Radiant Barriers and Building Codes

Ask The Expert – Q & ACategory: Building CodesRadiant Barriers and Building Codes
RIMA Expert Staff asked 5 months ago

I am a writer and am researching radiant barriers and building codes–specifically, which codes have incorporated radiant barriers as part of a prescriptive compliance path. I am aware of California’s Title 24, but am having trouble efficiently researching what other states or municipalities have similar language.

Someone mentioned Honolulu and Florida. I did find something about a “radiant barrier credit” in the Honolulu code but am afraid I don’t understand what that means. I also found something from Florida’s 2007 code but don’t know if that is still in effect.

Can you offer some guidance or point me to someone who can?

Can you explain the following statement in California’s Title 24? “The Title 24 prescriptive compliance approach requires a radiant barrier in climate zones with significant cooling loads (zones 2-15). The performance approach does not require a radiant barrier in any climate zone.”

1 Answers
Best Answer
RIMA Expert Staff answered 5 months ago

At present, radiant barriers are not included in the “prescriptive path” in the building codes.  You mentioned several states that include references to RADIANT BARRIER, but they are not required building materials to meet code.

Several RESNET approved software programs include credits for radiant barrier as part of the Energy Rating Index Performance Path in the IECC.

We have a California based trade member that reports on Title 24 – my understanding was that the language for the updated 2016 version of the code had removed the prescriptive requirement – the 2016 language is below – and you are correct, there is still a prescriptive requirement with the exception of structures with “below-deck” insulation.  Thank you for the feedback and correction.

The prescriptive requirements call for a radiant barrier in Climate Zones 2 through 15, except when below-deck insulation is installed. The radiant barrier is a reflective material that reduces radiant heat transfer caused by solar heat gain in the roof. Radiant barriers reduce the radiant gain to air distribution ducts and insulation located below the radiant barrier, typically within the attic space. In the performance approach, radiant barriers are modeled as separate adjustments to the heating U-factor and the cooling U-factor. The duct efficiency is also affected by the presence of a radiant barrier when using the performance approach.