this will be our first Energy Star-rated remodeling project.

We will update the entire exterior of the building and install new windows and doors. In unit 21 we will install renewable energy equipment, specifically a geothermal heat pump with desuperheater for heat and hot water and photovoltaic panels for electricity. The other unit will be refitted with conventional, gas fired heat and hot water systems. This will allow us to compare the energy costs of each unit to get an accurate payback for the renewable equiptment installed.

The structure, built in 1988, according to code contains R-11 fibergalss-batt wall insulation and R-30 fiberglass-batt ceiling insulation with thermal-pane, double-hung windows. We will install cellulose (recycled newspaper) insulation in the walls with an exterior wrap of two-inch, rigid styrofoam, thereby improving the wall R-factor to R-25. The flat ceiling will contain blown-in loose fill cellulose (R-50). The sloped ceiling will contain blown-in cellulose covered by a two-inch layer of rigid polyisocyanurate insulation (R-40). In the basement ceiling we will reuse the fiberglass batt insulation in the walls and ceilings, layering it to R-30. We'll place Tyvek wrap on the basement ceiling to seal the loose  fiberglass in place. We'll replace all double-hung windows with Andersen 400-series, high-performance, low-e 4 casement units.

The two units differ in terms of insulation and energy systems. We will not gut unit 19; it will retain its R-factors. An upgraded, gas-fired heating system and traditional hot water tank will be installed. Unit 21 will receive a new Florida Heat Pump ground source heat pump with desuperheater to preheat hot water. Hot water will be heated by a Rinnai on-demand hot water heater, more efficient than a tank heater due to the elimination of standby loss. A two-kilowatt capacity Evergreen Solar photovoltaic array will provide one hundred percent of the unit's electricity needs when the sun is shining. 102 square feet of south-facing glass will provide passive solar heating. An extra layer of sheetrock will provide the additional thermal mass needed to store the solar energy.  All south facing glass is shaded by overhangs sized to prevent overheating from the sun during the summer months. Solar heat will provide the equivalent of 100 gallons in free heating oil yearly.

When completed, unit 21 will be Energy Star certified and gold rated by the National Association of Home Builder's Green Homebuilding Program. We will use green products, such as cellulose insulation, Hardiplank composite siding, and Timbertec composite decking on the exterior building envelope. Inside, we'll use formaldehyde free cabinets, low VOC paint, engineered hardwood flooring. We will equip all light fixtures with LED or CFL lighting. We'll use Energy Star rated appliances and ventilation. We'll insulate all hot water pipes and insulate, seal, and test all heating ducts  to meet Energy Star specifications.

According to energy modeling conducted by Energy Star, unit 21 will have a HERS rating of 38. A home built to current building codes would have a HERS rating of 100. So, the unit will use 38 percent of the energy a conventionally-constructed building would use. We will be able to verify this model by comparing the energy consumption of the two units.  We will also calculate the payback for the renewable energy measures.