The builder, homeowners, and Built Green verifier met early in the process to plan out how the home would meet the many stringent Emerald Star requirements. TC Legend Homes dedicated one of its team members to track documentation, source materials, and act as the liaison between the builder, homeowner, and verifier during the construction process. This project is only the second home in Seattle to meet the stringent requirements of the Emerald Star checklist!

Built Green Highlights

Site and Water

• 10,000 gallons of on-site rainwater storage and filtration system
• 80%+ reduction in water use from conservation and site collection and filtration
• Low-flow faucets and toilets
• Green Factor Score of 0.816
• 100% of on-site stormwater infiltration
• 100% pervious surfaces for driveways, walkways, and parking areas
• 100% of irrigation from rainwater
• Walk Score of 74

Energy Efficiency

• Home Energy Rating System (HERS) score of zero with solar PV (41 without PV)
• Walls: R-29, 6" Graphite SIPs taped at all interior and exterior joints
• Roof: R-49, 10" Graphite SIPs taped at all interior and exterior joints
• Foundation: R-23 ICF stem walls, R-20 rigid foam under slab
• Windows: triple-pane, wood-framed, low-e windows, U=0.14
• Air sealing: 0.48 ACH 50
• Ventilation: Zehnder HRV
• HVAC: Chiltrix air-to-water heat pump w/ 4.5 COP for in-floor radiant hydronic heat on ground floor and ceiling-mounted air distribution heads on second and third floors
• Hot water: Chiltrix air-to-water heat pump with tank storage
• Lighting: 100% LED
• Appliances: ENERGY STAR refrigerator, clothes washer, range hood; induction cooktop
• Solar: 9.9-kW PV
• Two electric vehicle charging stations (one in garage and one outside)
• Energy Star v. 3.1 Certified
• DOE Zero Energy Ready Home Certified

Guest Author: Cybil Tribie, Senior Project Associate, Evergreen Certified

Both the new code and Built Green offered a few surprises with their updates. Code now includes the Fuel Normalization Credits (Table R406.2); and Built Green now offers three different pathways to meet their energy efficiency requirements. Two of those three paths for projects permitted under the residential code are modeling-based utilizing a performance approach, and the last is a prescriptive approach – selecting additional credits from WSEC 2018 Table R406.2 & R406.3. While all three paths are viable ways to meet their requirement, this post will only focus on the prescriptive approach for residential projects.

If you aren’t already familiar with it, the WSEC requires that units (based on size categories) obtain a certain number of credits from Tables R406.2 and R406.3 (the full table can be found here on pages RE-41 – RE-48). Those credit options span from thermal envelope improvements to HVAC upgrades to Energy Star appliance and even reducing overall air leakage. While most of the categories limit you to only choosing one option per category, you can mix and match all the different categories to obtain the minimum credit number required for your unit size.

The table below breaks down how many credits are required per unit size:

*Small units must have less than 300SF of fenestration otherwise they fall into the medium category
**Additions greater than 500SF but less than 1500SF fall into the small category

Earlier I mentioned that the new code threw in a surprise, the Fuel Normalization Credits (Table R406.2). Table R406.2 provides you with additional (or negative) points depending on the primary heating source being used for the units. For example, if you’re planning on using ductless mini-splits and electric resistance heaters (System Type 4 in Table R406.2), you’ll obtain 0.5 credits that is applied towards the total number required in the table above. That means that throughout Table R406.3, you’d only have to claim 2.5 credits, 5.5 credits, and so on depending on the unit size.

So now that we’ve gone through how the new code changed, let’s look at a couple suggestions on how to just meet code depending on your unit size.

The tables above represent two different options for how to meet your energy credit requirements for code. While going all electric with a hybrid heat pump water heater gets you above and beyond the 3.0 credit requirement, it will also help propel you forward with the Built Green prescriptive approach and being eligible for green building incentive programs, like Seattle’s Priority Green. Priority Green – faster permitting with the City of Seattle – requires that your project achieve 2.0 credits in addition the R406 requirements for new dwelling units, the same as Built Green 4-Star certification, so why not double dip and meet your Built Green and Priority Green requirements all in one shot?

Built Green 4-Star certification requires that you get (depending on star level) 3-Star - +1.0pt, 4-Star - +2.0pts, and 5-Star - +3.0pts beyond the minimum required for code based on your size level and fuel type. So, let’s review what that would look like.

*Small units must have less than 300SF of fenestration otherwise they fall into the medium category
**Additions greater than 500SF but less than 1500SF fall into the small category

The following tables provide examples of what a 4-Star Built Green project might want to consider claiming if pursuing the prescriptive approach for Built Green’s energy efficiency requirements. Note that the Priority Green program does not allow for natural gas to be used in the home and projects must select electric-only options to qualify.

Small Units (less than 1,500 SF)

Small units with less than 1,500 SF of conditioned floor area, with less than 300 SF of fenestration, benefit the most from electric ductless mini-split systems for space heating. If space allows in the small unit for a heat pump water heater, it will reach the required prescriptive credits with less action items.

Medium Units (1,500 SF-5,000 SF)

What about a medium sized unit (1,500SF-5,000SF) using different space and water heating options? There are a multitude of mix-and-match options that you can utilize, but below are some examples of how to get there for code and Built Green. It’s important to remember though that when using the Built Green prescriptive approach, less than 50% of your WSEC credits can come from PV.  

Large Units (5,000+SF)

And we can’t forget about the large units (5,000SF+). Below are just a couple options for how to obtain those Built Green points prescriptively.

Multifamily R-2 Occupancies

All the tables above demonstrate a variety of different compliances paths to meeting Energy Code as well as Built Green. Below are two ways to do that for R-2 Occupancies. The important thing to keep in mind is that the points values in Tables R406.2 & 406.3 are different for R-2 Occupancy.

All of the above tables provide options for exceeding the 2018 WSEC-R and meeting the requirements for Built Green certification and Priority Green expedited permitting. Builders will need to evaluate which prescriptive credits work best for the project’s site, design, size, and budget. To do this we recommend discussing options with your energy consultant or Built Green Verifier during the design process. Lastly, by selecting electric-only options builders will also earn additional indoor air quality credits to further their Built Green certification, future code-proof their energy designs, and provide more resilient and desirable homes for their buyers.

This webinar provides a detailed look into the prescriptive energy efficiency code credit options for residential projects that meet the 2018 Residential Washington State Energy Code and Built Green requirements. Speakers include representatives from Evergreen Certified and Built Green. Access webinar HERE.

The dead-end alley was named after Edson “Dad” Abbott, who brought Dream Theater to Sedro-Woolley in the 1930s, ushering in and fostering a sense of community for the town. To honor this history, the end of the alley provides a new “Dream Theater” as a gathering spot for movies, music, and other outdoor events. This feature proved to be a crucial community amenity during the COVID-19 quarantine, allowing community members to gather outside with masks and plenty of distance to safely enjoy movies together and share stories around the firepit.

Creating homes that provide for a flexible lifestyle was a key component of the project. The ground floors are fully accessible; they are set up for a future kitchen, have private entrances, and include a bathroom with an accessible shower. City zoning mandated commercial use on the ground floor, but banks don’t typically like mixed-use homeowner mortgages. The solution was to build individual structures that meet single-family criteria for a traditional homeowner mortgage loan, but also satisfy the requirements of the land use code. The International Residential Code acknowledges these live/work units as single family. Despite being a novel idea in this town when first proposed, this last year has been a good reminder that reviving the old way of “living above the shop” has a myriad of benefits.

With a simple design and careful attention to construction details, Martha Rose Construction was able to achieve a HERS Index of -10 on each of the six live/work homes in this enclave in downtown Sedro-Woolley. This was accomplished through a variety of techniques, including the “Martha Wall,” excellent air sealing, beefed-up insulation, and careful attention to equipment choices. A 9.9 kW solar array tops each building. Martha shared that, “After living in my home for three winters, I’ve never used all of the electricity generated on the roof, even with charging an EV!” Construction materials were chosen for health, proximity to the job site, easy maintenance, durability and beauty. Hard surfaces were used on the floors and there is no crawl space. Plumbing fixtures meet or beat WaterSense criteria.

Despite the high percentage of impervious surface, 100% of the stormwater is managed on site. The city allowed the project to install a giant infiltration basin made of railroad ballast under the paved alley. The 160 yards of granite ballast provide the structure for the road while providing 40% voids to contain rainwater while it slowly seeps into the ground.

Homeowners benefit from the Marth Rose’s detailed focus on indoor air quality. Five fresh air changes every day, made possible with a very high efficiency heat recovery ventilator that runs continuously, is one leg of the healthy home strategy. During the 2020’s wildfire smoke-filled air, these homes were smoke-free. During the pandemic, these homes offered a higher level of protection because of the year-round conditioned fresh air.

Built Green Highlights

Site and Water

• 40% void infiltration bed below development manages 100% of stormwater onsite
• New landscaping emphasized native vegetation
• Existing vegetation that was removed was replanted or donated for reuse
• No turf grass
• Pesticide-free integrated pest management plan
• Low-flow plumbing fixtures
• High efficiency 0.8 GPF toilets
• Main floor is an accessible studio/commercial space

Energy Efficiency

• HERS index -10
• 120% better than code, Net Positive Energy!
• 100% electric, fossil-fuel free operations
• 9.9 kW solar PV on each unit
• EV charging ready
• Energy Star and DOE Zero Energy Ready Home certified
• R-20 sub-slab insulation
• Blown-in cellulose walls and ceiling (~85% recycled content)
• Blower door score of 1.2 ACH
• "Martha Wall" utilizes 1" of closed-cell foam under the exterior plywood for continuous thermal break

Health and Indoor Air Quality

• EPA Indoor airPLUS certified
• No carpet in the units
• No garages
• All paints, finishes, and materials are low-VOC and NAUF
• Roof overhangs of 24” and 36”
• Heat recovery ventilators with ECM motors

Materials Efficiency

• Deconstructed existing 600 SF house and reused onsite salvaged materials
• Used locally salvaged lumber for concrete forms, siding, and finish shelving
• Interior walls designed for flexible spaces
• Abundant use of local and regional materials
• Polished concrete slab floor
• Cork stair treads
• Metal siding installed
• Pantry with open shelves, cabinets, and counters using local, recycled materials and some steel
• Reclaimed diamond blocks for landscape walls