Insulation Installation in San Juan Bautista, CA

Local Context

Adobe Carries the Day's Heat; a 1980s Attic Carries Nothing

San Juan Bautista has a wide daily temperature swing, and insulation is what decides whether you feel it. Summer afternoons run from the high 70s into the high 80s, then the evening drops back near 50 as marine air comes through the Pajaro gap. Winter days reach the high 50s and low 60s and the nights fall to the high 30s with occasional frost. That is roughly a 30-degree swing in both seasons, which is exactly the climate where attic R-value earns its keep.

The two building eras handle it in opposite ways. Thick adobe walls work by thermal mass: they absorb heat all afternoon and release it after dark, which is why those buildings stay livable without much mechanical help. Mass is not the same as R-value, though, and an adobe wall does nothing for the roof above it. The 1970s–90s ranch homes have the reverse problem — a framed wall with a modest cavity, and an attic insulated to a standard set decades ago and never revisited since.

In a town with this much termite and rodent activity, what goes back in matters. Borate-treated cellulose carries a mineral salt through the material itself, which makes it inhospitable to insects instead of a nesting substrate. It is not a termite treatment and we will not sell it as one. But on a San Juan Bautista attic where we have just finished a removal and exclusion job, it is worth raising before the new material goes down, because that is the only moment the choice is easy.