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The Natural Choice
What is indoor environmental ergonomics?
What is radiant based HVAC?
HVAC is the acronym for Heating, Ventilation and
Most people including many industry professionals wrongly assume
that HVAC exclusively means thermal comfort and air quality, but this
limited interpretation prevents many to appreciate the more
accurate meaning, let us explain;
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 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 and dilution would be better than a
lower ventilation rate but if the outdoor air is moisture
laden and contaminated with toxic gases, particulate matter
and odours bringing more air in from outside
actually makes the inside worse, ergo ventilation does not
equal indoor air quality.
Air Conditioning (AC) or conditioning the air
is about decontamination, deodorization and
de(humidification) as well as temperature regulation and air velocity control ergo it is not just
thermal comfort cooling.
can see now that the H in HVAC is not exclusively heating
comfort, the V is not exclusively air quality and the AC is not
exclusively cooling comfort.
you can get beyond HVAC as being an air based system for thermal
comfort and air quality you can begin to understand the value of
incorporating the building itself
and materials of construction into the definition of HVAC
and by doing so can assign the thermal comfort component to a
radiant surface and assign the ventilation and conditioning of
incoming air to a direct ducted or as many in ASHRAE have
adopted, a “dedicated
outdoor air system” or DOAS.
dedicated outdoor air system can be as basic as an
ERV or HRV
and it could include the use of stand alone or integrated high
performance humidification and filtration equipment. It could be
defined by separate exhaust fans with a makeup air unit which
could offer many options for conditioning incoming air such or
the DOAS might be defined as an integrated system using
desiccants and renewable resources for regeneration.
Regardless of the DOAS, the removal of the sensible cooling and
heating for comfort results in significantly smaller ducted
One can be riding up a ski lift freezing your buns off but
inhaling great air quality or one could be totally comfortable
laying back on the sofa but inhaling radon gases - so never
confuse air quality with thermal comfort and vice versa.
air in a space by itself does not make you comfortable. See
radiant based HVAC.
space does not control the quantity of moisture in the air. See Myth #9 in
You can be thermally comfortable in an environment with poor air
Conditioned air can be cool-dry and dirty or hot-moist and
clean...ideally it should be clean and between 35% to 55% rh and
65 deg F to 80 deg F. See
indoor air quality.
When discussing HVAC with your builder or mechanical
contractor please understand the folks designing your
environment very rarely study the relationship between
architecture, mechanical systems and human physiology.
Unfortunately that's our North American system.
indoor environmental quality
available, is based on science, is desirable, specifiable and
obtainable in your new or refurbished building.