Five upgrades that actually cut a Valley home's cooling bill

1. Start in the attic, not at the thermostat

On a 100-degree afternoon an under-insulated attic can sit well above 130 degrees, and every duct and ceiling below it is fighting that. Bringing attic insulation up to a proper depth is usually the cheapest degree of comfort you can buy.

2. Seal the leaks before you add anything

Insulation slows heat; it does not stop air. Can lights, top plates, duct boots and the gap around the attic hatch move conditioned air out all day. Sealing those first is what makes the insulation perform the way the label claims.

3. Give the attic a way to exhaust

Intake at the eaves and exhaust at or near the ridge let the heat leave instead of soaking into the ceiling. Where passive ventilation is not enough, a powered or solar attic fan takes the peak off the hottest hours.

4. Replace the worst windows, not all of them

Single-pane glass on a west or south elevation is where the heat gain concentrates. Replacing those openings with dual-pane low-E units, properly flashed, does more than swapping every window on the house at once — and it leaves budget for the rest of the list.

5. Size the air conditioning to the house you now have

Once the envelope is tighter, the old system is often oversized. An oversized unit short-cycles, leaves rooms uneven and wears out early. We size from a load calculation after the envelope work, which is the order that saves money twice.

None of these five is exotic. Done in this order, they are the difference between a house that copes with August and one that never quite catches up.