Butler Residence

Brian Butler and his company Boston Green Building recently retrofitted and remodeled his home in Medford, MA (a continental climate). The house was undertaken as part of a pilot program administered by the regions electric and gas company National Grid. To demonstrate the feasibility of reducing energy use in existing structures by 50% or more, the untility provided partial funding for this and several other deep-energy retrofit projects in Rhode Island and Massachusetts.

The house is a two-family Dutch colonial built in 1908. It has two apartments totaling 3,200 square feet. Though previous owners had replaced the siding, its thermal performance was dismal. The wall cavities weren’t insulated, as were most of the third-floor ceiling cavities. The gambrel rafters had some loose batts, and there was spotty cellulose in the attic ceiling. Space heating was provided by an overworked pair of natural-gas boilers and distributed by steam radiators, with domestic hot water from 50-percent-efficient standing-pilot tank-type heaters. Blower-door tests showed that both units leaked around 3,500 cfm.

Brians plan for the renovation aimed to insulate the exiting framing cavities, wrap the entire structure in rigid foam, replace windows, and upgrade mechanical systems including the addition of a solar PV array. Brian moved into the upper level while work commenced meaning the second unit wouldn’t get the interior insulation or air-sealed drywall. While this would result in a slightly lower insulation values the project opened up a new market of retrofitting condos and apartment style housing alike.

Post-project blower-door tests showed air infiltration reduction from 3,500 cfm to just 350 cfm in the lower unit while the upper, untouched on the interior, reduced to 1,800cfm. With the combined effects of this projects deep energy retrofit and leased PV solar array energy costs have plomited. The house represents an 82% reduced annual energy consumption from its baseline of 37,389 kwh to just 6,819 kwh. Given the houses overall performance in combination with the PV solar array the house’s energy consumption is reduced 97% to a mere 846 kwh annually – an average of 70.5 kwh a month. Brian has retrofitted a building to generated energy while conserving it. This brings attention to the untouched methodologies of home renovation.

Quick Facts

General

Location
24 Princeton St
Medford, MA02155
United States
Building Type Two-family residence
Project Type
Basis of Performance Claim
Bedrooms
Conditioned Floor Area 3 200

Energy Summary

Energy Data Type
Renewable Energy System Type(s)
Ratings
Annual renewable energy generated 7 439

Envelope and Mechanicals

Subslab assembly
Foundation wall assembly
Above grade wall assembly

Dense-pack cellulose blown into existing 2x4 stud wall cavities , 7/8” existing board sheathing wrapped with HardieWrap weather barrier. Second stud wall, 2x3, was constructed behind the existing to create another layer of blown packed celluslose. 2 layers of 2” foil faced polyiso board and a single layer of 1” layed onto the exterior – all seams staggered and sealed with Dow Weathermate Tape. A minimal amount of screws were used for the first two layers.

Door Assembly
Air Changes per hour, ACH50

Project Team:

Other Team Members:

Ratings:

Awards:

Completion

Completion Date:

Scope

Type of Construction
Number of buildings
Floor area of each building
Bedrooms
Stories
Conditioned Building Volume
Conditioned Floor Area 3 200

Location and Climate Details

Two-family residence

Address
24 Princeton St
Medford, MA02155
United States
Location Type Urban
Climate Region Zone 5
Köppen Climate Type Dfb
Lat. / Long. POINT (-71.1094842 42.4059811)
Elevation 20
Solar Insolation 4.47 kWh/m2/day
Annual CDD and Base Temp |
Annual HDD and Base Temp |

Site

Site Conditions:

Site Description:

Monthly Energy Data and Utilities

Energy Data Type:

Electric Utility: National Grid

Gas Utility: National Grid

Renewables and Energy Balance

Renewable Energy Sources:Renewable energy is generated within the building footprint (e.g. solar PV on the roof),

Renewable Energy System Description & Details:

Annual renewable energy generated 7 439
Annual Renewable Energy Generated Data Type
Power Rating 7Watts
Renewable Energy System Type(s)
Source of Annual Production Data

Walls and Roof

Subslab assembly
Subslab R-value
Slab edge assembly
Slab edge R-value
Foundation wall assembly
Foundation wall R-value
Above grade wall assembly

Dense-pack cellulose blown into existing 2x4 stud wall cavities , 7/8” existing board sheathing wrapped with HardieWrap weather barrier. Second stud wall, 2x3, was constructed behind the existing to create another layer of blown packed celluslose. 2 layers of 2” foil faced polyiso board and a single layer of 1” layed onto the exterior – all seams staggered and sealed with Dow Weathermate Tape. A minimal amount of screws were used for the first two layers.

Above grade wall R-value 54.00
Cathedral ceiling assembly
Cathedral ceiling R-value

Windows and Doors

Window Assembly:

Door Assembly:

Average window U-factor 0.19
Door U-Factor
Door Area

Mechanical Systems

Space cooling - Manufacturer & Model Mitsubishi mini split,
Space heating - Manufacturer & Model Mitsubishi mini split,
Domestic hot water - Manufacturer & Model
Domestic hot water - capacity
Ventilation - Manufacturer & Model Zehnder HRV,
Lighting Manufacturer and Model
Lighting Efficiency
Mechanical Equipment Installation Details and Comments

Three-head ductless minisplit from Mitsubishi provides heat from the downstairs until; the upper apartment is heated with an AO smith water heater piped to a Unico fan-coil system. Each unit is also equipped with its own 90-perfect-efficient Zehnder HRV. A grid connected 7kw photovoltaic array supplies the lower unit with electricity.

Envelope

Air Changes per hour, ACH50
Air Changes per hour, CFM50

General Process

Design for Adaptability:

Software Tools

Software Tools:

General modeling information:

Lessons Learned

Outcome of Project Goals:

Discrepancies:

Rebates and Financial Incentives

Federal incentives
Local incentives
State incentives
Utility incentives
Other incentives
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