1. Laurent SOCAL Ediclima s.r.l. / Italy socal@iol.it
Calculation of the integrated energy performance of buildings EN 15316: Heating systems in buildings Method for calculation of system energy requirements and system efficiencies Part 2-3: Space heating distribution systems
Laurent SOCAL
Ediclima s.r.l. / Italy

2. The EU CENSE project (Oct. 2007 - March 2010)
Aim of the project:
To accelerate adoption and improve effectiveness of the EPBD related CEN- standards in the EU Member States
These standards were successively published in the years and are being implemented or planned to be implemented in many EU Member States. However, the full implementation is not a trivial task
Main project activities:
To widely communicate role, status and content of these standards; to provide guidance on the implementation
To collect comments and good practice examples from Member States aiming to remove obstacles
To prepare recommendations to CEN for a “second generation” of standards on the integrated energy performance of buildings

3. Brief introduction
A brief introduction to the CENSE project and the CEN-EPBD standards is provided in a separate presentation:

4. More information More information and downloads: www.iee-cense.eu
Disclaimer:
CENSE has received funding from the Community’s Intelligent Energy Europe programme under the contract EIE/07/069/SI
The content of this presentation reflects the authors view. The author(s) and the European Commission are not liable for any use that may be made of the information contained therein.
Moreover, because this is an interim result of the project: any conclusions are only preliminary and may change in the course of the project based on further feedback from the contributors, additional collected information and/or increased insight.

5. Fitting into the puzzle
SERVICES
BUILDING
NEEDS
TECHNICAL
SYSTEMS
DISTRIBUTION
GENERATION
OVERALL
PERFORMANCE
DHW
LIGHTING
EN 15193 EN
15193
VENTILATION
HEATING
COOLING
EN 13790
EN 15241
EN 13790
EN 15243 EN EN
15243
EN 15241 EN EN EN
EN XX EN
15243
This standard gives both detailed and simplified methods for the calculation of heat losses and auxiliary energy needs of the distribution sub-system for heating. It is part of the EN series for the calculation of heating system energy requirements and system efficiencies. The picture shows the position of the distribution calculation subsystem in the general system structure.
Pipe sizing is not covered by this standard. Its purpose is calculating the in-use energy performance of a given heating system distribution network, either existing or as designed and sized.
 The domestic hot water distribution sub-system is treated in EN , even though there are many common concepts.
 This standard covers water based distribution networks. Heat losses from air ducts are covered in the ventilation standards: EN clause and EN clause E.1.2.
EN 15603
slide 5

6. Distribution system energy balance
14/09/2018
WH,dis,aux Auxiliary energy
COSTS
QH,dis,in
QH,dis,out
Useful effect
Basic energy balance of the distribution subsystem
Heat input from generation QH,dis,in = QH,gen,out =
+ net heat output to emission QH,dis,out = QH,em,in
– recovered auxiliary energy QH,dis,aux,rvd
+ total losses QH,dis,ls
Heat recovery may be taken into account as a reduction of losses in the subsystem. If so, total losses QH,dis,ls are replaced by non-recovered losses QH,dis,ls,nrvd in the distribution subsystem energy balance
Losses QH,dis,ls
Not useful effect
14/09/2018
Ing. SOCAL - Rendimenti impianti
Ing. SOCAL - Dlgs 311/06 e certificazione energetica

7. Available methods Heat losses Auxiliary energy
Detailed calculation § 7.2 and § 7.3
Simplified calculation § A3  simplified input to detailed method
Tabulated values § A4  nationally precalculated values, according to detailed method
Auxiliary energy
Detailed calculation § 6.2 and § 6.3
Simplified calculation § A1  simplified input to detailed method
Tabulated values § A2  nationally precalculated values, according to detailed method
Water temperature calculation § 8
To be connected to the calculation shown in the generation part
This standard allows three levels of calculation of heat losses and auxiliary energy:
detailed approach;
detailed approach with simplified input  simplified input to detailed method;
tabulated values  tables shall be generated nationally according to the detailed method
Water temperature calculation is required because:
distribution losses depend on the mean water temperature
heat generator performance (losses) depends on mean temperature in the generator
condensing boiler performance depends on return temperature to the generator
heat pump performance depends on required flow temperature
Water temperature calculation shall be completed with the method highlighted in the generation part, (e.g. EN ) which takes into account hydraulic connection and water circulation in the generator(s).

8. Energy recovery Auxiliary energy recovery § 6.6 Heat recovery § 7.2.4
Recovery to heating medium
Recovery to heated space
Heat recovery § 7.2.4
Holistic method: recoverable losses are calculated to be summed to recoverable losses from other subsystems
Simplified method: heat recovery is directly accounted for as a reduction of losses within the distribution subsystem
Heat recovery to the heating medium is accounted for directly within the distribution energy balance (see § 6.6 equation 21)
Some losses can be towards the heated space and are therefore recoverable. This standard allows both explicit and implicit calculation of recovered heat losses:
Explicit calculation (holistic approach) means that recoverable losses are given as an output of this calculation. These data are used, together with recoverable losses from other parts, to calculate actual recovered losses that reduce heating needs (see EN 15603);
Implicit calculation (simplified approach) means that recovered losses are taken into account as a reduction of losses within the distribution part. There is no data output for recoverable losses.

9. Heat recovery: holistic (explicit)
Explicit calculation means that recoverable losses are given as an output of this calculation. These data are used, together with recoverable losses from other parts, to calculate actual recovered losses that reduce heating needs (see EN 15603).

10. Heat recovery: simplified (implicit)
Implicit calculation means that recovered losses are taken into account as a reduction of losses within the distribution part.
In this case there is no data output for recoverable losses.
This is the most common option for tabulated values.
Care must be taken to include information about assumptions on heat recovery when supplying tabulated values.
This is the most common option for tabulated values.
Information on assumptions about heat recovery should be included when supplying tabulated values

11. Detailed calculation of losses, §7.2
The principle is to sum up all losses from pipe elements
For each element the following data is needed:
Lj pipe length in m;
Ψj linear thermal transmittance (loss factor) in W/m·K
θw,j temperature of water inside the pipe in °C;
θe,j surroundings temperature in °C.
Ψj is calculated using basic physics formulae
top is the operation time
§ 7.2 Detailed calculation of thermal losses
The most challenging data are the temperatures.
Temperature evaluation shall be correlated to operation time.

12. Linear transmittance § 7.3
dint: insulation inner diameter in m (= pipe outer diameter)
dext: insulation outer diameter in m (or dint + thickness of insulating layer);
λD thermal conductivity of insulating layer in W/m·K;
αair external heat transfer coefficient in W/m²·K.
§7.3 Linear transmittance calculation
The linear thermal transmittance of the pipe element has to be calculated according to the following values:
dint: insulation inner diameter (= pipe outer diameter) in m
dext: insulation outer diameter in m (or dint + thickness of insulating layer);
λD thermal conductivity of insulating layer in W/m·K;
αair external heat transfer coefficient in W/m²·K.
For embedded or underground pipes, the following additional data are also required
depth from ground surface in m;
thermal conductivity of walls or ground in W/(m·K);
distance between pipes running parallel to each other.
Any non-insulated piping element is also taken into account explicitly.
They may be also taken into account as an equivalent length of 10 to 20 times longer insulated pipes.

13. Simplified method for heat losses
Simplified method (§ A.3) = Detailed method with simplified input
PIPE LENGTH:
LV = horizontal distribution
LS = vertical distribution (shafts)
LA = terminal connection pipes
Length for each part is estimated according to the floor area and the external dimensions of the building with correlation formulae
PIPE LINEAR TRANSMITTANCE
Linear thermal transmittances are given in tables according to building age and type.
§ A3 Simplified method for heat losses
The basic idea is to use the detailed method with simplified input data:
the distribution network is divided into three parts: horizontal distribution, vertical distribution and terminal connection pipes
a total length for each part is estimated according to the floor area and the external dimensions of the building; the total estimated length is used instead of the individual element lengths;
linear thermal transmittances are given in tables according to building age and type.
The correlations between building size and pipe length and the tables for linear thermal transmittances may be modified on a national basis to reflect local building practices and dates of changes to regulations.
Non-insulated elements may be taken into account with an equivalent length of (insulated) pipe.

14. Simplified method for heat losses
Values
Unit LV
Distribution to the shafts LS
Vertical shafts LA
connection pipes
Mean surrounding temperature °C
13 respectively 20 20
Pipe length in case of shafts in outside walls Li m
2 .LL+ 0, LL . LW2
0,025 . LL . LW .hlev .Nlev
0,55 . LL . LW . Nlev
Pipe length in case of shafts inside the building
2 . LL + 0, LL . LW + 6
LL = Length of the building hlev = floor heighth
LW = Width of the building Nlev = number of floors
Default correlation table for pipe length from § A 3.3
Default correlation table for pipe length

15. Tabulated method for heat losses
Example: Italian table of efficiencies
There are other tables according to distribution type
Values include recovered heat losses
Values were calculated according to detailed method
TABULATED VALUES
Distribution heat losses (kWh/year) are given in tables for each type of distribution system.
Values in the tables may be calculated at national level with the simplified or detailed method.
Great care must be given in specifying boundary conditions for such tables. Boundary conditions may include:
insulation levels;
network topology;
temperature levels;
type of water circuit;
position of pipes (inside/outside) with respect to building insulation
Example taken from UNI-TS :2008

16. Distribution auxiliary energy: detailed § 6.3
Starting point: required hydraulic energy Phydr,des
Phydr,des [W]= 0,2778⋅Δpdes [kPa]⋅V’des [m³/h]
… then this is corrected by a series of multiplying correction factors
β takes into account part-load operation of the heating system
fS, takes into account supply flow temperature control (takes into account the presence or absence of outdoor temperature compensation)
fNET takes into account hydraulic networks (differentiates between ring line, star type or vertical column network) fSD takes into account any oversizing of the heat emitters;
fHB takes into account any hydraulic unbalance;
fGPM takes into account integrated management of the circulation pump within the heat generator;
fη takes into account pump mechanical efficiency;
fPL takes into account pump performance at part load;
fPSP takes into account correct selection of the pump compared to design requirement;
fC takes into account the type of pump control.
§ 6.3 Detailed calculation of distribution auxiliary energy:
The calculation starts from the knowledge of flow rate and heat loss from which the mechanical energy required to circulate the water in the distribution circuit is calculated.
The effects of pump type, pump control mode, varying flow rate and the distribution network typology, according to varying heat requirements, are described by a series of multiplying factors.

17. Distribution auxiliary energy: simplified
Simplified method § A.1
The number of correcting factors is reduced
Tabulated method § A.2
Tables of precalculated values are given according to floor area or other relevant properties.
Example: tabulated values
In the following table, distribution auxiliary energy (kWh/year) is given as a function of:
Floor area AH,z
Type of pump control
§ A.1 Simplified calculation of distribution auxiliary energy

18. Auxiliary energy example
NOMINAL POWER 180 W
DESIGN CONDITION 125 W
AVERAGE OPERATION 50 W
Illustration of the different level of auxiliary power of a pump
This example comes from an actual system, 16 flats, 100 kW generator, radiators with thermostatic valves, proportional pressure controlled pump in a site with 2400 degree/days:
the installed pump has a nominal (maximum) power of 180 W  this can be read on the pump plate;
design point operation (maximum actual flow rate 5 m³/h @ 40 kPa) requires 125 W  this is calculated when sizing the system
average operation after one year was 2 m³/h @ 30 kPa requiring an actual average power of 50 W  this is the correct value for energy performance calculation
14/09/2018
Ing. SOCAL - Rendimenti impianti

19. Calculation of network temperatures
Calculation procedure (chapter 8)
Emitter average temperature is calculated According to heat output and emitter size
Distribution circuits analysis: Flow and return temperature are calculated taking into account control strategy The effect of mixing valves or any other control device is taken into account here
Distribution collectors: Return temperature shall be averaged
Generation circuits: The effect of the hydraulic connection of generators (direct/independent flow rate,…) is taken into account here (see and other)
EN also includes a method (clause 8) to calculate water temperature (flow and return) within the distribution network at actual operating conditions. This is required for detailed calculation of losses as well as for performance calculation of boilers and heat pumps, in connection with further calculation steps defined in EN
Flow and return temperatures at emitter level is calculated first. They depend on:
type of emitters (radiators, embedded panels, air heaters);
size (nominal power) of installed emitters;
monthly load (actual operating average power);
type of control of the emitters;
operation time.
Three basic types of emitter control are specified :
constant flow rate, varying temperature (parallel connection of emitters without local control);
constant flow temperature, continuously varying flow rate (thermostatic valves);
both flow rate and flow temperature constant, on/off operation (room thermostat control).
The effect of the hydraulic connection shall also be taken into account. Three basic types of connections have been considered:
direct connection;
mixing valve;
by-pass control.
This highlights the effect of hydraulic connections. Ignoring this fact may prevent condensation even with low temperature emitters whilst proper design allows attainment of the highest efficiencies with condensing boilers even in the coldest months and using radiators.

20. Direct connection Nominal 1 kW @ 80/60
Direct connection of heat emitters to the boiler room collectors.
Typical for thermostatic valves.
Distribution network temperature is the same as emitters temperature
Flow rate in the distribution network is the same as in the emitters.

21. Mixing valve connection
Nominal
1 80/60
Emitter connection through a mixing valve.
Typical for central control or for lower temperature emitters.
Distribution network temperature is the same as emitters temperature
Flow rate before the mixing valve is less than in the emitters..

22. Emitter connection with a by-pass
By-pass connection
Nominal
1 80/60
Emitter connection with a by-pass
Typical for the connection of HVAC hot heat exchanger or single pipe circuits.
Distribution network losses increase when the emitter power is reduced.
Flow rate in the network is greater than required by the emitters causing higher auxiliary energy needs.

23. Practical issues Distribution network calculation requires much care:
Tabulated values
The correct tables shall be used
If all boundary conditions, also hidden ones, are not fulfilled then the detailed calculation should be used (see following example, tables would give )
Simplified method
Correlations are suitable only for simple building shapes and well defined network topology
Detailed calculation method
Temperature shall be calculated consistently with operation time
Temperature hall be calculated according to hydraulic circuit type
Relative position of pipes and building insulation shall be taken into account
Both tabulated and detailed calculation method shall be used carefully.

24. Losses of a vertical shafts distribution network
Vertical shafts are within external walls
Distribution is operated at variable temperature: 27…49 °C
Heat to distribution 2600 … kWh/month
Distribution losses 1000…6000 kWh/month
Net losses
240…1710 kWh/month
Yearly efficiency 92%
This network is not insulated but
most heat is recovered because pipes are running on the inner side of walls
network temperature is the same as that of emitters (i.e. relatively low)
14/09/2018
Ing. SOCAL - UNI-TS

25. i.e. 250 m³ natural gas for each flat Distribution efficiency 90…35%
NETWORK LOSSES
100 MWh/year
i.e. 250 m³ natural gas for each flat
Distribution efficiency 90…35%
40 FLATS
Though well insulated, continuous 24/24 operation at high temperature causes very high yearly losses
DISTRICT HEATING
Actual case: 40 flats in northern Italy (2400 degree·days), heat supply by district heating, 40 dhw and heating modules in the flats
System operation:
daily 24/24 and yearly 365/365 at 80 °C flow temperature
domestic hot water produced via local instantaneous heat exchangers with priority (1st 3 way valve in each module)
heating controlled by zone thermostat (1 per flat)
the network is insulated with polyurethane, average thickness 40 mm with DN 50 pipes.
Results: distribution efficiency from 90 % in January (max. load) down to 35% in July (min. load)  italian tabulated value 99%
Losses have been verified through calculation, energy signature and reading of local heat meters (40, 1 per flat) compared to central heat meter. All results are consistent.
In connection with previous slide, this highlights that distribution efficiency
… IS NOT ONLY A QUESTION OF INSULATION
THIS INSULATED NETWORK IS LESS EFFICIENT THAN THE PREVIOUS ONE, WHICH IS NOT INSULATED BUT OPERATES AT A MUCH LOWER TEMPERATURE
14/09/2018
Ing. SOCAL - UNI-TS

26. More information More information and downloads: www.iee-cense.eu
Disclaimer:
CENSE has received funding from the Community’s Intelligent Energy Europe programme under the contract EIE/07/069/SI
The content of this presentation reflects the authors view. The author(s) and the European Commission are not liable for any use that may be made of the information contained therein.
Moreover, because this is an interim result of the project: any conclusions are only preliminary and may change in the course of the project based on further feedback from the contributors, additional collected information and/or increased insight.