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.

By framing their walls with two 2x4s, they have the flexibility to stagger studs so they do not align, reducing the potential for thermal bridging. Thermal bridging occurs when a more conductive material (such as a wood stud) provides a direct path between the cold outside air and the warm inside air. By staggering 2x4 studs, Dwell is able to break up that path with a cavity of insulation, which helps to minimize that transmission. They are also able to leave a gap between the two walls and change how thick their walls are.

For the Bagley projects, the walls are roughly 10 inches thick and completely filled with blown-in cellulose insulation. Having such a thick, well-insulated exterior wall makes these houses very quiet and easily able retain to heat or cold produced by the HVAC system.

Although the three houses are composed of two different projects, all three units are heated using ductless mini-split heat pumps, with Envi wall heaters as supplemental heat. Water heating is done via a hybrid heat pump water heater with a temperature-based recirc system. Since all of Dwell’s houses are 100% electric, homeowners can offset all their energy usage by adding solar panels; Dwell prewires for solar.

In fact, one of the Bagley houses included a 14.25kW solar system, which made the final HERS score -2. This means that the house produces more energy than it uses! This offset was possible by keeping the home’s loads (how much energy the home needs) low with Energy Star appliances, including a washer/dryer; 100% LED lighting with installed dimmers; an induction range; and previously mentioned features.

In addition to energy efficiency measures, Dwell also focuses heavily on making houses safe and healthy. All their houses use low- to no-VOC products and have no carpet installed, which allows for better indoor air quality. They also install HRVs that constantly supply the houses with fresh filtered air!

What?

The Built Green® Net Zero Energy Label indicates that a project has demonstrated via an energy model that it will produce as much renewable energy onsite as it will consume over the course of a year.

Most commonly, though not necessarily, this renewable energy is generated by solar panels. This definition for net zero energy specifies a year-long timeframe because solar panels produce more energy during the sunny summer months; excess energy not used immediately at the home is sold back to the utility and banked as a credit. In the winter, when a building is using more energy and the solar panels are producing less, this banked credit is applied to the bill.

Other forms of renewable energy fluctuate in their production based on weather and season as well. What matters to Built Green is that, in a year, the building has produced as much or more renewable energy than it has consumed.

Why?

Net zero energy homes have a significant role to play in addressing the climate crisis. According to the Drawdown solutions to reverse global warming, net zero energy buildings are one of the 100 important strategies. Even in Seattle, where homes receive carbon neutral electricity from Seattle City Light, net zero energy building has the potential to reduce greenhouse gas emissions by freeing up electric supply for transportation, which accounts for 64 percent of the city’s emissions. According to Built Green’s post-occupancy study, 4-Star homes save enough electricity to power an electric vehicle for a year. Obviously, the potential from net zero energy homes is even greater! Buildings have the ability to help clean the transportation sector through renewable electricity production.

On top of the environmental benefits, net zero energy homes also signify comfort and quality. Because these types of projects are not yet the norm (though we hope that soon they will be!), the designers and builders are putting extra thought into them and are often using some of the best examples of homebuilding technology and methods there are. The final product will be more comfortable thanks to the home’s efficient envelope and controlled ventilation. Residents of Built Green certified net zero energy homes have expressed their delight at how comfortable their homes are. And remember how credit for excess energy is banked by the utility? Well, that means residents’ electricity bills might even be negative—in other words, the utility will pay them!

Hopefully you’re convinced that net zero energy homes are a great thing, but why is the label itself important? We want to better support net zero energy building and spread the word about its benefits. At the present moment, it is a minority of builders doing these projects and we feel their accomplishments should be broadcasted. Not only will spreading the word acknowledge their hard work, but we believe it will help accelerate a market transition that is already happening and we would like to speed along.