Rhodes Architecture + Light believes it’s important to inform when substantial changes occur in our profession affecting our clients. On March 15th, 2024, Washington will be adopting new residential energy requirements that will directly affect all new construction and substantial renovations. Natural gas is on its way out for heating and hot-water generation, and Washington State is mandating all-electric sources of energy. Here we will walk you through what you can expect as the changes affect the building thermal envelope. You may be asking, “What is the building thermal envelope and why does this matter?” To start, let’s break it down into two words: thermal and envelope.
Wingspan Residence, Photography by Quanta Collectiv
The highest level of sustainability drove the design of the Wingspan Residence. High-efficiency heat pump (heating and cooling), water heating, appliances, energy recovery ventilation system, lighting and controls and electric vehicle charging is provided by the sun and 45 photo-voltaic panels (hidden on the roofs). The house produces more energy than it uses. All aspects of the design and construction from robust insulation and building envelope, doors + windows and landscape, to the use of healthy interior finishes and the recycling of construction materials were guided by maximum sustainability. The completed residence received a 5-star + Built Green Certification in 2022.
For thermal, simply think warm, cold, and how can we mitigate or contain each. Now the envelope: let’s envision an actual envelope. We typically place items within the envelope to shield, protect, and conceal them, which is the intent of your home’s envelope. It’s designed in a manner that protects the project from mother nature’s elements. Now, let’s add back in thermal and we create an assembly that is not only protecting you from the elements but is shielding you from hot and cold days and assisting in containing the desired temperature in your interior spaces. To combat thermal conduction, insulation is used to resist the transference of heat through the envelope. The better the resistivity of the insulation, the more likely you are to reduce energy loss in your home. New residence insulation values are being impacted by the new adopted code changes and windows and doors will also need to be better insulated.
Wingspan Residence
According to Seattle Building Code Council (SBCC), the Washington State Energy Code building components being affected include your ceiling/roof, exterior walls, and slab on grade. For the ceiling/roof assembly, you can expect an increase from R-49 to R-60. That’s a substantial change, as it will likely affect the sizing of your roof’s structural members to achieve R-60. The change may result in more closed roof systems (unvented), to be able to utilize closed-cell spray foam insulation, which in most cases, have a higher R-value per inch.
Wingspan Residence
Exterior walls on the other hand, see a slightly different adjustment. The old energy requirement was a minimum of R-21. The new requirements add continuous insulation (rigid) outside the walls of the residence. New wall insulation is required to be both within the framing cavity and proud of the cavity, adding up to the one of the following values: 20 + 5 or 13 + 10. The primary value represents cavity insulation, typically fiberglass or rockwool. The second value represents the continuous insulation (wrapping the walls of your new home). Dependent on how the exterior wall assembly is designed, these values may increase the overall size of the wood or metal framing studs.
Lowman Beach Residence, Subtle Light Photography
A myriad of thoughtful details make the Lowman Beach House an impressive example of sustainable design and building practices. The most significant measure was the addition of 50 Voltaic solar panels which generate enough electricity to sell a surplus back to the Seattle city light grid. Other sustainable choices included high efficiency LED lighting, tinted west facing windows, rainwater irrigation, low maintenance Shou Sugi Ban Yakisugi siding.
"They did a good job sourcing green materials instead of just going with the tried and true. We put enough solar panels on that we don’t have a power bill. They knew we were environmentally oriented.” –Lowman Beach Owners
The last major building component we will mention is your slab/foundation. The new energy code requirement, dependent on location and amended jurisdictions, states that new under-floor-slab insulation extend four feet (versus two feet currently). Perimeter insulation is still required, at a minimum R-value of R-10 (continuous insulation). This signifies that regions in Washington now are considered to have a deeper frost depth; the added foundation insulation prevents structural damage during winter months of the year as the ground freezes.
What do these changes mean for you, the end-user? Depending on the desired square footage of your home, these new WA Building Codes energy requirements play a sizable role in the building assemblies (walls, roofs, etc.), which impact overall construction cost. On a positive note, you can expect a more complete, insulated, and sealed home that will use less energy; this will help reduce your utility bills and put more dollars in your pocket.