White Claw Farm Net Zero Deep Energy Retrofit

We bought an 1,142 sf one story house with full basement, gutted and superinsulated it, and added 192 sf on piers. The initial blower door test was 3,117 CFM50. Interior finishes were in poor shape; the floor plan was worse. We wanted to fix an existing building on a developed site rather than build new, even with the attendant compromises. Windows, doors, fiberglass batts, and mechanicals were salvaged for others’ use. All systems and interior finishes were replaced.

 

The basement walls were insulated with three inches of polyiso foam, about R-18. Retrofit insulation hasn’t yet been applied to the slab, R-10 is installed beneath appliances and stairs. 2x4 flat horizontal strapping was applied to the existing 2x6 walls and 2x10 rafters, separated by small pieces of 1-1/2 inch polyiso foam, so as to create a thermal break and a deeper cavity. Walls are 8-1/2 inches and the roof is 12-1/4 inches, and both are filled with water-blown spray foam, first three inches of closed cell, then open cell. Effective R values are R-32 walls and R-44 roof. The exposed floor is R-50. The blower door is 141 CFM50, over 20X reduction.

Windows are Alpens with foam in the hollow fiberglass pultrusion. Half the glazing faces south. Casements/awnings have triple, SHGC 0.59 argon-filled glazing with two Cardinal 180 low-e coatings – the NFRC U value is 0.18. South-facing fixed windows have a low- iron outer pane to bump the SHGC to 0.62; U value is 0.16. The skylight is a Wasco with similar triple glazing.

Doors are foam-filled fiberglass with double low-e argon-filled glazing which will be replaced with high R value glazing.

Lighting is screw-base LED. The house is beautifully daylit. Appliances are Energy Star and the range has an induction cooktop. An eMonitor provides energy data on most circuits.

A 3⁄4 ton ducted (350 CFM) Fujitsu heat pump (AOU9RLFC, 12.2 HSPF/21.5 SEER) provides heating and cooling. Ducts are sealed with mastic and heavily insulated. Space setpoint is 70F with no setback (I have found little savings setting minisplits back). We expect reduced consumption this next year from solving a control quirk in the heat pump that caused excess energy usage. A Zehnder ComfoAir 200 provides ventilation at close to 90% efficiency via a dedicated duct system.

A Stiebel Eltron HPWH makes hot water. PEX piping is insulated, with short runs. The HPWH extracted energy is roughly equal to the waste heat from the 15 ft3 freezer and PV inverter. Delta H20 Kinetic showerheads deliver a great shower with low flow. A horizontal axis washer saves water and drying energy.

Onsite power is a roof-mounted, grid-tied 4.76 kW Sunpower system which generated 22% more energy than was used. Total energy use was 13 kBTU/sf/yr or 41 kWh/m2/yr.

A woodstove provides ambiance and heat during outages – it was not operational during the data period.

Our location facilitates cycling to work and errands, reducing our transportation energy. The 1,128 kWh excess produced could power an electric vehicle over 3,000 miles as well!

Quick Facts

General

Location
235 Great Plains Road
West Tisbury, MA02575
United States
Building Type Single-family residence
Project Type Zero Energy
Basis of Performance Claim Verified,
Bedrooms 3
Conditioned Floor Area 1 334

Energy Summary

Energy Data Type Measured,
Renewable Energy System Type(s) Photovoltaics,
Ratings
Annual renewable energy generated 6 148

Envelope and Mechanicals

Subslab assembly

No added insulation as yet - 2" planned

Foundation wall assembly

The basement walls were insulated with three inches of polyiso foam.

Above grade wall assembly

Walls are 8-1/2 inches, filled with water-blown spray foam, three inches of closed cell, then open cell.

Door Assembly

Doors are foam-filled fiberglass with double low-e argon-filled glazing which will be replaced with high R value glazing.

Air Changes per hour, ACH50
Rosenbaum after southwest view Rosenbaum before southeast view Rosenbaum after southeast view Rosenbaum after west addition view Rosenbaum final blower door test Rosenbaum interior strapping detail view Rosenbaum after spray foam view Rosenbaum northeast bedroom daylighting Rosenbaum great room looking east Rosenbaum great room looking west

Project Team:

Other Team Members:

Matt Coffey, architect
Pascal Albanese, builder
Ben Brungraber, structural engineer
Peter Romaniello, lighting design
Matt Viaggio and Ned Reynolds, insulation
Sean Welch, electrician
Phil Forest, SMC, PV installer

Ratings:

Awards:

Completion

Completion Date: Friday, November 1, 2013

Scope

Type of Construction Renovated,
Number of buildings
Floor area of each building
Bedrooms 3
Stories 1
Conditioned Building Volume
Conditioned Floor Area 1 334

Location and Climate Details

Single-family residence

Address
235 Great Plains Road
West Tisbury, MA02575
United States
Location Type Suburaban
Climate Region Zone 5
Köppen Climate Type Dfb
Lat. / Long. POINT (-70.630337 41.412775)
Elevation 80
Solar Insolation 4.51 kWh / m2 / day
Annual CDD and Base Temp 480 | 78
Annual HDD and Base Temp 5835 | 68

Site

Site Conditions:

previously developed land, running water, preexisting structure(s),

Site Description:

Monthly Energy Data and Utilities

Energy Data Type: Verified,

Electric Utility: NSTAR

Gas Utility:

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: 4.76 kW Sunpower system with 5 kW SMA inverter

Annual renewable energy generated 6 148
Annual Renewable Energy Generated Data Type Measured,
Power Rating 5Watts
Renewable Energy System Type(s) Photovoltaics,
Source of Annual Production Data Measured at a dedicated meter post-inverter

Walls and Roof

Subslab assembly

No added insulation as yet - 2" planned

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

The basement walls were insulated with three inches of polyiso foam.

Foundation wall R-value 18.00
Above grade wall assembly

Walls are 8-1/2 inches, filled with water-blown spray foam, three inches of closed cell, then open cell.

Above grade wall R-value 32.00
Cathedral ceiling assembly
Cathedral ceiling R-value

Windows and Doors

Window Assembly:

Windows are Alpens with foam in the hollow fiberglass pultrusion. Half the glazing faces south. Casements/awnings have triple, SHGC 0.59 argon-filled glazing with two Cardinal 180 low-e coatings – the NFRC U value is 0.18. South-facing fixed windows have a low- iron outer pane to bump the SHGC to 0.62; U value is 0.16. The skylight is a Wasco with similar triple glazing.

Door Assembly:

Doors are foam-filled fiberglass with double low-e argon-filled glazing which will be replaced with high R value glazing.

Average window U-factor 0.18
Door U-Factor
Door Area

Mechanical Systems

Space cooling - Manufacturer & Model Fujitsu heat pump,
Space heating - Manufacturer & Model Fujitsu heat pump AOU9RLFC / ARU9RLF ducted single zone heat pump,
Domestic hot water - Manufacturer & Model Stiebel Eltron HPWH
Domestic hot water - capacity 80
Ventilation - Manufacturer & Model Zehnder ComfoAir 200,
Lighting Manufacturer and Model LED Green Creative,
Lighting Efficiency
Mechanical Equipment Installation Details and Comments

Duct Blaster test 27 CFM25

Envelope

Air Changes per hour, ACH50
Air Changes per hour, CFM50 141.00

General Process

Once we bought the new house in the fall of 2012, we began to work on the new design. We were starting with a one bedroom house of 1,142 sf, on one level with a full basement.

There were some framing oddities that were revealed as the gutting process proceeded. The house, though very leaky, had 2x6 walls and 2x10 rafters. It had a low wall plate height of about 7'6" but most of the house had ceilings that followed the roof line. Its south side faced about 11 degrees east of true south. We had good solar access, which was improved with some selective tree cutting. There was a separate outdoor entrance to the basement, but it cut off east light to the house.

Given that we both might end up working at home in years to come, we wanted three bedrooms. Although it’s a bit of a luxury, we had developed an appreciation for having two bathrooms for when guests visit (and for eventual resale of the house). After the sun-drenched quality of Nerdwood we never got used to the paucity of natural light in the main public space of House 5, especially in the winter when it was shaded by the house to the south, so a well-glazed south façade was a key program element. And we wanted a good entry space with a generous closet and space for a bench.

I worked on several schemes, including variations that added a small addition to the existing one floor house, and variations that added a partial second floor. I had some solutions that would be good but added too much new space, which drives up the cost. I drew my SMC architect colleagues Ryan Bushey and Matt Coffey into the process, and both were instrumental in improving the design. Finally Matt bore done on the design one evening and with a few deft strokes drew a scheme that vastly improved anything I had done while keeping the new addition to 12’x16’. I’ve made a few tweaks to his design, but what we’re building is fundamentally true to his concept and as the spaces took shape we are so grateful for his intervention. The final design has a generous entry space and closet, two small bedrooms and a modest master bedroom, two baths, and a thirty foot long great room space on the south.

Given that it is a one story house, my design had a few small skylights to bring in top light. I had passed the design around to other friends in the design biz, and Jamie Wolf of Wolfworks had some of his usual insightful questions, and the one that really hit home was, why so many skylights? That prodded me to look at each one carefully, and we’ve ended up with only one, above the kitchen island. Having a one story house with cathedral ceilings enabled us to use awning windows high in the gable ends to bring light high into the bedrooms without putting a hole in the roof. Thanks Jamie! In the photo below you can see we've pushed the windows hard against the wall so as to use the wall most effectively as a reflector to bounce light across the room.

Matt’s design solved one of our conundrums, which was how to get easily from the house to the basement. We wrung our hands about giving up an exterior access to the basement, but justified it because of having so much storage/shop space in our outbuildings. My architect brother-in-law Paul Hajian of Hajian Architects looked the plans over, and said, your basement stair has a landing 2/3 of the way down that is on the outside wall, you could cut the foundation there and access that landing from outdoors too. Great idea! So we cut a notch and built an exterior stair. Once inside, the stairs down are to the right, which might make it challenging to get something long into the basement, so we hinged the main run of stairs at the top, so they can be hoisted up out of the way if we want to get a kayak or suchlike down there.

We’ve been so fortunate to have so many talented designers looking over our shoulder and making this little house sing. Thanks all!

Design for Adaptability:

Software Tools

Software Tools:

General modeling information:

Proprietary Excel model

Lessons Learned

Outcome of Project Goals:

It always costs more than you think!

Discrepancies:

Rebates and Financial Incentives

Federal incentives
Local incentives
State incentives
Utility incentives
Other incentives
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