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Accessory dwelling units on the rise as more Americans embrace the multigenerational home

By Integrity Windows November 10, 2011

Multigenerational housing is experiencing a comeback as financial woes and unemployment have forced many families to share the same roof.

Or, roofs, rather.

Accessory dwelling units (ADUs) are popping up across the country. As secondary homes built on residential lots, ADUs are sometimes referred to as backyard cottages, granny flats or mother-in-law apartments. They are small in stature, but generally long on savings due to their energy efficient size and features. The only real compromise? Say goodbye to your backyard.

According to Tuesday article in the New York Times, several areas of the country are adjusting their housing ordinances to promote the building of ADUs.

“According to the American Planning Association, at least four states — California, Massachusetts, Vermont and Washington — have enacted laws encouraging or requiring changes to the zoning rules to permit the so-called accessory dwelling units, also called A.D.U.’s. Architects said that parts of Oregon, Colorado, Texas and Virginia had also become more accommodating.”

Sam Hagerman is the owner of green builder Hammer & Hand, which is based in Portland, Ore., a city that’s seen a rapid resurgence of ADUs of late. ADUs were more common before World War II. The post-World War II changed the ideal from tightly woven neighborhoods to a desire for privacy and sprawling land lots.

“Your typical accessory dwelling unit is inherently ‘eco-friendly’ because it’s small and embedded in an existing neighborhood, usually with easy, walkable access to parks, schools, shops and transit,” Hagerman said. “Now if you take the size and location of that typical ADU and make it extremely efficient, then you can create something special – a sustainable home.”

Next week, Hagerman and Hammer & Hand will host an open house to show off its recently completed Alameda Ridge ADU, which features:

1.    Thermally-broken insulated slab. The ADU’s foundation is built on top of 4 inches of EPS geofoam.
2.    Liquid-applied air barrier. A vapor permeable, weather resistant air barrier forms a continuous layer on exterior sheathing through into all window and door openings.
3.    High performance insulation. High-density cellulose, low-density spray foam, and polyiso foam contribute to the structure’s superinsulated envelope.
4.    Ductless mini-split. A high-efficiency Mistubishi inverter heat pump system heats the ADU.
5.    Integrity and Marvin windows and doors. This high-quality millwork provides beauty and durability that also performed well in the project’s airtightness testing.
6.    Extensive testing. The team performed the requisite Earth Advantage and Energy Star testing, plus extra Hammer & Hand testing using theatrical fog and a blower door fan to verify the performance of the air barrier.

ADUs may create an exciting area of opportunity for builders willing to refill their pipeline with new, interesting work.

These small homes might just turn out to be a big deal.