The Davis House

This renovation transformed this building from an energy guzzler to a resilient and healthy spacious 2-family, designed to use less energy than it produces. Careful planning resulted in high efficiency of the building envelop, of the heating, cooling and ventilation systems. The solar panels provide the energy needed to run this two family.

This is important because:

Existing structures, outnumbering new housing nearly 300-to-1

"The greenest building is the one that’s already built, in almost every case.”

There are 130million housing units that already exist. 80 % will still be here in 2050. This is where many of our efforts should be.

The goal was to reduce the energy use and increase the usability of the building within the same footprint by:

New envelop:     Roof R-60 to 62.5, Walls R-48, Bsmt-Walls R-23, Slab R-20 3 pane windows: (SW,
NW,NE) U 0.21, SHG 0.19, VLT 0.32
(SE) U 0.25, SHG 0.31, VLT 0.34
Retained 60% more solar gain on the SE for passive solar heat.

Windows added by 50% to South, removed by 50% to North

Provided solar shading ACH .85 to 1.2 @ 50P
Equipment:
A hybrid solar system with 56 Sunpower solar panels for PV combined with 12 Sundrum panels attached
under the PV panels provide power and hot water. The hot water is for
both domestic use and for the basement radiant slab.

3 minisplits per unit provide both heating and cooling.
Each unit has a HRV which provides preconditioned air to  all rooms and works with booster fans to
exhaust bath and kitchen air. The condensing washer-dryers don’t require an exhaust fan. With these
strategies we minimized the number of exterior envelop penetrations from the mechanical equipment
and provide for a much healthier indoor
environment with constant fresh air supply

Each unit has a HRV which provides preconditioned air to  all rooms and works with booster fans to exhaust bath and kitchen air. The condensing washer-dryers don’t require an exhaust fan. With these strategies we minimized the number of exterior envelop penetrations from the mechanical equipment and provide for a much healthier indoor environment with constant fresh air supply.

Layout:
Redesigned layout with combined rooms for spaciousness. Expand interior to exterior with decks and added windows. Expand living space to basement & in attic by lowering floors and adding daylight.

Minimize visual clutter, use transparent materials (see stairs).The sustainability of the design is enhanced by resource efficiency: many of the building materials used are reused or recycled, for example bathroom floor tiles are the former slate roof. The floors were reinstalled. Demolished chimney bricks were reused. One staircase was rebuilt, a stair and cabinet built with wood from a nearby demolition site, recycled ceramic tiles and recycled tire decking etc.

The healthy indoor environment is due to using no or low off-gazing building materials and a continuously operating ventilation fan supplied preheated out door air. The redesigned room layout assures the spacious feel for the interiors. Although the apartments are small, about 1360 SF, with a lot of daylight and transparent adjacencies between the non-private rooms, the space feels generous. New decks also expand the interior spaces to the exterior.

Recycled furniture in both apartments complete the sustainability of the project.

Quick Facts

General

Location
13 Elmwood Street
Somerville, MA01244
United States
Building Type 2-family residence
Project Type
Basis of Performance Claim
Bedrooms
Conditioned Floor Area 3 130

Energy Summary

Energy Data Type
Renewable Energy System Type(s)
Ratings
Annual renewable energy generated 8 586

Envelope and Mechanicals

Subslab assembly
Foundation wall assembly
Above grade wall assembly
Door Assembly
Air Changes per hour, ACH50

Project Team:

ArchitectTeam Member: Franziska Amacher

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 3 130

Location and Climate Details

2-family residence

Address
13 Elmwood Street
Somerville, MA01244
United States
Location Type Urban
Climate Region Zone 5
Köppen Climate Type Dfb
Lat. / Long. POINT (-71.126418 42.4000709)
Elevation 50
Solar Insolation 4.47 kWh/m2/day
Annual CDD and Base Temp 1016 | 75
Annual HDD and Base Temp 5754 | 68

Site

Site Conditions:

Site Description:

Monthly Energy Data and Utilities

Energy Data Type:

Electric Utility: NSTAR Electric

Gas Utility:

Renewables and Energy Balance

Renewable Energy Sources:

Renewable Energy System Description & Details:

Annual renewable energy generated 8 586
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 23.00
Above grade wall assembly
Above grade wall R-value 48.00
Cathedral ceiling assembly
Cathedral ceiling R-value

Windows and Doors

Window Assembly:

Door Assembly:

Average window U-factor 0.21
Door U-Factor
Door Area

Mechanical Systems

Space cooling - Manufacturer & Model mitsubishi,
Space heating - Manufacturer & Model mitsubishi,
Domestic hot water - Manufacturer & Model Solar Thermal System, 120 gal solar tank with 4500w electric backup
Domestic hot water - capacity
Ventilation - Manufacturer & Model Lifebreath,
Lighting Manufacturer and Model
Lighting Efficiency
Mechanical Equipment Installation Details and Comments

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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