Heating energy demand

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The heating requirement indicates which thermal energy is necessary for heating . The heating energy requirement (Q h , HEB) variable is specifically available for structural engineering applications .

Heating requirement

The heating requirement is a quantity of energy ( amount of heat ) and is expressed in joules  (J), also kilojoules (kJ) or megajoules (MJ), or (in terms of measurement technology outdated, but still widespread in technology) in kilowatt hours  (kWh) or megawatt hours ( MWh) (1 kWh = 3.6 MJ). So he measures himself

Heating requirement = thermal output in kilowatts  (kW) × heating time in hours  (h)

It is useful to measure the heating requirement for one heating period (or one year) and then give the annual energy requirement in joules or kilowatt hours per  year  (kWh / a) or watts, in units of the power (physics) of the heating system heat flow transferred to the building or the necessary heating load . Monthly information is also common.

The heating fuel requirement is interesting for the economic calculation , therefore the heating requirement is converted into units of the heating medium quantity:

Heating requirement = calorific value (in J or kWh / m 3 or kg) × amount of heating medium (weight or volume, in units of kilograms  kg, tons  t, cubic meters  m 3 , liters  l or similar, depending on the material)

This results in the necessary supply quantity. For the comparison calculation, the heating oil equivalent  (oe) or the hard coal unit  (SKE) are available here.

From the dimension of size , area × mass ÷ time 2 (L 2 · M · T −2 ), it can be seen that, in addition to the structure, time in particular has the power of two . Of course, the energy requirement is typical for a building on the one hand, but on the other hand it fluctuates enormously with the weather conditions of the year, which is why, in addition to the current heating requirement, an average heating requirement is also given , which is based on the average meteorological data (usually measured over 30 years) of the location .

From this, the heating energy index (in kilo- / megawatt hours per square meter and year, kWh / m²a or MWh / m²a) is calculated as a parameter based on the living space ( energy reference area ). For example, this is used to create classes on the energetic quality of a building method / renovation measure ( energy standard ).

In order to specifically compare buildings from a structural point of view regardless of location and use, a specific building parameter, the (specific) heating energy requirement , is also given. It is calculated per  heating time and square meter and then determined.

Annual heating requirement = (specific) heating energy requirement × building area × heating time (in Wh / m²a)

Heating energy demand

The heating energy requirement (Q h , HEB) is the amount of energy that is necessary for heating a building. ( EN 832 )

In relation to the mass of the building, the (specific) heating energy requirement is only dependent on the time, but on that in the third power : The heating energy requirement is a quantity that is and will be characteristic of a building in terms of its structural shape, its location and its use named for example according to ÖNORM B 8110-1 area- related heating demand and designated HWB BGF . Reference for the area is not the living space , but according to valid in Germany standard ( EnEV ), the floor space in Austria (OIB guide u. A.) The heated gross floor area and in Switzerland, the energy reference area (also gross, missile-related).

According to EN 832, the sum of the heat quantities through thermal conduction is calculated :


Q T : Transmission heat loss due to heat conduction in the components and heat transfer to the surfaces
Q V : Ventilation heat losses due to air exchange
Q i : internal heat gains as a result of the operation of electrical devices, artificial lighting and body heat of people
Q s : solar heat gains via transparent components
η: degree of utilization of the heat gains (simplified 1.00 for heavy construction methods to 0.90 for light construction methods)

According to certain types of calculation, one subdivides into heating demand (HWB) and heating technology energy demand (HTEB) and calculating the hot water heat demand (WWWB) separately or together


As a specific variable, it is also determined in a simplified manner from the annual degree of utilization Hh of the heating system (ÖNORM H 5055).

HEB = HWB / hH

The annual degree of utilization is a value of the heat supply system, heat distribution system, control measuring system, and is a numerical factor ( dimensionless quantity ) which gives (decimal) the percentage of time that the heating system must be in operation in order to keep the indoor temperature constant at the target value (Generally the heating period in days, more specifically the heating time in hours, or more precisely determined from the local heating degree days , which in addition to the time also gives the mean temperature difference between the normal indoor temperature and the long-term mean outdoor temperature).

Heating demand

The heating requirement  (HWB, partly also useful heating energy index  NEZ) is the calculated amount of energy that has to be supplied per building area within the heating period in order to maintain the desired indoor temperature, e.g. B. how is given by radiators to a heated room.

It is a construction parameter , i.e. typical for a special building, and is determined by the building envelope (shape, insulation), location (large and small climatic conditions) and its structural use, but is independent of user behavior. The design of the building is based on the compactness , the thermal insulation on the heat transfer coefficients (U-values) of the outer and separating surfaces, it also contains the total energy transmittance (g-values) of all window surfaces, including orientation and possible shading of the glass surfaces, i.e. heat gains through Sun exposure (ÖNORM B 8110-1).

In general, the heating requirement is used to define energy standards for houses. According to the German Energy Saving Ordinance (EnEV), for example for the low-energy house standard, a specific heating requirement of ≤ 50 kWh / m²a is required for newly built houses . For unrenovated old buildings , the value is typically over 150 to well over 300 kWh / m²a.

Hot water heat demand (drinking water heat demand)

The hot water heat demand (WWWB), also drinking water heat demand (TWWB) is the amount of energy that has to be added to the water with drinking water quality for heating. Losses in energy conversion (e.g. losses from the boiler), distribution and other technical losses are not included. The hot water heating requirement is a measure of use, in particular the number of people in the household. In some processes, the drinking water heat demand is set at a flat rate of 12.5 kWh / m²a. This corresponds to a requirement of 23 l per person per day. According to ÖNORM B 8110-5, the hot water heating requirement for residential buildings is 35 Wh / m² and day. It is half that for offices and twice that for hospitals.

Heating technology energy demand

The heating technology energy requirement (HTEB) is the amount of energy that is necessary for the operation of the heating system, such as circulation pumps for the central heating, ignition energy for electric ignition, fan of the furnace for wood gasifiers and pellets, motor of the conveyor for pellets and wood chips, control electronics, etc. (ÖNORM H 5056 -1).

Heating energy demand and energy balance

The heating energy requirement results together with the cooling energy requirement KEB for the summer cooling period, consists of the cooling requirement KB itself and the cooling technology energy requirement KTEB for the system (ÖNORM H 5058-1), the lighting energy requirement BelEB (ÖNORM H 5059-1) and the air conditioning energy requirement RLTEB, this includes the energy consumption of climate control and ventilation such as fresh air / air exchange, humidity control (ÖNORM H 5057) and the final energy requirement (EEB) of a building

EEB = HEB + KEB (= KB + KTEB) + BelEB + RLTEB ( energy requirement calculation in accordance with Directive 2002/91 / EG EPBD , in accordance with OIB guidelines for energy performance of buildings or in accordance with ÖNORMEN B 8110, H 5055 – H 5059)

This results in the primary energy requirement , the energy efficiency and the energy balance of the building via the energy losses , and directly the CO 2 emissions of the building (as a factor in the environmental balance ).

Because the energy is calculated with the heating energy requirement in order to compensate for ongoing losses , the energy required for (initial) heating of the heat storage mass of the building (masonry, stored moisture) as well as any heat gains due to heat irradiation on the masonry from outside (solar radiation, atmospheric counter-radiation) are not used the bill. Lowering the indoor temperature at night can therefore lead to a higher heating energy requirement than the calculation shows because of the subsequent heating that is required.

Heating energy demand and heating degree days

The heating energy requirement results (according to ÖNORM B 8135) from the heating degree days (also: degree days ), the climatological parameter for the heating requirement:

in kWh
p 0 : specific heating load
A : Energy reference area
HGT: heating degree days
f BEN : usage factor
η a : annual efficiency

This is a rough estimate from mean meteorological data; more precise calculations are carried out for special locations and situations.


Web links

Individual evidence

  1. EN 832 Thermal behavior of buildings - Calculation of heating energy demand - residential buildings. German DIN EN 832: 2003-06 (previous version 1998-12), Austrian ÖNORM EN 832: 1999-07.
  2. a b Austrian Institute for Structural Engineering: OIB guidelines for the energy-related behavior of buildings. April 2019, OIB-330.6-028 / 19 ( PDF file; 1.6 MB ).
  3. a b ÖNORM H 5055: 2002 energy certificate for buildings. Space heating and water heating.
  4. ↑ Key energy figures , OÖ Energiesparverband, accessed January 31, 2019.
  5. approximately as the characteristic length lc ,, the gross heated volumes and areas (ÖNORM B 8110-1)
  6. ÖNORM B 8110 thermal insulation in building construction .
  7. ÖNORM H 5056-1 Total energy efficiency of buildings - Part 1: Heating technology energy requirements .
  8. ÖNORM H 5058-1 Overall energy efficiency of buildings - Part 1: Cooling technology energy requirements .
  9. ÖNORM H 5059-1 Overall energy efficiency of buildings - Part 1: Lighting energy requirement (National supplement to ÖNORM EN 15193) - Quick method for the calculation.
  10. ÖNORM H 5057 Overall energy efficiency of buildings - air conditioning - energy requirements for residential and non-residential buildings.
  11. Directive 2002/91 / EC of the European Parliament and of the Council on the overall efficiency of buildings . Energy Performance of Buildings Directive (EPBD)
  12. Information in: Sustainable Oriented and Long-lasting Unique Team for energy self sufficient Communities (SOLUTION): Analysis Report on Simulation and Evaluation Results of New Eco-Buildings. High-level energy efficiency in new eco buildings. TREN / 06 / FP7EN / 239285 / ”SOLUTION”, Deliverable D2Ha.2.1, WP No .: 2Ha.2, Concerto, 30-04-11, Section 3 Approach to achieve the deliverable , 3.1 Building Characterization. P. 5 ( pdf ( memento of November 25, 2015 in the Internet Archive ), solution-concerto.org, English).