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News
April 22, 2014

Overview of EN 15251: Part 1 – Addressing indoor air quality, thermal environment, lighting and acoustic

On 26th of March in 2014 I have connected online to participate in a web seminar on “CEN standards for the energy performance of buildings: Results and revision overviews”. The web seminar (or webinar) focused on Pan European target group of local / regional / national authorities and facilitators, and building professionals.

I, as engineer / researcher, was very interested in a presentation by Bjarne Olesen, Member of the CEN Task Leaders Team, DTU (Denmark). The presentation topic was „Status of EN15251 Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics“.

Bjarne started his presentation in splitting building costs in four main parts where the major weight is put in peoples´ comfort-productivity, and then ten-timeless weight is put in maintenance and financing, and finally the energy weight is only 1/100 compared to peoples´ weight.

“Buildings are for people and not really for saving energy”.

The existing international standards dealing with indoor environmental parameters are:

  • ISO EN 7730-2005: Ergonomics of the thermal environment – Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort effects
  • ASHRAE 55-2004: Thermal environment conditions for human occupancy
  • ASHRAE 62.1 and 62.2-2004: Ventilation and indoor air quality
  • EN 15251: Indoor environmental input parameters for design and assessment of energy performance of buildings – addressing indoor air quality, thermal environment, lighting and acoustic
  • EN 13779: Ventilation for non-residential buildings – performance requirements for ventilation and room-conditioning systems

The new EN 15251 standard will be rewritten to include normative text and accompanied by a technical report (TR15251) and a new series of standardizes occupant schedules will be used in energy calculations.

Indoor environmental criteria are based on different categories from I to IV, i.e. category I: high level of expectation for spaces occupied by very sensitive persons, category II: normal level of expectation to be used in new buildings and renovation, category III: acceptable level of expectation to be used in existing buildings, and category IV: values outside the criteria for the above categories to be used only for a limited part of the year.

The conditions in moderate environments can be defined by general thermal comfort parameters (predicted mean vote – PMV, predicted percentage dissatisfied – PPD, operative temperature) and local thermal discomfort parameters (radiant temperature asymmetry, draught, vertical air temperature difference, floor surface temperature). Recommended categories for design of mechanical heated and cooled buildings are split in three categories where for category I: PPD < 6% (-0.2 < PMV < +0.2), category II: PPD < 10% (-0.5 < PMV < +0.5), and category III: PPD < 15% (-0.7 < PMV < +0.7).

“For the PPD / PMV it is normally recommended to use category II.”

The operative temperature ranges for hourly energy calculation of cooling and heating energy are split in three categories for indoor environment for offices, open plan offices, conference rooms, auditorium, cafeteria, restaurant, class rooms (with sedentary activity ~1,2 met). The heating for winter season is set for clo of ~1,0 and cooling for summer season is set for clo of ~0,5. The category I: heating ranges 21,0-23,0°C and cooling 23,5-25,5°C, category II: heating ranges 20,0-24,0°C and cooling 23,0-26,0°C, and category III: heating ranges 19,0-25,0°C and cooling 22,0-27,0°C.

“In most typical spaces, set point for temperature for heating is close to 20°C and for cooling not above 26°C, i.e. category II.”

And I must say that I was not disappointed in Bjarne´s excellent overview of existing standards dealing with indoor environmental parameters.