Building Services Engineering Research & Technology

This paper reviews published information on 'sick building syndrome', the cause of a reputedly high incidence of sickness among occupants of sealed, mechanically ventilated buildings. It discusses symptoms, common features of 'sick buildings' and postulates possible causes. On the basis of reported cases, there appears to be no single cause but a series of contributing factors.

A ventilation heat recovery unit was installed in an Electricity Council Research Centre test house. The unit consists of a cross flow heat exchanger augmented by a small heat pump. It supplies warm air to all inhabited rooms, while extracting air from kitchen and bathroom. Trials were run during the winter of 1986/87. The unit provided a ventilation air flow of 180 m ³ h^-1, and a gross heat input to the house of 1.7 kW; this figure is averaged over time, and includes the effect of defrost periods. An overall coefficent of performance of 3 was achieved. Such a system can provide the greater part of the heating requirement of a low-energy house, and has its own advantages over other heating systems.

The capital and annual energy consumption costs of an air conditioning system were evaluated to assess the economic application of variable compressor speed for refrigeration system capacity control. This system was compared with two other capacity control systems, hot gas bypass and cylinder unloading, for both continuous and intermittent operation. It was concluded that variable compressor speed control is only economically viable when used for continuous operation.

The standard prediction method for assessing the risk of condensation in layered structures in the steady state is discussed, and it is pointed out that this is essentially an analysis method for a case which has to be pre-defined. Designers may prefer to have methods of synthesising a construction which avoids condensation under given humidity and temperature conditions, or of finding the limiting conditions for condensation to be avoided with a given construction. Equations are presented for the calculation of the necessary thermal and vapour properties of layers added to existing designs in order to eliminate condensation risk and permit a chosen safety margin, and for calculation of the limits on humidity for elimination of condensation in a given construction. Examples are given to illustrate the use of the equations.

Significant changes in the way HVAC systems are designed would be made possible by the application of optimal search techniques to find the 'best' design for any given criterion. A suite of programs has been developed which implements this type of optimisation; it was necessary to develop HVAC component models which are more extensive than the conventional performance or energy models used in contemporary system simulation. The paper describes the development of component models which: reproduce the characteristics of ranges of manufactured products; execute quickly when linked to form system models; and model on three levels: performance, economics and constraints. An example is given of the use of the models in the optimisation of a heat pump system for minimum energy consumption.

The motivation for collating data on solar irradiation intercepted by inclined and vertical surfaces is given; the information is of interest to building services engineers, architects, agriculturalists and others. Details are given of UK stations measuring horizontal hourly diffuse and global irradiation, and day-integrated diffuse and global irradiation.