Study On Experimental Method Of Natural Ventilation In Residential Buildings

Indoor environment plays a huge part of our lives, and focus on a good and healthyindoor environment should be prioritized. However, the tightening of buildingenvelopes has caused another increasing problem, which is the need for moreventilation. Due to this, new laws and standards and ventilation measurementtechniques are needed to evaluate indoor environments.The study is based on experimental measurements in laboratory and residentialbuildings for single-zones. For the development of a new method, the following stepswere taken: literature review, study on existing methods and their advantages andlimitations, assumptions and requirements for different approaches, influence of mixingfans, development of a new constant injection method, validation in laboratory andtesting the method applicability in real-time situations, comparing the tracer gas methodwith ventilation models.Experiments showed that fan mixing is obligatory in ventilation measurements insingle-sided ventilation, else incomplete mixing of the tracer gas will bias the ACHmeasurements. A new method to measure air change rates using CO2as the tracer gaswas also put forward. This method uses dry ice to release a constant rate of CO2as atracer gas for the air change rate measurements and is suitable for both natural andmechanically ventilated rooms and can be used with or without people present.Full-scale experiments were also conducted, improving ventilation rate measurementmethods in residential buildings. It was further investigated that the buoyancy plays animportant role in the concentration uniformity. The concentration measured in the roomclosest to the opening was the lowest, if no mixing fan was used. It was also found thatonce the indoor and outdoor temperature difference exceeded3°C, huge impact on theuniformity would occur. A ventilation model proposed by Larsen, which adds theinfluence from several parameters, eg. window size, temperature difference, wind speedand wind direction, etc., was also compared with the dry ice method, with over100hours worth of data for the comparison.