• Solar load: Roofs cook all day; attics become ovens that overwork the AC.

• Ducts in hot spaces: Cold air passing through a 120–140°F attic loses efficiency and can sweat.

• Air leaks: Humid outdoor air slips through gaps, raising indoor RH and stressing the system.

Step 1 – Air-seal first

Seal the top plates, recessed lights (mind IC-rating), bath fan penetrations, and the attic hatch (weatherstrip + insulated cover). We verify with smoke/thermal imaging and document before/after.
Why it matters: Insulation resists heat; it doesn’t stop humid air. Tightening the lid delivers instant comfort and protects against condensation.

Step 2 — Hit the right R-value

Attic upgrades here typically target R-30 or higher. With blown-in cellulose/fiberglass, you get there by maintaining uniform depth across the attic (use depth rulers and photos). If you insulate the roof deck with spray foam (open- or closed-cell), performance depends on the whole assembly—but ducts effectively move into the conditioned space, lowering loads.

Step 3 — Vented or unvented?

Vented attic: Works when the attic floor is sealed and insulated and intake/exhaust are balanced (soffits + ridge). Attic fans won’t fix air leaks and can depressurize the house if sealing is poor.
Unvented attic (spray-foamed roof deck): Foam at the roof underside turns the attic into part of the conditioned envelope. This tames humidity, helps with “hot rooms,” and reduces duct sweat. It’s often the best choice when ducts run in the attic.

Materials at a glance

• Blown-in (cellulose/fiberglass): Fast, cost-effective way to top up open attics; pair with air-sealing.

• Batts (fiberglass/mineral wool): Great value if you’re already opening ceilings/walls; workmanship matters (no gaps/compression).

• Spray foam (open/closed-cell): Insulation and air-sealing in one; ideal for roof decks or complex cavities.

Quick checklist before you install

1. Photo the current condition (depth, penetrations, fixtures).

2. Air-seal leaks at plates, lights, fans, stacks, and hatch.

3. Protect non-IC fixtures and heat sources.

4. Install depth rulers and verify coverage (blown-in).

5. Check duct leakage/insulation so you don’t lose gains.

6. Vent bath fans outdoors, never into the attic.

Mistakes that waste money

• Adding insulation without air-sealing (the “jacket with the zipper open”).

• Uneven blown-in depth from foot traffic.

• Compressed or gapped batts that create thermal bypasses.

• Spray foam applied without proper temperature/mix or prep.

• Ignoring leaky ducts in a hot attic.