CEN/TC 228

Date: 2025-12-11

prEN 15316‑7‑1:2025

Secretariat: DIN

Energy performance of buildings — Method for calculation of system energy requirements and system efficiencies — Part 7-1: DHW instantaneous heat recovery — Module M8-13

Energetische Bewertung von Gebäuden — Verfahren zur Berechnung der Energieanforderungen und Nutzungsgrade der Anlagen — [German title]

Systèmes de chauffage dans les bâtiments — Méthode de calcul des besoins énergétiques et des rendements des systèmes — [French title]

CCMC will prepare and attach the official title page.

Contents Page

Introduction 5

1 Scope 6

2 Normative references 9

3 Terms and definitions 9

4 Symbols and abbreviations 10

4.1 Symbols 10

4.2 Subscripts 10

5 Description of the methods 11

5.1 Output of the method 11

5.2 Alternative methods 11

5.3 System boundary 11

5.4 Auxiliary energy 11

6 Calculation method 11

6.1 Output data 11

6.2 Input data 12

6.2.1 Product data 12

Figure 1 — Temperatures involved in the definition of η_dwhr 13

6.2.2 Process design description and data 14

Figure 2 — Example of connection type A 16

Figure 3 — Example of connection type B 17

Figure 4 — Example of connection type C 18

6.2.3 Operating conditions data 19

6.2.4 Control options 20

6.2.5 Constants and physical data 20

6.3 Calculation time intervals 20

6.4 Calculation procedure flow chart 20

6.5 Calculation procedure 20

6.5.1 General 20

6.5.2 Domestic hot water needs related to DWHRD 21

6.5.3 Efficiency of the DWHRD with balanced flow rate 22

6.5.4 Recoverable heat and DWHRD heat exchanger actual efficiency 23

6.5.5 Correction factor for transient operation 25

6.5.6 Recovered heat 26

6.5.7 Auxiliary energy 27

6.5.8 Recoverable heat losses 27

7 Quality control 28

7.1 Calculation report 28

7.2 Error reporting 28

8 Compliance check 28

Annex A (normative) Template for input data 29

Annex B (informative) Default values 33

Annex C (informative) Calculation flow chart 37

Figure — A.1 37

Bibliography 38

European foreword

This document (prEN 15316‑7‑1:2025) has been prepared by Technical Committee CEN/TC 228 “Heating systems and water-based cooling systems in buildings”, the secretariat of which is held by DIN.

This document is currently submitted to the CEN Enquiry.

Introduction

This document is part of a series of standards aiming at international harmonization of the methodology for the assessment of the energy performance of buildings, called “set of EPB standards”.

All EPB standards follow specific rules to ensure overall consistency, unambiguity and transparency.

All EPB standards provide a certain flexibility with regard to the methods, the required input data and references to other EPB standards, by the introduction of a normative template in Annex A and informative default choices in Annex B.

EPB standards deal with energy performance calculation and other related aspects (like system sizing) to provide the building services considered in the EU EPBD Directive.

CEN/TC 228 deals with water-based heating and cooling systems in buildings. Subjects covered by CEN/TC 228 are:

— energy performance calculation for heating and cooling systems;

— inspection of heating systems;

— design of heating systems and water-based cooling systems;

— installation and commissioning of heating systems.

This document specifies how to calculate the energy performance of instantaneous domestic hot water heat recovery for domestic hot water preparation.

This document covers only instantaneous heat recovery. Storage heat recovery is not included.

For the correct use of this document, Annex A specifies the required choices and input data. Default choices and input data are proposed in Annex B. In case the standard is used in the context of national or regional legal requirements, mandatory choices may be given at national or regional level for such specific applications, e.g. for the application within the context of the transposition of EU Directives into national legal requirements. These national or regional choices can be made available as National Annex or as separate (e.g. legal) document that override partly or entirely informative Annex B.

If the default values and choices proposed in the Annex B of this document are not followed due to national regulations, policy or traditions, it is therefore expected that:

— either the national standardization body will consider the possibility to add or include a National Annex in agreement with the template of Annex A;

— or the national or regional authorities will, in the building regulations, reference the standard and prepare data sheets and/or application documents containing the national or regional choices and values, in agreement with the normative template given in Annex A to this document.

This calculation module applies to instantaneous domestic hot water heat recovery using a counter-flow heat exchanger between the drain water and the incoming domestic cold water. This module calculates the recovered heat, to be taken into account in the overall calculation procedure of the energy performance of the building.

The scope of this document is to standardize the:

— required inputs;

— calculation methods;

— required outputs;

of the instantaneous heat recovery from domestic hot water drains.

This document provides a calculation method for one calculation interval.

This calculation is intended to be connected to the whole building calculation model and takes into account the external conditions and system controls that may influence the instantaneous heat recovery from domestic hot water drains.

This document does not apply to storage heat recovery or the use of drain water as a source for heat pumps.

This document does not apply to sizing or inspection of domestic hot water heat recovery devices.

Table 1 shows the relative position of this document within the set of EPB standards in the context of the modular structure as set out in EN ISO 52000‑1.

NOTE 1 The same Table is found in CEN ISO/TR 52000‑2, with, for each module, the numbers of the relevant EPB standards and accompanying technical reports that are published or in preparation.

NOTE 2 The modules represent EPB standards, although one EPB standard might cover more than one module and one module might be covered by more than one EPB standard, for instance a simplified and a detailed method respectively. See also Clause 2 and Table A.1 and Table B.1.

Table 1 — Position of this document, within the modular structure of the set of EPB standards

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

NOTE Additional references are identified by the EPB module code number and the default references are specified in Table B.1 (informative default references) according to the template given in Table A.1 (normative template with the list of required references).

EN ISO 52000‑1:2017, Energy performance of buildings — Overarching EPB assessment — Part 1: General framework and procedures (ISO 52000‑1:2017)

EN ISO 7345:2018, Thermal performance of buildings and building components - Physical quantities and definitions (ISO 7345:2018)

For the purposes of this document, the terms and definitions given in EN ISO 7345:2018 and EN ISO 52000‑1:2017 and the following apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp/

— IEC Electropedia: available at https://www.electropedia.org/

3.1

Instantaneous domestic hot water heat recovery device

DWHRD

heat exchanger and related optional auxiliary devices intended to instantaneously recover heat from drain water to preheat incoming cold domestic water

Note 1 to entry: An auxiliary device may be e.g. a pump used to lift drain water.

3.2

drain water

water flowing out from the shower device

3.3

preheated water

domestic water flowing out from the DWHR device heat exchanger after heat recovery

3.4

primary of the DWHR device

the high temperature side of the DWHR device, where drain water is flowing

3.5

secondary of the DWHR device

the low temperature side of the DWHR device, where the incoming cold domestic water is flowing

3.6

shower device

fixture where one can take a shower

Note 1 to entry: A shower device can be a shower cabin or a bathtub equipped with a shower.

For the purposes of this document, the symbols given in EN ISO 52000‑1, and the specific terms listed in Table 2 apply.

Table 2 — Symbols

For the purposes of this document, the subscripts given in EN ISO 52000‑1, and the specific subscripts listed in Table 3 apply.

Table 3 — Subscripts

The abbreviation and acronyms used in this document are listed in Table 4.

Table 4 — Acronyms

The method described in this module covers the calculation of:

— Recovered heat Q_{W;dwhr;rvd;ci}

— Recovered heat to the shower mixer Q_{W;dwhr;rvd;shw,ci}

— Recovered heat to the water heater Q_{W;dwhr;rvd,wh,ci}

— Preheated water temperature θ_W;pre,ci

— Energy for auxiliaries W_dwhr;aux,ci

— Recoverable heat losses to the heated space Q_{W;dwhr;ls;rbl}

This method is intended to be used for monthly and hourly calculation intervals.

There is only one method. The calculation path depends on the type of connection. The considered types of connections are identified by the identifier DWHR_CONN with values given in Table 9.

The system boundary defines the components of the domestic hot water systems that are considered in this module.

For the domestic water recovery subsystem, the system boundary includes:

— the domestic hot water heat recovery device;

— the preheated water pipes;

— the shower device;

— the drain water connection from the shower to the DWHRD, including any pump to raise drain water.

The auxiliary energy of an optional drain water lifting pump is considered, if installed.

The output data are listed in Table 5.

Table 5 — Output data of this method

Product description data (qualitative)

There is no applicable product description data.

Product technical data

List of product technical data

The required technical data for this calculation procedure are listed in Table 6.

Table 6 — Input product technical data list

Steady-state efficiency of the heat exchanger with balanced flow rates

The efficiency of the DWHRD η_dwhr,X in condition X is defined as the following ratio of temperatures:

(1)

where

NOTE Formula (1) is always true (also for unbalanced operation) because the flow rate on the secondary side is always less than or equal to the flow on the primary side of the DWHRD and there is the same fluid (water) on both sides.

Figure 2 identifies the above listed temperatures.

Key

1 DWHR device

Figure 1 — Temperatures involved in the definition of η_dwhr

The efficiency of the DWHRD η_dwhr is declared by the manufacturer:

— for steady-state, balanced operating conditions (temperatures are measured after they have reached steady-state conditions given the testing flow rates);

— for at least two flow rates (conditions A and B), that should encompass the foreseen actual domestic hot water secondary flow rate.

Testing can be performed according to EN DWHRD. The steady-state efficiency can also be based on data collected during tests performed before the publication of EN DWHRD according to relevant national standards, if the collected data include the required temperatures after steady-state condition is reached.

EXAMPLE Test according to NEN 8801:2022 – Annex U

Primary and secondary flow rate at balanced test condition X

The flow rate V′_dwhr;X is the value of the primary and secondary flow rate when measuring η_dwhr;X at balanced test condition X. Default values for the testing flow rate are given in Table B.2.

The value of V′_dwhr;X is declared by the manufacturer together with the corresponding value of η_dwhr;X.

Volume of water in the DWHRD

The volume of water in the DWHRD V_dwhr;w is the total volume of cold domestic water and drain water accumulated in the primary and secondary side of the DWHRD during steady-state operation.

The value of V_dwhr;w is declared by the manufacturer.

NOTE 1 The volume of water in the secondary side is the geometrical internal volume because domestic cold water is pressurized. The volume of water in the primary side is usually less than the geometrical internal volume because of open channel and gravity flow in the drain pipes.

NOTE 2 The total volume is required. It will be multiplied by 0,5 in Formula (25) of this document to take into account the effect of the temperature profile along the DWHRD.

Mass of the DWHRD heat exchanger

The mass of the heat exchanger of the DWHRD m_dwhr;exc is the value declared by the manufacturer.

The mass m_dwhr;exc shall include all the materials that are in contact with cold water and drain water. If this value is not known, the total mass of the device is used.

NOTE The total mass is required. It will be multiplied by 0,5 in Formula (25) of this document to take into account the effect of the temperature profile along the DWHRD.

Specific heat of the DWHRD heat exchanger material

The specific heat of the materials of the DWHRD heat exchanger c_dwhr;exc is the value declared by the manufacturer.

If no data is available, default values for selected materials are given in Table B.3.

Rated power of auxiliaries

For DWHRDs that require auxiliary energy, the power of auxiliaries P_dwhr;aux during DWHRD operation (e.g. the pump to lift drain water) is the value declared by the manufacturer for the same test conditions as for the efficiency measurement.

If no auxiliary energy is required, then P_dwhr;aux,X = 0.

The factor k_dwhr;aux is the fraction of time that the auxiliary is on during showering. If not declared by the manufacturer, a default value is given in Table B.4.

List of process design data

The process design data are given by the identifiers listed in Table 7.

Table 7 — Process design identifiers

and by the following values

Table 8 — Process design data

Connection type DWHR_CONN

The DWHRD can be connected in the domestic hot water system so that the preheated water is feeding:

— both the domestic hot water heater and the cold water tap, which is called connection type A, see Figure 2;

— only the cold water tap, which is called connection type B, see Figure 3;

— only the domestic hot water heater, which is called connection type C, see Figure 4.

The connection types are indicated by the identifier DWHR_CONN. The possible values of DWHR_CONN are listed in Table 9.

Table 9 — Values for the identifier DWHR_CONN

Key

DH Domestic hot water heater

OTH To other fixtures

SEW To sewer

Figure 2 — Example of connection type A

Key

DH Domestic hot water heater

OTH To other fixtures

SEW To sewer

Figure 3 — Example of connection type B

Key

DH Domestic hot water heater

OTH To other fixtures

SEW To sewer

Figure 4 — Example of connection type C

Volume of water in the shower and drain V_shw;drain

The volume of water in the shower and drain V_shw;drain is the total volume of water which is accumulated during steady-state operation of the shower in:

— the shower floor and walls;

— the shower drain and syphon;

— the drain pipe from the shower drain up to the DWHRD primary inlet.

If this value is not known, default values are given in Table B.5.

The value can be less than the geometrical volume of the siphon and drain pipe due to open channel, gravity flow.

Length and inner diameter of the preheated water pipes

These are the lengths L_pre,i and corresponding inner diameters D_in;pre,i of all the preheated water pipes connecting the DWHRD secondary outlet to:

— the domestic hot water heater;

— and/or the cold water tap of the shower mixer.

NOTE The domestic hot water pipes from the domestic hot water heater outlet up to the hot water tap of the shower mixer will not be considered here. They are already taken into account in the distribution losses, module 8–5.

Location of preheated water pipes

The identifier ZT_W_PRE_i specifies in which thermal zone the preheated water pipe i is installed.

A valid thermal zone identifier shall be specified. This may include heated space unheated spaces and external environment.

Recoverable fraction of preheated water pipes losses

The recoverable fraction of preheated water pipes losses k_pre;rbl,i depends on the pipe location.

Default values are specified in Table B.6.

NOTE Depending on energy need calculation options, the required information can be either the location of the preheated water pipes or the recoverable fraction of preheated water pipes. See the accompanying TR for more details.

Number of fixtures

The number of fixtures counts the type of domestic hot water fixtures and identifies how many are connected to a DWHRD.

The required operating conditions data for this calculation procedure are listed in Table 10.

Table 10 — Operating conditions data list

The operating conditions are calculated in the module specified in the column “origin module” of Table 10.

The following data can be specified locally, if not provided together with the definition of domestic hot water needs in module M8-1:

Default values for the data that are or may be specified locally are given in Table B.7 and Table B.9.

There are no control options for this calculation module.

The required constants and physical data are listed in Table 11.

Table 11 — Constants and physical data

The method described in this module is suitable for hourly and monthly calculation intervals.

The output calculation interval is the same as the input calculation interval.

This method is static. Dynamic effects within a shower event are taken into account by a utilization factor.

The reference flow chart of the calculation described in this Clause 6 is given in informative Annex C.

If there are several DWHRDs in a domestic hot water service area, the calculation according to this module shall be performed independently for each DWHRD and then the results summed (e.g. recovered heat) or averaged (e.g. preheated water temperature).

General

Heat recovery occurs only for the domestic hot water flow related to shower devices (shower cabin or shower on a bathtub) that are connected to a DWHRD. Depending on the type of domestic hot water needs passed to this module, the following corrections of the input value of domestic hot water needs to this module may be required:

— a correction to consider that only part of the domestic hot water needs is related to showering;

— a correction depending on how many shower devices are connected to a DWHRD and on overall number and type of domestic hot water fixtures.

The type of domestic hot water needs that are passed to this module are specified by the identifier WND_TYPE and the possible values of WND_TYPE are listed in Table 12.

Table 12 — Values for identifier WND_TYPE

NOTE For more details, see the accompanying technical report.

Domestic hot water needs related to showering

If

WND_TYPE = WND_TYPE_TOT (2)

then the domestic hot water needs related to showering Q_W;nd;sh,ci are given by:

otherwise, if

WND_TYPE = WND_TYPE_SHW (4)

then the domestic hot water needs related to showering Q_W;nd;sh,ci are given by:

where

Domestic hot water needs related to drain water heat recovery devices

If

WND_TYPE = WND_TYPE_DWHR (6)

then the domestic hot water needs related to domestic hot water heat recovery Q_W;nd;dwhr,ci are given by:

otherwise, the domestic hot water needs related to domestic hot water heat recovery Q_W;nd;dwhr,ci are given by:

Q_{W;nd;dwhr,ci=} Q_W;nd;shw,ci (8)

where

k_btub is a coefficient that weights the use of domestic hot water in bathtubs related to showers;

k_hyb is a coefficient that weights the use of domestic hot water in fixtures that allow either taking a bath or a shower (e.g. a bathtub with a shower device);

N_shw;dwhrd is the number of fixtures whose drain is connected to a DWHRD;

N_shw is the number of fixtures dedicated to showering (shower cabins);

N_btub is the number of bathtubs without showering device;

N_hyb is the number of fixtures where one can take either a bath or a shower (bath-tub with a shower device).

Default values of k_btub and k_hyb are given in Table B.8.

The corresponding volume of domestic hot water for showering and heat recovery V_W;nd;shw,ci, is given by

V_W;nd;dwhr,ci (9)

where

ρ_W is the density of water as specified in 6.2.5;

c_W is the specific heat of water as specified in 6.2.5;

θ_W;draw is the domestic hot water draw off temperature, defined in module M8–2;

θ_W;cold is the domestic cold water temperature, defined in module M8–2.

The efficiency η_dwhr,ci of the DWHRD with balanced flow rate is given by:

(10)

where

η_dwhr,X is the steady-state efficiency of the DWHRD at balanced operation in condition X, as defined in 6.2.1.2.2 (with X = A and X = B);

V′_dwhr,X is the balanced flow rate in condition X, as defined in 6.2.1.2.2;

V′_shw,ci is the shower event flow rate during calculation interval ci, as defined in 6.2.3;

A and B are the nearest testing conditions, considering the primary flow rate. If there are more than 2 testing conditions available, A and B shall be chosen so that the efficiency is obtained by interpolation or extrapolation from the nearest points.

When the actual flow rate V′_shw,ci is lower than the minimum tested flow rate, the extrapolation shall be limited to 10 % of the difference between the nearest tested flow rates. For lower flow rates, the efficiency is considered constant.

NOTE See the accompanying TR for more details.

General

Depending on the value of the identifier DWHR_CONN:

— the fraction of recoverable heat in the calculation interval ci k_dwhr;rbl,ci;

— and the efficiency of the heat exchanger of the DWHRD at calculation interval ci η_dwhr,ci;

are calculated

— according to 6.5.4.2 if DWHR_CONN = DWHR_CONN_A;

— according to 6.5.4.3 if DWHR_CONN = DWHR_CONN_B;

— according to 6.5.4.4 if DWHR_CONN = DWHR_CONN_C.

Recoverable heat and DWHRD heat exchanger efficiency for connection type A

The recoverable fraction of needs for type A connection at calculation interval ci k_{dwhr;rbl;A,ci} is given by:

(11)

where

θ_W;drain is the domestic hot water temperature at the shower drain, as defined in 6.2.3.

The efficiency of the heat exchanger of the DWHRD for type A connection at calculation interval ci η_dwhr,ci;A is given by

(12)

Recoverable heat and DWHRD heat exchanger efficiency for connection type B

The recoverable fraction of needs k_{dwhr;rbl;B,ci} and the efficiency of the heat exchanger of the DWHRD η_dwhr,ci;B for type B connection at calculation interval ci k_{dwhr;rbl;A,ci} is calculated with the following iterative procedure.

The initial value of the DWHRD efficiency η_dwhr,ci;0 is given by:

(13)

The initial value of the thermal length of the DWHRD heat exchanger NTU_dwhr,0 is given by:

(14)

The initial value of the ratio of flow rates of the DWHRD heat exchanger C*_dwhr,0 is given by:

(15)

where

For each iteration i, the following values are calculated:

— a new value of the thermal length of the DWHRD, NTU_dwhr,i:

(16)

— a new value of the efficiency of the DWHRD heat exchanger, η_dwhr,ci;i:

(17)

— a new value of the ration of the flow rates of the DWHRD heat exchanger C*_dwhr,i:

(18)

The iteration is repeated N times until the change in efficiency is less than 0,01, that is:

(19)

N is the index i for the last iteration.

When the iteration is completed,

— the recoverable fraction of needs with type B connection at calculation interval ci k_{dwhr;rbl;B,ci} is given by:

(20)

— the efficiency of the DWHRD heat exchanger at calculation interval ci η_dwhr,ci;B is given by:

(21)

where N is the index of the last iteration, when convergence is reached.

Recoverable heat and DWHRD efficiency for connection type C

The initial value of the efficiency η_dwhr,ci;0 is given by:

(22)

The initial value of the thermal length of the DWHRD heat exchanger NTU_dwhr,0 is given by:

(23)

The recoverable fraction of needs for type C connection at calculation interval ci k_{dwhr;rbl;A,ci} is given by:

(24)

The relative flow rate on the secondary side of the DWHRD heat exchanger C*_dwhr;C is given by:

(25)

The thermal length of the DWHRD heat exchanger in unbalanced operation NTU_dwhr,C is given by:

(26)

— the efficiency of the DWHRD heat exchanger at calculation interval ci η_dwhr,ci;C is given by:

(27)

The volume of water drawn during each shower event V_shv,ci is given by

where

The equivalent volume of water for the heat capacity of the DWHRD heat exchanger V_dwhr,eq;W is given by:

(29)

where

m_dwhr;exc is the mass of the DWHRD heat exchanger as defined in 6.2.1.2.5;

c_dwhr;exc is the specific heat of the DWHRD heat exchanger material as defined in 6.2.1.2.6;

ρ_W is the density of water as specified in 6.2.5;

c_W is the specific heat of water as specified in 6.2.5.

The volume of preheated water during DWHRD operation V_pre is given by:

(30)

where

The equivalent volume of preheated water lost because of transient operation per shower event V_trans is given by:

(31)

where

The utilization factor for transient operation k_dwhr;ut is given by:

(32)

The heat recovered by the DWHRD at calculation interval ci Q_{W;dwhr;rvd,ci} is given by

(33)

where

index X shall be A, B or C depending on the connection type (see 6.5.3).

The preheated water temperature at calculation interval ci θ_W;pre,ci is given by

(34)

The recovered heat through the connection to the shower mixer tap Q_{W;dwhr;rvd;shw;X,ci} depending on the connection type is given by:

— for connection type A:

(35)

— For connection type B:

— For connection type C:

The recovered heat through the domestic hot water heater connection Q_{W;dwhr;rvd;wh,ci} is given by:

where

The operation time of auxiliaries t_dwhr;aux,ci is given by:

(39)

The auxiliary energy used for the DWHRD W_dwhr;aux,ci is given by:

(40)

where

P_dwhr;aux is the power of auxiliaries, as defined in 6.2.1.2.7;

k_dwhr;aux is a factor that takes into account the actual running time of the pump, as defined in 6.2.1.2.7.

The identifier DWHR_LS_RBL_CALC indicates if the recoverable losses shall be calculated or neglected.

The possible values of DWHR_LS_RBL_CALC are given in Table 3.

Table 13 — Values for identifier DWHR_LS_RBL_CALC

Default values of DWHR_LS_RBL_CALC are given in Table B.10.

If DWHR_LS_RBL_CALC = DWHR_LS_RBL_CALC_YES, then the recoverable losses are given by:

(41)

where

θ_int,pre is the indoor temperature of the thermal zone where the preheated water pipes are installed, see 6.2.3.

The thermal zone identifier ZT_W_DWHR_PRE is the identifier of the thermal zone where the preheated water pipes are located.

NOTE 1 Recoverable heat of hot water pipes from the domestic hot water heater to the domestic hot water fixtures are already included in the distribution losses (see module M3–6).

NOTE 2 Recoverable heat of drain water is considered negligible because drain water flows down to the sewer.

If DWHR_LS_RBL_CALC = DWHR_LS_RBL_CALC_NO, then the recoverable losses are neglected and:

The calculation report shall include the values of the following data for each calculation interval.

For a printed report, the hourly values shall be aggregated and presented as monthly values together with a sample hourly set for a typical day.

The following error conditions shall be reported, when occurring:

— efficiency of DWHR device for connection type B fails to converge;

— any division by 0;

— input value of θ_W;dis,ci being lower than θ_W;draw.

To check if the calculation procedure was applied correctly to the installed system, check that the following items were correctly identified:

— type of connection;

— DWHR device steady-state efficiency;

— distribution temperature;

and that the resulting values for

are consistent with the connection type and DWHR heat exchanger product data.

1. 
   (normative)
   
   Template for input data
   1. General

The template in Annex A of this document shall be used to specify the choices between methods, the required input data and references to other documents.

NOTE 1 Following this template is not enough to guarantee consistency of data.

NOTE 2 Informative default choices are provided in Annex B. Alternative values and choices can be imposed by national/regional regulations.

If the default values and choices of Annex B are not adopted because of the national/regional regulations, policies or national traditions, it is expected that:

— national or regional authorities prepare data sheets containing the national or regional values and choices, in line with the template in Annex A; or

— by default, the national standards body will add or include a national annex (Annex NA) to this document, in line with the template in Annex A, giving national or regional values and choices in accordance with their legal documents.

NOTE 3 The template in Annex A is applicable to different applications (e.g. the design of a new building, certification of a new building, renovation of an existing building and certification of an existing building) and for different types of buildings (e.g. small or simple buildings and large or complex buildings). A distinction in values and choices for different applications or building types could be made:

— by adding columns or rows (one for each application), if the template allows;

— by including more than one version of a Table (one for each application), numbered consecutively as a, b, c, … For example: Table NA.3a, Table NA.3b;

— by developing different national/regional data sheets for the same standard. In case of a national annex to the standard these will be consecutively numbered (Annex NA, Annex NB, Annex NC, …).

NOTE 4 In the section “Introduction” of a national/regional data sheet information can be added, for example about the applicable national/regional regulations.

NOTE 5 For certain input values to be acquired by the user, a data sheet following the template of Annex A, could contain a reference to national procedures for assessing the needed input data. For instance, reference to a national assessment protocol comprising decision trees, tables and pre-calculations.

The shaded fields in the tables are part of the template and consequently not open for input.

• 1. References

Table A.1 — References (See Clause 2)

• 1. DWHRD product data

The default value of the balanced flow rate V′_dwhr;X when measuring η_dwhr;X shall be provided according to the format given in given in Table A.2.

Table A.2 — Default values of testing flow rates under balanced operation

Default values of the specific heat of the heat exchanger material c_dwhr;exc shall be provided according to the format given in Table A.3.

Table A.3 — Default specific heat of the heat exchanger material

For DWHR devices with an auxiliary pump, if not declared by the manufacturer, the default value of the fraction of time with the auxiliary on during showering k_dwhr;aux shall be provided according to the format given in Table A.4.

Table A.4 — Default value of the fraction of time with auxiliary on during showering

• 1. System design data

The default value of the volume of water in the shower and drain V_shw;drain shall be provided according to the format given in in Table A.5.

Table A.5 — Volume of water in the shower and drain V_shw;drain

The default value of the recoverable fraction of preheated water pipes losses k_pre;rbl shall be provided according to the format given in Table A.6.

Table A.6 — Recoverable fraction of preheated water pipes losses

• 1. Default operating conditions data

The default value of the fraction of domestic hot water needs related to showering k_W;nd;shw shall be provided according to the format given in Table A.7.

Table A.7 — Fraction of domestic hot water needs related to showering

The default relative weight of fixtures shall be provided according to the format given in Table A.8.

Table A.8 — Default values of fixture weighting parameters

The default values to define a shower event shall be provided according to the format given in Table A.9.

Table A.9 — Default operating conditions data for a shower event

• 1. Default calculation options

Default values of identifier DWHR_LS_RBL_CALC shall be provided according to the format given in Table A.10.

Table A.10 — Default operating conditions data

1. 
   (informative)
   
   Default values
   1. General

The template in Annex A shall be used to specify the choices between methods, the required input data and references to other documents.

NOTE 1 Following this template is not enough to guarantee consistency of data.

NOTE 2 Informative default choices are provided in Annex B. Alternative values and choices can be imposed by national/regional regulations.

If the default values and choices of Annex B are not adopted because of the national/regional regulations, policies or national traditions, it is expected that:

— national or regional authorities prepare data sheets containing the national or regional values and choices, in line with the template in Annex A; or

— by default, the national standards body will add or include a National Annex (Annex NA) to this document, in line with the template in Annex A, giving national or regional values and choices in accordance with their legal documents.

NOTE 3 The template in Annex A is applicable to different applications (e.g. the design of a new building, certification of a new building, renovation of an existing building and certification of an existing building) and for different types of buildings (e.g. small or simple buildings and large or complex buildings). A distinction in values and choices for different applications or building types could be made:

— by adding columns or rows (one for each application), if the template allows;

— by including more than one version of a Table (one for each application), numbered consecutively as a, b, c, … For example: Table NA.3a, Table NA.3b;

— by developing different national/regional data sheets for the same standard. In case of a national annex to the standard these will be consecutively numbered (Annex NA, Annex NB, Annex NC, …).

NOTE 4 In the section “Introduction” of a national/regional data sheet information can be added, for example about the applicable national/regional regulations.

NOTE 5 For certain input values to be acquired by the user, a data sheet following the template of Annex A, could contain a reference to national procedures for assessing the needed input data. For instance, reference to a national assessment protocol comprising decision trees, tables and pre-calculations.

The shaded fields in the tables are part of the template and consequently not open for input.

• 1. References

The references, identified by the module code number, are given in Table B.1.

Table B.1 — References (see Clause 2)

• 1. DWHRD product data

The default value of the balanced flow rate V′_dwhr;X when measuring η_dwhr;X are given in Table B.2.

Table B.2 — Default values of testing flow rates under balanced operation

Default values of the specific heat of the heat exchanger material c_dwhr;exc are given in the following Table B.3.

Table B.3 — Default specific heat of the heat exchanger material

For DWHR devices with an auxiliary pump, if not declared by the manufacturer, the default value of the fraction of time with the auxiliary on during showering k_dwhr;aux is given in Table B.4.

Table B.4 — Default value of the fraction of time with auxiliary on during showering

• 1. System design data

The default value of the volume of water in the shower and drain V_shw;drain is given in Table B.5.

Table B.5 — Volume of water in the shower and drain V_shw;drain

The default value of the recoverable fraction of preheated water pipes losses k_pre;rbl is given in Table B.6.

Table B.6 — Recoverable fraction of preheated water pipes losses

• 1. Default operating conditions data

The default value of the fraction of domestic hot water needs related to showering k_W;nd;shw is given in Table B.7.

Table B.7 — Fraction of domestic hot water needs related to showering

The default relative weight of fixtures is given in Table B.8.

Table B.8 — Default values of fixture weighting parameters

The default values to define a shower event are given in Table B.9.

Table B.9 — Default operating conditions data for a shower event

• 1. Default calculation options

Default values of identifier DWHR_LS_RBL_CALC are given in Table B.10.

Table B.10 — Default operating conditions data

1. 
   (informative)
   
   Calculation flow chart

This annex illustrates the calculation sequence of this procedure. The same headings of the sections are used in the accompanying spreadsheet.

Figure C.1

Bibliography

[1] CEN/TR XXXXX, Energy performance of buildings — Method for calculation of system energy requirements and system efficiencies — Explanation and justification of EN 15316-DWHR — Module M8-13

[2] CEN/TS 16628, Energy Performance of Buildings — Basic Principles for the set of EPB standards

[3] CEN/TS 16629, Energy Performance of Buildings — Detailed Technical Rules for the set of EPB-standards

[4] The potential of waste water heat recovery systems in reducing the energy demand for water heating in the EU in a cost-efficient way — University of Innsbruck — 2022

[5] The Government’s Standard Assessment Procedure for Energy Rating of Dwellings – SAP 10.2 – Version 10.2 – BRE — 2022

[6] NTA 8800:2024 — Energy performance of buildings — Determination method

[7] Arrêté du 4 août 2021 — Méthode de calcul Th-BCE 2020

[8] Shower drain heat recovery – an introduction – Rehva Journal 02/2023

[9] EN DWHRD, Product standard on DWHR currently under development under CLC TC59X WG4.1. Actual number and title will be added when they will be defined