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June 19, 2019

Wrestling a Bear – Advancing Programs Under Complex Codes

A house in mid-construction.

Written by: Thomas Anreise - Technical Manager

The Washington State Energy Code is a Bear

For builders aiming to comply with WSEC, for raters and energy consultants providing modeling and inspection services, and for above-code utility and home certification programs, the stringency and complexity of the current code, while both necessary and beneficial overall, also present a few hurdles in our efforts to continue providing homes that perform substantially better than code.

The need for tradeoffs

Advancing the energy performance of code homes beyond the levels stipulated under prior versions of Washington code presents an important challenge: builders must undertake one or more fairly aggressive spec upgrades. These upgrades may span across several areas of the home and represent a considerable departure from what were formerly considered conventional building practices. In order to keep code compliance feasible across the wide range of builder and housing types, the code offers flexibility for builders to choose upgrades that are most accessible, salable or least costly for their production processes and buyer base. Ducts inside conditioned space, advanced air sealing practices with heat recovery ventilation, drain water heat recovery, “best in class” heating and hot water equipment—these are just a few examples of the options builders may select under Section R406 to achieve the requisite number of energy credits for their project.

Meeting vs. exceeding

Section R406 of the Washington code outlines the required “additional energy efficiency requirements” for residential dwellings, stipulating a minimum number of energy credits that must be selected from Table R406.2 in order to comply with code. The number of required energy credits changes based on the square footage, fenestration area and occupancy type.

  • “Small” dwelling units (less than 1,500 sq. ft. of conditioned floor area with less than 300 sq. ft. of fenestration area) must achieve 1.5 energy credits
  • “Large” dwelling units (units exceeding 5,000 sq. ft. of conditioned floor area) must achieve 4.5 energy credits
  • “Medium” dwelling units (all units not meeting the description of “small” or “large” units) must achieve 3.5 energy credits.
  • Dwellings that fall under the “medium” or “large” unit descriptions, but categorized as R-2 occupancies (typically stacked multifamily units in buildings of three stories or fewer) must only achieve 2.5 energy credits
  • There is a separate set of rules for additions to existing buildings, which we won’t go into here

Sound confusing? It is… and above-code certification programs have an additional challenge in determining how their program homes perform relative to code. A home designed to exceed code significantly will not only meet its requisite Table R406.2 energy credits, but will also incorporate a range of other upgrades, some of which are also included as options in Table R406.2 and others which aren’t.

To date, very little research has been conducted to ascertain which combinations of energy credits are most commonly selected by builders. So, for a home that is designed to exceed code by incorporating an array of upgrades, programs must determine which upgrades were included to meet code vs. those that were included to exceed code.

Building a baseline

“Baseline” is the point at which programs measure against to determine how much energy a home saves and how it performs relative to standard practice or code minimum. In the case of the 2015 WSEC, we have multiple program baselines that are specific to each home’s:

  • Size category from Section 406 (to determine how many energy credits were required to meet code)
  • Heating system configuration (central system vs. zonal systems have differing credit selection assumptions)

These baselines assume a standardized suite of energy credits from Table R406.2, developed in concert with regional stakeholders and designed to spread the energy credit upgrades across a number of home components to ensure against unintended skewing of results. To see how this skewing effect would come into play in an above-code program, let’s look at an example.

For this example, let’s assume that “medium” sized homes with central heating systems achieve 2.0 of their required 3.5 energy credits by selecting the most stringent suite of shell upgrades from Table R406.2 (Efficient Building Envelope – 1c) and the remaining 1.5 energy credits from water fixture and hot water equipment upgrades (Efficient Water Heating – 5a, 5b).

In this scenario, any home in an above-code program would see very little or negative savings associated with its shell and hot water upgrades and would need to achieve all of its savings from the remaining home components: infiltration reduction, ventilation and heating equipment, ducts, controls, lighting and appliance upgrades. In some of these categories, there just isn’t a lot of room to improve over the base requirements of code. While this challenge is not necessarily unique to our example, our inclusion of the stringent shell upgrades into the baseline also means that the energy savings with the greatest longevity aren’t available for programs and utilities to incentivize, which is a subject to tackle in another post.

Instead, our baseline assumes smaller incremental upgrades across a larger range of home components, allowing for a greater diversity of savings opportunity in each home. While this is an improvement over the example above, we still have a lingering challenge—above-code homes in Washington really must “do it all,” which is to say that builders must incorporate upgrades across most, if not all, areas of the home in order to qualify for certifications and incentives in Washington. However, builders may find that their options for program participation and savings opportunities open up significantly in the following scenarios:

  • Builders commit to a deeper change to one or more home components, such as:
    • High-performance walls that eliminate thermal bridging and reduce infiltration via continuous insulation or double-wall construction
    • Window upgrades (U-.25 or lower) to augment overall thermal performance of the walls and building shell
    • Advanced air sealing practices, accompanied by balanced, distributed ventilation via a heat recovery ventilator (HRV)
    • Building with ducts inside conditioned space or using high-efficiency mini-split heat pumps
  • Homes that fall under the “small” size category under WSEC
  • Homes with “zonal” heating strategies incorporating mini-split heat pumps

The future direction of the Washington energy code is uncertain, but it is safe to assume that efficiency requirements will continue increasing. Now is the time to strive for deeper upgrades. Utility incentives are available in many areas throughout the region to offset the cost of incorporating advanced products and practices. The BetterBuiltNW team is standing by to support your efforts with technical and training resources. Email today to get started.