Insulation-Related Updates to Title 24

A building scientist in the insulation sector answers common questions about how Title 24 will affect builders.

Title 24’s recent update is now in play.  It includes key changes to lighting, mechanical ventilation systems, wall and attic insulation, and general approaches to overall energy-efficiency compliance.

The updates are expected to have substantial effects on the overall energy efficiency and costs associated with residential buildings. According to the California Energy Commission, under the new code, single-family homes should expect to see a 7% decrease in overall average energy consumption and an $80 decrease in heating, cooling, and lighting bills.

Here, Johns Manville Building Scientist and insulation expert, JR Babineau, answers common questions about the new Title 24 requirements and how home builders can use insulation best practices to crack the code.

What are the biggest changes expected from this iteration of Title 24, specifically related to residential building insulation?

One of the biggest changes to the updated Title 24 code involves high-performance attics and walls – areas that typically use increased amounts of insulation to reduce cooling in the summer and heating in the winter.

While high-performance attics and walls were originally implemented as a prescriptive requirement in 2016, previous versions of Title 24 allowed photovoltaic solar equipment to be used as a limited tradeoff. Now, to encourage and prioritize both energy efficiency and renewable energy production, photovoltaic solar is a requirement and no longer an available trade-off against efficiency measures.

Additional changes that impact the residential building envelope are simplification of attic insulation requirements and changes to wall insulation requirements. Most builders in California achieve Title 24 compliance via the Performance path (versus Prescriptive), which does allow some amount of trade-off between materials such as insulation, windows, lighting, and HVAC performance, a result of the collaboration between the builder and their energy consultant.

The Performance path, and the trade-off opportunities this approach creates, allow builders and insulation contractors to deliver innovative insulation solutions that meet the new energy standards and desired budget of homeowners, all while improving the building’s thermal envelope, comfort, and environmental conditions.

To vent or not to vent? Considering the simplification of prescriptive attic options, what should be noted regarding vented vs. unvented (Prescriptive path vs. Performance path) attics?

While the options for prescriptive, vented, attics have been somewhat simplified, unvented attics still have multiple benefits over their vented counterparts. Unvented attics are Performance path compliant and allow for reduced air leakage and energy loss from leaky ductwork, while also reducing the size of an overall HVAC system. Unvented attics must be air sealed at the roof deck, eaves, gables, and penetrations, instead of at the plane of the ceiling. Insulation, such as spray polyurethane foam, can play a fundamental role in providing both air-sealing and insulation in one installation step.

Johns Manville has several insulation solutions that meet the unvented attic insulation requirements of Title 24, including:

  • R-30+ Johns Manville Formaldehyde-Free Fiberglass Batts (air-seal the roof deck, eaves, and gables before installation)
  • R-22+ Johns Manville Corbond Spray Foam (SPF) (insulates and air seals in one step)

Johns Manville also offers insulation solutions for prescriptive, vented attics. For vented attics with HVAC equipment and ducts in the attic space, the most common JM insulation solutions are:

  • JM Climate Pro loose-fill fiberglass on the attic floor (R-30 or R-38, depending on climate zone)
  • JM unfaced Formaldehyde-Free Fiberglass Batts, R-19, under the roof deck in all climate zones

Vented attics with HVAC and ducts in conditioned space do not require insulation under the roof deck.

Changes to insulation requirements in one area often lead to changes in others. What about new requirements for walls?

There are a few changes to requirements for walls. First, for walls framed with 2×6 framing, the new mandatory minimum cavity insulation is R-20. The second change is that the performance requirements for walls improved by about 6% (except in California climate zones 6 and 7). For example, this means that a wall with 2×4 wood framing (16” on-center) previously insulated with R-13 fiberglass batts and R-9.3 foam sheathing (1½”), will now require R-13 fiberglass batts and R-10 foam sheathing (1⅝”). For builders who have been building high-performance walls and using foam sheathing, this shouldn’t be a substantial change.

Title 24 now mandates Quality Insulation Installation, or QII, as a prescriptive requirement. What does a QII job look like, and how does it differ from previous Title 24 requirements?

Quality Insulation Installation (QII) requires that insulation and air sealing materials be installed so they can deliver the performance intended. For insulation materials, this means cavity insulation should be properly installed without gaps, voids, or excessive compression, and in contact with the air barrier. Products will be properly trimmed and fit around obstacles, as called for by manufacturers’ instructions. QII applies to all insulation materials, not just fiberglass batts, and requires inspections by a Home Energy Rater (HERS), a certified industry professional who will grade the work of the air sealing and insulation contractor.

Although the new iteration of Title 24 establishes QII as a prescriptive measure, it’s not a new concept. The 2013 and 2016 versions of Title 24 awarded optional compliance credits for installations that pursued QII. For contractors who already provide QII, the inspection will simply be a formality and recognition of the service they already provide to builders.

As energy-efficient solutions continue to evolve, home builders and insulation experts need to stay up to date on new building standards like Title 24 to ensure newly constructed buildings perform effectively, efficiently and sustainably. With the right knowledge and processes, builders, contractors and other professionals can crack these codes to lower costs and deliver innovative solutions and products that cater to evolving homeowner wants and needs.

JR Babineau is a research manager and the principal building scientist for Johns Manville. For over 20 years, he has been involved in research and development of building products, as well as providing education and consultation on building systems, with an emphasis on health, air, moisture, noise, and energy efficiency.