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Cost-Effective Options for Meeting 2018 WSEC, Built Green, and Priority Green

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

In March of 2021, the Residential 2018 Washington State Energy Code (WSEC) came into effect, and with it came the new 2021 Built Green Single Family/Townhome New Construction and Multifamily Checklists.

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:

Unit Size

WSEC 2018

Small units* (less than 1,500 SF of conditioned floor area)

3.0 credits

Medium (between 1,500SF – 5,000SF)

6.0 credits

Large (greater than 5,000SF)

7.0 credits

Dwellings serving R-2 occupancies

4.5 credits

Additions less than or equal to 500SF**

1.5 credits

*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.

A small unit (less than 1,500SF) using electric space heating and gas water heating could select the following credit options:

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

0.5

Credit 3.4

Ductless mini-split with electric resistance – HSPF 10

1.5

Credit 5.3

Energy Star gas water heater - UEF 0.91

1.0

TOTAL POINTS

3.0


But if you’re thinking of going all electric, here’s a path forward for code:

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

0.5

Credit 3.4

Ductless mini-split with electric resistance – HSPF 10

1.5

Credit 5.5

Heat pump water heater – NEEA Tier III

2.0

TOTAL POINTS

4.0



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.

Unit Size

WSEC 2018

Built Green 4-Star/Priority Green

Small units* (less than 1,500 SF of conditioned floor area)

3.0 credits

5.0 credits

Medium (between 1,500SF – 5,000SF)

6.0 credits

8.0 credits

Large (greater than 5,000SF)

7.0 credits

9.0 credits

Dwellings serving R-2 occupancies

4.5 credits

6.5 credits

Additions less than or equal to 500SF**

1.5 credits

3.5 credits

*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.

Ductless electric space heating and gas water heating

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

0.5

Credit 3.4

Ductless mini-split with electric resistance – HSPF 10

1.5

Credit 5.3

Energy Star gas water heater - UEF 0.91

1.0

CODE TOTAL POINTS

3.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.2

2.0ACH air leakage
HRV with SRE 0.65

1.0

Credit 7.1

Energy Star appliances with ductless dryer

0.5

BUILT GREEN TOTAL POINTS

5.0


Ductless electric space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

0.5

Credit 3.4

Ductless mini-split with electric resistance – HSPF 10

1.5

Credit 5.5

Heat pump water heater – NEEA Tier III

2.0

CODE TOTAL POINTS

4.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.1

3.0ACH air leakage
High efficacy exhaust fan

0.5

BUILT GREEN TOTAL POINTS

5.0


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.  

Gas space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 1)

Combustion heating equipment

0.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.2

2.0ACH air leakage
HRV with SRE 0.65

1.0

Credit 3.1

Energy Star Furnace

1.0

Credit 4.2

All HVAC equipment and ducts in conditioned space

1.0

Credit 5.5

Heat pump water heater – NEEA Tier III

2.0

Credit 7.1

Energy Star appliances

0.5

CODE TOTAL POINTS

6.0

Credit 6.1

2,400kWh of solar

2.0

BUILT GREEN TOTAL POINTS

8.0


Ductless electric space heating and gas water heating

Option

Description

Credit

Fuel Normalization (Type 2)

Heat pump space heating with no electric resistance

1.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.2

2.0ACH air leakage
HRV with SRE 0.65

1.0

Credit 3.6

Ductless mini-split with minimal electric resistance – HSPF 10

2.0

Credit 5.3

Gas water heater – UEF 0.91

1.0

Credit 7.1

Energy Star appliances

0.5

CODE TOTAL POINTS

6.0

Credit 6.1

2,400kWh of solar

2.0

BUILT GREEN TOTAL POINTS

8.0


Ducted electric space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 2)

Heat pump space heating with no electric resistance

1.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 3.5

Air-source centrally ducted heat pump – HSPF 11.0

1.5

Credit 4.2

All HVAC equipment and ducts in conditioned space

1.0

Credit 5.5

Heat pump water heater - TIER III

2.0

CODE TOTAL POINTS

6.0

Credit 2.2

1.5ACH air leakage
HRV with SRE 0.75

1.5

Credit 7.1

Energy Star appliances with a ventless dryer

0.5

BUILT GREEN TOTAL POINTS

8.0


Ductless electric space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 2)

Heat pump space heating with no electric resistance

1.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.2

2.0ACH air leakage
HRV with SRE 0.65

1.0

Credit 3.6

Ductless mini-split with minimal electric resistance – HSPF 10

2.0

Credit 5.5

Heat pump water heater - TIER III

2.0

CODE TOTAL POINTS

6.5

Credit 6.1

1,200kWh of solar

1.0

Credit 7.1

Energy Star appliances

0.5

BUILT GREEN TOTAL POINTS

8.0


Ductless electric space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

0.5

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.3

1.5ACH air leakage
HRV with SRE 0.75

1.5

Credit 3.4

Ductless mini-split with electric resistance – HSPF 10

1.5

Credit 5.6

Heat pump water heater with a split air-to-refrigerant compressor located outside

2.5

Credit 7.1

Energy Star appliances with a ventless dryer

0.5

CODE TOTAL POINTS

7.0

Credit 6.1

1,200kWh of solar

1.0

BUILT GREEN TOTAL POINTS

8.0


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.

Gas space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 1)

Combustion heating equipment

0.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.3

1.5ACH air leakage
HRV with SRE 0.75

1.5

Credit 3.1

Energy Star furnace

1.0

Credit 4.2

All HVAC equipment and ducts in conditioned space

1.0

Credit 5.6

Heat pump water heater with a split air-to-refrigerant compressor located outside

2.5

Credit 7.1

Energy Star appliances

0.5

CODE TOTAL POINTS

7.0

Credit 6.1

2,400kWh of solar

2.0

BUILT GREEN TOTAL POINTS

9.0


Ducted electric space heating and gas water heating

Option

Description

Credit

Fuel Normalization (Type 2)

Heat pump space heating with no electric resistance

1.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.3

1.5ACH air leakage
HRV with SRE 0.75

1.5

Credit 3.5

Air-source centrally ducted heat pump – HSPF 11.0

1.5

Credit 4.2

All HVAC equipment and ducts in conditioned space

1.0

Credit 5.3

Energy Star gas water heater - UEF 0.91

1.0

Credit 7.1

Energy Star appliances with a ventless dryer

0.5

CODE TOTAL POINTS

7.0

Credit 6.1

2,400kWh of solar

2.0

BUILT GREEN TOTAL POINTS

9.0


Ducted electric space and electric water heating

Option

Description

Credit

Fuel Normalization (Type 2)

Heat pump space heating with no electric resistance

1.0

Credit 1.3

Windows: U-0.28
Floors: R-38
R-10 under entire slab

0.5

Credit 2.2

2.0ACH air leakage
HRV with SRE 0.65

1.0

Credit 3.5

Air-source centrally ducted heat pump – HSPF 11.0

1.5

Credit 4.2

All HVAC equipment and ducts in conditioned space

1.0

Credit 5.5

Heat pump water heater - TIER III

2.0

CODE TOTAL POINTS

7.0

Credit 6.1

2,400kWh of solar

2.0

BUILT GREEN TOTAL POINTS

9.0


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.

Ductless electric space heating and gas water heating

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

N/A

Credit 1.1

Vertical fenestration – U 0.24

0.5

Credit 2.1

0.30 cfm/ft2 @ 50Pa and 0.35 watts/cfm ventilation

1.0

Credit 3.4

Ductless mini-split with electric resistance

2.0

Credit 5.3

Energy Star gas water heater - UEF 0.91

1.0

CODE TOTAL POINTS

4.5

Credit 6.1

2,400kWh of solar

2.0

BUILT GREEN TOTAL POINTS

6.5


Ductless electric space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 4)

Ductless mini-split with electric resistance heaters

N/A

Credit 2.1

0.30 cfm/ft2 @ 50Pa and 0.35 watts/cfm ventilation

1.0

Credit 3.4

Ductless mini-split with electric resistance

2.0

Credit 5.5

Heat pump water heater - TIER III

2.5

CODE TOTAL POINTS

5.5

Credit 6.1

1,200kWh of solar

1.0

BUILT GREEN TOTAL POINTS

6.5


Ductless electric space heating and electric water heating

Option

Description

Credit

Fuel Normalization (Type 2)

Heat pump space heating with no electric resistance

1.0

Credit 3.6

Ductless mini-split with minimal electric resistance – HSPF 10

3.0

Credit 5.5

Heat pump water heater - TIER III

2.5

BUILT GREEN AND CODE TOTAL POINTS

6.5


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.

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