Author: Sonja O'Claire, Built Green Program Manager

In Washington State, the building and energy codes are updated in a 3-year cycle. When the state codes change, typically requiring a higher level of performance and energy efficiency, Built Green must update its checklists to ensure Built Green certifications are representing beyond-code, innovative, and high-performance building practices. Every credit is assigned a point value based on its level of impact, difficulty or cost to implement. Built Green develops its checklist credits with advisory from leading industry professionals to navigate state code changes, technological advancements, and leading-edge best practices. To help distinguish these changes, Built Green checklists are assigned a version number for the year they were implemented. You can see a summary of the previous 2017/2018 version here. In 2021, we released updates for our new construction checklists to respond to code changes.

Regardless of the checklist version, there are four different Built Green certification levels, referred to as star levels, that builders can choose to achieve. This allows builders the flexibility to choose the star level that best matches their experience level with green construction practices, their or their client’s goals, and the project’s site context. The Built Green checklists are designed to encourage green development wherever possible using a holistic approach. This approach goes beyond energy use and takes water use, indoor air quality, site, materials, and community impact into consideration. This post will walk you through the various Built Green certification levels available and help you understand the differences between them.

Energy

The first thing many are familiar with when it comes to high performance homes is energy efficiency. Built Green requires notable performance differences for each certification level. The table below provides an overview regarding the energy performance requirements.

The Built Green checklists provide multiple ways for builders to demonstrate improvements in energy use, but each option is designed to achieve the performance listed in the above table. An example of how a builder can increase performance is a building’s thermal envelope—the wall that provide a physical separation between the exterior environment and the interior of a building. If the thermal envelope is more insulated and air-tight (i.e., less drafty), then the building will require less energy to provide thermal comfort to occupants. Using the Built Green checklist, builders can demonstrate how they have improved the energy performance of the home to provide greater thermal comfort while reducing operational costs to the occupant.

In addition to the home’s design, installing Energy Star rated appliances, heat pump water and space heaters reduce the energy required by the largest energy consumers in a home. Using passive solar design and orientation, light-colored interior finishes, and energy efficient lighting can further improve a home’s performance and comfort. Using a combination of features, builders can achieve high levels of performance, while increasing comfort and decreasing utility bills for occupants.

5-Star, NZE Label homes by Martha Rose Construction

For 5-Star and Emerald Star Built Green homes, additional factors come into play. For example, any Built Green home could be oriented on the lot in a way that will optimize passive solar strategies, but 5-Star single-family homes must provide a designated rooftop location for the wiring and controls for any future solar photovoltaics, while multi-family buildings must have a minimum amount of solar PV installed. Emerald Star is required to achieve net zero energy (NZE)—meaning the building produces as much energy as it consumes in a year. To achieve NZE the building must use clean energy production through wind or solar, with the energy production either on site or within a quarter of mile of the lot.

Site and Water

Energy consumption might be the first thing that comes to mind when people think of high-performance homes, but it isn’t the only aspect. Site requirements ensure the footprint of the house has a minimal environmental impact. For example, one of the requirements for a 4-Star home is planting native, pollinator-friendly, or drought resistant plants, while also limiting thirsty turf grass to 25% or less of landscaped areas. This allows for the homeowner to enjoy beautiful landscaping while saving water and money through lower utility bills. 5-Star homes take stormwater management planning a step further by using pervious paving materials for at least 1/3 of the total area for driveways, walkways, and patios.

Total water use reduction in Built Green homes is made possible through EPA Water Sense and Energy Star low-flow fixtures and appliances, as well as landscaping that minimizes irrigation needs. Similar to home energy scores, the Water Efficiency Rating System (WERS) and Water Rating Index (WRI) are water efficiency scores that can be used to show a home’s water use reduction. The following is a table that provides an overview regarding Built Green’s water conservation requirements:

Indoor Air Quality

Indoor air quality has an impact on the health of the environment, construction employees, and occupants of a home. All Built Green star levels are required to use materials, sealants, adhesives and finishes that do not emit harmful levels of added formaldehydes and volatile organic compounds that can be detrimental to occupant health.  4-Star homes take it a step further and recommend actions such as separating or air sealing the garage with an automatic exhaust fan to avoid motor exhaust from entering the home. Built Green recognizes another major contributor to poor indoor air quality that often escapes attention – shoes. There are numerous checklist credits (required for 5-Star Homes) dedicated to decreasing the number of pollutants being tracked into Built Green homes by shoes such as designated shoe-removal areas, enclosed vestibules, permanently installed track-off mats, carpets, and/or shoe grates at the principle entryway of a building.

4-Star home by Isola Homes

Materials

The materials used in the project and how efficiently they are utilized is also incredibly important and considered when assigning a Built Green star level. Every star level requires builders to post and implement a recycling plan and some form of waste reduction and recycling to ensure materials will not be wasted. 5-star and Emerald Star home require ensuring material sustainability and efficiency by requiring at least 10 materials to include salvaged or recycled content.

Emerald Star home by Dwell Development

Embodied carbon in buildings is the greenhouse gas emissions associated with building construction that arise from extracting, transporting, manufacturing, and installing building materials on site, as well as the operational an end-of-life emissions associated with those materials. Built Green 5-Star and Emerald Star homes must calculate the embodied carbon through approved methods.

Built Green uses a House Size Matrix to assign increased value to building smaller more resource efficient homes. Smaller than average homes receive additional points added to their final total to achieve a targeted star level. Larger than average homes, regardless of star level, require additional steps to address their increased material usage and environmental impact. Builders can choose between earning additional materials credits or calculate the new building’s embodied carbon baseline and show at least a 10% reduction.

Equity and Social Justice

The three pillars of sustainability are planet, profit, and people. Most often in green construction certifications, the people aspect of sustainability is overlooked. Built Green recognizes as we commit to working for equity and inclusion in housing and the building trades, we must value the voices, experiences, cultures, knowledge, and multi-dimensionality of all people, including community members impacted by discrimination, bias, and systemic barriers. Understanding their perspectives is essential to removing these barriers. Creating these spaces of belonging and centering equity in turn provides economic and growth opportunities, reduction in turnover costs, and increased applicant labor pool for builders to capitalize on. This section is intended to support architects, builders, and developers in their efforts to promote equity and inclusion, one home at a time. With each Built Green star level, the qualitative positive impact on the community increases. As the builder progresses in each star level they must increase their efforts in universal design, community planning, equitable sourcing, and create an equity and social justice plan for each project.

ANEW PACE Training Program

Why Certify with Built Green?

While an Emerald Star-certified home is greener with a reduced environmental impact than a 3-Star Built Green home, it is important to remember both homes are designed with the environment, community, and the inhabitants in mind. 3-Star certification is a great way for builders new to green building to learn more about the Built Green program and then begin to ramp up the certification levels they aim for.

Every star level builds upon the next to create greener homes. The needs of the builder, the homeowners, the community, and the environment are all considered when any Built Green home is constructed. Providing builders with the flexibility to choose which features to incorporate into the home increases the probability that more builders will choose to build greener homes. The star level tiers help provide clarity on how green each project is.

But what really makes this project stand out is what they didn’t do. While most projects start by demolishing the original structure, releasing tons of embodied carbon emissions and contributing to climate change, nwBuilt chose a different path. They partnered with Nickel Bros to relocate the site’s original 730-square-foot bungalow, giving it a second life as an affordable home on Lopez Island. Pulling the home from Ballard was quite the neighborhood event. Relocating the house for reuse prevented tons of embodied carbon emissions and preserved around 30 trees worth of lumber, roughly equivalent to the amount one person could recycle in 50 years.

Through the combination of thoughtful salvaging, design, and a passion for green building, nwBuilt has been able to incorporate green products and equipment like HRVs and mini-splits to achieve their 5-Star goal. By over-framing the exterior, they created a sloped wall that serves as a design element and doubles as an overhang. Modern elements continue through the interior, with wide-plank FSC- and FloorScore-certified oak flooring throughout the upper floors and a polished concrete main floor.

Triple-pane windows, 2x8 exterior walls with blown-in cellulose, and a gas water heater help keep energy consumption low. A Lifebreath heat recovery ventilator (HRV), the lack of carpet, and the use of low- to no-VOC products will maintain indoor air quality so the homeowners can feel comfortable and remain healthy in their homes. The home is also pre-wired for a future PV array and is electric-car-charging ready.

By combining these features and others listed below, nwBuilt was able to create two well-rounded single-family residences that are sure to last and have a minimal impact on the environment.

Freehand Studio Architects engaged with the homeowner to create a multigenerational site for their family with the addition of this backyard cottage. The design features a bedroom and bathroom on each floor, as well as flex space and 2nd story deck. The soaring double height great room provides an airy, light-filled atrium which belies the 1000 SF floor area.

Lowering the Upfront Material Emissions

Using the BEAM tool, Targa set out from the beginning to use low embodied carbon materials wherever possible, and ultimately achieved a 30% reduction in material carbon emissions. The home is framed with reclaimed lumber provided by Sledge Seattle—a company that deconstructs homes that are otherwise slated for demolition. The centuries old Fir that comes out of these homes is dense, dry, and ready to serve another 100+ years. BEAM was utilized to show the team that using blown-in cellulose cavity insulation and cork exterior insulation makes a major impact on lowering the total kg CO2e for the project compared to the typical fiberglass and foam. Other notable decisions include using LP SmartSide lap siding (an engineered wood product) instead of the typical Hardie plank, as well as generally substituting wood based products for foam and plastic wherever feasible.

Exterior cork insulation

Dark color of reclaimed fir

While framing the home, the team was continually stunned by the tight grain of the reclaimed old growth Fir. The team could not let any of it go to waste, so the lead carpenter Matt Kull fabricated a custom end-grain butcher block countertop out of framing lumber. This centrally located focal point provides a visible connection to the invisible bones of the home.

Supplying Fresh Air in an Air-Tight Home

Superior Indoor Air Quality was a priority for architect and builder and the first step towards this is airtight construction. Starting with a fully taped sub-slab vapor barrier, the air barrier then wraps under the bottom plates which are sealed with sill seal foam and Contega HF flexible adhesive caulk. The bottom of wall is also sealed to the concrete stem wall using Siga tape for a belt & suspenders approach at this critical joint. Zip System sheathing with taped seams on the walls and roof form the primary air barrier above grade. The unvented roof is framed using a unique over-roof assembly (also known as “Monopoly Framing”) where rafter tails are applied on top of the structural roof sheathing after the roof sheathing and roof/wall joints are air sealed with tape. Rigid foam is then installed on top of the roof sheathing providing continuous insulation that keeps the sheathing above dewpoint at all temperatures. This high performance assembly avoids spray foam and is a much more durable and forgiving design.

The high glazing ratio can be a detriment to energy efficiency, so the team chose Vetta windows to mitigate this. These European made triple pane tilt/turn windows are made from FSC wood and clad in an aluminum exterior. Although the team found these to have a large carbon footprint, the beauty and fantastic durability were offsetting factors.

The team runs a preliminary blower door test just before insulation to identify and address any problem areas. This home scored a final blower door score of 0.02 CFM/SF shell (0.35 ACH50) placing it well below the PHIUS passive house air tightness standard. With extreme air tightness comes a necessity for ventilation and this home uses a Zehnder Energy Recovery Ventilator (ERV) running continuously to provide fresh filtered air and exhaust stale air. Low-emitting interior finishes are the final piece in a healthy IAQ home.

High Performance Systems and Fixtures

Heating and Cooling are primarily from two ductless minisplits, with backup bedroom heat from Ducoterra radiant panels on the ceiling. Hot water is made by a SanCO2 split system heat pump water heater. This unit uses CO2 refrigerant (much friendlier to the atmosphere) and runs at an astounding efficiency to quietly provide hot water year-round without electric resistance. A heat pump clothes dryer is also an efficiency upgrade and doesn’t require a penetration through the wall for exhaust. An induction cooktop and LED lighting round out the specs for the all-electric home.

To provide energy usage feedback to the occupants Targa installed a Leviton Smart LoadCenter electrical panel which reports usage for each individual circuit in the home to a smartphone app. Paired with the homes 3.6kW Solar PV array, occupants will be able to live as close to net zero as possible.

Low flow plumbing fixtures were chosen throughout including ultra-efficient Niagara 0.8 gallon per flush toilets. The team also chose to infiltrate rainwater on site using a drywell which wasn’t required by the city. Fireclay tile, Valinge engineered wood flooring, and Paperstone countertops were chosen as sustainable, functional, and attractive finishes.