English

This paper presents an evaluation of the local thermal discomfort level in a classroom equipped with cross ventilation, for a typical moderate summer day in Portugal. Three different ventilation configurations based on window and door opening were considered. In each, the thermal comfort, air quality and acoustical comfort conditions were also evaluated. This experimental study was made in the South of Portugal, exposed to a Mediterranean climate.

Ventilation, cooling and air-conditioning contribute significantly to the energy consumption of many existing office buildings, particularly when primary energy factors are taken into account. Lean building concepts however can diminish this energy consumption by natural ventilation and passive cooling strategies. Compared to fully air-conditioned buildings the resulting indoor temperatures float in a broader band during summer and might exceed the boundaries for thermal comfort for short periods.

Conventional methods of multi-zone airflow analysis ignore mechanical energy conservation in forming the system equations governing building airflows. As a result, airflows computed using these methods generally violate this fundamental conservation principal and thereby falsely create or destroy kinetic energy within building zones. While the impact of this fundamental oversight has yet to be fully evaluated, it need not be tacitly accepted.

The capability of HVAC systems is of interest when contracting specific function criteria such as room temperature. The probability of maintaining the criteria reflects the risk the building contractor will take when giving guarantees. The level of knowledge and use of probability in the HVAC sector is low since there are just a few tests in this area. These facts make it difficult for all actors (and especially the building contractor) to increase guarantees and develop new types of performance-oriented contracts.

In order to provide comfort in a low energy consumption building, it is preferable to use natural ventilation rather than HVAC systems. To achieve this, engineers need tools that predict the heat and mass transfer between the building's interior and exterior. This paper presents a method implemented in some building software, and the results are compared to CFD. The results show that the knowledge model is not sufficiently well described to identify all the physical phenomena and the relationships between them.

This paper describes a concept of probability-based design and its application in the field of ventilation. The path of probability-based design is followed with the help of examples concerning the air change rate caused by natural and mechanical forces. The object of this study is a low-rise building situated in two different climatic zones. Evaluation of the probability of failure gives a background for probabilistic design.

Earth heat exchange (EHX) through buried horizontal air ducts (EHXair-hor) can be an effective passive/hybrid system to reduce heating and cooling loads in temperate climate zones. This paper shows the results of field testing, by the authors, of a buried pipe system for a single family dwelling and the design development of a large EHXair-hor system for a High School building. The monitoring plan for the latter is also described. Considerations on critical aspects, such as the terrain warming effect of EHXair-hor systems are also outlined.

Night cooling is promoted worldwide as an effective tool to reduce refrigerative cooling demand. However it is clear that, as long as the potential for night cooling is not standardised and integrated into building energy performance calculations, its application will be strongly hampered. In this paper the practical experiences of night cooling in an office located in Belgium are first discussed.

This paper presents an experimental and numerical analysis of building cooling using night-time coldaccumulation in phase change material (PCM), otherwise known as the free-cooling or passive-cooling principle. The phase change materials were used in ceilings and floors. The free-cooling principle is explained and some of the types of PCMs suitable for summer cooling are listed. An experiment was conducted using paraffin with a melting point of 22 C as the PCM to store cold during the night and to cool hot air during the daytime in summer.

The cooling effect of indoor air movement from circulator fans has been discounted in many strategies for increased energy efficiency. Standards such as ASHRAE 55-2004 clearly provide thermostat offset guidance for indoor air movement to maintain the comfort of sedentary occupants. The Standard is ambiguous on the cooling effects of air movement for non-sedentary activity. US utility company Exeloncorp, has indicated that each 1C increase in summer thermostat setting will save 5.4% to 7.2% of cooling costs.