How HVAC Works: Thermal Load

How HVAC Works: Thermal Load
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Welcome to the fifth installment of our series, “How HVAC Works.” In our penultimate installment, we’re telling you everything you’ve ever wanted to know about thermal load. Or, maybe it’s everything you didn’t realize you wanted to know! We’re probably thinking about thermal load a lot more than you are, but here’s the thing: it has a BIG impact on your HVAC system, and on your comfort.

What is thermal load?

The windows in your home - and the direction they face - have a big impact on thermal load. Photo credit: http://kootenaybiz.com/

The windows in your home – and the direction they face – have a big impact on thermal load. Photo credit: http://kootenaybiz.com/

Thermal load is the amount of energy that needs to be added or removed from a space in order to keep occupants comfortable. To clarify, it’s the variables your HVAC system or air conditioner need to overcome in order to keep you comfortable. When your thermostat reaches the temperature you set, we say thermal load has been “satisfied.”

But here’s the deal: thermal load can really differ from room-to-room, even within the same house. Let’s talk about some of the variables that contribute to thermal load.

The low-down on factors affecting thermal load

The variables for thermal load can be positive (providing heat gain) or negative (causing heat loss). They can be natural (the warmth of the sun against the roof, or a cool breeze against the house) or man-made (a well insulated attic, or a window that doesn’t provide a tight seal). These variables are absolutely quantifiable, and they need to be taken into account for your HVAC to run as efficiently as it can while keeping your home comfortable.

For example, if you set your thermostat to 68 degrees, it’ll be 68 degrees – but only at your thermostat. If you walk into a room with ample southern exposure and big windows, it may be 72 degrees. In the warm summer months, the thermal load of such a room is higher than a darker, more shaded room on the north side of the house. That’s because the energy required to cool the room with southern exposure and lots of sun is greater than the energy required to cool the more shaded, northern facing room. One house, one system, and many, many different levels of thermal load. And the changing seasons even cause variance in thermal load on a room-by-room basis in the same home!

Why does it matter?

The truth is, no matter where the home or climate, thermal load is constantly changing and a system needs to be able to adapt in order to achieve comfort. There’s just one problem: no central HVAC system on the market accounted for these ever-changing conditions – until Ecovent.

Most HVAC contractors measure thermal load once at construction. But as you know, thermal load changes constantly. We made sure Ecovent compensates for thermal load with sensors that continually measure the variables that go into it: your home’s temperature, humidity, airflow, and even barometric pressure.

Now, how impressed are your friends going to be when you casually drop a few thermal load facts into the dinner conversation tonight?

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