The environment in which we live and work directly affects our physical and mental state. Thermal comfort in work and family environment is an essential condition for achieving psychological and physical well-being of a person.
The direct means of acting on us in the area of heat distribution is the heating system. Therefore, it is important to pay attention to the correct choice of heating system when constructing a new building or reconstructing an existing building. In the area of housing stock construction, the heating system will affect not only us but also our closest - children and our parents. Therefore, the impact of the heating system must also be assessed in terms of the impact on all family members. In the working environment, thermal comfort can be a decisive element for the commercial use of a building when renting premises. It affects the achievement of employees' work performance and their health.
Possibilities of heating system selection
The choice of the heating system is possible according to the physical principle of heat distribution for which they are designed. There are two options to choose from:
1.Distribution of heat by convection.
2.Distribution of heat by radiation - electromagnetic waves in the infrared spectrum.
Plate radiators, fan coils and hot-air heating using air-handling units are typical representatives of this type of distribution. The physical principle can be described on board radiators. The radiator transfers heat to its surroundings, which is bound to the air molecules. Heated air increases its specific volume. It becomes lighter than the cooler ambient air and rises toward the ceiling of the room. Heat is transferred to the ceiling of the room. When heat is transferred, the air cools down, reducing its volume and increasing the specific gravity. Earth's gravity pulls cool and heavier air to the floor. Subsequently, the cooled air from the floor is drawn into the vicinity of the convector surfaces of the plate radiator, where it heats up and begins to rise to the ceiling. The cycle is repeated as long as the panel radiator is warmer than its surroundings.
From the description of the functional principle, the following examples are described:
- All heating systems working on this principle will achieve a significant difference in heating temperatures between the air temperature below the ceiling and above the floor - the effect of cold feet. This difference increases in proportion to the air flow velocity. The higher the velocity, the greater the temperature difference between the floor and ceiling. The consequence of this phenomenon is that the fan coils and the hot-air system must manipulate the air and move the warmer from the ceiling area to the floor. This means that the air is constantly flowing without supplying heat from the heating system.
-The consequences of increased airflow speed are a feeling of discomfort for humans, swirling dust and bacteria in space.
-Cooling and cold flow can cause several health problems- muscle spasms, colds, eye inflammation, headaches and disabilities in the airway area.
- Fan coil units and hot-air heating with air handling units cause serious conflicts at workplaces, sometimes resulting in physical violence. People are looking for at least partial flow protection by making temporary makeshift barriers, as can be seen in the following figure.
-When building passive objects, especially when using fan coils and hot air heating and cooling, we significantly deteriorate the energy balance of the building and significantly increase primary energy consumption. When handling air, we use a large amount of primary energy to drive fan motors.
-Fancoil units as well as hot-air systems require, in addition to the initial investment, significant operating costs for regular annual service of the units. The total cost of cleaning and servicing during the life of the unit can be several times higher than the cost of the investment. The investor realizes this fact in many cases after installation. As a result, neglected thermal systems tend to be unsatisfactory in terms of hygiene, noise and energy efficiency.
- The life of fan coil units is usually shorter than 15 years, radiant systems have a life of 50 years.
Two types of infrared radiators are known:
Focus infra-red heaters
Typical representatives of focus-type infra-red heaters are gas, electric and WH water infra-red heaters.
Thermal systems using electromagnetic waves have adopted this principle from the natural environment. Life on Earth is dependent on the sun, which is the largest source of electromagnetic waves in our system. Everything living on our planet has learned over the years of evolution to use the sunlight to its advantage. We humans have adopted this process of heat distribution so much that we ourselves are a radiant source for our environment. We are able to send most of the heat to our surroundings in this way. Our bodies perceive the heat that falls on us in the form of radiation as highly comfortable.
When radiated, the infrared emitter produces -emitting electromagnetic waves that pass through the air and, upon impact, heat all solid and liquid substances they strike in their surroundings. It follows that radiation does not heat the air, but the surrounding areas, which have a higher temperature than air. Subsequently, the air is heated from the heated surfaces. One perceives thermal comfort as an effect of the temperature of the surrounding areas and air.
The functional principle implies the following facts:
- When heating, the surface temperature is 2 to 3 degrees higher than the air temperature. The same thermal comfort for humans can be achieved at a lower indoor air temperature and thus reduce heat consumption.
When cooling, the surface temperature is 2 to 3 degrees lower than the air temperature. The same thermal comfort for a person can be achieved at a higher indoor air temperature.
-Distribution of heat in the space is uniform and comfortable, there are no differences in legs and head.
- No swirl of dust and bacteria, no air flow.
-We consider radiant cooling as highly comfortable for our organism. It does not cause us any physical problems and we consider it to be sufficient even at lower performance.
- Radiant systems improve the energy balance in assessing the energy performance of buildings, save primary energy and enable the use of renewable energy sources.
More about radiant heating systems can be found in the separate section - Radiant heat systems for passive buildings.