Zero Cottage 2012 in Review, All, Custom, Green, LEED, Townhouses
San Francisco, California


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Aerial view of Zero Cottage in Revit 4D software.

Zero Cottage is an investigation of compact, sustainable urban development and a contemporary approach to living and working. The cottage is composed of a 712-square-foot living space set over a 430-square-foot workshop. It pairs with an existing building to complete a flexible, mixed-use compound that also includes a two-bedroom flat, studio apartment and storefront space.

The free-standing addition presented an opportunity to explore advanced sustainable design, construction techniques, materials and technologies, with a goal of achieving Passive House and Net-Zero Energy certification. The cottage is certified LEED for Homes Platinum. It is expected to be the first Passive House-certified home in San Francisco when certification is confirmed later this year. Net Zero Energy certification is expected after a year of actual energy use monitoring.

Zero Cottage is part of the Shotwell Design Lab

Building features

  • A simple form that is efficient to construct and enables flexible interior spaces.
  • An easy-to-install exterior rain-screen system designed and prototyped by David Baker Architects. Salvaged and new metal shingles quickly slide into the custom metal clips and can be quickly moved or replaced. Planter box panels add a playful functionality and are relocated throughout the seasons.
  • Robust Passive House construction combining continuous exterior foam insulation, a near airtight membrane, and triple-glazed windows. The resulting air-change-per-hour rating of around 0.5 necessitates a 92% efficient heat-recovery ventilating (HRV) system that captures heat generated by day-to-day use (appliances, computers, people) and warms incoming air, eliminating the need for conventional heating. On warmer days, the high level of insulation and building mass greatly minimizes heat gain.
  • Charred-wood siding made from maple flooring salvaged from a previous adaptive re-use project.
  • A mix of advanced LED fixtures, most dimmable, to greatly reduce the total wattage used for lighting
  • A vegetated roof featuring drought-tolerant garden (designed by David Fletcher of Fletcher Studio), composting, urban agriculture, and a “bread-box” solar water heater. 
  • A three-kilowatt photovoltaic system, mounted on a custom fabricated frame by Henry Defauw, covers the stair and generates more energy than the cottage uses.


Interior features

  • An open two-level plan that blurs boundaries to achieve a streamlined livability.
  • Interiors aesthetically aligned with the main flat, yet distinct in their materials and finishes.
  • Salvaged wood floors (the same used for the charred siding) are simply treated with a VOC-free, easy-to-maintain monocoat flaxseed oil.
  • Custom cabinetry made from the cottage's construction waste, leftover wood, and the previously salvaged wood floor.
  • Plaster walls have no VOCs, require limited maintenance over time, and increase the building mass (which is key to passive heating/cooling)
  • Custom daybed and desk by David Pierce, Ohio Design.
  • Custom bed designed and made by David Baker.
  • Carefully sited windows frame views without compromising privacy.
  • A light monitor enhances light and natural ventilation, and provides access to the roof.
  • Energy and space-efficient appliances.

 

Landscape and grounds

  • Updated landscape designed by David Fletcher, Fletcher Studio: drought resistant, permeable and organic.
  • Mural by artist Andrew Schoultz.
  • "Why," a remnant of the "17 Reasons Why" sign, a former local landmark, remains on site.

Image: Matthew Millman

Shotwell Compound

The cottage continues the evolution of an urban site that predates the 1906 earthquake. The original compound comprised an upstairs flat set above a ground-floor grocery store, and additional living quarters in the rear yard. Today, the Zero Cottage stands in back, the studio apartment is rented through Airbnb, and David Baker and his partner, Yosh Asato, have launched StoreFrontLab, a community-focused cultural initiative that gives the historic commercial space a new public purpose, rooted in the neighborhood's contemporary culture. Over time, the flexibility of the compound's components will support a wide range of uses and configurations.

The Prickly Pear on the vegetated roof.

GREEN ROOF

The roof of Zero Cottage hosts a vegetated roof, vegetable planters, composting, solar electric generation panels, a passive solar hot water collector and storage system, and a passive solar roof monitor that provides access as well. A lot going on in 430 sf.

The Luminalt guys connecting the PV panels.

Click here to view solar system output.

The Photovoltaic solar collector array is sized at 3KV, enough to generate more energy than the Zero Cottage uses on a net yearly basis.

Custom rainscreen clip development: Original prototype, modification, and folded clip ready to install.

Image: Matthew Millman

RAINSCREEN

The exterior metal siding is a "rainscreen", or a ventilated weather and UV barrier over rigid insulation and a water/air barrier.

The tiles are 12" wide by 17.5" high. The highlight tiles are industrial waste from the Zahner Company, sheet metal fabricators of many well know buildings designed by star architects. Field metal was fabricated locally from mild steel which is allowed to rust, galvanized steel, and mirror stainless steel. I wouldn't recommend this for a client as there are some interesting reflection and glare effects which might get you into trouble in a more public space.

The tiles are help on with a Dbarchitect designed custom micro-manufactured stainless steel clip. This allows the tiles to be individually removed and replaced. 

There were three custom planter tiles fabricated from stainless steel. These hang from the same clips and can be relocated anywhere on the tiled elevation.

There is also a clear plastic tile as a window t the batten and ridgid insulation view.

The tiles rattle a bit in the wind. I choose to think of this as a charming effect sililar to rain on a steel roof. Others might not be so amused.

The charred wood finish test.

Charred wood siding installed.

CHARRED WOOD

Salvage wood flooring from one of our projects, the Pasta Factory at Tassafaronga, was not only used for the living area flooring but also was charred for use as exterior siding.

Integral Impact's graph of energy use versus production.

The Zero Cottage is actually a NET PLUS building as this graph documents. The use not only includes two residents cooking, showering, and washing clothes but also the DBA Workshop which is a full time small production facility.

ENERGY PERFORMANCE

Primary Energy Demand:        26.6 kBTU/(ft2yr)

Annual Heat Demand:             3.88 kBTU/(ft2yr)

Heating Load:                            2.47 BTU/(ft2hr)

Cooling Load:                            0 BTU/(ft2hr)

Total Site Energy Demand:     3012 kWh/yr

Total Onsite PV Production:    3876 kWh/yr

Pressurization Test Result:     0.43 ACH50

PASSIVE HOUSE DESIGN

Envelope: 

Roof- R-51.2

Walls: R-29.2

Floor: R-41.3

Windows and Doors:

Sorpetaler TF 78B triple argon

U-Frame: 0.23 BTU/hr.ft2.F

U-Glazing: 0.123 BTU/hr.ft2.F

SHGC: 0.49

Systems:

HRV (Heat Revovery Ventilator): Zehnder ComfoAir 200 •

Space Heating: Electric radiant

PV: Sanyo HIT Double 195 PV

Solar DHW: Sunearth Passive “Breadbox”

CERTIFICATIONS

 

As an experimental dwelling we decided to pursue several third party certifications.

Passivhaus

Zero Cottage is certified as a Passive House by Passive House Institute US | PHIUS.

Zero Cottage is certified at the Platinum level of LEED for Homes.

LEED for Homes Platinum

Zero Cottage has received Platinum certification from the USGBC.

Zero Cottage is Green Point Rated.

GreenPoint Rated

This regional residential certification from Build It Green has a threshold of 50 points. Zero Cottage achieved 203 points. Visit the Build It Green web site for more information: http://www.builditgreen.org/

NetZero Certification by the Living Bui;ding Challenge.

International Living Building Challenge Net Zero Certification

Pending one year of actual use data. More information at ILBI.org/lbc/netzero

Image: Matthew Millman

Image: Matthew Millman

INTERIOR

Interior materials are no VOC (Volatile Organic Compounds): For example, the walls are plaster with no paint; the floor is recycled factory flooring from a project the firm did in Oakland finished with pigmented flaxseed oil. The same wood is used for the exterior charred-wood siding.

The bathroom tile is primarily Heath factory seconds.

2012.03.02

CONSTRUCTION TIMELINE

2012.02.12

2011.11.14

2011.10.21

2011.10.07

2011.06.17 The foundation is done and ready for framing.

The w1ndows are taped into the continuous membrane.

The salvage floor being installed.


PDF Icon20816 Shotwell Cottage Set 2011 July 08

PDF set of construction drawings

 

Zero Cottage Area Tabulation

Living

     Level 3     313 SF 

     Level 2     399 SF

Total Living   712 SF

Studio

     Level 1     430 SF

TOTAL         1,142 SF

Check out the Zero Cottage Blog for updates and detailed information: http://zerocottage.net

awards

Constructed Realities Honor Award: Small Projects
AIA San Francisco

publications

Energy Equilibrium
"Anecdatal" Evidence

project details

Landscape Architect

Fletcher Studio

Contractor

Falcon Five Design Build

Sustainability Consultant

Integral Impact

Permalink

www.dbarchitect.com/ZeroCottage

project data
Shotwell Zero Cottage 20816
San Francisco, California
Completed November 2013
certification
LEED for Homes Platinum
GreenPoint Rated Certified
PassivHaus Certified