In warmer parts of the country where basements aren’t common, the default location for the HVAC equipment is often the only space available—the attic. And unless the attic is conditioned, hot summers make it especially hard for the equipment to do its job. It’s sort of like trying to make ice in an oven.

“BurbankGreenGuy” (BGG, for short) has a 90-year-old home in a sunny part of Climate Zone 3C, and he writes here that he’s updating his attic and the HVAC mechanicals it houses. The 1000-sq.-ft. attic has two small gable vents, the AC/furnace system is 25 years old, the roof is a 6-7/12 pitch covered in clay tiles, and on hot days the attic temperature can reach 130°F.

BGG had an energy audit done, which informed his plan to remove the existing fiberglass batts, air-seal the attic, install a ducted heat pump system, then blow in cellulose insulation.

He asks if, while the attic is empty, it is a good time to perform other upgrades. He is particularly interested in whether mechanical ventilation should be added.  His gable vents are small and the roof doesn’t have soffits, so adding ridge and soffit vents would be difficult.

He also wants to know how much difference added ventilation would make, and whether it is worth the effort and upfront costs. This is where we will pick up our Spotlight conversation.

Maybe ventilation isn’t the problem

One reader points out that the air circulating through the existing vents is too miniscule to have any effect on the attic temperature, and recommends burying the ductwork.

BGG responds with a quote from Joe Lstiburek: “In a hot climate, the primary purpose of ventilation is to expel solar-heated hot air from the attic or roof to reduce…