Not even the most powerful residential air conditioning unit on the market is enough to keep Ryan Welch’s Alabama home cool and comfortable.
With the HVAC equipment located in what sounds like an underinsulated attic, temperatures in the second-floor living area may not reach 72°F until 10 in the evening—only after the attic has cooled.
“Our attic has varying levels of insulation,” Welch writes in a Q&A post, “and the weak spots are under the attic floorboard, which has been nailed down, making it difficult to remove.” Parts of the attic floor are insulated to R-19, other areas to R-30 (Alabama is in Climate Zone 3, where the International Residential Code, or IRC, requires attic insulation rated at R-38).
Welch runs two powered attic ventilators constantly, with the AC set at 75° during the day. But the system simply can’t keep up.
Moving the HVAC equipment is not an option, Welch says. So, he is considering several other options: disconnecting the attic ventilators, adding more insulation to the attic floor, and spraying a layer of foam on the underside of the roof deck, which would create a conditioned attic.
What’s the best plan? Welch’s dilemma is where we begin this Q&A Spotlight.
GBA Editor Brian Pontolilo suggests that if moving the HVAC equipment is truly impossible, Welch should make the attic part of the conditioned space. But he adds a caveat.
“Keep in mind that your insulation R-values are only part of the equation,” he writes, “and that air-sealing is likely a bigger issue, including around those [non-IC-rated] can lights that need to be isolated from your insulation asap.”
Pontolilo points Welch toward a GBA article on the issue (see the “Related Articles” sidebar for a link). The article says that in some situations,…