Indoor Environmental Quality with Radiant Based Heating and Cooling from Healthy Heating.


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Some things you should know about building efficiency...

One of the principals of heat transfer is heat always goes from hot to cold. Always. Some people think heat rises but this is not true. If it were, then 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 heated by your blood, to the cooler surfaces.

Do you know what physicians and building scientists call this sensation?

That's right, its called
radiant cooling.

Designers can 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 warmer surface it absorbs energy in the form of heat which makes 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 which causes discomfort.

That's why conditioning surface temperature is so important in the comfort equation.

Its why this front entrance will feel cool.  Image how it would feel if it didn't have radiant heating to compensate for the losses.

Learn More About Thermography

 

 

 

 

 

 

eJournal of Indoor Environmental Quality

 


 

The Perfect HVAC Systems is The Human Body

Thermal images of the human body
Credit:
TONY MCCONNELL/SCIENCE PHOTOLIBRARY

This thermograph shows a human drying off in front of a panel radiator. The different colors show the variations in surface temperatures. Have you ever heard the term "white hot"? Can you tell which way the water is flowing through the radiator? This person feels warm because the hotter surface is radiating towards him just like the sun does.

Blood flow in the hand
Credit: MEHAU KULYK/SCIENCE PHOTO LIBRARY

The variations in skin surface temperature shown in the thermograph above are in part due to the regulation of blood flow. Blood travels through the arteries that branch out to form the capillaries. The blood then leaves through an extensive network of veins as shown in this illustration. Can you imagine the veins and arteries as radiant PEX tubes and your skin as a living radiator?

controlling blood flow for cooling and heating regulation of body temperature.
Credit: JOHN BAVOSI/SCIENCE PHOTO LIBRARY

The regulation of blood flow happens when the nerves (yellow) stimulate the artery muscle to  contract, thereby maintaining blood pressure. Increase in stimulation causes constriction of the vessel and an increase in blood pressure. Decreases in stimulation causes a dilation of the vessel and a drop in blood pressure. The change in pressure regulates flow just like in a hot water heating system. The warmer the internal body temperature, the greater the blood flow to the skin where heat is radiated, convected, evaporated and conducted away for cooling. Can you imagine your arteries and veins as performing the same function as PEX pipe used for radiant heating and cooling systems?

The brain is the perfect thermostat
Credit: Health Archives (Publisher Unknown)

The instruction to dilate or constrict blood flow comes from the brain which gets input from nerve sensors in the body. The name for the part in your brain that is responsible for your bodies temperature regulation is called the hypothalamus. Your hypothalamus is the perfect thermostat and its wired to your skin sensors through your nervous system.

Thermal sensors in the skin
Credit: FRANCIS LEROY, BIOCOSMOS/SPL

The average adult body is covered by a nominal 20 sq. ft. of skin, which has over 166,000 thermal sensors connected to the brain. The sensors in your skin are stimulated by  pressure, heat, cold and pain. That stimulation is sent to the brain for interpretation. The skin is also rich in blood vessels; shown here, arterial capillaries appear red, venous blue. To protect vital organs, the blood flow is reduced to the skin when the body gets cold. Goose bumps are caused by the skin tightening up around your hair follicles. Picture your head popping out of your coat after buttoning it up on a cold winter day.

thermography for studying human physiology

 

 

 

 

 

 


Credit: DR. ARTHUR TUCKER/SPL

 

The human body is a living heating and cooling systems which is very effective at staying healthy with radiant transfer. Can you now imagine how this baby might feel crawling across a cold floor? The colors represent different temperatures, from the cold feet to the hotter forehead.

The body at rest absorbs and releases over 50% of its sensible heat by radiation and the temperature of the skin is regulated by blood flow.

With this knowledge in mind, knowing humans, (especially babies) like warm surfaces in winter and cool surfaces in summer, what type of heating and cooling systems makes sense for you and your family? What would you recommend to others?

 

Want to know how other industries do thermal comfort research?
Visit our web page on Comfort Instrumentation and Thermal Manikins.

Want to expand your knowledge on human physiology and comfort?
Visit our web pages on
Indoor Environmental Quality

Want to familiarize yourself with the basics of architectures and radiant based HVAC systems ? Visit our schematics pages.

Want to read about insulation, working with contractors, heat pumps, radiant cooling, hardwood floors and radiant systems? Visit the links at one of our solutions page where you can find many articles on several topics.

Want to have fun simulating your ideal environment by playing with air velocity, clothing, activity, and humidity? Visit the Comfort Calculator page.

...or just join us at the online forum to discuss your healthy heating options in Total Comfort System for homes and cottages.

The images on this page were made available through the financial generosity of our corporate sponsors and individuals who have downloaded the Guide to Indoor Quality Comfort and the Architectural Guide to Radiant Based HVAC Systems. If this material was of use to you, please consider sponsoring a page or donating so we can continue to offer high quality educational materials on indoor comfort quality (ICQ).

   

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