Specific heating characteristic of the building table. Thermal characteristic of the building and calculation of heat demand for heating by integrated meters

All buildings and structures, regardless of type and classification, have certain technical and operational parameters that must be recorded in the relevant documentation. One of the most important indicators the specific thermal characteristic is considered, which has a direct impact on the amount of payment for the consumed thermal energy and allows you to determine the energy efficiency class of the structure.

The specific heating characteristic is usually called the value of the maximum heat flow, which is necessary for heating the structure with a difference between the internal and outdoor temperature equal to one degree Celsius. Average indicators are determined by building codes, recommendations and rules. At the same time, any nature of deviation from the normative values ​​allows us to speak about the energy efficiency of the heating system.

The specific thermal characteristic can be both actual and calculated. In the first case, in order to obtain data as close as possible to reality, it is necessary to examine the building using thermal imaging equipment, and in the second case, the indicators are determined using the table of the specific heating characteristics of the building and special calculation formulas.

Recently, the determination of the energy efficiency class has been a mandatory procedure for all residential buildings. Such information should be included in energy passport buildings, since each class has a set minimum and maximum energy consumption during the year.

To determine the energy efficiency class of a building, it is necessary to clarify the following information:

• type of structure or building;
• building materials that were used in the process of construction and decoration of the building, as well as their technical parameters;
• deviation of actual and calculated and standard indicators. Actual data can be obtained by calculation or by practical means. When making calculations, it is necessary to take into account the climatic features of a particular area, in addition, regulatory data should include information on the costs of air conditioning, heat supply and ventilation.

Improving the energy efficiency of a multi-storey building

Estimated data, in most cases, indicate the low energy efficiency of multi-apartment housing. When it comes to increasing this indicator, it must be clearly understood that it is possible to reduce heating costs only by carrying out additional thermal insulation, which will help reduce heat loss. Of course, it is possible to reduce heat energy losses in a residential apartment building, but solving this problem will be a very time-consuming and expensive process.

To the main methods of improving energy efficiency high-rise building may include the following:

• elimination of cold bridges in building structures (improvement of performance by 2-3%);
• installation window structures on loggias, balconies and terraces (method efficiency 10-12%);
• use of micro-systems of micro-ventilation;
• replacement of windows with modern multi-chamber profiles with energy-saving double-glazed windows;
• normalization of the area of ​​glazed structures;
• increase in thermal resistance building structure by finishing the basement and technical premises, as well as wall cladding using highly efficient thermal insulation materials (increase in energy saving by 35-40%).

An additional measure to improve the energy efficiency of a residential multi-storey building can be the implementation by residents of energy-saving procedures in apartments, for example:

• installation of thermostats;
• installation of heat-reflecting screens;
• installation of heat energy meters;
• installation aluminum radiators;
• installation of an individual heating system;
• reduction in ventilation costs.

How to improve the energy efficiency of a private house?

It is possible to increase the energy efficiency class of a private house using various methods. An integrated approach to solving this problem will provide excellent results. The size of the cost item for heating a residential building is primarily determined by the characteristics of the heat supply system. Individual housing construction practically does not provide for the connection of private houses to centralized systems heat supply, so heating issues in this case are solved with the help of an individual boiler room. The installation of modern boiler equipment, which is different high efficiency and economical work.

In most cases, for the heat supply of a private house, gas boilers, however, this type of fuel is not always appropriate, especially for areas that have not undergone gasification. When choosing a heating boiler, it is important to take into account the characteristics of the region, the availability of fuel and operating costs. Equally important from an economic point of view for the future heating system will be the availability additional equipment and options for the boiler. Installing a thermostat, as well as a number of other devices and sensors, will help save fuel.

For circulation of the coolant in autonomous systems heat supply is mainly used pumping equipment. Undoubtedly, it must be of high quality and reliable. However, it should be remembered that the operation of equipment for forced circulation of the coolant in the system will account for about 30-40% total costs electricity. When choosing pumping equipment preference should be given to models with an energy efficiency class "A".

The efficiency of using thermostats deserves special attention. The principle of operation of the device is as follows: using a special sensor, it determines the internal temperature of the room and, depending on the indicator obtained, turns off or turns on the pump. The temperature regime and the response threshold are set by the residents of the house independently. The main advantage of using a thermostat is to turn off the circulation equipment and the heater. Thus, residents receive significant savings and a comfortable microclimate.

The installation of modern plastic windows with energy-saving double-glazed windows, thermal insulation of walls, protection of premises from drafts, etc. It should be noted that these measures will help not only increase the numbers, but also increase the comfort in the house, as well as reduce operating costs.

To evaluate the thermal performance of the adopted design and planning solution, the calculation of heat losses by the building fences is completed by determining specific thermal characteristic of the building

q beats \u003d Q with about / (V n (t in 1 - t n B))(3.15)

where Q with o- maximum heat flow for heating the building, calculated according to (3.2), taking into account infiltration losses, W; V n - construction volume of the building according to external measurement, m 3; t in 1 - average air temperature in heated rooms.

Value q beats, W / (m 3 o C) is equal to the heat loss of 1 m 3 of the building in watts at a temperature difference of 1 ° C between indoor and outdoor air.

Calculated q beats compared with indicators for similar buildings (Appendix 2). It should not be higher than reference q beats, otherwise the initial costs and operating costs for heating increase.

Specific thermal characteristic buildings of any purpose, can be determined by the formula of N. S. Ermolaev

q beats \u003d P / S + 1 / H (0.9 k pt \u003d 0.6 k pl)(3.16)

where R - building perimeter, m; S- building area, m 2; H - building height, m; φ o- glazing coefficient (the ratio of the glazing area to the area of ​​vertical external fences); k st, k ok, k fri, k pl- heat transfer coefficients of walls, windows, floors top floor, floor of the lower floor.

For staircases q beats usually accepted with a coefficient of 1.6.

For civil buildings q beats tentatively determine

q beats \u003d 1.163 ((1 + 2d) F + S) / V n,(3.17)

where d- the degree of glazing of the outer walls of the building in fractions of a unit; F- square external walls, m 2 ;S- building area in plan, m 2; V n - construction volume of the building according to the external measurement, m 3.

For buildings of mass residential development tentatively determine

q beats \u003d 1.163 (0.37 + 1 / N),(3.18)

where H - building height, m

Energy saving measures(Table 3.3) should be provided with work on the insulation of buildings during major and current repairs.

Table 3.3. Aggregated indicators of the maximum heat flow for heating residential buildings per 1 m 2 of the total area q o , Tue

Use of specific thermal characteristic.

In practice, the estimated heat output of the heating system is necessary to determine the heat output of the heat source (boiler house, CHPP), order equipment and materials, determine the annual fuel consumption, and calculate the cost of the heating system.

Approximate heat output of the heating systemQ c.o, W

Q c.o \u003d q beats Vn (t in 1 - t n B) a,(3.19)

where q beats- reference specific thermal characteristic of the building, W / (m 3 o C), adj. 2; a- coefficient of local climatic conditions, adj. 2 (for residential and public buildings).

Estimated room heat loss determined by (3.19) . Wherein q beats accepted with a correction factor that takes into account the planning location and floor (Table 3.4.)

Table 3.4. Correction factors for q beats

The influence of space-planning and constructive solutions buildings on the microclimate and heat balance of the premises, as well as thermal power heating systems.

From (3.15)-(3.18) it can be seen that on q beats the volume of the building, the degree of glazing, the number of storeys, the area of ​​​​external fences and their thermal protection affect. q beats also depends on the shape of the building and the area of ​​construction.

Buildings of small volume, narrow, complex configuration, with an increased perimeter have an increased thermal characteristic. Cube-shaped buildings have reduced heat losses. The smallest heat loss is due to spherical structures of the same volume (minimum external area). The construction area determines the heat-shielding properties of the fences.

The architectural composition of the building must have the most favorable form in terms of thermal engineering, the minimum area of ​​​​external fences, the correct degree of glazing ( thermal resistance external walls are 3 times more glazed openings).

It should be noted that q beats can be reduced by the use of highly efficient and cheap insulation for external fences.

In the absence of data on the type of development and the external volume of buildings The maximum heat inputs for heating and ventilation are determined by:

Heat flow, W, for heating residential and public buildings

Q′ o max = q o F (1 + k 1)(3.20)

Heat flux, W, for ventilation of public buildings

Q′ v max = q o k 1 k 2 F (3.21)

where q o - an aggregated indicator of the maximum heat flow for heating residential buildings per 1 m 2 of the total area (Table 3.3); F- total area residential buildings, m 2; k 1 and k2- heat flow coefficients for heating and ventilation of public buildings ( k 1 = 0,25; k2= 0.4 (before 1985), k2= 0.6 (after 1985)).

Actual (installation) thermal power of heating systems, taking into account useless heat losses(heat transfer through the walls of heat pipes laid in unheated premises, accommodation heating appliances and pipes at external fences)

Q′ s. o \u003d (1 ... 1.15) Q s. about(3.22)

Heat consumption for ventilation of residential buildings, without supply ventilation, do not exceed 5 ... 10% of heat costs for heating and are taken into account in the value of the specific thermal characteristic of the building q beats.

test questions. 1. What initial data must be available to determine the heat loss of a room? 2. What formula is used to calculate heat losses in rooms? 3. What is the peculiarity of calculating heat losses through floors and underground parts of walls? 4. What is meant by additional heat loss and how are they taken into account? 5. What is air infiltration? 6. What can be the heat input into the premises and how are they taken into account in the heat balance of the premises? 7. Write down an expression for determining the heat output of the heating system. 8. What is the meaning of the specific thermal characteristic of a building and how is it determined? 9. What is the specific thermal characteristic of a building used for? 10. How do space-planning decisions of buildings affect the microclimate and heat balance of premises?11. How is the installed capacity of a building's heating system determined?

Specific heating characteristic buildings is a very important technical parameter. Its calculation is necessary to perform design and construction work, in addition, knowledge of this parameter will not interfere with the consumer, since it affects the amount of payment for thermal energy. Below we will look at what the specific heating characteristic is and how it is calculated.

The concept of specific thermal characteristic

Before getting acquainted with the calculations, we will define the main terms. So, the specific thermal characteristic of a building for heating is the value of the highest heat flux that is necessary to heat the house. When calculating this parameter, the temperature delta, i.e. the difference between room and outdoor temperature is usually taken as one degree.

In fact, this indicator determines the energy efficiency of the building.

Average parameters are determined by regulatory documentation, such as:

• Construction rules and recommendations;
• SNiPs, etc.

Any deviation from the designated norms in any direction allows you to get an idea of ​​​​the energy efficiency of the heating system. The parameter is calculated according to SNiP and other existing methods.

Method of calculation

The thermal specific characteristic of buildings is:

• Actual- To obtain accurate indicators, a thermal imaging survey of the building is used.
• Settlement and normative- is determined using tables and formulas.

Below we consider in more detail the features of the calculation of each type.

Advice! To obtain the thermal characteristics of the house, you can contact the specialists. True, the price of such calculations can be significant, so it is more expedient to carry them out on your own.

In the photo - a thermal imager for surveying buildings

Settlement and normative indicators

Calculated indicators can be obtained using the following formula:

q zd \u003d + + n 1 * + n 2), where:

It must be said that given formula not the only one. The specific heating characteristics of buildings can be determined according to local building codes, as well as certain methods of self-regulatory organizations, etc.

The calculation of the actual thermal characteristic is carried out according to the following formula

This formula is based on the actual parameters:

It should be noted that this equation is simple, as a result of which it is often used in calculations. However, it has a serious drawback that affects the accuracy of the resulting calculations. Namely, it takes into account the temperature difference in the premises of the building.

To get more accurate data with your own hands, you can apply calculations with the determination of heat consumption by:

• Indicators of heat loss through various building structures;
• Project documentation.
• Consolidated indicators.

Self-regulatory organizations usually use their own methods.

They take into account the following parameters:

• Architectural and planning data;
• Year of construction of the house;
• Correction coefficients for outdoor air temperature during the heating season.

In addition, the actual specific heating characteristic of residential buildings should be determined taking into account heat losses in pipelines passing through "cold" rooms, as well as air conditioning and ventilation costs. These coefficients can be found in special tables of SNiP.

Here, perhaps, is the whole basic instruction for determining the specific thermal parameter.

Energy efficiency class

The specific heat characteristic serves as the basis for obtaining such an indicator as the energy efficiency class of a house. In recent years, the energy efficiency class has to be determined in without fail for residential apartment buildings.

This parameter is determined on the basis of the following data:

• Deviation of actual indicators and settlement and normative data. Moreover, the former can be obtained both by calculation and by practical means, i.e. using thermal imaging.
• Climatic features of the area.
• Regulatory data, which should include information on heating costs, as well as.
• Building type.
• Technical characteristics of the used building materials.

Each class has certain values ​​​​of energy consumption throughout the year. The energy efficiency class must be marked in the energy passport of the house.

Conclusion

The specific heating characteristic of buildings is important parameter, which depends on a number of factors. As we found out, you can determine it yourself, which in the future will allow.

From the video in this article, you can learn some Additional information on this topic.

For thermal evaluation of design and planning solutions and for estimated calculation heat loss of buildings is used as an indicator - the specific thermal characteristic of the building q.

The value q, W / (m 3 * K) [kcal / (h * m 3 * ° C)], determines the average heat loss of 1 m 3 of the building, referred to the calculated temperature difference equal to 1 °:

q \u003d Q zd / (V (t p -t n)).

where Q zd - calculated heat loss all areas of the building;

V - the volume of the heated part of the building to the external measurement;

t p -t n - the estimated temperature difference for the main premises of the building.

The value of q is determined as a product:

where q 0 - specific thermal characteristic corresponding to the temperature difference Δt 0 =18-(-30)=48°;

β t - temperature coefficient, taking into account the deviation of the actual calculated temperature difference from Δt 0 .

The specific thermal characteristic q 0 can be determined by the formula:

q0=(1/(R 0 *V))*.

This formula can be converted into a simpler expression using the data given in the SNiP and taking, for example, the characteristics for residential buildings as a basis:

q 0 \u003d ((1 + 2d) * Fc + F p) / V.

where R 0 - resistance to heat transfer outer wall;

η ok - coefficient taking into account the increase in heat loss through the windows compared to the outer walls;

d - the proportion of the area of ​​​​the outer walls occupied by windows;

ηpt, ηpl - coefficients that take into account the reduction in heat loss through the ceiling and floor compared to the outer walls;

F c - area of ​​outer walls;

F p - area of ​​the building in terms of;

V is the volume of the building.

The dependence of the specific thermal characteristic q 0 on the change in the design and planning solution of the building, the volume of the building V and the resistance to heat transfer of the outer walls β relative to R 0 tr, the height of the building h, the degree of glazing of the outer walls d, the heat transfer coefficient of the windows k he and the width of the building b.

The temperature coefficient β t is:

βt=0.54+22/(t p -t n).

The formula corresponds to the values ​​of the coefficient β t , which are usually given in the reference literature.

Characteristic q is convenient to use for thermal evaluation of possible design and planning solutions for the building.

If we substitute the value of Q zd into the formula, then it can be brought to the form:

q=(∑k*F*(t p -t n))/(V(t p -t n))≈(∑k*F)/V.

The value of the thermal characteristic depends on the volume of the building and, in addition, on the purpose, number of storeys and the shape of the building, the area and thermal protection of external fences, the degree of glazing of the building and the construction area. The influence of individual factors on the value of q is obvious from the consideration of the formula. The figure shows the dependence of qo on various characteristics of the building. The reference point in the drawing, through which all the curves pass, correspond to the values: q o \u003d O.415 (0.356) for the building V \u003d 20 * 103 m 3, width b \u003d 11 m, d \u003d 0.25 R o \u003d 0.86 (1.0), k ok =3.48 (3.0); length l=30 m. Each curve corresponds to a change in one of the characteristics (additional scales along the abscissa) with other things being equal. The second scale on the y-axis shows this relationship as a percentage. It can be seen from the graph that the degree of glazing d and the width of the building b have a noticeable effect on qo.

The graph reflects the effect of thermal protection of external fences on the total heat loss of the building. According to the dependence of qo on β (R o \u003d β * R o.tr), it can be concluded that with an increase in the thermal insulation of the walls, the thermal characteristic decreases slightly, while when it decreases, qo begins to increase rapidly. With additional thermal protection of window openings (scale k ok), qo noticeably decreases, which confirms the feasibility of increasing the heat transfer resistance of windows.

q-values ​​for buildings various appointments and volumes are given in reference manuals. For civil buildings, these values ​​vary within the following limits:

The heat demand for heating a building can differ markedly from the amount of heat loss, therefore, instead of q, you can use the specific thermal characteristic of the heating of the building qot, when calculating which, according to the upper formula, the numerator is substituted not for heat loss, but for the installed heat output of the heating system Qot.set.

Q from.set \u003d 1.150 * Q from.

where Q from - is determined by the formula:

Q from \u003d ΔQ \u003d Q orp + Q vent + Q texn.

where Q orp - heat loss through external enclosures;

Q vent - heat consumption for heating the air entering the room;

Q texn - technological and household heat releases.

Values ​​qfrom can be used to calculate the heat demand for heating a building using integrated meters using the following formula:

Q \u003d q from * V * (tp-t n).

The calculation of thermal loads on heating systems according to enlarged meters is used for approximate calculations when determining the need for heat in a district, city, during design district heating etc.

AT last years the interest of the population in the calculation of the specific thermal characteristics of buildings has increased significantly. This technical indicator is indicated in the energy passport of the apartment building. It is necessary for the implementation of design and construction work. Consumers are interested in the other side of these calculations - the cost of heat supply.

Terms used in calculations

The specific heating characteristic of a building is an indicator of the maximum heat flux that is needed to heat a particular building. In this case, the difference between the temperature inside the building and outside is determined at 1 degree.

We can say that this characteristic clearly shows the energy efficiency of the building.

There are various regulatory documents that indicate average values. The degree of deviation from them gives an idea of ​​how effective the specific heating characteristic of the structure is. The principles of calculation are taken according to SNiP " Thermal protection buildings."

What are the calculations

The specific heating characteristic is determined by different methods:

• based on the calculated and normative parameters (using formulas and tables);
• according to actual data;
• individually developed methods of self-regulating organizations, where the year of construction of the building and design features are also taken into account.

When calculating actual figures, pay attention to heat loss in pipelines that pass through unheated areas, ventilation (air conditioning) losses.

At the same time, when determining the specific heating characteristics of a building, SNiP “Ventilation, heating and air conditioning will become a reference book. Thermal imaging inspection will help to determine the energy efficiency indicators most correctly.

Calculation formulas

The amount of heat lost by 1 cubic meter building, taking into account the temperature difference of 1 degree (Q) can be obtained by the following formula:

This calculation is not ideal, despite the fact that it takes into account the area of ​​\u200b\u200bthe building and the dimensions of the external walls, window openings and gender.

There is another formula by which you can calculate the actual characteristics, where the calculation is based on annual consumption fuel (Q), average temperature regime inside the building (tint) and outside (text) and heating season(z):

The imperfection of this calculation is that it does not reflect the temperature difference in the premises of the building. The most convenient is the calculation system proposed by Professor N. S. Ermolaev:

The advantage of using this calculation system is that it takes into account the design characteristics of the building. A coefficient is used that shows the ratio of the size of glazed windows in relation to the area of ​​\u200b\u200bthe walls. In the Ermolaev formula, the coefficients of such indicators as the heat transfer of windows, walls, ceilings and floors are used.

What does the energy efficiency class mean?

The figures obtained from the specific heat characteristic are used to determine the energy efficiency of the building. By law, starting in 2011, all apartment buildings must have an energy efficiency class.

In order to determine energy efficiency, repelled from the following data:

• The difference between settlement and normative and actual figures. The actual ones are sometimes determined by the method of thermal imaging examination. AT normative indicators reflects the cost of heating, ventilation and climatic parameters of the region.
• Consider the type of building and building materials from which it was built.

The energy efficiency class is recorded in the energy passport. Different classes have their own indicators of energy consumption during the year.

How can the energy efficiency of a building be improved?

If the calculation process reveals the low energy efficiency of the structure, then there are several ways to correct the situation:

1. Improvements in the thermal resistance of structures are achieved by cladding the outer walls, insulating those floors and ceilings above basements heat-insulating materials. These can be sandwich panels, polypropylene shields, ordinary plastering of surfaces. These measures increase energy saving by 30-40 percent.
2. Sometimes you have to resort to extreme measures and bring in line with the norms of the area of ​​​​glazed structural elements building. That is, to lay extra windows.
3. Additional effect gives the installation of windows with heat-saving double-glazed windows.
4. Glazing of terraces, balconies and loggias gives an increase in energy saving by 10-12 percent.
5. Control the supply of heat to the building by modern systems control. So, installing one thermostat will save fuel by 25 percent.
6. If the building is old, they change completely obsolete heating system to a modern one (installation of aluminum radiators with high efficiency, plastic pipes in which the coolant circulates freely.)
7. Sometimes it is enough to thoroughly flush "coked" pipelines and heating equipment in order to improve the circulation of the coolant.
8. There are reserves in ventilation systems, which can be replaced with modern ones with micro-ventilation installed in windows. Reducing heat loss from poor-quality ventilation significantly improves the energy efficiency of a home.
9. In many cases, the installation of heat-reflecting screens gives a great effect.

AT apartment buildings it is much more difficult to achieve energy efficiency improvements than in private ones. Additional costs are required and they do not always give the expected effect.

Conclusion

The result can only A complex approach with the participation of the residents of the house, who are most interested in saving heat. The installation of heat meters stimulates energy savings.

Currently, the market is saturated with equipment that saves energy. The main thing is to have a desire and produce correct calculations, specific heating characteristics of the building, according to tables, formulas or thermal imaging survey. If this cannot be done on your own, you can turn to specialists.