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The Natural Choice
What is indoor environmental ergonomics?
What is radiant based HVAC?
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The Complete
Definition of
HVAC
HVAC is the acronym for Heating, Ventilation and
Air Conditioning.
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 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.
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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.
You
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.
Once
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 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.
The
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
system.
Conclusion
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.
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Heating the
air in a space does not make you comfortable. See
radiant based HVAC.
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Heating a
space does not control the quantity of moisture in the air. See Myth #9 in
Radiant Mythology.
-
You can be comfortable in an environment with poor air
quality.
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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.
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When discussing HVAC with your builder or mechanical
contractor please understand the folks designing your
interior
environment very rarely study the relationship between
architecture, mechanical systems and human physiology.
Unfortunately that's our North American system.
Fortunately good
information on
indoor environmental quality
is readily
available, is based on science, is desirable, specifiable and
obtainable in your home or cottage.
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