Page 45 - Green Builder Magazine May-June 2019 Issue

The Big Picture
38-45 GB 0519 ADU.indd
An ADU may be smaller, but it’s just as
challenging to build as a full-sized dwelling.
BY LISA MENARD
TEVE SNYDER AND HIS WIFE JACKIE ELLENZ first learned about
Accessory Dwelling Units (ADUs) through their designer, Libby
Holah. She and her husband Greg had previously designed a
bathroom for Snyder and Ellenz, and they were a natural first
choice when it came to remodeling part of their home in
S Portland, Ore.
“Our garage was falling down, so we asked them to look at what we could
do with it,” Snyder recalls. “[Libby] asked, ‘Have you ever considered an ADU?’
We asked, ‘What’s that?’ So she took us around to look at some other ADUs.”
For Snyder and Ellenz, there were a lot of good reasons to build an ADU.
They like the idea of supporting density and infill, and they’re also committed
to energy efficiency. Meanwhile, Greg Holah is especially interested in how
building technology can help ameliorate climate change.
“I thought this could be a really cool sort of thing to do—to help a contractor
think about energy-efficient design, including ideas from Passivhaus,” Snyder
says. “It could be a learning experience for everyone engaged, and perhaps
even for a broader audience.”
Lots to learn
As they worked with the Holahs to design their ADU, Snyder and Ellenz kept
in mind the lessons learned from years of reading books about small space
design, Passivhaus design and simple living.
According to Holah, the design considerations for an ADU are very similar
to the design considerations for any home. “ADUs still need all the basics:
kitchen, bathroom, living room, and bedroom,” he says. “Freestanding ADUs are
just small houses; a lot of the program is similar to designing a one-bedroom
apartment. They have all the same components as a house and we have to be
smart about how we make everything work.”
Energy efficiency was the primary guiding factor in the design. Whenever
they design an ADU, the Holahs make it energy efficient, with sustainability
in mind. “Creating a well-insulated envelope is important,” Greg Holah says.
“Since it’s not a lot of volume to heat, if we create a well-insulated shell, it
doesn’t take a lot to condition the space. [In addition], good quality windows
and a well-insulated exterior are very important things.”
As a result, Snyder and Ellenz’s ADU includes a laundry list of sustainability
features:
■ The windows are triple-glazed and most of the windows face south to take
advantage of passive solar heating.
■ The concrete slab is insulated to create a thermal break from the ground.
■ Additionally, the concrete slab acts as a thermal sink in summer and winter,
absorbing heat through the southern windows, storing it during the daytime
and releasing it at night.
■ The wall system uses staggered stud construction with eight-inch top and
bottom plates to reduce thermal bridging (the transfer of heat through the
exterior walls).
■ The walls have two inches of foam “outsulation” attached to the sheathing,
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