Those who still stand firm in the belief that the V in HVAC is exclusively about delivering indoor air quality might want to read this clause:
"A-6.2.1.7.(2) Outdoor Design Conditions. In the past, the practice of ventilating buildings with outdoor air assumed that the outdoor air was of better quality than the indoor air. It has become evident that the outdoor air in some areas of Canada may not be of an acceptable quality for ventilating buildings unless certain particles and gases are first removed or reduced. A recent estimate suggests that 30% of Canadians are exposed to contaminated outdoor air via buildings’ ventilation systems, which may lead to health problems such as cardiovascular and cerebral vascular diseases, respiratory irritation and illnesses, asthma, allergies, cancer, mucus membrane disorders and possibly death."
As we have stated before, the general populations misunderstanding of HVAC is that H is exclusively heating comfort, V is indoor air quality and AC is comfort cooling. This misunderstanding also extends regrettably to a large segment of the construction industry.
This is how we define HVAC:
- Heating (H) influences the relative humidity, surface and interstitial vapour pressures, surface temperatures, drafts, material durability, and material VOC emission rates ergo its more than heating for thermal comfort.
- Ventilation (V) in and by itself does not guarantee air quality as its function is to exhaust indoor air and replace it with outdoor air. One would think that a higher ventilation rate would be better than a lower ventilation rate but if the outdoor air is contaminated with ozone or has a high humidity, bringing more air in from outside actually makes the inside worse.
- Air Conditioning (AC) or conditioning the air allows the designer to treat the air through dilution, filtration, deodorization, temperature regulation, dehumidification, humidification, and air velocity control ergo it is not just cooling for thermal comfort.
Thus, the H in HVAC is not exclusively heating comfort, the V is not exclusively air quality and the AC is not exclusively cooling comfort.
If I had it my way we would change the HVAC to HVCA thus we would have a much better descriptor with Heating, Ventilation and Conditioning of Air.
For a back ground on the topic be sure to read these resources:
