Case Study

Vital Stats Location: Seattle Star Level: 5-Star Checklist: Single Family/Townhome Verifier: Tom Balderston, Conservation Services Group Section Points Site and Water 133 Energy Efficiency 160 Indoor Air Quality 161 Material Efficiency 189 House Size Multiplier: 1.05 Total Score 672

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Martha Rose Construction - Seattle, WA
Project: City Cabins

City Cabins is a Built Green 5-Star two-townhome project in north Queen Anne in Seattle. Built by Martha Rose construction, the homes were modeled to a 40 percent improvement over the current state energy code. A massive 75 percent of the site remains pervious, and each home as a 300-gallon collection tank for rainwater. The landscaping features natives, edibles and drought tolerant species, and juniper timbers were used for outdoor landscaping. To ensure high quality indoor air, a heat recovery ventilator with a HEPA filter was installed, and low toxic finishes and wood products were used throughout. The homes achieved a recycling rate of over 90 percent through separation of the waste types on the project site. A large amount, about 3,000 to 4,000 board feet, of lumber was provided through repurposing trees from the site, and 7,000-board-feet of decking was re-used. The project also features recycled-content hard-surface tile and salvaged wood flooring from Oregon.

Some of the many green features of the project include:

Site and Water Protection

• Home achieved a Walk Score of 71
• Vegetated roof system on garages and entry roofs
• Each home has 300-gallon rainwater catchment tank
• 70 percent of hard surfaces on site are pervious
• Landscaping used natives and edibles
• Juniper timbers used for outdoor landscaping
• Vegetable oil used as form releaser
• Dual flush toilets used throughout homes
• 1.5 gpm showerheads and 0.5-gpm lavatory faucets were used

Energy Efficiency

• Homes modeled to achieve 40 percent improvement over Washington energy code
• HERS score of 32 and 52 on the two units
• Heat recovery ventilator installed
• Mitsubishi dual heat pump system installed
• Advanced insulation features R-75 attic, R-31 walls, R-30 under slab and R-60 under wood floor
• Quadruple pane windows net u-value of 0.15
• Blower door test showed air tightness of 2.5 ACH50
• Crawl space is fully conditioned
• All lighting but one fixture is compact fluorescent or LED
• Energy Star refrigerator, dishwasher and washing machine

Indoor Air Quality

• Installed whole-home radiant system
• No wood or MDF products with added urea-formaldehyde
• Garage detached from units
• Low-VOC paints, low-toxic water-based sealants and adhesives
• Heat recovery ventilator with HEPA filter
• Shoe storage provided on porch and inside entry
• Envelope professionally inspected
• All wood trim is solid wood, no medium density fiberboard

Material Use

• Overall recycling rate of 90 percent by source separation
• Extensive use of salvaged materials including:
  
  • 3,000 to 4,000 board feet of lumber
  • 7,000 board feet of 2x8 decking
  • Wood flooring from dismantled warehouse in Oregon
• Used 25 percent fly ash in concrete
• Hard surface tile is 49 percent recycled content
• Frames of quadruple pane windows are fiberglass
• Installed recycled content siding and roofing

Still Images

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Photos courtesy of Martha Rose.

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