A LEED Gold Green Building Laboratory

Urbanretreat-a3c

Ann Arbor, Michigan architectural firm A3C has turned its building into a showcase for a number of green building components, and managed to produce a LEED-CI Gold renovation of the existing two-story building while they were at it.  The firm wanted to have a showcase for a variety of green building options, as well as providing themselves with firsthand experience with a number of different systems.

Named the UrbEn Retreat, the third floor addition provides a conference and meeting room. The small space looks out over the roof at the rest of the building which has been turned into a walkable garden space with a number of green roofing systems that make it an extraordinary space in the middle of the downtown.

The roof of the renovation was recently featured in Environmental Design + Construction magazine. Instead of just adding insulation to improve thermal performance and using a single roofing system to cover it, the roof on A3C's building is an experimental lab to study a variety of roofing options, including both flat roof membranes and vegetated roof systems.

A3cplan

Rather than weighing the options and then choosing and applying a single green roof system, there are several different configurations installed next to one another, including both tray and monolithic installations, and examples of both intensive (shallow growth media) and extensive (deeper growth media) systems included in the mix. Part of the decision was based on what would work structurally with the existing building roof, so the lightest weight vegetated systems were placed where the roof could only support the lighter weight, and deeper, heavier vegetated assemblies were then placed in other areas where there was additional support capacity. A rainwater catchment system is connected to the irrigation system for the vegetated roof, as well.

Further away from the conference room, the other part of the roof (seen upper right on the plan, above) is outfitted with a membrane roof, but here, too, it's not so simple. Working with faculty from the University of Michigan, temperature sensors were installed under a series of different colored roof membranes, so that the effect of roof color could be measured and compared. Measurements of the temperature under each type of roof, as well as the ambient outdoor temperature are collected at 4 minute intervals throughout the day, to develop a profile of how the roof membranes perform relative to each other, as well as in comparison to the vegetated roof.

Insulation-truth-window The conference room itself showcases a number of features, too. Something that is found in many straw bale construction projects is a "truth window," a framed opening in the interior wall finish that lets visitors look behind the plaster to see the "truth" that the building is, in fact, built of straw. A3C took a similar approach and has a strip along the south wall of the space showing different kinds of batt insulation installed in the cavities between adjacent studs. Each of these is also outfitted with a small digital thermometer to display the temperature on the wall just to the inside, so that different insulation types can be compared.

Gathering data from actual buildings will help architects and engineers better understand how choices of building systems affect the building, and the benefits and drawbacks to different systems.  And, by allowing the community to use the UrbEn Retreat on evenings and weekends, the space becomes an amenity, as well as a demonstration of the possibilities of green building.

Links: A3C Sustainability, ED+C.
Images via: A3C,
ED+C, Dave Lewinski.


  • Anonymous

    I would be interested to see the results of their roofing experiment. That seems like such a simple thing, I can’t believe no one has done that before?

    Kudos to them for trying to design better buildings.

  • http://mportlandrealestate.com/ Portland Condo Auctions

    I hope that they do a study and publish the data that they find on which type of roof works the most efficiently.

    -Tyler

Popular Topics on Jetson Green