Under California Title 24 energy efficiency standards, which cool roof requirement applies to low-sloped residential roofs (slopes ≤ 2:12)?
Correct Answer
D) Minimum thermal emittance of 0.75 and solar reflectance of 0.63
Title 24, Part 6, Section 150.1(c)7 requires low-sloped residential roofs to have minimum thermal emittance of 0.75 and solar reflectance of 0.63. These cool roof standards reduce building energy consumption by reflecting solar heat, which is particularly important in California's hot climate zones.
Why This Is the Correct Answer
Title 24, Part 6, Section 150.1(c)7 sets two thresholds for low-sloped residential roofs (≤ 2:12): minimum solar reflectance of 0.63 and minimum thermal emittance of 0.75. The high reflectance bounces solar radiation away before it heats the roof deck, and the high emittance efficiently radiates absorbed heat back out. Together they significantly reduce cooling loads in California's hot climate zones.
Why the Other Options Are Wrong
Option A: No cool roof requirements for residential applications
Title 24 does apply cool roof requirements to residential construction, including low-sloped applications. California's energy code is one of the most comprehensive in the nation; there is no residential exemption for low-slope roofs.
Option B: Minimum thermal emittance of 0.85 and solar reflectance of 0.55
A solar reflectance of 0.55 is below the 0.63 threshold required by Title 24 for low-sloped residential roofs. While a thermal emittance of 0.85 exceeds the minimum, the lower reflectance figure makes this answer non-compliant.
Option C: Minimum thermal emittance of 0.75 and solar reflectance of 0.20
A solar reflectance of 0.20 is far below the 0.63 minimum and would provide very little heat-reduction benefit. This pairing describes a poor-performing roof assembly, not a compliant cool roof.
Memory Technique
For low-slope residential roofs, remember '63 and 75': reflectance ≥ 0.63, emittance ≥ 0.75. Think of a '63-75 zone' — the roof must score in that range or higher on both metrics.
More trade-general-building Questions
When installing engineered lumber joists (I-joists) in California residential construction, what is the primary code requirement for web stiffeners?
What is the required attic ventilation ratio when a vapor retarder is installed on the warm-in-winter side of the ceiling according to the California Residential Code?
In California's Wildland-Urban Interface (WUI) areas, which underlayment requirement applies to Class A fire-rated roof assemblies?
In California, when installing a tankless water heater in a seismic zone, what additional requirement must be met beyond standard installation practices?
According to the California Building Code (CBC), what is the minimum lap splice length for #4 rebar in a concrete foundation wall in normal weight concrete with f'c = 3000 psi?
According to CBC requirements for retaining walls in California, what additional design consideration must be addressed for retaining walls over 4 feet in height located in seismic design categories D, E, and F?
When constructing retaining walls in California that exceed 4 feet in height, which CBC requirement must be met regarding drainage?
Under California regulations, when is a reduced pressure principle (RPP) backflow prevention assembly required for a residential water service connection?
Under California Title 24, what is the minimum electrical service size required for new single-family residential construction?
According to the California Building Code, buildings located in Seismic Design Category D must comply with which specific seismic design requirements?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
Under California Building Code requirements for seismic design, what type of sheathing attachment is required for wood structural panels in Seismic Design Category D?
Next Question
When designing shear walls in California, which of the following best describes the load path requirement for lateral forces?