Cool roof rules for a reroof in Chico (Climate Zone 11)
Chico, Durham, Oroville and the valley floor are California Climate Zone 11, one of the hot zones where the state energy code expects a replacement roof to reflect the sun. Most homeowners first hear about it from the inspector. Here is the rule and how it is met.
The rule
When more than half of a steep-slope roof is replaced on a house in Climate Zone 11, the Title 24 energy code requires the new covering to be a cool roof: an aged solar reflectance of at least 0.20 and a thermal emittance of at least 0.75, or a solar reflectance index of 16 or more. Those are not exotic numbers. The major shingle makers sell rated lines in ordinary colours, including greys and browns, and nearly all painted metal roofing qualifies.
Flat and low-slope roofs on houses are exempt from the alteration rule in Zone 11, though a white membrane passes anyway. The area under a solar array is exempt.
The exceptions
The code offers trade-offs for a steep-slope reroof that does not use a rated product: R-38 or better insulation on the attic floor, a radiant barrier in the attic, or R-2 insulation above the deck. Many Chico houses built since the 1990s already have R-38 in the attic, which means the shingle colour is free. We check the attic before the bid so you know which path you are on.
Why it matters beyond the inspection
A rated shingle runs cooler, which keeps the attic cooler, which keeps the bedrooms cooler and the shingles alive longer. On the Ridge, above the valley heat, the rule still applies by zone but the benefit is smaller, and a darker roof that sheds snow is a reasonable choice where the insulation exception allows it.
Common questions
No. Rated lines come in weathered wood, slate grey, brown and the rest of the usual chart. The reflectance comes from the granule coating, not the colour.
The rule is by climate zone, and the Ridge towns fall in the same zone as the valley for this purpose. The insulation exceptions apply there too. We confirm the zone and the exception by address.
Utility rebates come and go. We will tell you what is current when we bid; do not count on one.
Have a question about your own roof?
Say what the roof is doing, what kind of roof it is if you know, and which town you are in. We call back to talk it through and set a time to look at it. If water is coming in right now, skip the form and call.