Staying cool from roof to wall

By Emma Peterson. 

Learn a bit about the science behind having a cool home and why it’s so important. 

As the pressure of rising heat levels continues to emerge, issues like urban heat islands and overstressed energy grids are becoming more and more common. In this AskARoofer podcast episode, Megan Ellsworth and Lauren White speak to Sarah Schneider and Audrey McGarrell of the Cool Roof Rating Council (CRRC) to learn how homes are being redesigned to account for these issues. CRRC is a nonprofit that works on ensuring free data and information surrounding urban cooling and energy efficiency is widely available to homeowners and contractors. Sarah is CRRC’s deputy director and Audrey is a project manager for the team. 

In the most basic of terms, a cool roof is one that reflects sunlight and re-emits heat that is typically absorbed by traditional roofs. Audrey explained a bit more, “We're really looking at solar reflectance and thermal emittance. These both fall under the umbrella of what we call radiative properties, and they're both measured on a scale of zero to one. Zero would be basically no reflectance, no emittance, whereas one would be the most reflective or emissive that you could get.” Getting closer to that one means that the roof itself would be cooler, which keeps the home cooler and means there is less need for internal air conditioning.  

But this work is not limited to the roof. Audrey explained, “The exterior wall side is a newer topic that's coming on the scene as communities are looking for more ways to combat heat as the world continues to be warmer. With a cool exterior wall, it's exactly the same concept in that it has a higher solar reflectance, a higher thermal emittance, and keeps the building cooler inside.” One of the biggest challenges to expanding the conversation to exterior walls is the misconception that the impact is negligible.  

While a cool roof makes logical sense given the direct exposure to the sun, walls often don’t get direct sunlight all day. But they still play a key role in keeping a home cool. Audrey explained why they are equally important, “Studies have shown, at least in the state of California, that walls have only about half as much insulation as your attic or your roof does. That lesser insulation coupled with slightly less solar radiation kind of cancels itself out and we see quite similar benefits from cool exterior walls as we do with cool roofs.” 

Read the transcript or Listen to the entire episode to find out more about what keeps a roof and a home cool.