English

Designing for grille and diffuser noise is of paramount importance. Neil Jarman looks at the data currently provided by manufacturers and provides some design tips.

This study has the objective of applying the "age of air" concept and tracer gas techniques in the evaluation of ventilation characteristics of workplaces equipped with a general ventilation system. A Class I OK cleanroom was selected for this study and C02 was used as a tracer gas. After the tracer gas was released in the form of a pulse into the cleanroom, its concentration was measured as a function of time at various locations by non-dispersive infrared photometers. The average age of air at each location was then calculated from the C02 concentration data.

The Centre for Building Performance Research at Victoria University School of Architecture has recently concluded R&D for the Energy Efficiency Clause of the New Zealand Building Code. This report, contributed to the BEPAC Newsletter, discusses some of the issues that arose in the course of the work.

As active noise control systems begin to penetrate the market place, are the days of the passive attenuator numbered? Andrew Brister looks at the likely future for anti-noise.

Is fighting sound with sound the future for noise control? James Macneil hears how active noise technology is slowly being fine-tuned for commercial use.

To evaluate the health risk posed by particles emitted from sound absorbent materials used in ventilation channels, the number, size, shape and composition of fibers and other particles must be characterized. A method of studying those particle characteristics has been developed. The number concentration of small particles in the testing chamber was measured with a condensation nucleus counter. Both scanning electron microscopical and optical microscopical analyses were possible for filter samples because of the low particle concentration of background particles in the testing chamber.

The sound insulation provided by similar types of windows varies considerably. This paper describes experiments on a number of elements which affect sound insulation, including the sealing of openable panes, the type of frame material, the size of the window panes, and the spacing of panes in multiple pane systems. It identifies the main factors and lists the potential insulation values for various types of window. This paper will be of interest to architects, planners and acoustic consultants.

Building diagnosticians routinely use measurements of differential pressures, building and duct system airtightness, and mechanical system airflow when investigating air quality, comfort, durability, and energy use problems in commercial and residential buildings. Unfortunately, wind and other sources of noise can create large pressure fluctuations which significantly increase the variability of these measurements, often to the point where they can not be relied upon in the diagnosis of performance problems, or as quality control indicators.

This paper gives guidance on assessing the risk of surface condensation and mould growth at thermal bridges around openings in the external elements of buildings, and describes a method of assessing their effect on overall heat loss. It supports the 1995 revision of the Building Regulations for conservation of fuel and power.