California enacted upgrade to its Title 24 energy standard earlier this year, mandating new energy efficiency regulations for residential construction projects. The new requirements include updates for LED lighting, reduced air leakage, tankless water heaters and increased R-value requirements for duct work in attics. But one of the most significant changes in the code is the requirement of high performance attics and walls in all homes.
These requirements provide builders with the opportunity to offer customized solutions to increase energy efficiency, but also meet code within a desired budget. Here are three keys to achieving California’s energy standards that can benefit builders across the country.
Understanding Climate Zone-Specific Requirements
Determining which insulation products will match the new energy standards relies on understanding the different R-value and U-factor requirements and the project’s climate zone. Climate zones are determined based on energy use, temperature, weather and a variety of other factors. For specific climate zones, visit http://www.energy.ca.gov.
R-value measures the resistance to heat flow and the higher the R-value, the greater resistance and the more powerful the insulating system. U-factors are used to rate door or window units, as well as wall assemblies including insulation and framing. The lower the U-factor, the more energy efficient the system will be.
Creating High Performance Walls
The requirements for high performance walls are based on assembly U-factors, rather than insulation R-value. This approach provides builders with a wide array of options for achieving compliance. Consideration of wall framing type and spacing, cladding systems, as well as cavity and continuous insulation R-value, can all factor into system choice. The U-factor requirements vary based on climate zones, following this breakdown:
• Climate zones 1-5 and 8-16: the maximum U-factor for wall assemblies is U-0.051; R-19 cavity insulation plus R-5 rigid insulation in 2×6 framing or R15 cavity insulation plus R-8 rigid insulation in 2×4 framing would be two possible options.
• Climate zones 6 and 7: the maximum U-factor for wall assemblies is U-0.065; R-19 cavity insulation plus R-2 rigid insulation in 2x6 framing or R-15 cavity insulation plus R-4 rigid insulation in 2x4 framing would be two possible options.
One popular way to balance code compliance with diverse product needs and budgets is using hybrid solutions. For example, combining a spray foam product with fiberglass batts and rolls brings together the code compliant advantages of spray foam and the cost-effective thermal and sound-control performance of fiberglass. These types of combinations can help enhance the building envelope by reducing overall air leakage, helping control draftiness and extending the life of the HVAC system, all while keeping the project at a manageable cost.
Don’t Forget the Attics
Another key component of Title 24 is new codes for vented and unvented attics. For vented attics, three options for complying with and implementing an efficient attic system are available. Each option is determined by the project’s climate zone and whether the air handlers and ducts exist in the attic or in an alternate conditioned space. Prescriptive Options A and B apply for spaces with air handlers and ducts in the attic, while Option C pertains to homes where the air handler and ducts are in conditioned space. Specific product and R-value requirements for each of the options can be found in this energy code fact sheet.
Prescriptive Options A & B combine traditional air sealing and insulation at the attic floor, with additional insulation and/or radiant barriers at the roof deck. The additional products installed above or below the roof deck are primarily to reduce the demand on the air handler and ducts due to being in the attic space. Products to help meet attic requirements would include loose-fill fiberglass for the attic floor, as well as fiberglass batts for under the roof deck (Option B) or rigid insulation for over the roof deck (Option A).
Attics in particular offer one more compliance option. If a builder is achieving compliance with the standards by the Performance option, an unvented attic may also be used. An unvented attic eliminates all attic venting and moves all air-sealing and insulation to the roof deck and any gable ends. The benefit of an unvented attic is that now the air handler and ductwork is in “semi-conditioned” space, inside the thermal envelope. This approach can provide substantial energy benefits that show up in the whole-home energy modeling required as part of the Performance compliance option.
Product options for unvented attics most often incorporate spray foam, to combine the air-sealing and insulating performance these products deliver. However, hybrid or fiberglass options are available depending on the climate zone and roof type. Hybrid or fiberglass solutions require careful consideration to avoid potential moisture issues.
As with any project in any climate zone or state, install quality is key to creating a high-performance system. An understanding of the codes for each specific climate zone and the products that can be utilized to meet them can help builders deliver high-performing wall and attic systems regardless of whether or not the project needs to align with California’s energy standards.