mechanical ventilation

Increasing use of air-conditioning in India is applying upward pressure on energy demand and may have implications on dependability. Electrical energy can be saved if favourable outdoor conditions are effectively utilized for cooling buildings with the minimum use of energy. This could be specifically applicable to residences where night-time use is more predominant for cooling by air conditioning systems but also aligns favourably with suitable outdoor conditions to be used as ventilative cooling.

The scientific literature often reports example of educational buildings with extremely poor ventilation performance. An in-field investigation for the environmental and energy assessment of a kindergarten in Milano, confirmed that operable windows were not operated when the average daily temperature dropped below 14 °C, jeopardizing indoor air quality and kids learning performance.

In an extensive simulation study using a multi-zone airflow and contaminant transport calculation software (CONTAM) recommendations for the supply air rates for residential housing were derived as input for the revision of the Austrian standard ÖNORM H 6038 (2014). The floor plan, the occupancy and the contaminant and humidity sources are modelled to represent a typical Austrian housing situation. A humidity buffering model is also implemented. Based on common thresholds for CO2, relative humidity (r.h.) and TVOC the so-called relative threshold deviation is determined.

This paper presents results from an on-going project concerning new design procedures for mechanical ventilation systems with low energy use. Conventional constant air volume (CAV) systems are usually balanced using flat plate dampers. The purpose of using balancing dampers is to intentionally introduce pressure drops in the duct system thus nominal airflows are achieved throughout the ductwork within specified tolerances.

With the continuous improvement of the energy performance of buildings, ventilation plays a crucial role in the control of pollutants from indoor sources and related comfort and health effects. However, the ventilation system itself could possibly also be a source of indoor air pollutants such as microbial contaminants. Profound scientific and technical knowledge on the impact of the design, installation and maintenance on the real performances of ventilation systems is currently lacking.

Hybrid ventilation (HV), as a combination of automated natural ventilation (NV) and balanced mechanical ventilation (MV), provides opportunities to use the advantages of both ventilation systems during the seasons in order to reduce energy demand and at the same time obtain comfortable indoor climate.

This paper describes the results of a Dutch national study into performance of mechanical ventilation systems and its effect on the self-reported health and perceived indoor environmental quality of occupants.

In a great portion of Danish primary schools the mechanical ventilation systems is outdated or simply rely on opening of windows to ventilate the classrooms. This leads to high energy consumption for fans and/or ventilation heat losses and poor indoor environment, as the ventilation systems cannot provide a sufficient ventilation rate. A recent study with 750 Danish classrooms show that 56 % had CO2-concentrations over a 1000 ppm, which is the recommended limit by the Danish working environment authority and this adversely affects the performance and well being of the pupils.

In many locations mechanical ventilation has been the most widely used principle of ventilation over the last 50 years but the conventional system design must be revised to comply with future energy requirements. This paper examines the options and describes a concept for the design of mechanical ventilation systems with minimal pressure loss and minimal energy use.  This can provide comfort ventilation and avoid overheating through increased ventilation and night cooling.

Total heat exchanger model based on experimental results was incorporated in the entire buildingmodel with the stay and internal generation of heat and with window opening-closing schedule, andenergy-saving effects of total heat exchangers were evaluated including regional features in Japan.Regional differences were found in the effects, and it was found that the reduction rate of heating andcooling loads was in the range of about 2 15%, and the reduction amount of heating and coolingloads was in the range of about 0.1 11 GJ.