| || |
|Vital Stats |
|Location: Redmond |
|Star Level: 4-Star |
|Checklist: Single Family |
|Verifier:Tom Balderston, |
Conservation Services Group
|Section ||Points |
|Site and Water ||105 |
|Energy Efficiency ||229 |
|Indoor Air Quality ||108 |
|Material Efficiency ||113 |
|House Size Multiplier ||1.1 |
|Total Score ||610.5 |
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Case study written by Tom Balderston, Conservation Services Group
This project is an excellent demonstration of net-zero energy townhomes at an affordable price. The homes had a score of over 600 points, but due to the small site, they could not include all of the prerequisites for 5-Star Built Green certification.
Site and Water
This project includes four townhomes clustered on a small site in downtown Redmond, Wash., an increasingly popular and very walkable neighborhood with excellent transit and all kinds of services within a few blocks of the site. The front units have small yards with patios facing the street constructed with concrete containing 25-percent fly ash. All of the plantings emphasize drought tolerant and native plants.
The plumbing fixtures are low-flow for water conservation. Faucets and showerheads were tested at 0.1 and 1.5 gallons/minute for excellent hot water and water savings. Hot water use is a significant part of the energy load, so this is a big benefit on the overall energy performance.
This is a net-zero energy project and one of the few to receive the 50-point bonus in Built Green certification. There is a 6.0 KW photovoltaic solar ystem on each of the units' roofs. A HERS rating model showed that the system would use between 0 and 1 million BTUs (MMBtu) per year, and the HERS index is 6. The annual energy cost, not including service charges, is estimated at $14.
The units are heated with radiant floors using nonstructural radiant-heat panels, manufactured by Ichijo USA Co., LTD, that responds quickly to changes in temperature and spreads the heat out. This project demonstrates new technology very well in that both the heat and hot water are provided by a "Cool Fire" air-to-water heat-pump system. These units look much like the ductless pplit systems that are more familiar, but since they heat water instead of air, they can cover both the domestic hot water and radiant floor heating.
The envelope is excellent, with a wall system that includes 19.2" on center advanced framing, R23 blown-in blanket insulation and 2" EPS foam on the exterior. The roof is a 12" Ichijo SIP panel, and all floor slabs are insulated with continuous R15 rigid foam.
Indoor Air Quality
The project was certified for Built Green 4-Star. All materials were chosen for low-VOC emissions and no added formaldehyde. Many of the finishes and the windows are Ichijo's own products, which are low emission products by company policy.
The whole house ventilation system includes fresh air inlet ports in the bedrooms and Panasonic whisper green fans. These were tested and commissioned for air flow and proper ducting. The garages include exhaust fans that are tied to the door opener. The garages were pressure tested for good sealing and separation from the house.
The exterior was detailed with rainscreen siding, a flashing system and a durable fiber-cement siding.
The project documented a 99-percent recycling diversion rate for construction site waste. The interior trim is very simple to minimaize material use and constructed with recycled and no-added-formaldehyde MDF products. The flooring is an FSC-certified bamboo product.
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