Earth Advantage certification projected for new Accessory Dwelling Unit: OPEN HOUSE November 16

Sponsored by H&H, Integrity Windows by Marvin & Portland Millwork, event features hot cider & eco-building revelations.

(NOTE: see this event announcement for the Nov. 16 Cider Mixer & Open House.)

Accessory Dwelling Units (aka “Backyard Cottages” or “Granny Flats”) boast many virtues.  They offer flexible living options, whether as a remodeling or new home building project..  They’re affordable and easy to develop.  When rented, they create positive cash flow.  They’re often embedded in existing, vibrant neighborhoods that support walking, biking, and transit and offer easy access to services close by.  And they carry a small footprint, both literally and environmentally.

So if you take an ADU project replete with all these assets and you build it “green”, you can get a pretty special end result.  We saw this play out with our recent Super-Efficient ADU, which drew on Passive House techniques to create a high performance backyard cottage rental in Portland’s Concordia neighborhood.  Now we’re seeing it again with our latest ADU creation, the Alameda Ridge ADU, which casts a broader sustainable construction net.  The project is projected to receive certification from the Earth Advantage Institute in recognition of its superior:

  • Energy efficiency
  • Healthy indoor air quality
  • Resource efficiency
  • Environmental responsibility
  • Water conservation

The Alameda Ridge ADU sports Integrity and Marvin windows and doors supplied by Portland Millwork, and both Marvin and Portland Millwork have partnered with us to co-sponsor the festivities at the Open House:

Alameda Ridge ADU Open House
Wednesday, November 16, 2011
4-6 pm
featuring cider libations and green building revelations
4217 NE 30th Ave, Portland
Please join us!

I spoke yesterday with Skylar Swinford, captain of our building science team, to get his rundown on the building energy performance features designed into the Alameda Ridge ADU and built by Hammer & Hand lead carpenter Will Richmond and his team.

Here are the highlights:

  1. Thermally-broken insulated slab.  The ADU’s foundation was set on top of 4 inches of EPS geofoam insulation, creating a “break” that will keep thermal energy from leaking out of the house into the ground.  We also used this technique at the Super Efficient ADU and the Karuna Passive House, though with thicker foam (much thicker at Karuna).  (Read more about why building on geofoam is a good idea.)
  2. Liquid-applied air barrier.  This liquid-applied system provides a continuous air barrier on the exterior sheathing of the building and through into all window and door openings.  It’s a seamless, vapor permeable, water-resistive barrier, and it gained the project an “innovation point” in Earth Advantage Institute’s certification calculations.
  3. High performance insulation.  For the walls, we blew in high-density cellulose insulation.  For the roof, we applied low-density spray foam and installed a continuous layer of polyiso foam over the rafters to reduce thermal bridging through said rafters.
  4. Ductless mini-split.  The ADU uses a high-efficiency Mitsubishi inverter heat pump system.
  5. Extensive testing.  In addition to the requisite Earth Advantage blower door test (NOTE: the Integrity windows performed quite well, our co-sponsors will be glad to hear!) and ENERGY STAR insulation inspection, Hammer & Hand conducted an independent blower door test to verify performance of the liquid-applied air barrier system.  We filled the ADU with theatrical fog and simulated a 50 mph wind inside the structure to detect and fix any leaks or flaws in the air barrier.

Check out these construction photos.  The first and last come courtesy of the client.  The ones in between were shot by Skylar…

Garage to removed, Accessory Dwelling Unit to be built in its place. Portland
BEFORE: garage in disrepair, to be dismantled and replaced with ADU.

Portland Accessory Dwelling Unit, project to receive Platinum certification from Earth Advantage Institute.
Liquid-applied air barrier has been applied to window and door openings.

Marvin Integrity windows installed into Portland Accessory Dwelling Unit.

Will installs an Integrity window.

High performance insulation in Portland Accessory Dwelling Unit.
High density cellulose insulation in the walls, polyiso over the rafters.

Portland Accessory Dwelling Unit, project to receive Platinum certification from Earth Advantage Institute.
Will applies the air barrier to the rest of the structure.

Portland Accessory Dwelling Unit, project to receive Platinum certification from Earth Advantage Institute.
Once the air barrier application is complete, siding can be added, and the project nears completion.

We should hear official word from Earth Advantage Institute soon about the ADU’s projected certification, and I’ll be sure to share that news here.  In the meantime, please mark your calendars for the ADU Open House on Wednesday, November 16, 4-6 pm.  We hope to see you there!

– Zack

Back to Field Notes