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Overview of EN 15251: Part 2 – Design airflow rates, emissions pollutions and residential buildings
April 29, 2014

Overview of EN 15251: Part 2 – Design airflow rates, emissions pollutions and residential buildings

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 presentation by Bjarne Olesen, Member of the CEN Task Leaders Team, DTU (Denmark) on 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” was excellent overview of existing parameters and overview.

The required ventilation rates for diluting emissions (bio effluents) from people for different categories are for category I: 10 l/s/person with expected percentage dissatisfied 15%, category II: 7 l/s/person with expected percentage dissatisfied 20%, category III: 4 l/s/person with expected percentage dissatisfied 30%, and category IV: 4 l/s/person with expected percentage dissatisfied above 30%.

“Studies have shown that minimum basic required ventilation rates need to be 4 l/s/person.”

In EN 15251 the required airflow for basic ventilation are divided in three types of buildings such as very low polluting building, low polluting buildings and non low polluting building. This basic ventilation for building emissions pollutions is established to give those who produce low emission polluting materials some benefit.

20140331 Airflow for pollutions

“When can you say that you have low and very low polluting material?”

The answer lies in using another table from EN 15251 which states what are the values for VOCs, TVOC, formaldehyde and any C1A and C1B classified carcinogenic VOC.

20140331 Polluting materials

Above mentioned parameters helps you to establish the total ventilation rate which is the sum of number of persons in a room multiplied by ventilation rate for occupancy per person (l/s/person) and room floor area (m2) and ventilation rate for emissions from buildings (l/s/m2). There is also a need to calculate ventilation rate supplied by the ventilation system which is the ratio of total ventilation rate for the breathing zone (l/s) to the ventilation effectiveness (based on EN 13779).

“Nowadays we calculate the total ventilation rate, and also include system independent criteria versus system dependent criteria.“

Comparison of standards is shown in the following table.

20140331 Comparison of standards

“Red marked area shows the comparison of the most used category in ventilation rates in a building.”

Requirements for residential buildings for various categories including air change rate, supply and exhaust air flow.

20140331 Residential buildings

Bjarne finished his presentation with mentioning alternative methods for ventilation which are still being discussed. The alternative methods are dealing with un-clarity of residential ventilation, how to take into account demand controlled ventilation and ventilation based on maximum of people or building components.