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Some things you should know about
heat...
We've heard this before, "heat rises". But this is not true
for radiant energy. If it were we would need to put heat
lamps on the floor and the earth (preferably the
side you're standing on) would always have to be above the sun. When you put it in those
terms heat rising becomes a silly thought, agree?
There are other ways to think about everyday heat transfer. Ask yourself why you feel cool in the supermarket freezer section or underground parkade on a hot summer day.
The reason why you feel cool in the freezer section or parkade, is your blood is much warmer than the cold display glass or concrete walls so the heat from your body travels via radiation from the skin which is
warmed up by your blood, to the
cooler
surrounding surfaces.
Do you know what physicians and building scientists call this sensation?
That's right, its called
radiant cooling.
HVAC designers can deliberately provide radiant cooling by sending chilled water through PEX pipes located in the floor, wall or ceiling just like a radiant heating system.
In fact, a radiant floor used for heating and cooling is called a reversible floor.
Click on the image below. Can you imagine that the
PEX pipes might represent your arteries and veins. Can you see how a radiant heating and cooling systems is almost like
your body?
Photo Credit: NRDC,
Click to enlarge.
One of the major methods your body regulates its internal temperature is by the flow of blood to the skin.
When your body is exposed to a warm to hot surface it
prevents your body from releasing heat via radiation
and it may absorb energy in the form of heat - both which make you feel warmer.
When your body is exposed to a cooler surface you release energy which takes away heat which makes you feel cooler.
A warmer or cooler surface in a building is based on its energy efficiency and/or by "conditioning" the surfaces with PEX pipes or other forms of radiators.
The less efficient a building the greater the temperature difference between your skin and the temperatures of the walls, windows, doors floors and ceilings.
It is the temperature differences between you and the
building which in part, causes discomfort.
That's why conditioning surface temperature is so important in the comfort equation.
It's one of the reasons why this front entrance will feel cool. Image how it would feel if it didn't have radiant heating to compensate for the losses.
Suggested Reading
Cortical, thalamic, and hypothalamic responses to
cooling and warming the skin in awake humans
Egan, Johnson, Farrell et al
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