What is Comfort and How to Define It

What is comfort and if we understand it, then how do we define it?
It turns out that the “comfort” is a whole science full of studies, research, formulas and other complex things which are beyond the grasp of an average homeowner. To make things simple, it is first essential to understand how the thermal exchanger in the human body works.

An average adult human body during the phases of low physical activity produces as much energy as a 100W light bulb, or about 350 BTU’s per hour.
In order for the person to feel comfortable, the balance between produced and released energy must be maintained.
During stages of high physical activity, whether work or exercise, a person produces more heat and requires conditions which allows him/her to release this energy at higher rates. Similarly, a person during stages of low activity produces much less thermal energy and therefore requires a lower energy release rate to maintain the feeling of comfort.

How human body gets rid of heat

Comparison of thermal profiles - human, radiant heat, forced air, and baseboard

There are four natural processes which assist in releasing the heat produced by the human body:

1 - Convection

The process of convection involves the movement of air between warmer and cooler objects. The air heated by a baseboard radiator moves up to the ceiling while being replaced by the cooler air from the floor. When the hot air cools off, it moves down to the floor level and the process repeats. Similarly, the hot air heated by the body is displaced by cooler air. This is the process of convection.  

2 - Evaporation

A wet towel hanged outside in the shade quickly cools due to evaporation of water molecules from its’ surface. Rubbing alcohol, when applied to skin feels cool because it quickly evaporates. In other words, evaporation is a process where the water (in our case) transfers from liquid to vapor, or gas state of matter. Wind accommodates the evaporation process and is the reason why a person feels cooler in the wind then without it. The humidity level in the surrounding atmosphere is also an important factor. The higher the humidity, the lower is the rate of evaporation.  

3 - Conduction

When the two objects with different temperatures come in contact, the heat transfer process takes place. Sitting on the warm sand will make the person feel warmer because of the heat transferred between the hot sand and the body, whereas leaning against a cold glass will engage the reverse process.  

4 - Radiation

Under normal conditions, as much as half of the energy produced by the human body can be released through the radiant heat transfer process. Cooler objects in the room – a table, a window, a sink – will absorb the heat, allowing the process to take place. Holding a hand near a glass with an ice cold drink is another example.

Under normal condition, the body adjusts its operation to maintain the above processes in balance, both directly (such as sweating in hot weather or raising the body temperature at high humidity) and indirectly (desire to get into and stay in a warm building when it’s cold outside). When the body has to or is unable to compensate any of these processes by adjusting the others, the feeling of discomfort and displeasure appears.

Keeping your head cool and your feet warm

A simple infrared photo will show that an average person has the highest body temperature at the top of the torso (the heart region), including neck and lower part of the head and the lowest body temperature at the end of the limbs, or more specifically, the feet. The reason is quite simple – the closer it is to the heart (neck, chest, etc.), the warmer it is; the further from it (feet, fingertips) - the cooler. During chilly winter months when feet are in contact with a cooler floor, the heat conduction occurs, draining the thermal energy from the body and forcing it to adjust the other processes to try and maintain comfort. Logically, to assist the body in maintaining the thermal balance, it would be necessary to keep the feet warmer while keeping the head cooler.
The solution is simple - it is radiant heated floors.

How heating systems may increase and decrease comfort

There are (3) main types of heating systems on the US market today:

The most prevalent is the forced air system, where an electric or gas furnace heats the air and forces it though air ducts into a room. Unfortunately, this heating method is also the least comfortable, since it creates uneven air temperatures throughout the room together with an uneven and unnatural air movement and forces the human body to constantly respond and adjust to these changes. We also should mention that it also keeps the dust and pet dander suspended in the air at all times.

The second in the amount of installations is the hot water or electric baseboard/radiator heating system, which operates using the principle of convection. The air is heated by the element inside the radiator and the hot air naturally rises to the ceiling, cools down and lowers to the floor level and goes through the same process again. This type of system is also unfortunately very uncomfortable, as it dries the air forcing the body to precipitate more and creates an imbalance in temperatures – hot air at the head level and cool at the feet.

The third one is radiant floor heating. In a radiant heated floor, an electric heating element (cable or mats) or pipe with hot water are installed under the surface of the floor (usually embedded in cement). When operating, the heating element heats the floor which further transfers it to the surrounding atmosphere, including people, furniture, walls, etc. An analogy is walking on warm sand after the sunset - the sand gives off the heat it accumulated during the sunny day. No blowing wind, no dry air, no temperature imbalance – only comfort.

HeatTechProducts.com provides underfloor heating solutions for residential and light commercial applications and is aimed to deliver the highest level of comfort and satisfaction with minimal impact on the budget and the environment.