Lately I’ve been thinking that I don’t talk enough about architecture and about buildings on Architect This City. So today I’m going to step away from transit, driverless cars, and the other topics I’ve been discussing lately, and instead talk about something a bit more technical: mechanical systems and Energy Recovery Ventilation (ERV) units. If you’re thinking about buying or investing in a condo, I think you’ll find it useful.

Buildings work in many ways just like people do. They breathe in fresh air and they exhale out stale air. And just like you and I, once air has been exhausted out, it needs to be replaced, or made up, with more fresh air. In the world of buildings, this replacement air is called “makeup air.”

It’s for this reason that you’ll often see no smoking signs directly outside of buildings. It’s because if you happen to be smoking next to a fresh air intake, you’d actually be distributing cigarette smoke throughout the entire building. The same goes for idling trucks and other pollutants.

The amount of fresh air that needs to be pumped into a building will vary. For some uses – like hospitals and laboratories – the requirement for fresh air can be significantly higher. Sometimes as high as 100%. And that’s because you don’t want a building with toxic smells or lots of sick people to be relying on too much recirculating air.

You might then be wondering why we don’t rely on 100% fresh air in all buildings. And the reason is that it is incredibly expensive to do so. When you take in fresh air from outside, it needs to be conditioned before it can be distributed. And that takes energy. In the winter when it’s -10 degrees outside (hello Toronto), you need to heat up that air. Whereas recirculating air is already conditioned. So you just, well, recirculate it.

In most condo buildings, makeup air is supplied by dumping air into the corridors. To check if your condo functions like this, just look for a big vent outside in your hallway. This air then gets sucked into the individual suites by way of slits or openings around your front door.

So another way to check if your building operates this way is to see if your front door is letting in air from the hallway (or if it’s sealed). There’s nothing necessarily wrong with this approach, but sometimes you might end up pulling in smells from outside of your suite.

This now brings us to Energy Recovery Ventilation (ERV) units.

The way an ERV works is very simple. Let’s use our winter example, where it’s -10 outside (and you’re questioning why you live in a place that’s so cold). In this scenario, you’d be pulling in freezing air and exhausting out warm air from your apartment.

What the ERV does is transfer some of the warmth from the warm exhaust air to the cold intake air. This means the fresh air ends up coming inside your place at a warmer temperature and doesn’t need to be heated up as much. It’s “preconditioned.”

This saves energy. And it saves in utility costs.

But the other benefit of these ERV units is that, instead of pulling fresh air (or makeup air) from the corridor, it pulls it directly from outside of your condo suite. In other words, your front door is sealed and each suite is responsible for its own fresh air demands. The overall result is typically better indoor air quality, better energy efficiency, and lower utility costs.

At both DUKE and Kingston&Co, which are two condo projects that I’m currently working on a TAS, we’re putting an ERV unit into every suite. We think it make sense. But there are always questions around how much purchasers actually care about measures like this. Things like fancy countertops and appliances are usually what sells. Not some hidden mechanical unit that you’ll never see or even know exists.

But I think details like this matter. What about you?