If you’re moving out for the first time, there are all sorts of things to think about. Car. Exciting new job. New life, new friends. You’ve probably not thought much- if at all- about HVAC, and we wouldn’t blame you.

HVAC- heating, ventilation and air conditioning- all work on the same principles. Considering how important these things are, we think that everybody should know at least a little about how they work. So: how does HVAC work? Let’s find out!

How does HVAC work

Image courtesy of Storyblocks.

How does HVAC work? Heating

Originally, if you wanted to heat your house, you had a stove or a fireplace. But you could only feel the heat of your stove if you were sat quite close to it, and it could only realistically heat one room. If you wanted to warm your whole house, you would need more than one. To get around that problem, we invented what’s called ‘central heating’. One heating source can heat your whole home.

There are a few different ways of achieving this. Most common here in the U.S. are furnaces, which are what they sound like, and heat pump systems, which draw heat from the outside air and bring it inside. In days gone by, furnaces used wood and coal as fuel. Today, they more commonly use natural gas. But unlike the stoves of older times, furnaces (and boilers, too) drive hot air or steam around the home through pipes, which warms every room of the house.

Heat pumps essentially work like air conditioning, but in reverse. Basically, the unit passes warm refrigerant through pipes on the inside of the home, and cool refrigerant through pipes on the outside of the home. While outside, the refrigerant picks up heat from the surrounding atmosphere, which is then transferred inside, to warm the air. Inside the unit are all sorts of mechanical bits and pieces, but all that you need to know is the basic fact that a heat pump picks up warmth from the outside and brings it inside. What’s difficult to get your head around at first is that this works even when the outside air is colder than the air inside. Strange, huh?

How does HVAC work? Ventilation

Ventilation is the easiest part of HVAC to understand. All it means is that the air inside is gradually swapped out and replaced by the air outside. This is so that the air you’re breathing stays fresh. Have you ever been on an airplane, and thought that the air seemed different to usual? That’s because it’s the same air, that’s just recycled time and time again. It’s easier to recycle the air than it is to have air flow between the inside and outside, because of the difference in air pressure. So if you don’t have adequate ventilation in your house, the air starts to taste ‘stale’ over time.

Ventilation is achieved through two ways: either natural ventilation, or mechanical (‘forced’) ventilation. Natural ventilation, despite the name, doesn’t involve flax seeds or homeopathy. It also doesn’t just mean leaving a window open. Natural ventilation involves windows, louvers (a fancy word for shutters) and trickle vents (the little adjustable bars above your window, if you have them) which allow air to flow in and out. Mechanical ventilation is any ventilation provided by a fan or similar electronic or mechanical equipment. Mechanical ventilation allows for a greater amount of air to be processed in and out, but obviously, this comes at the cost of the energy required.

How does HVAC work? Air conditioning

Air conditioning systems are fairly simple to get your head around, if you understand the basics. It’s the exact opposite of how heat pumps work. This time, the refrigerant picks up warmth from the air inside the house and takes it outside. Again, this works no matter what the starting temperature inside and outside the house. Because it works on the same principle as a heat pump, some models allow you to reverse their function, so that your AC works as heating in the winter.

There are actually a few different kinds of air conditioning system! You can have window units- which you can recognise because they’re sat next to the window- or portable air conditioners, which can be detached from their mooring and moved to a different area of the house. Or you can also have ductless AC, which doesn’t need ducts to work. It’s less obvious and has a smaller profile than older, bigger models. You don’t just have to rely on air conditioning to cool your home, though, as we point out in our post on some of the AC basics. These tips, like keeping your doors and windows shut and keeping your thermostat in the shade, allow your AC to work more efficiently, and for longer, before breaking down. Speaking of which…

How does HVAC work? Repair and maintenance

Like everything in your house, from your plumbing to your electrics, your HVAC needs to be maintained. This involves having a repairman visit every now and again, just to make sure your HVAC is in good working order. He or she will perform some basic diagnostic checks, essentially looking to see that your system is working at the right pressure. Low pressure can be a sign of leaks or damage to the system.

If you have a more modern, electronic HVAC system then repair can be more complex, and your repairman might have to send off for parts. If you have an older, mechanical system, they can often fix your problem then and there!