Like for everything else in nature, there is a principle of energy balance in buildings. Or, to put it more simply, the total energy required for maintaining the temperature in an facility is always equal to the total energy losses of the building, reduced by the amount of energy gains in the building.
Energy gains in a facility, or so-called passive energy sources are a combination of solar energy, internal energy and negative thermal bridges. By default, these are free sources of energy.
Solar energy theoretically enters the building through all sunlit surfaces. In the winter period, the gains of solar energy through the walls and the roof is negligible, but special attention should be paid to the solar energy that can be gained through the windows. For this purpose are necessary glasses with a higher solar factor, so in this way up to 18% of the required energy for maintaining the temperature can be obtained through the windows. But in summer, such windows can lead to overheating of the building, and therefore, the change of the angle of the sun in summer and in winter must been taken into consideration, together with measures to shade the windows properly. In the summer period, it can often come to heat penetrating the roof, and therefore it is necessary to pay attention to the type of roofing, as well as the roof isolation.
Internal heat sources, in the construction of energy-efficient buildings, should not be overlooked. This includes the heat released by people and animals, various household appliances and machines, as well as the amount of warm water used and cooking. No matter how insignificant this energy may look like, it can bring up to 12% of the required energy for heating the facility in the winter months. And in the summer months it should be taken as a heat load in the energy balance.
The benefits from negative heat bridges do not actually represent real gains, but can be explained as better isolated places than other parts of the facade, through which energy losses are smaller.
Galazing Solar GainsIn order to better distribute all these heat gaps throughout the building, it is advisable to use ventilation systems with recuperation.
In order to better distribute all these heat gaps throughout the building, it is advisable to use ventilation systems with recuperation.
However, these free passive energy sources are limited and the best way to reduce the need for active energy is to minimize energy losses. Most of the energy losses take are through conduction, or by transferring heat through the shell of the building. These includes thermal bridges that can participate up to 15% of total energy losses. Therefore, in addition to insulation, it is necessary to reduce or eliminate thermal bridges.
However, the losses that occur through convection, or more precisely through the poor air permeability of the shell of the building or so-called AIR LEAKAGE THERMAL LOSSES (energy losses through air leaks), are not negligible at all. These losses can make up to 30% of the total losses in one facility, which shows that they seriously participate in the heating and cooling budget. This is a phenomenon that is of great importance in achieving energy efficiency, but in Macedonia it is almost never a subject of consideration. According to the laws of thermodynamics, the heat transfer by conduction is always from warmer to cooler, while by the convection the warm air always moves upward. Starting from these two rules, we can conclude that the hot air in the building moves to the roof (regardless of number of floors and the size of the building) and comes out through all cracks, imperfections or construction gaps (in walls, windows and doors, but mostly through roof and around the windows). These cracks and openings are often invisible to the naked eye, but the draft and money losses are felt pretty much. When the heated air with relative humidity of about 40% penetrates through the cracks and cools down, condensation occurs inside the walls or in the roof insulation. Through a micro-crack with a length of 1m, for 24 hours through condensation can be collected up to 300gr. Water. This shows that poor building airtightness contributes to major health problems, but also to destruction of the insulation or other parts of the building.
As in nature there is always a balance, so there must be a balance of air in buildings.
The amount of hot air that will come out through the cracks is compensated by withdrawing cold and polluted air into the lower parts of the building. In summer, this phenomenon is with reverse directions of air movement.
It is important to note that too sealed building brings other problems that directly affect the air quality in facilities and the health of users. Therefore, this issue should be left exclusively to professionals.