Now that winter is fully underway, those of us with older houses are probably starting to hear the familiar popping and cracking characteristic of winter nights. If this is your first year in an old house, don't be alarmed! Most of the noises that a house makes in the winter can be explained quite simply, and they aren't a problem. A house is made of all sorts of different materials, and as they cool during a cold winter night they expand and contract at different rates, causing them to rub against each other. If the sound you're hearing goes on all day, or doesn't sound like popping and cracking, you may have some repair work to do. If you're worried about a noise and you can't determine what's causing it, your first step should be to get a home inspection in order to find out what's going on.

Knocking, clanking or gurgling from your heating system
A little knocking and clanking when you turn on your heating system - especially if you use a water boiler - is pretty much par for the course. As the hot water moves through your system, pipes expand and knock against walls and each other. Bill Richardson, former president of the American Society of Home Inspectors, warned that if the knocking and clanking is coming from inside the boiler itself, you may have a bigger problem. This could mean that your circulator pump is about to fail, he said, which means you'll have to get it repaired as soon as possible.

If you hear gurgling from inside your radiator - kind of like the sound you make when you're gargling mouthwash - it could be that your radiator isn't pitched right, says This Old House. Thankfully, this is a relatively easy fix - just put some shims under the radiator legs to make sure that the steam is going toward the steam trap.

Moaning, scratching or clattering

Depending on where the noise is coming from, this could be a couple of different things. If you hear a deep moaning or clattering coming from the outside of your house on windy days, what's most likely happening is that your vent dampers are getting old, says HouseLogic. The vents to the outside of your house for things like the laundry exhaust have dampers, which are meant to keep cold air from getting back into the house via the same opening. When they get old, they tend to flap about, making a clattering noise and letting air back into the house. The only thing to do here is to get new dampers. They'll set you back about $85, but they're most likely worth it for the saved heating costs and better sleep you'll get.

If you hear any of these noises coming from inside your walls or in your attic, especially scratching, you might have a more immediate problem. Animals love to get inside houses to get out of the cold, and they can steal insulation to make nests or even chew through electrical wires, potentially starting a fire. Check for animal droppings in all the usual places and either set traps or call a professional. After that, make sure you figure out where they got in and seal it up - you don't want more animals to take their place.

Water running

If you hear running water inside your house, but no one has a tap open, you could have an immediate problem. Cold weather can freeze pipes solid, causing them to burst. Once a pipe has burst in your wall or ceiling, water will start flowing freely as soon as it thaws. To check, find your water mains and shut it off. If the sound stops, you've got a leak. There isn't much you can do yourself to fix this problem, unfortunately, unless you're extremely handy. Call a plumber right away.

Once you've solved your problem, or if you can't find out what a noise is, it's time for a home inspection. A qualified home inspection professional can diagnose your problem, recommend solutions that will save you money, and notice potential problems before you do.