INTRODUCTION:
Every heating system affects the health, productivity, and general well-being of numerous people over many years.
The ability of that system to provide thermal comfort is of paramount importance and should be the primary objective of any heating system designer or installer.
Most people appreciate a warm comfortable house on a cold winter day. A place that encourages a sense of well-being and relaxation.
In many cases, people who have lived with uncomfortable heating systems don’t realize what they have been missing.
Contrary to common belief, comfort during the heating season is not solely determined by indoor air temperature.
Comfort is achieved and maintained by controlling how the body loses heat. When interior conditions allow heat to leave a person’s body at the same rate as it is generated, that person feels comfortable. If heat is released faster or slower than the rate it is produced, some degree of discomfort is experienced.
A normal adult engaged in light activity generates heat through metabolism at a rate of about 400 Btu/hr. The body releases this heat through several processes, including convection, radiation, evaporation, and conduction.
For indoor environments in colder weather, thermal radiation and convection typically account for almost 75% of the total heat output from the body. Heat loss by thermal radiation alone can be 50% to 60% of the total heat loss, especially within buildings that have cold wall, floor, or ceiling surfaces.
Properly designed hydronic systems control the air temperature as well as the surface temperature of rooms to maintain optimal comfort.
A hydronically heated floor can raise the average surface temperature of rooms. Since the human body is especially responsive to radiant heat loss, these warm surfaces significantly enhance comfort.
Factors such as activity level, age and general health determine what a comfortable environment is for a given individual. When several people are living or working in a common environment, any one of them might feel too hot, too cold, or just right. Heating systems that allow different zones of a building to be maintained at different temperatures can adapt to the comfort needs of several individuals. Hydronic heating systems are easy to zone using several different approaches.
ENERGY SAVINGS:
Buildings with hydronic heating systems have demonstrated a tendency for lower heat loss compared to equivalent structures with forced-air heating systems.
Hydronic heat emitters that transfer most of their heat output by thermal radiation reduce, and in some cases eliminate, undesirable air temperature stratification. This reduces heat loss through ceilings and allows comfort to be maintained at lower air temperatures.
| The figure shows a comparison between the undesirable air temperature stratification created by forced-air systems operating with poorly placed registers versus the desirable “reverse” stratification created by hydronic radiant floor heating. | |
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Hydronic floor heating system | Forced – air heating system |
Properly designed hydronic systems use significantly less energy to move heat from where it is produced to where it is needed. A well-designed hydronic system, using a modern high-efficiency circulator, can deliver a given rate of heat transport using less than 10% of the electrical energy required by the blower of a forced-air heating system transporting heat at the same rate.
A single system can be designed to supply space heating, domestic hot water and specialty loads such as pool heating. These “multi-load” systems reduce installation costs because redundant components are eliminated. They also improve the efficiency of boilers and reduce fuel usage relative to systems where each load is served by its own heat source.
Hydronic systems can combine a variety of heat emitters for space heating. For example, hydronic radiant floor heating may be used to maintain comfort in a basement, while the first and second floors are heated by panel radiators.
