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Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltrat

slide 2. Outline. The EU CENSE projectScope of the StandardPrinciple of the methodMechanical air flow calculationPassive and hybrid duct ventilationCombustion air flowAir flow due to windows openingExfiltration and infiltration . slide 3. The EU CENSE project (Oct. 2007 - March 2010). Aim

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Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltrat

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    1. Ventilation for buildings - Calculation methods for the determination of air flow rates in buildings including infiltration EN 15242 Hicham LAHMIDI CSTB / France hicham.lahmidi@cstb.fr Presentation of EN 15242 on calculation methods for the determination of air flow rates in buildings including infiltrationPresentation of EN 15242 on calculation methods for the determination of air flow rates in buildings including infiltration

    2. slide 2 Outline This is the outline of the presentation, which also includes a short description of the CENSE project This is the outline of the presentation, which also includes a short description of the CENSE project

    3. slide 3 The EU CENSE project (Oct. 2007 - March 2010) Aim of the project: To accelerate adoption and improved effectiveness of the EPBD related CEN- standards in the EU Member States These standards were successively published in the years 2007-2008 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 The CENSE project is active since 2007. All activities are related to the EPBD-related CEN-standards, where EN15242 is one of them The CENSE project is active since 2007. All activities are related to the EPBD-related CEN-standards, where EN15242 is one of them

    4. slide 4 Brief introduction A brief introduction to the CENSE project and the CEN-EPBD standards is provided in a separate presentation: Several documents are available from this project Several documents are available from this project

    5. slide 5 More information More information and downloads: www.iee-cense.eu Which you can easily access at the CENSE home page Which you can easily access at the CENSE home page

    6. slide 6 This standard describes the method to calculate ventilation airflows rates for buildings to be used in applications such as energy calculations, heat and cooling load calculations, summer comfort and indoor air quality evaluations. EN15242 defines the correct way to calculate airflows to be used in: Energy calculations Calculation of heating and cooling loads Calculation of indoor air quality Evaluation of summer comfort The input parameters and calculation method can be adjusted or complemented for these different applications. Clause 7 of the standard explains what must/can/should be taken into account for each application, and which method should be used in each case. 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.This standard describes the method to calculate ventilation airflows rates for buildings to be used in applications such as energy calculations, heat and cooling load calculations, summer comfort and indoor air quality evaluations. EN15242 defines the correct way to calculate airflows to be used in: Energy calculations Calculation of heating and cooling loads Calculation of indoor air quality Evaluation of summer comfort The input parameters and calculation method can be adjusted or complemented for these different applications. Clause 7 of the standard explains what must/can/should be taken into account for each application, and which method should be used in each case. 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.

    7. slide 7 Three methods are proposed in the standard: Direct method The calculation of mechanical airflows, combustion airflows and window opening airflows, are all based on systems characteristics, external conditions and design airflows. They do not depend on the internal pressure condition: the interaction between the ventilation systems and the leakages is neglected. For this reason, we can use a direct method to calculate infiltration and exfiltration airflows following § 6.7 of the present standard. Iterative method The iterative method is required when the interaction between the ventilation systems and the leakages can not be neglected. This method is therefore required when passive duct ventilation is used. Statistical analysis for energy calculation This method can be specified at the national level for energy calculations. The requirements for the methods are given in §7.2.3.3 of the present standard. Three methods are proposed in the standard: Direct method The calculation of mechanical airflows, combustion airflows and window opening airflows, are all based on systems characteristics, external conditions and design airflows. They do not depend on the internal pressure condition: the interaction between the ventilation systems and the leakages is neglected. For this reason, we can use a direct method to calculate infiltration and exfiltration airflows following § 6.7 of the present standard. Iterative method The iterative method is required when the interaction between the ventilation systems and the leakages can not be neglected. This method is therefore required when passive duct ventilation is used. Statistical analysis for energy calculation This method can be specified at the national level for energy calculations. The requirements for the methods are given in §7.2.3.3 of the present standard.

    8. slide 8 Mechanical air flow calculation The calculation is based on the required airflows, which are not part of the present standard (see EN 13779). The values are corrected to take into account: The position of the air handling unit (indoor or outdoor) The fact of the switching on-off The ventilation effectiveness, which is determined by the pollutant concentration in the extract air, and in the breathing zone The accuracy of the system design in relation to the component description. It expresses the fact that it is not possible to provide exactly the required amount of air when this value is required as a minimum The air flow through duct leakages The air leakages taking place in the air handling unit. These leakages can be neglected for indoor ducts and the AHU, if the AHU has been tested according to EN 1886 and the class obtained is at least L3. For outdoor ducts and the AHU, these leakages can be neglected provided they are constructed to comply For calculation, direct method shall be used. The calculation is based on the required airflows, which are not part of the present standard (see EN 13779). The values are corrected to take into account: The position of the air handling unit (indoor or outdoor) The fact of the switching on-off The ventilation effectiveness, which is determined by the pollutant concentration in the extract air, and in the breathing zone The accuracy of the system design in relation to the component description. It expresses the fact that it is not possible to provide exactly the required amount of air when this value is required as a minimum The air flow through duct leakages The air leakages taking place in the air handling unit. These leakages can be neglected for indoor ducts and the AHU, if the AHU has been tested according to EN 1886 and the class obtained is at least L3. For outdoor ducts and the AHU, these leakages can be neglected provided they are constructed to comply For calculation, direct method shall be used.

    9. slide 9 Passive and hybrid duct ventilation The aim of the calculation is to calculate the air flow in the system, taking into account outdoor and indoor conditions. The calculation is based on the characteristics of the cowl ( pressure loss coefficient and wind effect) determined in accordance with EN 13141-5. The method gives the relationship between the air velocity in the duct and the pressure loss through the cowl, which depends on the meteorological conditions prevailing (which are specified as input conditions). The method takes into account: The wind velocity outside the building The pressure loss coefficient of the cowl The roof angle and the position and height of the cowl The passive and hybrid flows are obtained only by iterative calculation.The aim of the calculation is to calculate the air flow in the system, taking into account outdoor and indoor conditions. The calculation is based on the characteristics of the cowl ( pressure loss coefficient and wind effect) determined in accordance with EN 13141-5. The method gives the relationship between the air velocity in the duct and the pressure loss through the cowl, which depends on the meteorological conditions prevailing (which are specified as input conditions). The method takes into account: The wind velocity outside the building The pressure loss coefficient of the cowl The roof angle and the position and height of the cowl The passive and hybrid flows are obtained only by iterative calculation.

    10. slide 10 Air flow due to opening windows The method takes into account : The surface of windows The wind turbulence The wind speed Stack effect The inside and outside temperature User behaviour The standard specifies: A method for calculating the air flow through open windows of a given aperture (including windows hinged at the lower edge) A method for calculating the required opening of a given window as a proportion of its total area Cross ventilation has to be taken into account, either with iterative method or directly as defined. The method must be defined at the national level. The method takes into account : The wind turbulence The wind speed Stack effect The inside and outside temperature User behaviour The airflows through open windows are obtained by using the direct calculation method (see : §6.5 of the present standard) The standard specifies: A method for calculating the air flow through open windows of a given aperture (including windows hinged at the lower edge) A method for calculating the required opening of a given window as a proportion of its total area Cross ventilation has to be taken into account, either with iterative method or directly as defined. The method must be defined at the national level. The method takes into account : The wind turbulence The wind speed Stack effect The inside and outside temperature User behaviour The airflows through open windows are obtained by using the direct calculation method (see : §6.5 of the present standard)

    11. slide 11 Combustion air flow The standard provides a method to calculate the additional air flow for combustion The device factor The power heat The fuel flow factor The standard gives a direct method to calculate the additional air flow for combustion taking into account : The appliance system factor (the calculation method is given in the standard) The appliance heating fuel input power The fuel flow factor The combustion airflows are given by a direct method (see §6.4 of the present standard). The standard gives a direct method to calculate the additional air flow for combustion taking into account : The appliance system factor (the calculation method is given in the standard) The appliance heating fuel input power The fuel flow factor The combustion airflows are given by a direct method (see §6.4 of the present standard).

    12. slide 12 Exfiltration and infiltration Two methods are available to calculate the air leakages through external envelope components : An iterative method A direct method if there is no passive duct system Iterative method This method is based on the calculation of the indoor reference pressure. The calculation requires the values of all the air flows which depends on the reference pressure. Hence an iterative method is needed to solve the implicit problem. Direct method In this simplified approach, does not take into account directly (an estimation is given by the standard) the positive or negative pressure in the building due to the differences between supply and exhaust. The standard gives two methods to calculate the leakage through external envelope components: An iterative method This method is based on the calculation of an indoor reference pressure. The calculation requires the values of all the airs flow presented above to be known, and as they depend on the reference pressure, an iterative method is needed to solve the problem. A direct method if there is no passive duct system This simplified approach does not take into account the overpressure or under pressure due to the difference between supply and exhaust airflows. Instead, an estimate is supplied in the standard. The standard gives two methods to calculate the leakage through external envelope components: An iterative method This method is based on the calculation of an indoor reference pressure. The calculation requires the values of all the airs flow presented above to be known, and as they depend on the reference pressure, an iterative method is needed to solve the problem. A direct method if there is no passive duct system This simplified approach does not take into account the overpressure or under pressure due to the difference between supply and exhaust airflows. Instead, an estimate is supplied in the standard.

    13. slide 13 Application The standard provides some examples to calculate : Energy calculations Heating and cooling load Summer comfort Indoor air quality The standard provides some examples of applications in clause 7. These examples cover : Energy calculations (the standard gives some default values) Heating load Cooling load Summer comfort calculation Indoor air quality The standard provides some examples of applications in clause 7. These examples cover : Energy calculations (the standard gives some default values) Heating load Cooling load Summer comfort calculation Indoor air quality

    14. slide 14 French case : illustration of implementation To illustrate the implementation of EN 15241 and EN 15242 this French example is provided. It corresponds to a typical low energy small dwelling. To illustrate the implementation of EN 15241 and EN 15242 this French example is provided. It corresponds to a typical low energy small dwelling.

    15. slide 15 Results obtained with Natural supply and Balanced ventilation systems are presented above. Effect of exfiltration is more important with DF and in presense of the wind.Results obtained with Natural supply and Balanced ventilation systems are presented above. Effect of exfiltration is more important with DF and in presense of the wind.

    16. slide 16 The same example is used to present the implementation of the standard on French regulation. As DF containts 2 fans, consumption of fans with DF is higher than with SF. The same example is used to present the implementation of the standard on French regulation. As DF containts 2 fans, consumption of fans with DF is higher than with SF.

    17. slide 17 More information More information and downloads: www.iee-cense.eu More information and downloads are available on www.iee-cense.eu More information and downloads are available on www.iee-cense.eu

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