A professional energy audit is worth having. The blower door test alone measures something you genuinely cannot estimate by eye, and a thermal camera in trained hands finds problems hidden inside walls.
But most houses have a handful of obvious, ordinary problems that account for a large share of wasted energy, and you can find those yourself in a weekend with a flashlight. This walkthrough goes room by room in the order that finds the biggest problems first.
One rule before you start: this is a looking exercise, not a fixing exercise. Anything involving gas appliances, combustion venting, electrical panels, or knob-and-tube wiring stops at the observation stage and goes to a licensed professional.
What to gather
- A bright flashlight and a phone for photographs
- A stick of incense, or a lit candle you can safely carry
- A tape measure and a notepad
- Twelve months of utility bills, or the usage history from your provider’s website
- Old clothes, gloves, and a dust mask for the attic and crawlspace
Step one: read your bills before you look at anything
Pull twelve months of usage — kilowatt-hours and therms or gallons, not dollars. Prices move around; usage tells you about the house.
Plot it by month. You are looking for the shape. A summer peak points to cooling and to the building envelope. A winter peak points to heating and to the same envelope. What matters most is the baseline: the lowest month of the year, typically a mild spring or autumn month with little heating or cooling. That number is what your house consumes just by existing — refrigerator, water heater, standby loads, lighting.
If that baseline is high relative to the peaks, your problem is appliances and standby draw rather than the envelope, and you should weight the rest of this audit accordingly.
Step two: the attic, because it is almost always the answer
Warm air rises and leaves through the top of the house, pulling cold air in at the bottom to replace it. The attic is where most of that escape happens, and it is where the cheapest improvements live.
Measure the insulation depth in several places with your tape measure. Much of the country wants somewhere between fourteen and twenty inches of blown insulation; considerably less than that is common in houses built before the 1990s. Note whether the coverage is even, or whether someone has walked paths through it and compressed it flat.
Then look for the air leaks, which matter more than the insulation depth. Insulation slows heat transfer, but it does nothing to stop moving air. Find: the attic hatch itself, usually uninsulated and unweatherstripped; gaps around plumbing vents and chimneys; the tops of interior walls, visible as long open channels; recessed light fixtures poking up from below; and bathroom fans that vent into the attic rather than outside, which is both an energy problem and a moisture problem.
Dark or dirty patches in the insulation are worth photographing. That discoloration is dust filtered out of air passing through, which means you have found an active leak.
Step three: the smoke test
Pick a windy day if you can. Close every window and exterior door. Turn off combustion appliances at the thermostat, then switch on the kitchen range hood and every bathroom fan. This puts the house under slight negative pressure so outside air is being pulled in through every available gap.
Now walk the house with your incense stick held near the places air might enter, watching for the smoke to bend or scatter. Check window frames and sashes, door frames and thresholds, electrical outlets and switch plates on exterior walls, where pipes and cables enter, the dryer vent, recessed lights, the fireplace damper, and the joint where the foundation meets the framing.
Photograph everything that moves the smoke. By the end you will have a list of a dozen or more spots, and the aggregate of those small leaks is frequently the equivalent of leaving a window open all winter.
Step four: the basement or crawlspace
The rim joist — the band of framing at the top of the foundation wall where the floor structure sits — is one of the leakiest parts of a typical house and is often completely uninsulated. It is also one of the easier improvements to make.
While you are down there, look at the ductwork. Feel along the seams with the system running for air escaping into a space you are not trying to condition. Note whether ducts passing through unconditioned areas are insulated. Check hot water pipes for insulation on the first several feet leaving the tank. And look for daylight around the foundation vents, the crawlspace access, and any place a pipe passes through the wall.
Step five: appliances and standby load
Note the age of the refrigerator, water heater, furnace, and air conditioner. Anything past fifteen years is likely to be substantially less efficient than a current model, and knowing the age tells you which replacement is coming.
Check the water heater’s thermostat setting. Many are set to 140°F when 120°F is adequate for most households, and the difference runs continuously all year.
Then walk the house after dark and count the small glowing lights. Each one is a device drawing power to do nothing. Individually trivial, collectively worth investigating — which is what a plug-in energy monitor is for.
Turning the list into a plan
You will finish the weekend with a long, unordered list. Sort it by cost, not by how annoying each item feels.
| Tier | Typical items | Rough cost |
|---|---|---|
| Do this month | Weatherstripping, outlet gaskets, caulk, water heater setting, pipe insulation, LED swaps | Under $200 total |
| Plan for this year | Attic air sealing, attic hatch insulation, rim joist insulation, duct sealing | $300 to $2,000 |
| Budget over time | Adding attic insulation, window replacement, equipment upgrades | $2,000 and up |
Work top to bottom. Air sealing before insulation, always: insulation over an unsealed attic floor is a filter, not a barrier. And check whether your utility offers a subsidized professional audit before you spend on the larger items — many do, and having the blower door number gives you something to measure your work against.
The weekend costs you two days and about thirty dollars in supplies. In most older houses it finds several hundred dollars a year of waste, and considerably more comfort than that.