In much of the country, winter is a home owner’s worst enemy. Extreme cold and the cycle of thawing and freezing attack your home’s critical systems and sap expensive heat and energy. Sure, turning down your thermostat helps, but only so much—and who wants to shiver? Truly preparing your house for winter can protect vital systems, greatly reduce energy bills and make you more comfortable. But what if time or money doesn’t allow you to make every winter preparation? No problem. Here’s what to do for the best result and to get the most bang for your buck…

Prioritize. Every house is an ongoing progression of problems. When one problem is fixed, another eventually will appear—and usually there are multiple problems at once. In the weeks and months before winter, however, you should focus your attention on fortifying your home to keep warm air in…and to keep cold air and water out. Since heat rises and water and cold air fall, you must concentrate your finite time and resources on shoring up the roof and insulating the attic—in that order.

Invest in a roof inspection. Hire a roofer to conduct an inspection before you spend a single dollar anywhere else. The reason? If you have even a trickle of water coming in through the roof, it can turn into a huge headache.

The tiniest leak may not be a big deal in the fall. But when that thin stream of water freezes and expands as ice in winter, your tiny leak will become a big leak, which will then freeze and ­expand even more. Water rots your home’s wood frame, saturates and ruins insulation, creates a breeding ground for dangerous mold and generally causes havoc inside the home.

Keeping water out in winter should be your number-one priority—and water is most likely to enter through the roof, where even the most observant home owner might not be able to spot a small leak. Faulty roofs also enable the formation of ice dams, which are ridges of ice that prevent water and melting snow from properly draining off the roof. Ice dams, which form when uneven roof temperatures cause snow to melt and then refreeze in concentrated areas, can cause catastrophic damage to ceilings, walls, insulation and the roof itself.

The national average cost for a roof inspection is $217, according to Home Advisor.com, although it could be as low as $75 or as high as $700. If you have it, spend it. Hopefully, your inspector will tell you that your roof is in great shape, get in his/her truck and leave. If that’s the case, it’s time to move on to insulation. However, if the inspector finds some problems that need fixing, expect to spend $770 for the average roof repair, according to ­HomeAdvisor.com. (The typical range is $331 to $1,223.) You won’t enjoy writing that check, but keep in mind that replacing damaged portions of the roof and dealing with water damage inside in the spring would come with a much less forgiving price tag.

Insulate your attic—big time. Unless you have the means to cloak your home in a thermal barrier by hiring a crew to insulate your walls, garage, basement and rafters, you should plug the heat leaks in order of priority. The attic is your ­priority—that’s where rising warm air tries to escape from inside and sinking cold air tries to enter from outside. If you wouldn’t go outside in a blizzard without a warm hat, don’t let winter ­arrive without a well-insulated attic.

Many attics are already insulated…poorly. Either insulation is where it should be but there’s not enough of it…or some parts are insulated but others aren’t. And some attics, even in cold ­regions, aren’t insulated at all, sometimes because insulation was removed to perform work on the underlying structure and simply never replaced. Insulation should cover the attic floor, fill the gaps between joists, protect any open penetrations around piping and fill knee walls, which are walls with attic space immediately behind them.

The average cost to have a professional insulate an attic ranges from $1,357 for blown-in cellulose insulation to $1,574 for roll or batt fiberglass insulation—that’s the familiar fluffy pink stuff—to $2,170 for spray-foam insulation. (Some builders find that the denser and more rigid rockwool, also called mineral wool, batt insulation performs better than fiberglass rolls, even if it can be more difficult to work with. Rockwool batts add about 25% to 50% to the cost of fiberglass, installed.)

Attic insulation can pay for itself fairly quickly through lower energy costs. The Department of Energy website ­Energy.gov/energysaver/types-insulation can help you sort out the pros and cons of different types, including how well they lend themselves to do-it-yourself (DIY) projects. Because it’s dusty work in a cramped environment, installing attic insulation generally is not considered a DIY project, but it can be done. It must, however, be done right. Even small gaps left behind can dramatically reduce R-value, which is a measurement of heat retention by which all insulation is classified. This Old House offers a primer on insulating your own attic, which is a good place to start. Go to ThisOldHouse.com and search “insulate attic.”

Consider a home-energy audit. Poorly insulated attics bleed more energy than any other part of the home, but your entire structure has vulnerabilities that are likely invisible to you. This is where a home-energy audit comes in. Home-energy auditors examine houses from top to bottom with equipment such as thermal imagers, special fans and prods to find leaks, drafts, weak spots, shoddy insulation, exposed pipes, inefficient appliances and other chinks in your home’s energy armor.

Energy.gov and the federal Energy Star program (EnergyStar.gov) will help you learn what to expect from an ­audit. Contact your utility company, and ask whether it offers free or discounted home-energy audits, which many utilities do. If not, the average cost to hire a professional is about $394. While that’s a hefty price tag for many people, it will be money well-spent if the audit unmasks your home’s neediest points.

Things you can do for less…or for free. Clean your gutters, or have them cleaned, before freezing weather comes. Clogged gutters encourage the formation of ice—which can push or pull your gutters loose, lead to destructive ice dams and even result in injuries from massive falling icicles.

Upgrading older, energy-inefficient windows is a worthwhile but expensive improvement. If that’s not possible, consider buying transparent insulating film that adheres to the glass portion of your existing windows. It doesn’t obstruct your view—in fact, you can leave it on year-round if you choose—but it can significantly reduce window-based energy bleed in both winter and summer. Example: The Gila LEG361 Heat Control Residential Window Film, which says it cuts cooling costs by up to 30%, sells for about $30 and includes a roll that measures 36 inches by 15 feet.

If you’re confident that you can safely do so, flush your water heater through its drain valve to clear out sediment and sludge, which can improve efficiency and reduce costs in the high-demand winter months. If this isn’t something you want to do yourself, pay a plumber to do it (about $100)—it should take less than an hour and is worth it.

Heat escapes and cold air enters through gaps under exterior doors. A $10 draft guard can prevent most of that waste. Virtually all homes will benefit from weather-stripping tape applied to doors and windows. Each roll costs about $5 and can service two or three doors. If you have forced-air heating, replacing the filters for about $10 each can take enormous pressure off your heating system, reducing the cost of running it.

Finally, walk around the exterior of your house, and examine the siding for holes and gaps. When you find a gap, fill it with regular household caulk, which costs $5 to $10 per tube and can be applied with a $15 caulk gun.