David Baker Architects

Zero Cottage

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Image: Matthew Millman

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 the first Passive House-certified home in San Francisco and officially achieved Net Zero Energy Building Certification in June 2014. The International Living Future Institute comprehensively evaluates buildings for certification in terms of Growth, Energy, Rights to Nature, Inspiration + Education, and Beauty + Spirit. 

Yosh Asato and David Baker in front of the Zero Cottage. Image: Aubrie Pick

PDF IconZero Cottage User Manual

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.

Shotwell Design Lab


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.

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.

Zero Cottage is part of the Shotwell Design Lab

Zero Cottage is part of the Shotwell Compound.

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 just planted vegetated roof, featuring recycled motorcycle tires.

The Luminalt guys connecting the PV panels.

2012.09.04 The solar frame without 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



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 transparent rainscreen tile allows a view of how the clip system works.

Burned salvage maple siding and relocatable metal shingle rain-screen siding.

The charred wood finish test.

Charred wood siding installed.

Charred Wood Rainscreen


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.


This shows how the battens are configured in the wood rainscreen.

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.


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



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


HRV (Heat Revovery Ventilator): Zehnder ComfoAir 200 •

Space Heating: Electric radiant

PV: Sanyo HIT Double 195 PV

Solar DHW: Sunearth Passive “Breadbox”



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


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

Certified in May 2014 after one year of actual use data. More information at ILBI.org/lbc/netzero

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Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman



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.


Bathroom on the third level. Image: Matthew Millman

The ground level is a studio space currently used as a workshop for David Baker Architects. Image: Matthew Millman







2011.06.17 The foundation is done and ready for framing.

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Site plan.

PDF Icon20816 Shotwell Cottage Set 2011 July 08

PDF set of construction drawings


Zero Cottage Area Tabulation


     Level 3     313 SF 

     Level 2     399 SF

Total Living   712 SF


     Level 1     430 SF

TOTAL         1,142 SF

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

Level 1: Workshop

Level 2

Level 3 Plan

presentation plan roof

presentation plan level 2

presentation plan level 2

ground floor presentation plan

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

View of Zero Cottage from the living area of 339 Shotwell. Image: Matthew Millman

View of Zero Cottage from the living area of 339 Shotwell. Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

Image: Matthew Millman

The small kitchen features Energy Star energy-efficient appliances.

View from the sleeping loft towards the bath.

View from the third-level landing into the bath.

The bathroom features Heath tile.

A detail of the shelves fabricated from wood salvaged from the previous existing shed structure.

HRV air exhaust louvers in bathroom with LED light fixture.

HRV louver at the top of the light monitor picks up the warmest air in the house for exhaust and heat extraction.

This simple A based ceiling fixture uses a high efficiency dimmable LED bulb made by Sylvania. The quality of light from state of the art LEDs is very high: this one has a CRI rating of 95.

LED light by PABLO provides task lighting for the bed.

The mirror with LED light built in provides subtle bathroom lighting.

HRV controller and Nest thermostat.

The Zehnder HRV unit located in the ceiling of the workshop WC. http://zehnderamerica.com

Tankless electric variable temperature water heater. The variable temperature is essential for this to function efficiently with the solar DHW collection system with integral storage.

The solar photovoltaic system has an efficient Aurora inverter to convert DC electricity into AC. http://www.power-one.com/renewable-energy/products/solar/string-inverters/aurora-uno-single-phase/pvi-30363842-north-america/series

Solar rack being hoisted up onto roof.

CONSTRUCTION: 2012.06.28


2012.04.18 The dawn breaks with no scaffolding.

The stair rail is a minimal stainless web.

An interchangeable rain-screen planter tile.

The metal rainscreen allows planter tiles as an option that can be relocated.


Battens are screwed through the XPS to create an airspace and to provide a solid base for the rain-screen.

The XPS foam has been covered with high performance building paper: Green Guard Raindrop.

The Green Guard Raindrop high tech building paper is installed.


2012.02.12 The view from the passage.

The w1ndows are taped into the continuous membrane.

2012.01.22: Another view of the window corner trim.

2012.01.22: The window frames are sealed to the exterior water/air barrier with bituthene tape.

The triple glazed Sorpateler windows have massive frames. Note the sill flashing as well.

2012.01.24 The south facing monitor provides winter solar gain and access to the roof.






The salvage floor being installed.

2012.01 Teo sorts the salvaged flooring. Joe Barker, the electrician, is standing on the stair.

The south facing roof monitor produces daylight and passive solar gain while providing roof access.

Integral Impact's breakdown of predicted energy loads.

Net Zero Certification report from the Living Futures Institute was achieved in May of 2014.

The negative energy bill from PG+E.

Information sheet. 2012.11.09

Aerial view of Zero Cottage in Revit 4D software.

View from deck of main house.

View from the pedestrian passage.

perspective view of the Zero Cottage from eye level in the courtyard

Axonometric view of Zero Cottage.

Metropolis Magazine, November 2013

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Gold Nugget Grand Award—Best Zero Net Energy Design
Pacific Coast Builders' Conference
Grand Winner—Green Custom Home
Custom Home Design Awards
Constructed Realities Honor Award—Small Projects
AIA San Francisco


Energy Equilibrium
Anecdatal Evidence

project details


All Projects, Custom Homes, LEED, Townhouses


San Francisco, California

Landscape Architect

Fletcher Studio


Falcon Five Design Build

Sustainability Consultant

Integral Impact



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