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Single-Family Housing and the Living Building Challenge

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Urban Grapevine’s Central Courtyardimage credit Lael Taylor of Meditch Murphey Architects

In 2015, the DC Living Building Challenge Collaborative sponsored the Affordable Living Design Competition (ALDC).  Over 20 teams from the DC area and beyond worked to design a small community (10-15 units) of single family dwellings capable of meeting the Imperatives of the Living Building Challenge without resorting to currently allowed Exceptions under that rating system.

Binder Regenerative Design partnered with Meditch Murphey Architects, Rain Underground and with Tom Serra (an independent engineering consultant) to enter the ALDC, competing against larger firms and other collaboratives of talented designers… and we WON!

Making a Community

The DC Department of Housing and Urban Development owns several properties in the Deanwood neighborhood of NE Washington DC.  This site  was previously developed but no structures are currently located there.  Neighboring lots are home to a combination of single family dwellings and (largely abandoned) commercial spaces.  The area has proud history as a home for African American soldiers returning from WWII, settling down and starting families.  For more information on the community, see the competition website.

The design includes four (4) 3-bedroom units (single story + basement), four (4) 4-bedroom units (2-story + basement) and two (2) 2-bedroom units (2-story + basement).  The overall site plan features two small semi-private courtyards which provided a protected space for residents to relax outdoors.  A larger central courtyard is intended as a public space for gardening and public education.  The community will be a seed from which an entire network of community gardens will sprout – this was one inspiration for the name of the project : Urban Grapevine*.  It is intended to be an oasis in what is currently a food desert.

 

Site Plan of Urban Grapevine Project
Site Plan of Urban Grapevine Projectimage credit Jenny Wienckowski of RainUnderground LLC and Lael Taylor of Meditch Murphey Architects

 

Landscaping used throughout the site was designed to create a robust ecosystem, providing food for residents and habitat for wildlife. The spaces and paths between them reinforce the image of a grapevine running through the site.  Much of the vegetation is irrigated using graywater from the homes.

The design is intended to create a strong sense of identity and community for the residents, but also to embrace to neighborhood around it, inspiring others to lead a healthier and more sustainable lifestyle, one defined not by scarcity but by abundance and beauty.

*By the way, the other inspiration for the project name was the song “I heard it through the grapevine” recorded by Marvin Gaye, who grew up in this neighborhood of DC.


Net-Zero Water

A major driver in the design was achieving the Net-Zero Water Imperative.  Our goal was to provide all potable water needs using rainwater harvested from the roof tops.  We selected a butterfly roof-form because it helps focus all captured rainwater for centralized storage and treatment.  The project includes a community greenhouse built around a 36,000 gallon cistern which literally makes water a centerpiece of the design.  This capacity should allow the community to operate even during periods of prolonged drought.

 

Water & Waste Flow Diagrams - click to enlarge
Water & Waste Flow Diagramsimage credit Mike Binder

 

The greenhouse also houses the water treatment system for the community, three successively finer layers of filtration followed by a UV sterilization system.  Each week, water is drawn from the cistern, treated and pumped to storage tanks in each dwelling.

Our calculations indicated that we could get the daily per capita potable water use down to 20 gallons (20 GCD).  To do this, we assumed that all toilets would be micro-flush (1 liter) composting units (see additional discussion below under waste).  We also included innovative reuse technologies like a recirculating shower system (see products like this).

The water budget even had a major role in defining the massing of the buildings.  The team realized early in the design process that in order to capture enough rainwater to meet our potable water needs, we would need to balance roof area against density.  Multi-story dwellings raise density – more people to consume water – and reduce footprint (less area to capture water from).  This trade is also discussed in an earlier blog posting (click here).

Graywater – water relatively free of biosolids from the shower, lavatories and clothes washer – is used for irrigation of the landscape (the only significant non-potable water load).  See the section below on waste for more information.


Energy

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Energy Infographic – click to enlarge - image credit Mike Binder

Our design process for the units began with a passive solar strategy.  The site is oriented with the long axis directly E-W, and we decided to maximize passive solar potential by orienting our dwellings the same way.  Deep overhangs protect the large south facing windows in summer and allow light through in the winter.  Using the BEopt software developed by The U.S. Department of Energy (as part of their Building America program), we experimented with various configurations and assumptions for fenestration, insulation, air-infiltration and mechanical systems.  We discovered (as others have before) that Passive House standards are needlessly prescriptive and we really stopped seeing much pay-back at around R-30 whole-wall insulation values (R-45 to R-50 in the roof).  Resources which proved useful in this process are noted below in the bibliography.

Our wall section is comprised of 9-1/2″ deep wood-composite I-beams turned vertically (used in previous Meditch Murphey projects) and blown-in cellulose insulation (R3.4 per inch).  The exterior of the sheathing is covered with a Prosoco liquid applied air-barrier and 1 inch (R-5) of XPS rigid foam.  The foam is protected by fiber-cement siding and panels.  This assembly provides great insulation and air-sealing capabilities and allows for moisture migration to fight mold in Washington DC’s mixed-humid climate.  The materials are largely recycled (and recyclable) and non-toxic.

Typical Wall Section - click to enlarge - image credit Marcie Meditch & Mike Binder
Typical Wall Section – click to enlarge - image credit Marcie Meditch & Mike Binder

The roof is comprised of 12-1/4″ thick SIPs panels (R-45 to R-52 depending on foam additives used).  The basement walls are factory-made insulated concrete panels (by Superior Walls) with R-21 in the interior cavities and an additional R-5 installed on the exterior (for a whole wall R-20 insulation value).

According to the Net-Positive Energy Imperative in the the Living Building Challenge, we need to generate 105% of all energy using renewable sources.  Wind energy is not considered economically viable in the DC Metropolitan area, so we our design focused on solar hot-water panels and photovoltaics.  The 15 degree slope of the butterfly roof (south facing portion) provides good solar insolation values averaged throughout the year.

Even though the arrays for each unit are distributed, along with the inverters, and each unit has its own meter, the battery back-up system for the community is centrally located and maintained.  The capacity of the system was sized to provide power for each unit’s refrigerator, water pump and basic lighting throughout the community.  This will help make Urban Grapevine resilient to disruptions in the municipal power grid.  The battery system and connection to the grid is located in the greenhouse (visible to the residents and the public, but protected from tampering or inquisitive  ‘eco-tourists’.

 

 

 

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Power Systems Schematic – image credit Mike Binder and Tom Serra

Waste

The ideal of regenerative design is that THERE IS NO WASTE.  The output from one process is input to another.  As a culture, we are slowly beginning to embrace this concept, and Urban Grapevine strives to set a precedent.

Of course, the residents of the community will be encouraged to recycle plastic and metal and paper as other citizens of the District are.  Each unit will include recycling centers and there will be a central drop off each week for curb-side recycling collection by the city.  Unlike most communities in DC, however, Urban Grapevine residents will also recycle organic waste like food scraps and, yes, poop.

All toilets in the design are micro-flush (or zero-water) composting toilets, with the composters in the basements.  These units will be professionally maintained (each household’s mortgage includes money held in escrow for maintenance of the water, waste and power infrastructure of the community).  That includes period removal of the composted material, which is taken offsite, tested and sterilized as needed to be used on commercial agriculture products (most fodder for grazing animals).  Composting toilets take what is normally considered a waste product and turns it into a useful product.  This is not actually all that unusual, though the decentralized composting and collection does represent an innovation for DC, and it will take some time for entrepreneurs to catch up with this model.

Food scraps can be safely composted in the centrally located units next to the greenhouse and will be used to fertilize the garden plots of residents and neighbors (see the diagram under the water section above).

Other aspects of the Living Building Challenge

The Living Building Challenge includes 20 Imperatives covering topics or Place, Water, Materials Energy, Health and Happiness, Equity and Beauty.  Most of these have been touched on in our description above, but not in detail.  For more information, visit the Living Building Challenge website.

 

Bibliography

Several articles we found useful here included the following:

Lstiburek, J. – Building Science Corporation, Conditioned Crawl Space Construction,Performance and CodesBuilding America Report – 0401,  November 2004.

Straube, J., et.al.,  Building America Special Research Project: High R-Value Enclosures for High Performance Residential Buildings in All Climate Zones,  Building America Report – 1005, October 2010 (Rev. 1 February 2011).

Straube, J.,  Insight : The Passive House Standard: A Comparison to Other Cold-climate Low-energy Houses, Insight-025, Building Sciences Corporation, October 2009.

Aldrich, R., et.al, Practical Residential Wall Systems – R30 and Beyond, Building America (undated).

Kneifel, J., Annual Whole Building Energy Simulation of the NIST Net Zero Energy Residential Test Facility Design, NIST Technical Note 1767, September 2012

Cortese, A., et.al., Net Zero and Living Building Challenge Financial Study: A Cost Comparison Report for Buildings in the District of Columbia, DC Department of the Environment ID# 0213-10-0PS, September 2013.

Capen, A., et.al., Living Building Challenge – Framework for Affordable Housing, International Living Future Institute, November 2014.