Top up the attic insulation

The cheapest thing you can do that changes the power bill. Most houses here are short of it.

How much attic floor?

square feet

This fits in a car

About 367 lb of materials. Comfortably inside what a car carries (200 lb), so any shopper can take it. ⚠️ 1 item on the list has no weight on file, so the real load is a little heavier than this.

Before you start

Keep insulation well clear of recessed lights, the chimney and anything that gets hot, and never bury anything electrical. If the attic has old cloth-covered wiring, or you cannot see where it is safe to step, stop and get somebody in.

What to buy — untick anything you have

Insulation

10 bags of unfaced fiberglass batts, R-30, 16 in wideUNFACED, not paper-faced — a second vapour layer over existing insulation is the one thing not to buy here. Bags are bulky rather than heavy; ten of them fill a car.
16 pieces of soffit vent bafflesThese keep the insulation off the eave vents so the roof can still breathe.
2 cans of expanding foam sealant
1 roll of foil tape

Lumber

2 boards of attic walk boards, 8 ft

Tools — already ticked off, since most people have them

Safety

1 N95 mask
1 Safety goggles· most people have this
1 Long sleeves and gloves· most people have this

Tools

1 Utility knife· most people have this
1 Work light· most people have this

It lands in the shopping form, where you can edit anything and say what you think each thing costs. Nothing is ordered until you send it.

How it goes · about a weekend · some experience

Go up when it is cool — early morning, never a summer afternoon. Walk only on the framing underneath or on the boards you brought — never on the insulation, and never on the ceiling between.
Put the baffles in at the eaves first, so the new insulation cannot slide down and block the vents.
Seal the obvious gaps around pipes and the top of interior walls with the foam.
Lay the batts across the framing at right angles to what is already there, snug against each other with no gaps.
Leave the recessed lights, the chimney and anything electrical clear rather than covering them.