English

Air infiltration continues to play a major role in the ventilation of houses, despite modern trends to increased airtightness of the building envelope. In colder climates, stack effect is the principal driving force for this natural air exchange. The neutral pressure level divides the envelope areas subjected to stack effect pressures driving infiltration from those subjected to pressures driving exfiltration. The neutral pressure level is therefore important to our understanding of stack driven air exchange and our ability to model it.

One of the options to increase the energy efficiency of buildings in the cooling season, is to extract heat from the building envelope during the night by natural or forced ventilation. The exploitation of this technique by architects and designers requires the development of guide lines and a predesign tool showing how the potential cooling power depends on the influence of opening sizes and positions and on the interaction with the thermal mass.

In occupational hygiene the common practice is to use dilution ventilation (MIXVENT) which ideally requires perfect mixing. Increasingly, however, displacement ventilation (DISPVENT) is being applied; ideally this involves fresh air displacing contaminated air without mixing. Keeping MIXVENT as a reference the approach of intervention was used to estimate the potential of DISPVENT for improving environmental conditions in a garment sewing plant. Air exchange efficiency of MIXVENT came to 49%. DISPVENT improved the efficiency to a level of 57%.

The paper describes measurements made on large doors - 10 to 20 m2 in 2 buildings in Narvik. The air change was measured with the tracer gas (SFg). The method of constant concentration or decaying concentration of the tracer gas was used. The dosing, measuring and calculation of the air change was made with a Briiel & Kjaer gas analyser type 1302 and computer. Use of the decaying method was best with short opening times. The opening of the door in 5 to 7 minutes gives an air exchange of 500 m³ to 1300 m³ or an air change from 0.2 to 1.0.

The paper presents a proposal of numerical procedure for air flow simulation in multi-zone buildings (up to 100 zones). This procedure can work with 1 hour time-step according torequirement of TRNSYS-a well-known modular system simulation programme. Co-operation between TRNSYS and my own programme is analysed, taking a typical Polish 5-storey dwelling house as an object of simulation. The proposed numerical procedure can also be run as an independent programme calculating the ventilation air flow, air change rate and heat losses due to infiltration.

The first part of this paper describes a detailed study of the flow of aerosol particles through large openings and the second part describes deposition characteristics of aerosol particles in a single-zone chamber lined with different types of materials, e.g. aluminium foil and carpet. Tracer-gas and aerosol particles were injected into a naturally ventilated room and their concentrations with time were monitored. The room was fitted with a number of windows which allowed examination of single-sided ventilation.

The equivalent leakage area algorithm is used to illustrate the use of statistical simulations to predict distributions of infiltration and energy loss for buildings. The important parameters in the model are: leakage at 50 Pa pressurisation, indoor and outdoor temperature, leakage in the ceiling and the floor, wind speed, building height and shielding class. Most of these parameters are not known accurately. In the statistical method we assumed for each a distribution based on measurement or good guess.

The use of sulphur hexafluoride (SF6), nitrous oxide (N2O) or carbon dioxide (CO2) as tracer-gases have been examined for the measurement of airflow in a two-zone environmental chamber. A series of measurements were carried out to examine airflows through a doorway under natural convection, forced convection and combined natural and forced convection. Results were compared with those predicted using the MULTIC computer program.

The LESO building is a three storey, medium-sized office building on the campus of the Swiss Institute of Technology in Lausanne. In this building component leakages have been carefully determined followed by extensive measurements of the boundary conditions as well as the air flows. This paper first gives some basic concepts of the evaluation and the sensitivity analysis. Then, the measured data are compared with results from simulations performed with the COMIS multizone air flow program.

It has been shown that thermal imaging can give an indication of air flow rates through small cracks. Using a finite difference analysis package it is possible to determine the surface temperature of an air transfer grille when subjected to airflow rates at higher temperatures than the grille surface. This paper will address this technique by presenting the results of the finite difference analysis package for a specific grille.