SIST EN 15242:2007
(Main)Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltration
Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltration
This European standard describe the method to calculate the ventilation air flow rates for buildings to be used for applications such as energy calculations, heat and cooling load calculation, summer comfort and indoor air quality evaluation.
The ventilation and air tightness requirements (as IAQ, heating and cooling, safety, fire protection…) are not part of the standard.
For these different applications, the same iterative method is used but the input parameter has to be selected according to the field of application. For specific applications a direct calculation is also defined in this standard. A simplified approach is also allowed at national level following prescribed rules of implementation.
The method is meant to be applied to :
- Mechanically ventilated building (mechanical exhaust, mechanical supply or balanced system).
- Passive ducts.
- Hybrid system switching between mechanical and natural modes.
- Windows opening by manual operation for airing or summer comfort issues.
Automatic windows (or openings) are not directly considered here.
Industry process ventilation is out of the scope.
Kitchen where cooking is for immediate use are part of the standards (including restaurants..)
Other Kitchens are not part of the standard
The standard is not directly applicable for buildings higher than 100m and rooms where vertical air temperature difference is higher than 15K
The results provided by the standard are the building envelope flows either through leakages or purpose provided openings and the air flows due to the ventilation system, taking into account the product and system characteristics.
Lüftung von Gebäuden - Berechnungsverfahren zur Bestimmung der Luftvolumenströme in Gebäuden einschließlich Infiltration
Diese Europäische Norm beschreibt das Verfahren zur Berechnung der durch die Lüftung verursachten
Luftvolumenströme in Gebäuden, die für Anwendungen wie z. B. Energieberechnungen, Heiz- und Kühllast¬berechnungen und Bewertungen der sommerlichen Behaglichkeit und der Raumluftqualität verwendet werden.
Die Lüftungs- und Luftdichtheitsanforderungen (wie z. B. Raumluftqualität, Heizung und Kühlung, Sicherheit, Brandschutz usw.) sind nicht Gegenstand dieser Norm.
Für diese unterschiedlichen Anwendungen wird dasselbe implizite Verfahren angewendet, jedoch müssen die Eingangsparameter dem Anwendungsbereich entsprechend gewählt werden. Für bestimmte Anwendungen sind in dieser Norm auch explizite Berechnungen festgelegt. Ein vereinfachter Ansatz ist auf nationaler Ebene zulässig, sofern die Vorschriften zu dessen Anwendung eingehalten werden.
Das Verfahren ist vorgesehen für die Anwendung auf:
- Gebäude mit ventilatorgestützter Lüftung (ventilatorgestützte Abluft , Zuluft oder kombinierte Ab und Zuluftsysteme);
- Luftleitungen;
- Hybridsysteme, bei denen zwischen ventilatorgestützter und freier Lüftung umgeschaltet werden kann;
- das manuelle Fensteröffnen zur Lüftung oder zur Verbesserung des Sommerkomforts.
Automatische Fenster (oder Öffnungen) sind hier nicht direkt berücksichtigt.
Die Lüftung von industriellen Betriebsabläufen fällt nicht in den Anwendungsbereich dieser Norm.
Küchen, in denen zum unmittelbaren Verzehr gekocht wird (einschließlich Restaurants usw.), sind Gegenstand der Norm.
Andere Küchen sind nicht Gegenstand dieser Norm.
Diese Norm gilt nicht direkt anwendbar auf Gebäude, die höher sind als 100 m und Räume, bei denen die vertikale Lufttemperaturdifferenz mehr als 15 K beträgt.
Ventilation des bâtiments - Méthodes de calcul pour la détermination des débits d'air y compris les infiltrations dans les bâtiments
Prezračevanje stavb - Računske metode za določitev zračnih tokov v stavbah, vključno z infiltracijo
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltrationVentilation des bâtiments - Méthodes de calcul pour la détermination des débits d'air y compris les infiltrations dans les bâtimentsLüftung von Gebäuden - Berechnungsverfahren zur Bestimmung der Luftvolumenströme in Gebäuden einschließlich InfiltrationTa slovenski standard je istoveten z:EN 15242:2007SIST EN 15242:2007en91.140.30VLVWHPLVentilation and air-conditioningICS:SLOVENSKI
STANDARDSIST EN 15242:200701-november-2007
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 15242May 2007ICS 91.140.30 English VersionVentilation for buildings - Calculation methods for thedetermination of air flow rates in buildings including infiltrationVentilation des bâtiments - Méthodes de calcul pour ladétermination des débits d'air y compris les infiltrationsdans les bâtimentsLüftung von Gebäuden - Berechnungsverfahren zurBestimmung der Luftvolumenströme in Gebäudeneinschließlich InfiltrationThis European Standard was approved by CEN on 26 March 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 15242:2007: E
EN 15242:2007 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.6 2 Normative references.6 3 Terms and definitions.7 4 Symbols and abbreviations.9 5 General approach.10 6 Instantaneous calculation (iterative method).12 6.1 Basis of the calculation method.12 6.2 Mechanical air flow calculation.13 6.3 Passive and hybrid duct ventilation.17 6.4 Combustion air flows.23 6.5 Air flow due to windows opening.25 6.6 Exfiltration and infiltration using iterative method.27 6.7 Exflitration and infiltration calculation using direct method.28 7 Applications.30 7.1 General.30 7.2 Energy.30 7.3 Heating load.35 7.4 Cooling loads.35 7.5 Summer comfort.35 7.6 Indoor air quality.36 Annex A (normative)
Data on wind pressure coefficients.37 Annex B (normative)
Leakages characteristics.43 Annex C (normative)
Calculation of recirculation coefficient Crec.46 Annex D (normative)
Conversion formulas.48 Annex E (informative)
Examples of fuel flow factor for residential buildings.51 Bibliography.52
EN 15242:2007 (E) 3 Foreword This document (EN 15242:2007) has been prepared by Technical Committee CEN/TC 156 “Ventilation for buildings”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2007, and conflicting national standards shall be withdrawn at the latest by November 2007. This standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association (Mandate M/343), and supports essential requirements of EU Directive 2002/91/EC on the energy performance of buildings (EPBD). It forms part of a series of standards aimed at European harmonisation of the methodology for the calculation of the energy performance of buildings. An overview of the whole set of standards is given in CEN/TR 15615, Explanation of the general relationship between various CEN standards and the Energy Performance of Buildings Directive (EPBD) ("Umbrella document"). Attention is drawn to the need for observance of relevant EU Directives transposed into national legal requirements.
Existing national regulations with or without reference to national standards, may restrict for the time being the implementation of the European Standards mentioned in this report. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EN 15242:2007 (E) 4 Introduction This standard defines the way to calculate the airflows due to the ventilation system and infiltration. The relationships with some other standards are as follows:
Figure 1 — scheme of relationship between standards Table 1 — Relationship between standards from To
Information transferred variables 15251 15243 Indoor climate requirements
Heating and cooling Set points
13779 15251 15242 Airflow requirement for comfort and health Required supply and exhaust Air flows 15242 15241 Air flows Air flows entering and leaving the building 15241 13792 Air flows Air flow for summer comfort calculation 15241 15203- 15315 ;15217 energy Energies per energy carrier for ventilation (fans, humidifying, precooling, pre heating), + heating and cooling for air systems 15241 13790 data for heating and cooling calculation Temperatures, humilities and flows of air entering the building
EN 15242:2007 (E) 5 15243 15243 Data for air systems Required energies for heating and cooling
15243 15242 Data for air heating and cooling systems Required airflows when of use 15243 13790 data for building heating and cooling calculation Set point, emission efficiency, distribution recoverable losses, generation recoverable losses 13790 15243 Data for system calculation Required energy for generation EN titles are: prEN 15217 Energy performance of buildings — Methods for expressing energy performance and for energy certification of buildings prEN 15603 Energy performance of buildings - Overall energy use and definition of energy ratings prEN 15243 Ventilation for buildings — Calculation of room temperatures and of load and energy for buildings with room conditioning systems prEN ISO 13790 Thermal performance of buildings — Calculation of energy use for space heating and cooling (ISO/DIS 13790:2005) EN 15242 Ventilation for buildings — Calculation methods for the determination of air flow rates in buildings including infiltration EN 15241 Ventilation for buildings — Calculation methods for energy losses due to ventilation and infiltration in commercial buildings EN 13779 Ventilation for non-residential buildings — Performance requirements for ventilation and room-conditioning systems EN 13792 Colour coding of taps and valves for use in laboratories EN 15251 Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics
The calculation of the airflows through the building envelope and the ventilation system for a given situation is first described (Clause 6). Applications depending on the intended uses are described in Clause 7. The target audience of this standard is policy makers in the building regulation sector, software developers of building simulation tools, industrial and engineering companies.
EN 15242:2007 (E) 6 1 Scope This European Standard describes the method to calculate the ventilation air flow rates for buildings to be used for applications such as energy calculations, heat and cooling load calculation, summer comfort and indoor air quality evaluation. The ventilation and air tightness requirements (as IAQ, heating and cooling, safety, fire protection…) are not part of the standard. For these different applications, the same iterative method is used but the input parameter should be selected according to the field of application. For specific applications a direct calculation is also defined in this standard. A simplified approach is also allowed at national level following prescribed rules of implementation. The method is meant to be applied to:
Mechanically ventilated building (mechanical exhaust, mechanical supply or balanced system).
Passive ducts. Hybrid system switching between mechanical and natural modes. Windows opening by manual operation for airing or summer comfort issues. Automatic windows (or openings) are not directly considered here. Industry process ventilation is out of the scope.
Kitchens where cooking is for immediate use are part of the standards (including restaurants.) Other kitchens are not part of the standard. The standard is not directly applicable for buildings higher than 100 m and rooms where vertical air temperature difference is higher than 15K.
The results provided by the standard are the building envelope flows either through leakages or purpose provided openings and the air flows due to the ventilation system, taking into account the product and system characteristics. 2 Normative references The following referenced documents are indispensable for the application 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. EN 1507, Ventilation for buildings — Sheet metal air ducts with rectangular section — Requirements for strength and leakage EN 1886, Ventilation for buildings — Air handling units — Mechanical performance EN 12237, Ventilation for buildings — Ductwork — Strength and leakage of circular sheet metal ducts EN 12792:2003, Ventilation for buildings — Symbols, terminology and graphical symbols
EN 15242:2007 (E) 7 EN 13141-5, Ventilation for buildings — Performance testing of components/products for residential ventilation — Part 5: Cowls and roof outlet terminal devices EN 13779, Ventilation for non-residential buildings — Performance requirements for ventilation and room-conditioning systems EN 14239, Ventilation for buildings — Ductwork — Measurement of ductwork surface area EN 15251, Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics prEN 15255, Thermal performance of buildings — Sensible room cooling load calculation — General criteria and validation procedures 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12792:2003 and the following apply. 3.1 building height height of the building from the entrance ground level to the roof top level 3.2 vertical duct duct or shaft, including flue or chimney, which is mainly vertical and not closed 3.3 building envelope leakage overall leakage airflow for a given test pressure difference across building 3.4 building volume volume within internal outdoor walls of the purposely conditioned space of the building (or part of the building) NOTE This generally includes neither the attic, nor the basement, nor any additional structural annex of the building. 3.5 building air temperature average air temperature of the rooms in the occupied zone 3.6 iterative method calculation method that requires a mathematical solver to solve an equation by iteration 3.7 direct method calculation method that can be applied manually 3.8 vent (or opening) opening intended to act as an air transfer device 3.9 reference wind speed at site wind speed at site, at a height of 10 m, in undisturbed shielding conditions
EN 15242:2007 (E) 8 NOTE 1 Shielding is accounted for in the wind pressure coefficients. NOTE 2 In some countries, the reference wind speed is taken as equal to the meteo data available for the site. If not, an appropriate method to extrapolate from the meteo wind speed to the reference wind speed at site should be used (see Annex A).
3.10 shielding effect classified according to the relative height, width and distance of relevant obstacle(s) in relation to the building
3.11 natural duct ventilation system ventilation system where the air is moved by natural forces into the building through leakages (infiltration) and openings (ventilation), and leaves the building through leakages, openings, cowls or roof outlets including vertical ducts used for extraction 3.12 mechanical ventilation system ventilation system where the air is supplied or extracted from the building or both by a fan and using exhaust air terminal devices, ducts and roof /wall outlets NOTE In single exhaust mechanical systems, the air have entered the dwelling through externally mounted air transfer devices, windows and leakages 3.13 airing natural air change by window opening NOTE In this standard, only single sided ventilation effects are considered which means that the ventilation effect due to this window opening is considered to be independent of other open windows or additional ventilation system flows. 3.14 ventilation effectiveness relation between the pollution concentrations in the supply air, the extract air and the indoor air in the breathing zone (within the occupied zone). It is defined as SUPIDASUPETAvcccc−−=ε
where: εv
is the ventilation effectiveness
cETA
is the pollution concentration in the extract air
cIDA is the pollution concentration in the indoor air (breathing zone within the occupied zone)
cSUP
is the pollution concentration in the supply air NOTE 1 The ventilation effectiveness depends on the air distribution and the kind and location of the air pollution sources in the space. It may therefore have different values for different pollutants. If there is complete mixing of air and pollutants, the ventilation effectiveness is one. NOTE 2 Another term frequently used for the same concept is “contaminant removal effectiveness”. 3.15 hybrid ventilation hybrid ventilation switches from natural mode to mechanical mode depending on its control
EN 15242:2007 (E) 9
4 Symbols and abbreviations Symbol Unit descriptionA m² area Asf ad Airtightness split factor (default value or actual) Cductleak ad Coefficient taking into account lost air due to duct leakages Cp ad wind pressure coefficient Crec ad Recirculation coefficient Csyst ad coefficient taking into account the component and system design tolerances Cuse ad Coefficient taking into account the switching on and off of fans Ccont ad coefficient depending on local air flow control irp Pa Internal reference pressure in the zone Osf
Opening split factor (default value or actual) qv(dP) curve or formulaairflow/pressure difference characteristic qv (dP) curve or formula partial air openings for altitude (z), orientation (or), tilt angle (Tilt) qv 4Pa,n or n50,n
L/s or m3/h external envelope airtightness expressed as an airflow for a given pressure difference, exponentqv 4Pa,n or n50,n L/s or m3/h partial air tightnesss for altitude (z), orientation (or), tilt angle (Tilt) qv-exh L/s or m3/hexhaust air flow according to EN 13779 (not extract) qv-exh -req L/s or m3/hrequired exhaust air flow
qv-sup L/s or m3/hSupply air flow Qv-sup-req L/s or m3/hrequired outdoor air flow θe °C external (outdoor) temperature θi °C internal (indoor) temperature ρair
kg/m3 Air volumetric mass
ρair ref kg/m3 Air volumetric mass at reference temperature T K Absolute temperature vmeteo m/s wind as defined by meteo at 10 m height vsite m/s wind at the building zo m depends on terrain class
EN 15242:2007 (E) 10 Indices used in the documents Index Explanation Index Explanation sup Concerns supply air as defined in EN 13779 comb Concerns combustion exh Concerns exhaust air as defined in EN 13779 comp Concerns each component req “required” : values required to be achieved inlet Concerns each air inlet leak Values of the variable for leakages passiveduct Concerns passive duct outdoorleak Values of the variable for outdoor leakages airing Concerns airing through windows AHUleak Values of the variable for leakages in the Air Handling Unit (AHU) stack Concerns stack effect ductleak Values of the variable for leakages in ductwork duct Values of the variable for the duct inf Concerns infiltrations wind Values of the variable due to winddiff Difference between supply and exhaust sw Stack and wind infred Infiltration reduction
5 General approach The air flows are calculated for a building, or a zone in a building. A building can be separated in different zones if: The different zones are related to different ventilation systems (e.g. one ventilation system is not connected to different zones). The zones can be considered as air flow independent (e.g. the air leakages between two adjacent zones are sufficiently low to be neglected, and there is no possibility of air transfer between two zones). The most physical way to do the calculation is to consider the air mass (dry air) flow rate balance. Nevertheless it is also allowed to consider the volume flow rate balance when possible.
Cases where using the mass flow rate is mandatory are: air heating systems, air conditioning systems. The formulas in Clause 6 and 7 are given for volume flow rates. The input data are the ventilation system air flows and the airflows vs pressure characteristics of openings (vents) and leakages.
EN 15242:2007 (E) 11 The output data are the airflows entering and leaving the building through Leakages, Openings (vents…), Windows opening if taken into account separately, Ventilation system, including duct leakages.
Air entering the building/zone is counted positive (air leaving is counted negative). The general scheme is shown in Figure 2: 23415 Key 1
ventilation 4
leakage 2
window opening 5
internal reference pressure 3
opening
Figure 2 — General scheme of a building showing the different flows involved The resolution scheme is as follows: 1. Establish the formulas giving the different air flows for a given internal reference pressure 2. Calculate the internal reference pressure irp balancing air flows in and air flow out 3. Calculate the air flows for this internal reference pressure The internal partition of a building is based in general on the following:
i) divide the building between zones
EN 15242:2007 (E) 12
Different zones are considered as having no, or negligible air flow between them ii) Describe each zone as sub zones connected to a common connection sub zone (in general it will be the circulations and hall spaces) if necessary (a zone can be also only one room) The general scheme (called afterwards the n+1 approach) is shown in Figure 3.
1 Key 1 map Figure 3 — General scheme for air flow pattern description
This scheme is a simplification of the more general one taking into account all possible connections. It can be furthermore simplified depending on the application (see application clauses). 6 Instantaneous calculation (iterative method) 6.1 Basis of the calculation method An iterative method is used to calculate the air handling unit air flow, and air flow through envelope leakages and openings for a given situation of: Outdoor climate (wind and temperature), Indoor climate (temperature), System running. This clause explains the different steps of calculation. 1. Calculation of mechanical ventilation
EN 15242:2007 (E) 13 2. passive duct for residential and low size non-residential buildings
3. Calculation of infiltration/exfiltration 4. combustion air flow fire places both for residential and non residential if necessary. Combined exhaust for ventilation and heating appliance ? Laundry
5. Calculation of additional flow for window openings 6. Overall airflow 6.2 Mechanical air flow calculation 6.2.1 Introduction The ventilation is based on required air flow (either supplied or extract in each room) which is defined at national level, assuming in general perfect mixing of the air. To pass from these values to the central fan, the following coefficients (and impacts) shall be taken into account: 1) Cuse: coefficient corresponding to switching on (Cuse=1) or off (Cuse=0) the fan
2) 0v: local ventilation efficiency
3) Ccont: coefficient depending on local air flow control 4) Csyst: coefficient depending on inaccuracies of the components and system (adjustment…etc) 5) Cleak: due to duct and AHU leakages 6) Crec: recirculation coefficient, mainly for VAV system 6.2.2 Required air flow qv-sup-req and qv-exh -req For each room, qv -sup-req and qv-exh -req are respectively the air flow to be provided or exhausted according to the building design, and national regulations. 6.2.3 Cuse coefficient This coefficient simply describes the fact of switching on-off the fan (or eventually different level from design one).
It is related to health and energy issues, and to the building or room occupation and occupant behaviour. For health issues, and for building where ventilation can be stopped or reduced during unoccupied periods, it is recommended (and can be mandatory at national level), to start the ventilation before the start of the occupancy period in order to purge the building, and to keep it for some time and the beginning of the unoccupied period. For energy issues, it can be useful to keep the ventilation during unoccupied period (night cooling) if it is energy efficient.
6.2.4 Ventilation effectiveness 0v
It is related to the concentration in the extract air, and the one in the breathing zone.
For efficient system 0v can be higher than 1. In case of short circuit system 0v can be lower than 1.
EN 15242:2007 (E) 14 The default value for 0v is 1 corresponding to a perfect mixing. 6.2.5 Local air flow control Coefficient Ccont For system with variable air flow, (demand controlled ventilation, VAV systems), the Ccont coefficient is the ratio for a given period of the actual air flow divided by the qv -sup-req or qv-exh -req values when this last one are defined as design values.
The Ccont coefficient has to be calculated according to the control system efficiency and can be related to the overall room energy balance.
NOTE It could possibly vary with month, external conditions etc. 6.2.6 Csyst coefficient The Csyst coefficient ( ≥ 1 ) takes into account the accuracy of the system design in relationship with the component description. It expresses the fact that it is not possible to provide the exact required amount of air when this value is required as a minimum. 6.2.7 Duct leakagecoefficient Cductleak The air flow through the duct leakage is calculated 3600.65,0ductductvductleakdPKAq= qvductleak
(m3/h)
:
air through the duct leakages Aduct :
duct area in m2. Duct area shall be calculated according to EN 14239.
dPduct :
pressure difference between duct and ambient air in Pa – unless otherwise
specified, this is: In supply air ductwork:
the average between the pressure difference at the AHU outlet and the pressure difference right upstream of the air terminal device. In extract air ductwork:
the average between the pressure difference right downstream of the air terminal device and the pressure difference at the AHU inlet
K
airtightness of duct in m3/(s.m2) for 1 Pa – the duct leakage shall be determined according
to EN 12237 (circular ducts), EN 1507 (rectangular ducts)
The Cductleak coefficient is therefore calculated by vsystcontvreqvductleakductleakCCqqCε+=1 This equation can be applied either with qv-req equal to qv -sup-req or to qv -exh-req
EN 15242:2007 (E) 15 6.2.8 AHU leakage coefficient CAHUleak This coefficient corresponds to the impact of the air leakages of the Air handling unit.
vsystcontvreqvAHUleakAHUleakCCqqCε+=1 With
qv-AHUleak: airflow lost by the AHU determined according to EN 1886. 6.2.9 Indoor and outdoor leakage Coefficient If the AHU is situated indoor Cindoor leak = Cduct leak
CAHUleak Coutdoorleak = 1 If the AHU is situated outdoor
Cindoorleak = 1 + Rindoorduct (1- Cduct leak)
Coutdoorleak = 1 + (1- Cductleak )(1 – Rindorrduct)
CAHUleak With Rindoorduct = Aindoor duct / Aduct Aindoor duct = area of duct situated indoor
NOTE In dimensioning of fans and calculating the air flows through the fans, the air leakages of ducts and air handling units (sections downstream of supply air fans and upstream of the exhaust air fans in the AHU) should be added to the sum of air flows into/from the rooms. This because these leakages do not serve the ventilation needed for the targeted indoor air quality.
6.2.10 Recirculation Coefficient Crec The recirculation coefficient (≥ 1) is used mainly for VAV system with recirculation. It takes into account the need to supply more outdoor air than required. Annex C provides a calculation method for it. 6.2.11 Mechanical air flow to the zone qv supply qv extra The mechanical air flows supplied to or exhausted from the zone are calculated by
vrecindoorleakcontreqvvCCCqqε.supsup= vrecindoorleakcontvexhreqvexhCCCqqε.=
EN 15242:2007 (E) 16 6.2.12 Mechanical air flow to the AHU The mechanical air flows supplied to or exhausted from the Air handling unit are calculated by
vrecleakcontreqvAHUvCCCqqε.supsup= vrecleakcontvexhreqvexhAHUCCCqqε.=
with Cleak = Cindoorleak+Coutdoor leak Two situations are taken into account depending on the position of the air handling unit in or out the heated/air conditioned area. For the ventilation calculation, it impacts only on the duct leakage effect but afterwards; it will have to be considered for heat losses. The different air flows to the AHU are shown in Figure 4. Case 2 corresponds to the situation when the AHU is in the conditioned area, case 1 when it is out of the conditioned area. This has to be taken into account for the whole calculation process.
EN 15242:2007 (E) 17
3415226
Key 1
duct leakages 4
duct system 2
fan 5
building or zone case 1 3
ventilation plant 6
building or zone case 2
Figure 4 — Air flows to the Air Handling Unit 6.3 Passive and hybrid duct ventilation 6.3.1 General A ducted natural ventilation system is composed of 1. Air inlets,
2. Cowl, 3. Duct, 4. Air outlets The aim of the calculation is to calculate the air flow in the system taking into account outdoor and indoor conditions.
EN 15242:2007 (E) 18 Hybrid ventilation switches from natural mode t
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.