Get ready... this is going to be another not-so-interesting post of mine.
But it's IMPORTANT!
So I'm going to try and make this topic as easy-to-understand as possible and I'm hoping it helps you as a homeowner, or even a designer.
Let's talk HVAC.
HVAC stands for Heating, Ventilation and Air Conditioning. This is the system of any building that regulates temperature, humidity, and air quality.
One of the main reasons I wanted to do a post about this, is that HVAC is one of the most important building systems for occupant health and comfort, as well as energy efficiency (which you must know by now is super important to me!). For this reason, the Ontario government has really been cracking down on HVAC requirements over the last few OBC (Ontario Building Code) revisions.
However, HVAC design, installation, and maintenance can sometimes be tricky business, and leaving it to a pro can often be the best option. But every homeowner should at least know the basics!
WHAT DOES IT DO?
The main function of an HVAC system, is to control the temperature of indoor air, also called "conditioned air", within the "conditioned space". It also controls moisture, filtration of air/air quality, the supply of fresh outdoor air, and the movement of air.
FACTORS AFFECTING HEAT LOSS/GAIN
The reason an HVAC system needs to keep adjusting levels of temperature and humidity is because air and energy are always moving and changing. Your HVAC system seeks to maintain a kind of homeostasis within the building.
You loose/gain heat through the building envelope (walls, floors, roof, windows, etc), depending on the time of year. People, appliances, and lights also affect indoor conditions.
Also, you need a certain amount of fresh outdoor air brought into a house to make sure the air doesn't grow stale. Ventilation brings in this fresh supply of oxygen, but it also brings in unconditioned air with it that needs to be conditioned.
HOW MUCH HVAC IS ENOUGH HVAC?
Different buildings and houses need different sized systems. For example, a house with a ton of windows will probably loose heat a lot faster in the winter, so you'll need a more powerful furnace to compensate the loss.
So, someone nerdy like me looks a different factors to determine how much juice your system will need to keep you cozy.
We look at factors such as:
- building orientation
- indoor and outdoor design temperatures
- the coefficient of heat transfer for the different elements of the building envelope
- the surface area of the different elements of the building envelope
Using this information, I would tell you how to size your system. Easy-peasy.
IT ALL COMES DOWN TO THE NUMBERS
The OBC has specific requirements for indoor temperatures that have to be maintained. Basically, this prevents anyone from living in a home that isn't safe. This is mostly relevant to heating, since it can get super cold up here.
There are also numbers that have to be met for ventilation. Ventilation can either be through windows (natural) or your HVAC system (mechanical).
These numbers are the foundation for which the system is designed from. They dictate how to size the system, the location of floor heat vents, the operation/location of windows, the size of air ducts, etc.
You don't need to know all of the numbers, just know someone who does!
Consider this your basic intro to HVAC!
If you feel curious and up to the challenge, we will be doing a more detailed follow-up post about specific components and operation of HVAC systems shortly.
Good-bye for now!