Indoor environmental quality assessment in passively ventilated classrooms in Germany and estimation of ventilation energy losses

In this field study we present an approach for the comprehensive and room-specific assessment of parameters with the overall aim to realize energy-efficient provision of hygienically harmless and thermally comfortable indoor environmental quality in naturally ventilated non-residential buildings. The approach is based on (i) conformity assessment of room design parameters, (ii) empirical determination of theoretically expected occupant-specific supply air flow rates and corresponding air exchange rates, (iii) experimental determination of real occupant-specific supply air flow rates and corresponding air exchange rates, (iv) measurement of indoor environmental exposure conditions of T , R H , c CO 2 , c PM 2.5 and c TVOC , and (v) determination of real energy demands for the prevailing ventilation scheme. Underlying assessment criteria comprise the indoor environmental parameters of category II of EN 16798-1: Temperature T = 20 °C–24 °C, and relative humidity RH = 25 %–60 % as well as the guide values of the German Federal Environment Agency for c CO 2 c PM 2.5 and c TVOC of 1000 ppm, 15 μg m −3 , and 1 mg m −3 , respectively. Investigation objects are six naturally ventilated classrooms of a German secondary school. Major factors influencing indoor environmental quality in these classrooms are the specific room volume per occupant and the window opening area. It is concluded that the rigorous implementation of ventilation recommendations laid down by the German Federal Environment Agency is ineffective with respect to anticipated indoor environmental parameters and inefficient with respect to ventilation energy losses on the order of about 10 kWh m −2 a −1 to 30 kWh m −2 a −1 . •IEQ and passive ventilation energy losses were assessed in a German school. •One-sided continuous ventilation and intermittent cross ventilation were analyzed. •Passive classroom ventilation is ineffective to meet minimum IEQ targets. •Area-specific ventilation energy losses of about 10 kWh m −2 a −1 to 30 kWh m −2 a −1 .