Thermal balance of the room.
Purpose – comfortable conditions or technological process.
The heat generated by people is evaporation from the surface of the skin and lungs, convection and radiation. The intensity of radiation by convection is determined by the temperature and mobility of the surrounding air, radiation - by the temperature of the surfaces of the fences. The temperature conditions depend on: thermal power CO, location of heaters, thermophysics. properties of external and internal fences, intensity of other sources of income (lighting, household appliances) and heat loss. In winter - heat loss through external fences, heating of outside air penetrating through leaks in fences, cold objects, ventilation.
Technological processes can be associated with the evaporation of liquids and other processes accompanied by heat consumption and heat release (moisture condensation, chemical reactions etc.).
Taking into account all of the above - the heat balance of the premises of the building, determining the deficit or excess of heat. The period of the technological cycle with the least heat release is taken into account (possible maximum heat release is taken into account when calculating ventilation), for household - with the greatest heat losses. The heat balance is compiled for stationary conditions. The non-stationary nature of thermal processes occurring during space heating is taken into account by special calculations based on the theory of thermal stability.
Determination of the estimated thermal power of the heating system.
Estimated thermal power of CO - compilation heat balance in heated rooms at design temperature outside air tн.р, = average temperature the coldest five-day period with a probability of 0.92 tn.5 and determined for a specific construction area according to the standards of SP 131.13330.2012. Changing the current heat demand is a change in the heat supply to devices by changing the temperature and (or) the amount of coolant moving in the heating system - operational regulation.
In steady-state (stationary) mode, losses are equal to heat gains. Heat enters the room from people, technological and household equipment, sources artificial lighting, from heated materials, products, as a result of exposure to solar radiation on the building. IN production premises may be carried out technological processes associated with the release of heat (moisture condensation, chemical reactions, etc.).
To determine the estimated thermal power of the heating system, Qot, draws up a balance of heat consumption for the design conditions of the cold period of the year in the form
Qot = dQ = Qlimit + Qi(vent) ± Qt(life)
where Qlim - heat loss through external fences; Qi(vent) - heat consumption for heating the outside air entering the room; Qt(household) - technological or household emissions or heat consumption.
Q life =10*F floor (F floor – living rooms); Q vent = 0.3* Q limit. =Σ Q basic *Σ(β+1);
Q basic =F*k*Δt*n; where F- s limit of structures, k – heat transfer coefficient; k=1/R;
n – coefficient, position of external design limit to outside air (1-vertical, 0.4-floor, 0.9-ceiling)
β – additional heat loss, 1) in relation to the cardinal directions: N, E, NE, NW = 0.1, W, SE = 0.05, S, SW = 0.
2) for floors = 0.05 at t adv.<-30; 3) от входной двери = 0,27*h.
Annual heat costs for heating buildings.
In the cold season, in order to maintain a given temperature in a room, there must be equality between the amount of heat lost and received.
Annual heat consumption for heating
Q 0year = 24 Q ocp n, Gcal/year
n- duration of the heating period, days
Q ocp - average hourly heat consumption for heating during the heating period
Q ocp = Q 0 ·(t in - t av.o)/(t in - t r.o), Gcal/h
t in - average design temperature inside heated rooms, °C
t av.o - average outside air temperature for the period under consideration for a given area, °C
t p.o - design temperature of outside air for heating, °C.
Specific thermal characteristics of the building
It is an indicator of thermal engineering assessment of design and planning solutions and thermal efficiency of the building - q sp
For a building of any purpose, it is determined by the formula of Ermolaev N.S.: W/(m 3 0 C)
Where P is the perimeter of the building, m;
A – building area, m2;
q – coefficient taking into account glazing (ratio of glazing area to fence area);
φ 0 = q 0 = 
k ok, k st, k pt, k pl – respectively, heat transfer coefficients of windows, walls, ceilings, floors, W/(m* 0 C), taken according to thermal calculation data;
H – building height, m.
The value of the specific thermal characteristic of the building is compared with the standard thermal characteristic for heating q 0 .
If the value of qsp differs from the standard q0 by no more than 15%, then the building meets thermal requirements. In the case of a greater excess of the compared values, it is necessary to explain the possible reason and outline measures to improve the thermal performance of the building.
An indicator of thermal energy consumption for heating and ventilation of a residential or public building at the stage of development of project documentation is the specific characteristic of thermal energy consumption for heating and ventilation of a building numerically equal to the consumption of thermal energy per 1 m 3 of heated volume of the building per unit time with a temperature difference of 1° WITH,
, W/(m 3 0 C). The calculated value of the specific characteristics of thermal energy consumption for heating and ventilation of the building,
, W/(m 3 · 0 C), is determined by a method taking into account the climatic conditions of the construction area, the selected space-planning solutions, the orientation of the building, the heat-insulating properties of the building envelope, the adopted building ventilation system, as well as the use of energy-saving technologies. The calculated value of the specific characteristic of thermal energy consumption for heating and ventilation of the building must be less than or equal to the standardized value, according to 
, W/(m 3 0 C):
≤
(7.1)
Where
- standardized specific characteristic of thermal energy consumption for heating and ventilation of buildings, W/(m 3 · 0 C), determined for various types of residential and public buildings according to table 7.1 or 7.2.
Table 7.1
, W/(m 3 0 C)
|
Building area, m2 |
With number of floors |
|||
|
1000 or more | ||||
Notes:
At intermediate values of the heated area of the building in the range of 50-1000m 2 values 
must be determined by linear interpolation.
Table 7.2
Standardized (basic) specific flow rate characteristic
thermal energy for heating and ventilation
low-rise residential single-apartment buildings, 
, W/(m 3 0 C)
|
Building type |
Number of floors of the building |
|||||||
|
1 Residential apartment buildings, hotels, dormitories | ||||||||
|
2 Public, except those listed in lines 3-6 | ||||||||
|
3 Clinics and medical institutions, boarding houses | ||||||||
|
4 Preschool institutions, hospices | ||||||||
|
5 Service, cultural and leisure activities, technology parks, warehouses | ||||||||
|
6 Administrative purposes (offices) | ||||||||
Notes:
For regions with a GSOP value of 8000 0 C day or more, standardized
should be reduced by 5%.
To assess the energy demand for heating and ventilation achieved in a building design or in an operating building, the following energy saving classes have been established (Table 7.3) in % deviation of the calculated specific characteristics of thermal energy consumption for heating and ventilation of the building from the standardized (base) value.
Designing buildings with energy saving class “D, E” is not allowed. Classes “A, B, C” are established for newly constructed and reconstructed buildings at the stage of development of project documentation. Subsequently, during operation, the energy efficiency class of the building must be clarified during an energy survey. In order to increase the share of buildings with classes “A, B”, the constituent entities of the Russian Federation must apply economic incentive measures to both participants in the construction process and operating organizations.
Table 7.3
Energy saving classes of residential and public buildings
|
Designation |
Name |
The magnitude of the deviation of the calculated (actual) value of the specific characteristic of thermal energy consumption for heating and ventilation of the building from the standardized value, % | |
|
When designing and operating new and reconstructed buildings |
|||
|
Very tall |
Economic stimulation |
||
|
From - 50 to - 60 inclusive |
|||
|
From - 40 to - 50 inclusive |
|||
|
From - 30 to - 40 inclusive |
Economic stimulation |
||
|
From - 15 to - 30 inclusive |
|||
|
Normal |
From - 5 to - 15 inclusive |
Events not are being developed |
|
|
From + 5 to - 5 inclusive |
|||
|
From + 15 to + 5 inclusive |
|||
|
Reduced |
From + 15.1 to + 50 inclusive |
Reconstruction with appropriate economic justification |
|
|
Reconstruction with appropriate economic justification, or demolition |
|||
Estimated specific characteristics of thermal energy consumption for heating and ventilation of the building,
, W/(m 3 0 C), should be determined by the formula
k about - specific heat-protective characteristic of the building, W/(m 3 0 C), is determined as follows
,
(7.3)
Where 
- actual total heat transfer resistance for all layers of the fence (m 2 С)/W;
- area of the corresponding fragment of the building’s heat-protective shell, m2;
V from - heated volume of the building, equal to the volume limited by the internal surfaces of the external fences of the buildings, m 3;
- coefficient that takes into account the difference between the internal or external temperature of the structure from those adopted in the GSOP calculation,
=1.
k vent - specific ventilation characteristics of the building, W/(m 3 ·C);
k household - specific characteristic of household heat emissions of a building, W/(m 3 ·C);
k rad - specific characteristic of heat input into the building from solar radiation, W/(m 3 0 C);
ξ - coefficient taking into account the reduction in heat consumption of residential buildings, ξ =0.1;
β - coefficient taking into account additional heat consumption of the heating system, β h = 1,05;
ν is the coefficient of reduction of heat input due to the thermal inertia of enclosing structures; recommended values are determined by the formula ν = 0.7+0.000025*(GSOP-1000);
The specific ventilation characteristic of a building, k vent, W/(m 3 0 C), should be determined by the formula
where c is the specific heat capacity of air, equal to 1 kJ/(kg °C);
β v- coefficient of air volume reduction in the building, β v = 0,85;
- average density of supply air during the heating period, kg/m3
=353/,
(7.5)
t from - average temperature of the heating period, С, to 6, table. 3.1, (see appendix 6).
n in is the average air exchange rate of a public building during the heating period, h -1, for public buildings, according to , the average value of n in = 2 is accepted;
k e f - recuperator efficiency coefficient, k e f =0.6.
The specific characteristics of the domestic heat emission of a building, k household, W/(m 3 C), should be determined by the formula
,
(7.6)
where q life is the amount of household heat generation per 1 m 2 of residential premises area (Azh) or the estimated area of a public building (Ar), W/m2, accepted for:
a) residential buildings with an estimated occupancy of apartments of less than 20 m2 of total area per person q life = 17 W/m2;
b) residential buildings with an estimated occupancy of apartments of 45 m2 of total area or more per person q life = 10 W/m2;
c) other residential buildings - depending on the estimated occupancy of apartments by interpolation of the value q life between 17 and 10 W/m 2;
d) for public and administrative buildings, household heat emissions are taken into account according to the estimated number of people (90 W/person) in the building, lighting (according to installed power) and office equipment (10 W/m2) taking into account working hours per week;
t in, t from - the same as in formulas (2.1, 2.2);
Аж - for residential buildings - the area of residential premises (Аж), which include bedrooms, children's rooms, living rooms, offices, libraries, dining rooms, kitchen-dining rooms; for public and administrative buildings - the estimated area (A p), determined in accordance with SP 117.13330 as the sum of the areas of all premises, with the exception of corridors, vestibules, passages, staircases, elevator shafts, internal open stairs and ramps, as well as premises intended to accommodate engineering equipment and networks, m 2.
The specific characteristic of heat input into a building from solar radiation, krad, W/(m 3 °C), should be determined by the formula
,
(7.7)
Where 
- heat gain through windows and skylights from solar radiation during the heating season, MJ/year, for four facades of buildings oriented in four directions, determined by the formula
- coefficients of relative penetration of solar radiation for light-transmitting fillings of windows and skylights, respectively, taken according to the passport data of the corresponding light-transmitting products; in the absence of data should be taken should be taken according to table (2.8); skylights with an angle of inclination of the fillings to the horizon of 45° or more should be considered as vertical windows, with an inclination angle of less than 45° - as skylights;
- coefficients taking into account the shading of the light opening of windows and skylights, respectively, by opaque filling elements, adopted according to design data; in the absence of data, it should be taken according to table (2.8).
- area of light openings of the building facades (the blind part of the balcony doors is excluded), respectively oriented in four directions, m2;
- area of light openings of skylights of the building, m;
- the average value of the total solar radiation during the heating period (direct plus scattered) on vertical surfaces under actual cloudy conditions, respectively oriented along the four facades of the building, MJ/m 2, determined by adj. 8;
- the average value of the total solar radiation (direct plus scattered) over the heating period on a horizontal surface under actual cloud conditions, MJ/m 2, determined by adj. 8.
V from - the same as in formula (7.3).
GSOP – the same as in formula (2.2).
Calculation of specific characteristics of thermal energy consumption
for heating and ventilation of the building
Initial data
We will calculate the specific characteristics of thermal energy consumption for heating and ventilation of a building using the example of a two-story individual residential building with a total area of 248.5 m2. Values of the quantities required for the calculation: tв = 20 С;
t op = -4.1С; 
= 3.28(m 2 С)/W; 
=4.73 (m 2 С)/W; 
=4.84 (m 2 С)/W; 
=0.74 (m 2 С)/W; 
=0.55(m 2 С)/W; 
m 2; 
m 2; 
m 2; 
m 2; 
m 2; 
m 2; 
m 3; 
W/m2; 
0,7;
0;
0,5;
0;
7.425 m2; 
4.8 m2; 
6.6 m2; 
12.375 m2; 
m 2; 
695 MJ/(m2 year); 
1032 MJ/(m 2 year); 
1032 MJ/(m 2 year); 
=1671 MJ/(m 2 year); 
= =1331 MJ/(m 2 year).
Calculation procedure
1. Calculate the specific heat-protective characteristic of the building, W/(m 3 0 C), according to formula (7.3) determined as follows
W/(m 3 0 C),
2. Using formula (2.2), the degree-days of the heating period are calculated
D= (20 + 4.1)200 = 4820 Cday.
3. Find the coefficient of reduction of heat input due to the thermal inertia of the enclosing structures; recommended values are determined by the formula
ν = 0.7+0.000025*(4820-1000)=0.7955.
4. Find the average density of supply air during the heating period, kg/m3, using formula (7.5)
=353/=1.313 kg/m3.
5. We calculate the specific ventilation characteristics of the building using formula (7.4), W/(m 3 0 C)
W/(m 3 0 C)
6. I determine the specific characteristics of the domestic heat release of the building, W/(m 3 C), according to formula (7.6)
W/(m 3 C),
7. Using formula (7.8), heat input through windows and skylights from solar radiation during the heating period, MJ/year, is calculated for four facades of buildings oriented in four directions
8. Using formula (7.7), the specific characteristic of heat input into the building from solar radiation is determined, W/(m 3 °C)
W/(m 3 °С),
9. Determine the calculated specific characteristic of thermal energy consumption for heating and ventilation of the building, W/(m 3 0 C), according to formula (7.2)
W/(m 3 0 C)
10. Compare the obtained value of the calculated specific characteristic of thermal energy consumption for heating and ventilation of the building with the standardized (base) one, 
, W/(m 3 · 0 C), according to tables 7.1 and 7.2.
0.4 W/(m 3 0 C) 
=0.435 W/(m 3 0 C)
≤
The calculated value of the specific characteristics of thermal energy consumption for heating and ventilation of the building must be less than the standardized value.
To assess the energy demand for heating and ventilation achieved in a building design or in an operating building, the energy saving class of the designed residential building is determined by the percentage deviation of the calculated specific characteristics of thermal energy consumption for heating and ventilation of the building from the standardized (base) value.
Conclusion: The designed building belongs to the “C+ Normal” energy saving class, which is established for newly constructed and reconstructed buildings at the stage of development of design documentation. The development of additional measures to improve the energy efficiency class of the building is not required. Subsequently, during operation, the energy efficiency class of the building must be clarified during an energy survey.
Test questions for section 7:
1. What value is the main indicator of thermal energy consumption for heating and ventilation of a residential or public building at the stage of developing project documentation? What does it depend on?
2. What classes of energy efficiency of residential and public buildings exist?
3. What energy saving classes are established for newly constructed and reconstructed buildings at the stage of developing project documentation?
4. Designing buildings with which energy saving class is not allowed?
CONCLUSION
Problems of saving energy resources are especially important in the current period of development of our country. The cost of fuel and thermal energy is rising, and this trend is predicted for the future; At the same time, energy consumption is constantly and rapidly increasing. The energy intensity of national income in our country is several times higher than in developed countries.
In this regard, the importance of identifying reserves for reducing energy costs is obvious. One of the areas for saving energy resources is the implementation of energy-saving measures during the operation of heat supply, heating, ventilation and air conditioning (HVAC) systems. One solution to this problem is to reduce the heat loss of buildings through the building envelope, i.e. reduction of thermal loads on DVT systems.
The importance of solving this problem is especially great in urban engineering, where about 35% of all extracted solid and gaseous fuel is spent on heat supply of residential and public buildings alone.
In recent years, an imbalance in the development of sub-sectors of urban construction has become sharply evident in cities: technical backwardness of engineering infrastructure, uneven development of individual systems and their elements, a departmental approach to the use of natural and produced resources, which leads to their irrational use and sometimes to the need to attract appropriate resources from other regions.
The demand of cities for fuel and energy resources and the provision of engineering services is growing, which directly affects the increase in morbidity among the population and leads to the destruction of the forest belt of cities.
The use of modern thermal insulation materials with a high value of heat transfer resistance will lead to a significant reduction in energy costs, the result will be a significant economic effect in the operation of DVT systems through a reduction in fuel costs and, accordingly, an improvement in the environmental situation of the region, which will reduce the cost of medical care for the population.
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The specific heating characteristic of a building is a very important technical parameter. Its calculation is necessary to carry out design and construction work; in addition, knowledge of this parameter will not hurt 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 characteristics
Before getting acquainted with the calculations, let's define the basic terms. So, the specific thermal characteristic of a building for heating is the value of the largest heat flow that is necessary to heat the house. When calculating this parameter, the temperature delta, i.e. The difference between room and street temperatures is usually taken as one degree.
In essence, 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 standards in any direction allows you to get an idea of the energy efficiency of the heating system. The calculation of the parameter is carried out according to SNiP and other current methods.
Calculation method
The thermal specific characteristics of buildings are:
- Actual– to obtain accurate indicators, thermal imaging inspection of the structure is used.
- Calculation and normative– determined using tables and formulas.
Below we will consider in more detail the features of the calculation of each type.
Advice! To obtain the thermal characteristics of your home, you can contact specialists. True, the cost of such calculations can be significant, so it is more advisable to perform them yourself.
In the photo - a thermal imager for inspecting buildings
Calculation and standard indicators
Estimated indicators can be obtained using the following formula:
q building = + +n 1 * + n 2), where:
It must be said that this formula is 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 characteristics is carried out using the following formula
This formula is based on 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 use calculations to determine heat consumption by:
- Indicators of heat loss through various building structures;
- Project documentation.
- Aggregated indicators.
Self-regulatory organizations usually use their own methods.
They take into account the following parameters:
- Architectural and planning data;
- Year the house was built;
- Correction factors for outdoor air temperature during the heating season.
In addition, the actual specific heating characteristics of residential buildings should be determined taking into account heat losses in pipelines passing through “cold” rooms, as well as the cost of air conditioning and ventilation. These coefficients can be found in special SNiP tables.
This is, perhaps, all the basic instructions for determining the specific thermal parameter.
Energy efficiency class
Specific heat characteristics serve as the basis for obtaining such an indicator as the energy efficiency class of a house. In recent years, the energy efficiency class must be determined mandatory for residential multi-apartment buildings.
This parameter is determined based on the following data:
- Deviation of actual indicators and calculated and normative data. Moreover, the former can be obtained both by calculation and by practical means, i.e. using thermal imaging examination.
- Climatic features of the area.
- Regulatory data, which should include information on heating costs, as well as.
- Building type.
- Technical characteristics of the building materials used.
Each class has certain energy consumption values throughout the year. The energy efficiency class must be noted in the energy passport of the house.
Conclusion
The specific heating characteristics of buildings is an important parameter that depends on a number of factors. As we found out, you can determine it yourself, which will allow you in the future.
You can get some additional information on this topic from the video in this article.
For thermal engineering assessment of structural and planning solutions and for approximate calculation of heat loss of buildings, the indicator used is 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, related to the calculated temperature difference equal to 1°:
q=Q building /(V(t p -t n)).
where Q building is the estimated heat loss from all rooms of the building;
V is the volume of the heated part of the building to the external measurement;
t p -t n - calculated temperature difference for the main rooms of the building.
The value q is determined as a product:
where q 0 is the specific thermal characteristic corresponding to the temperature difference Δt 0 =18-(-30)=48°;
β t is a temperature coefficient that takes 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 transformed into a simpler expression using the data given in SNiP and taking, for example, the characteristics for residential buildings as a basis:
q 0 =((1+2d)*Fс+F p)/V.
where R 0 is the heat transfer resistance of the outer wall;
η ok - coefficient that takes into account the increase in heat loss through windows compared to external walls;
d is the proportion of the area of the external walls occupied by windows;
ηpt, ηpl - coefficients that take into account the reduction of heat loss through the ceiling and floor compared to external walls;
F c - area of external walls;
F p - area of the building in plan;
V is the volume of the building.
Dependence of the specific thermal characteristic q 0 on changes in the structural and planning solution of the building, the volume of the building V and the heat transfer resistance of the external walls β relative to R 0, the height of the building h, the degree of glazing of the external walls d, the heat transfer coefficient of windows k it and the width of the building b.
Temperature coefficient β t is equal to:
βt=0.54+22/(t p -t n).
The formula corresponds to the values of the coefficient β t, which are usually given in reference literature.
Characteristic q is convenient to use for thermal engineering assessment of possible structural and planning solutions for a building.
If we substitute the value of Q in the formula, it can be reduced to the form:
q=(∑k*F*(t p -t n))/(V(t p -t n))≈(∑k*F)/V.
The magnitude of the thermal characteristic depends on the volume of the building and, in addition, on the purpose, number of storeys and 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 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 curves pass corresponds to the following values: q o =O.415 (0.356) for a building V=20*103 m 3, width b=11 m, d=0.25 R o =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 axis), all other things being equal. The second scale on the y-axis shows this dependence as a percentage. The graph shows that the degree of glazing d and the width of the building b have a noticeable effect on qo.
The graph shows the effect of thermal protection of external enclosures on the total heat loss of the building. Based on the dependence of qo on β (R o =β*R o.t.), we can conclude that with an increase in the thermal insulation of walls, the thermal performance decreases slightly, whereas 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.
Values of q for buildings of various purposes and volumes are given in reference books. 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, so instead of q, you can use the specific thermal characteristic of heating the building qot, when calculating it using the upper formula, the numerator is substituted not for heat loss, but for the installed thermal power of the heating system Q from set.
Q from.set =1,150*Q from.
where Q from - is determined by the formula:
Q from =ΔQ=Q orp +Q vent +Q techn.
where Q orp is heat loss through external fences;
Q fan - heat consumption to heat the air entering the room;
Q techn - technological and household heat emissions.
The qot values can be used to calculate the heat demand for heating a building using aggregated meters using the following formula:
Q= q from *V*(tп-tн).
Calculation of heat loads on heating systems using enlarged meters is used for approximate calculations when determining the heat demand of a region, city, when designing a central heating supply, etc.
To assess the thermal performance indicators of the adopted design and planning solution, the calculation of heat losses from the building fences ends with the determination specific thermal characteristics of the building
q beat = Q c o / (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 losses due to infiltration, W; V n - construction volume of the building according to external measurements, m 3 ; t in 1 - average air temperature in heated rooms.
Magnitude q beat, W/(m 3 o C) is equal to the heat loss of 1 m 3 of a building in watts with a temperature difference between indoor and outdoor air of 1 °C.
Calculated q beat compared with indicators for similar buildings (Appendix 2). It should not be higher than reference q beat, otherwise the initial costs and operating costs for heating increase.
Specific thermal characteristic buildings for any purpose, can be determined using the formula of N. S. Ermolaev
q beat = P/S + 1/H(0.9 k pt = 0.6 k pl)(3.16)
Where R - building perimeter, m; S- building area, m2; N - building height, m; φ o- glazing coefficient (ratio of glazing area to the area of vertical external fences); k st, k ok, k fri, k pl- heat transfer coefficients of walls, windows, ceilings of the upper floor, floor of the lower floor.
For staircases q beat usually taken with a factor of 1.6.
For civil buildings q beat roughly determine
q beat =1.163 ((1+2d)F+S)/V n,(3.17)
Where d- degree of glazing of the external walls of the building in fractions of a unit; F- area of external walls, m2; S- area of the building in plan, m2; V n - construction volume of the building according to external measurements, m3.
For mass residential buildings roughly determine
q beat =1.163(0.37+1/N),(3.18)
Where N - building height, m.
Energy saving measures(Table 3.3) must be provided with work to insulate buildings during major and current repairs.
Table 3.3. Integrated indicators of the maximum heat flow for heating residential buildings per 1 m 2 of total area q o , W
| Number of floors of a residential building | Building characteristics | Estimated outside air temperature for heating design t n B, o C | |||||||
| -5 | -10 | -15 | -20 | -25 | -30 | -35 | -40 | ||
| For construction before 1985 | |||||||||
| 1-2 | Without taking into account the introduction of energy saving measures | ||||||||
| 3-4 | |||||||||
| 5 or more | |||||||||
| 1-2 | Taking into account the introduction of energy saving measures | ||||||||
| 3-4 | |||||||||
| 5 or more | |||||||||
| For construction after 1985 | |||||||||
| 1-2 | For new standard projects | ||||||||
| 3-4 | |||||||||
| 5 or more |
Use of specific thermal characteristics.
In practice, an approximate thermal power of the heating system is needed to determine the thermal power of the heat source (boiler house, thermal power plant), order equipment and materials, determine annual fuel consumption, and calculate the cost of the heating system.
Approximate heating power of the heating systemQ c.o, W
Q c.o = q beat Vn (t in 1 – t n B)a,(3.19)
Where q beat- 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).
Approximate heat loss of premises determined by (3.19) . At the same time q beat accepted with a correction factor taking into account the planning location and floor (Table 3.4.)
Table 3.4. Correction factors for q beat
The influence of space-planning and design solutions of the building on the microclimate and heat balance of the premises, as well as the thermal power of the heating system.
From (3.15)-(3.18) it is clear that on q beat influence the volume of the building, the degree of glazing, the number of storeys, the area of external fences and their thermal protection. q beat It 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 performance. Buildings with a cube shape have reduced heat losses. The smallest heat loss of spherical structures of the same volume (minimum external area). The construction area determines the thermal insulation properties of the fences.
The architectural composition of the building must have the most advantageous shape in terms of thermal engineering, a minimum area of external fences, and the correct degree of glazing (the thermal resistance of external walls is 3 times greater than the glazed openings).
It should be noted that q beat can be reduced by using highly effective and cheap insulation materials for external fences.
In the absence of data on the type of development and the external volume of buildings The maximum heat consumption for heating and ventilation is determined by:
Heat flow, W, for heating residential and public buildings
Q′ about max = q about F (1 + k 1)(3.20)
Heat flow, W, for ventilation of public buildings
Q′ v max = q о 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 total area (Table 3.3); F- total area of residential buildings, m2; k 1 And k 2 - heat flow coefficients for heating and ventilation of public buildings ( k 1 = 0,25; k 2= 0.4 (before 1985), k 2= 0.6 (after 1985)).
Actual (installed) thermal power of heating systems, taking into account useless heat losses(heat transfer through the walls of heat pipes laid in unheated rooms, placement of heating devices and pipes near external fences)
Q′ p. o = (1…1.15)Q s. O(3.22)
Heat costs for ventilation of residential buildings, without forced ventilation, do not exceed 5...10% of heat costs for heating and are taken into account in the value of the specific thermal characteristics of the building q beat.
Test questions. 1. What initial data do you need to have to determine heat loss in a room? 2. What formula is used to calculate heat loss in rooms? 3. What is special about calculating heat loss 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 kind of heat input into the premises can there be and how are they taken into account in the heat balance of the room? 7. Write down an expression to determine the thermal power 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 solutions of buildings affect the microclimate and heat balance of premises?11. How is the installed capacity of a building's heating system determined?