English

One of a series of articles focussing on problem areas in buildings. 1) Examines condensation risks in buildings. Treats condensation processes, water vapour input and movement, conditions for surface and interstitial condensation in walls and roofs. 2) Treats condensation avoidance in general, humidity control, controlling vapour flow, adding insulation, heating, mould. Illustrates numerous examples diagrammatically from various building types.

Development of infiltration and interroom airflow calculation methods, driven by a concern for indoor air quality have led to a computer simulation of interroom contaminant movement. The model, which assumes fully mixed room air, shows that open doorways provide rapid mixing between rooms in buildings using forced air heating. It also confirms that it is most energy efficient to remove the contaminant nearest its source. Detailed modeling of the variations in contaminant concentration within a room is not presently feasible for long term energy analysis simulations.

A computational procedure to predict expected rates of natural ventilation for buildings at the design stage is investigated. This procedure integrates three computational methods, namely one to predict temperature induced pressures, another to compute wind generated pressure distributions around buildings, and the third to analyse the networks of resulting air flows in buildings. Experiments show that these methods are valid. The three methods can be used not only for the prediction of natural ventilation, but also for many other environmental engineering applications, e.g.

The objective of this paper is to highlight the range of air infiltration and ventilation models that are available to the designer and to indicate the appropriate level of associated computer hardware that is necessary to support these modelling methods. The description begins with a discussion on simple empirical methods intended for basic design calculations. The applicability of these methods is discussed and some of their shortcomings are highlighted.

In order to obtain means for determining realistic convective heat transfer coefficients, a hierarchy of interacting and interdependent calculation methods have been developed by the authors. Both higher and lower level models have been used to develop and verify an 'intermediate level' computer code, which formed the basis for generating input convective heat transfer data for dynamic building models. The contribution considers the computation of convective heat exchange within three-dimensional, rectangular enclosures when buoyancy effects are significant.

One of the recent major developments to the ESP (Environmental System Performance) building/plant energy simulation package has been the integration of a technique capable of performing dynamic air flow analysis as part of the building thermal analysis, thereby permitting simultaneous dynamic modelling of energy and air flow within the building envelope. This paper briefly describes the model and its data requirements. It compares and discusses differences in zone energy requirements and temperature levels (obtained from ESP) when 1. applying traditional air changes rates and, 2.

A program is presented which runs on Apricot, Sirius and IBM-PC microcomputers and calculates the heating energy requirements of single zone, intermittently heated buildings with reasonable accuracy. Calculation of preheating energy is based on the average internal temperature concept of CIBS Energy Code 2. Solar gains and long-wave radiation losses are treated crudely on the basis of regression equations for radiation as a function of daily average external temperature for different periods of the day.

The application of heat pumps to ventilation heat recovery in domestic houses is considered. It is shown that the most effective system is a combination of heat pump and heat recovery unit; a plate heat exchanger is the type commonly used. Such units are now commercially available, and can provide heat at a lower cost per kilowatt hour than the Economy 7 tariff. The performance of several units is presented, and seasonal running costs have been computed for a house equivalent to the Capenhurst low energy house design.

A new Building Research Establishment audio-visual package, 'Remedies for condensation and mould in traditional housing' sets out the findings of field trials of some available remedies for condensation and mould, carried out in England and Scotland on estates which had a history of complaints of dampness. This research has led to a new understanding of the factors involved in the occurence of condensation and the ways in which they interact. Condensation is most likely to be a problem in the homes which use the least heating.

Dampness on the inside surfaces of dwellings is a frequent source of complaint. It may be due to rising damp, rain penetration or a plumbing defect; or it may be due to condensation. Condensation and mould growth are widespread problems in all housing sectors but especially so in tenanted accommodation. In many cases it may be difficult to identify the underlying cause; this can often be complicated by social issues. Mild cases will often yield to simple changes in the heating and ventilation regime in the dwelling or to cosmetic treatments of redecoration, perhaps with fungicidal paint.