English

Existing experimental techniques for calculating air flow through building cracks are usually based upon relationships derived from experimental studies employing relatively simple procedures. Typically, a fixed pressure difference, dP, is established across the crack of interest and then the air flow Q through the crack is determined. Most crack flow equations take the pressure differential dP to be steady-state. In reality, the wind forces which generate much of the driving pressures represent highly fluctuating signals.

Since 1985 more than 170 very low energy houses, all of the same type and structure, were built in the Flemish Region, Belgium. Because conduction losses are very low, mean Urn-value 0.30-0.35 W/(m².K), ventilation losses become very important, up to 45% of the heat losses if no heat recovery is utilised. Three of the houses were monitored in detail for energy consumption, energy and ventilation efficiency. All houses are equipped with the same ventilation system: balanced mechanical ventilation with heat recovery.

The project described in this paper has performed simulations using a multi-zone air flow model (4(COMIS)) of three different passive stack ventilation systems. The objective of the simulation calculations was to evaluate system performances and to make suggestions for possible improvements of the systems.

While the use of heat energy has decreased since the middle of the 1970's the use of electricity in the Swedish stock of commercial buildings has increased dramatically. In the average Swedish office building, roughly 30 % of all electricity is used for heating, ventilation and air-conditioning WAC). Another 30 % is used for lighting, 20 % for office machines, and about 20 % for other loads. In order to study the use of electricity in Swedish office buildings in detail, the Swedish Council for Building Research initiated four monitoring and bddiing simulation projects in 1989.

Although the power law has been broadly accepted in measurement and air infiltration standards, and in many air infiltration calculation methods, the assumption that the power law is true over the range of pressures that a building envelope experiences has not been well documented. In this paper, we examine the validity of the power law through theoretical analysis, laboratory measurements of crack flow and detailed field tests of building envelopes.

The use of local exhaust is considered to be the most effective way to control pollutant dispersion from intense sources, such as in kitchens, in toilets, as well as in copy machine rooms. The optimum air exhaust rate required to prevent pollutants from escaping into the major occupant areas very much depends on the natural air exchange rate(AER) between the hooded room and the major room space. This paper presents a mathematical model and a test procedure of using tracer gas technique to quantify the AER.

Ad Hoc Group 4 of Working Group 2 of CEN TC156 (Ventilation) was set up to put forward standardised techniques for estimating ventilation rates in dwellings. The purpose of the standard is to ensure that different people carrying out calculations with the same input data will obtain the same result. This will allow the use of these results in energy, heating load, IAQ or other calculations. The methods proposed use two different techniques, an explicit and an implicit one. The explicit one involves more approximations, but can be carried out with a hand calculator.

The work presented in this paper is aimed at the definition of tracer gas experimental procedures for measuring the air change rate, the age of air and the air change efficiency in real buildings under mechanical ventilation conditions. The measurement procedures, based on the decay method, were validated in a special experimental chamber and implemented in two rooms of a building under real operating conditions. Measurements of volumetric flow rate through the air ducts of two buildings, performed by means of the constant emission rate method, will be shown and commented.

The homogeneous emission passive tracer gas technique is described. This technique relies on an even distribution of constant tracer gas emission rate within the object to be measured, so that the emission rate per volume unit is constant. The local steady state concentration of the tracer gas is directly proportional to the local mean age of air and the emission rate per volume unit.

Especially in modern buildings with small capacity of humidity storage it is necessary to reduce the humidity in the supply air. Normally this was done by using a refrigeration system mostly with CFC's. There are some alternative fluids available, but mostly they show a high global warming potential. All these systems need electrical energy to be driven and therefore it is necessary to consider other possibilities with alternative systems. The most promising systems are sorptive systems that are used now in open cycles.