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Construction

Orpinela Guest House and EcoroofSite
The siting of the building began with a desire to save as many existing trees as possible and the project team initially identified four trees that had to be removed. Unfortunately, a late visit by an arborist revealed that seventeen trees were diseased and had to be removed although only four were tagged. "It made me ill," notes Orpinela.

In lieu of a traditional foundation, sixteen 36" round cast-in-place concrete pier footing with 8" x 8" posts form the foundation system for the house. 4" x 12" Girts span the posts and form a platform for the house and perimeter decks. The footings required minimal excavation and were hand-dug to prevent erosion and root destruction. Heavy excavation equipment damages root systems and compacts soils thus decreasing their ability to absorb rainwater. Russo notes that the pier footing actually made more sense given the site conditions, "It’s a waterway (ravine) and was not conducive to a full foundation." The floor is made up of 12" joists and R-19 batt insulation that is vented. Russo indicates that this strategy did not result in any major cost difference compared to a conventional foundation on the same site.

Materials
All treated wood is arsenic- and chromium-free as specified but sourcing these materials was not easy in 2000. More specifically, the owners found it very difficult to find substructure support beams without arsenic and chromium pressure treating. The lumberyard that supplied the wood had to entirely drain their vats of the chromated copper arsenate (CCA) wood treatment and replace it with the specified alternative alkaline copper quaternary (ACQ) in order to accommodate their request. Today, the demand for alternative treatments has increased and made it much easier to source more safely pressure treated woods. Russo notes, "Now they (suppliers) have their act together".

The floor and interior walls are covered in three-quarter inch thick Saltillo Mexican tile or ‘Aglia’ natural paints and stains. The ¾" thick tile, in conjunction with a cementitious backer board and grout, adds thermal mass to the floor. The floor is sealed with a low VOC, AFM Mexi-seal sealer. Formaldehyde-free insulation, wheat board cabinets and built-ins, and other ‘safe’ materials such as stainless steel counters, and ceramic tile bathroom floors were used to maintain indoor health of the building. These materials are ultra low toxic, easy to clean, and non-absorbent thus reducing the amount of potentially irritating material accumulating in the space. The building also underwent a 30-day "burnout period" prior to occupation during which time the space was flushed with 100% outdoor air.

‘James Hardie’ cement board siding is the major exterior siding material. ‘Trex’ plastic composite lumber was specified for the decking because any other material would have molded given the building’s shady and moist setting. Trex has the advantage of being very low maintenance—does not need to be stained or sealed—but it does need 20" supports instead of the more standard 24".

Ecoroof
Structurally, the ecoroof is the first installation in Portland with a 4:12 (18%) slope. This required installation of a wooden trellis and two layers of cellulose netting to help prevent soil erosion. The late decision to integrate an ecoroof required structural upgrading to accommodate the ecoroof’s additional load of 12 pounds per square foot (saturated). This need was met by doubling the number of roof rafters and reinforcing a roof beam. This added approximately $12,000 in costs (not including $3,000 deduct for metal roof) that could have potentially been avoided if the ecoroof was included in the original design of the structure.

Erez Russo Architect designed the ecoroof. The soil and plant design and installation was provided and built by Ecoroofs Everywhere and a handful of volunteers. Russo got his hands dirty as well; "I probably volunteered about 50 hours of time because I’ve always wanted to design a sloping ecoroof."

An ecoroof had never been built in Clackamas County, however the process provided no hurdles and was put through process under a membrane type roof. Russo includes additional research, thorough detailing of the roof membrane and trellis structure as well as structural engineering as the most crucial elements in the successful implementation of the ecoroof.
 
Keys to Success - Construction:
  • Retain as many trees as possible
  • Avoid the use of heavy construction equipment to protect root structures and site hydrology
  • Specify chromium and arsenic free pressure treated wood
  • Design a foundation that retains the hydrological and ecological integrity of the site
  • Be willing to take the addition time necessary to ensure proper design and installation of new strategies