VC

A characterization and modeling process has been conducted in order to better account for ventilative cooling in the evaluation of energy performance of buildings. The proposed approach has been tested using a monitored zero energy Active House (Maison Air et lumière) located near Paris.

This work is based on the RESHYVENT project  in which the effectiveness of hybrid (i.e. combined natural and mechanical ventilation) was measured and investigated in the urban canyon of Athens, Greece – the most important conclusion being that natural ventilation is dominant. It is suggested that the individual reaction to Air Conditioned Buildings should be better investigated, since many people ask for the comfort associated with natural ventilation. 

Common experiences, standards, and laboratory studies show that increased air velocity helps to offset warm sensation due to high environmental temperatures. In warm climate regions the opening of windows and the use of desk or ceiling fans are the most common systems to generate increased airflows to compensate for higher environmental temperatures at the expense of no or relatively low energy consumption.

Public residential buildings in Singapore are designed as naturally ventilated. As climate changes, the indoor thermal comfort becomes critical as it depends greatly on the outdoor weather condition. The Predicted Mean Vote (PMV) model developed for Singapore (Givoni, et al., 2006) which depends on indoor air temperature and air speed is used to predict the indoor thermal comfort.

The climate of Greece is typical Mediterranean with wet, cool winters and hot, dry summers. The temperature range is on average between 5°C to 35°C without many extreme temperatures and weather events. The cool sea breeze on the islands makes summer conditions milder. According to researchers and assessment reports of the United Nations climate change is inevitable in the 21st century. Regional climate models related to Greece show low uncertainties.

Night ventilation has been applied successfully to many passively-cooled or low-energy office buildings. This paper analyses the thermal comfort achievable according to European standard EN 15251:2007 by applying this strategy in office buildings in Spain. Specifically, the comfort level is evaluated using the Degree Hours (DH) criteria and the maximum indoor temperature.

Passive cooling in the built environment is now reaching is phase of maturity.  Passive cooling is achieved by the use of techniques for solar and heat control, heat amortization and heat dissipation. Modulation of heat gain deals with the thermal storage capacity of the building structure, while heat dissipation techniques deal with the potential for disposal of excess heat of the building to an environmental sink of lower temperature, like the ground, water, and ambient air or sky.

It still remains heat loss and high risk of moisture condensation occurrence at glass of window because they have relatively poor insulating qualities and usually contribute the greatest heat loss by heat conduction in residential buildings. Although many attractive window systems are proposed to reduce heat loss such as double and triple glazing, low emissivity film coated glazing, argon gas injected glazing, vacuum insulated glazing, double-pane and triple-pane window etc., it has also demerits such as high initial cost and indoor air quality problem.

Accuracy in estimation of airflow through windows is the key parameter for modelling and designing of naturally ventilated buildings. The flow through windows is usually described by the orifice flow plate equation. This equation involves the discharge coefficient. In practice, often a constant value of discharge coefficient is used. The constant value of discharge coefficient leads to deceptive airflow estimation in the cases of centre-pivot roof windows. The object of this paper is to study and evaluate the discharge coefficient of the centre pivot roof window.

The paper in hand investigates the potentials and limitations of ventilative cooling strategies in the moderate Central Europe climate region of Vienna, Austria, offering a a basic load break down of the thermodynamic night ventilation sub-processes plus an overview over frewuent practical limtations and finally a recent monitoring result from a single family model home.