It is more useful to think of a house as a machine with named components than as a place you live. The machine has a power input, a water input, a waste output, a heat source and a thermal envelope, and every one of those has a specific part that fails first. Knowing which part, and in what order, turns a vague sense of unpreparedness into a short list of specific, boring, fixable items.

The failure sequence in the first week

Read the table as a set of deadlines rather than a prediction. Each row is something you can push further out with a specific, known purchase, and the earlier rows are much cheaper to move than the later ones.

Well and septic versus city water and sewer

These two houses have opposite risk profiles and the advice for one is often wrong for the other.

• Well and septic. You lose water the instant you lose power, but nobody else’s decisions affect you. A gravity septic keeps working as long as you can pour water into the bowl. Your single highest-value upgrade is usually the ability to get water out of the well without the grid — see Water.
• City water and sewer. Water often keeps flowing during a short outage because the utility has its own backup and elevated storage. What you inherit instead is dependence: boil-water notices, pressure loss when the utility’s generators fail, and sewer backups when lift stations stop. Storage and a good filter matter more than a pump.
• Mixed systems — city water with a septic tank, or a well with sewer service — are common and inherit one problem from each column. Check which you actually have rather than assuming.

The envelope decides how big everything else needs to be

Insulation, air sealing and window quality set the rate at which your house loses heat, and that rate sets the size of every heating solution you might buy. Air sealing a leaky rim joist and adding weatherstripping is unglamorous work that costs a few hundred dollars and permanently shrinks the problem in Heat & Cold. The same logic runs in the other direction in summer, where shade, attic ventilation and a single well-placed window unit on backup power beat trying to cool the whole building.

The building also holds two useful spaces most people ignore. A cool north-facing basement corner is a root cellar waiting to happen, which is free food storage — see Food Storage. And an attached garage or south-facing wall is often the cheapest place to add a greenhouse or a woodshed, covered in Grow Your Own.

The walk-around worth doing this weekend

• Find and test the main water shutoff, the gas shutoff and the main breaker. Label all three.
• Locate the well head, the pressure tank and the septic tank lid. Photograph them and note the depth and pump size from the well log if you have it.
• Read the nameplates on the furnace, water heater and well pump. Those numbers feed directly into Power & Backup.
• Check the age and battery status of every smoke and carbon monoxide alarm — see Health & Safety.
• Note which rooms have the fewest exterior walls. One of them is your winter room.

Once you know your own failure sequence, the question becomes how long an event you are planning for, which is covered in By Scenario, and the sanitation deadline in the table above is dealt with in Sanitation. If none of this is mapped yet, Start Here puts it in order.

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