UK Building Research Articles

Estimating Service Life

On-the-spot monitoring by the UK Building Research Establishment of 15 house-building sites in England revealed nearly 1000 different kinds of faults. Less than 10 percent were manufacturingfaults; the remaining 90 per cent were split almost equally between design and site. This review of the findings distinguishes between faults giving an immediate performance shortfall, and those, over one third of the total, in which that shortfall develops over time, with possible other ‘second order’ consequences. Ten examples of durability faults are given. It is concluded that the probability and timing of future deficiencies inpeifonnance are not readilypredictable, though such predictions are essential to cost-in-use appraisals.

Lumping radiant and convective exchange in a room

The convective heat exchange between the air in a room and one of its bounding surfaces at Tw can be described in terms of mean air temperature Tai, (which can be estimated from a single observation), together with the convective heat transfer coefficient hc. A radiation heat transfer coefficient hr can be written down for a simple system, but the transfer of heat by radiation from the several surfaces of a room to one of them cannot be described exactly in terms of a single temperature (to be estimated from a single observation), and hr as it stands. Yet for design purposes it is useful to postulate the existence of such a mean surface or radiant temperature Ts and to treat a weighted mean of Ts and Tai as a room index temperature, Ti. The heat flux from the room as a whole to a bounding surface at Tw is then computed in a design context as (Ti—Tw)hi, where hi is an equivalent heat transfer coefficient based on hc and hr. An account is given of the development of the ideas relating to this heat flow. The earliest work simply considered the mechanisms separately. Later the heat flow was treated as driven by the air temperature Tai but with a coefficient hi = hc + ∊hr. (∊ is surface emittance). The workers at the UK Building Research Establishment, on the basis of a simple model of radiant heat exchange, generalised this so that Ti became 1/3 Tai + 2/3 Ts and hi became hc + 6/5 Ehr. (E is a function of emittance). In the CIBS 1970 Guide, hi appears as hc + Ehr. The present author, using the full expression for radiant exchange, has demonstrated optimal versions for this expression; they are based on solutions which minimise the differences between the consequences of the exact model for radiant exchange, and the simplified model needed for design calculations. The emittance for each surface is introduced explicitly. Attention is drawn to the temperature node at which longwave radiation from a hot body heat source is introduced, and also to the difference in concept of an index temperature and a mean observable temperature.

Comparing Conventional and Electronic Room-Stats

An electronic and a conventional accelerator-heater room-thermostat were tested for performance in the UK Building Research Establishment's matched-house pair with simulated occupancy. A saving of between 2 and 3 per cent was found with the electronic type, although it is not yet clear by which physical method the saving was realised. For this reason the case for fitting such thermostats, though slightly encouraging, would require further evidence. The performance of the electronic model indicated no increase in the boiler cycling rate, but there was also no improvement in room temperature variability. On balance, the electronic control performed satisfactorily, the authors conclude, but suggest that further work is needed to establish its full potential for saving energy in occupied houses.

The Stability of Large Structures

A major part of this issue deals with topics that hare recently attracted the attention of CIB working group W 23. which is concerned with loadbearing walls. Beginning this section, the following paper presents an analysis of the problem of instability in large structures and develops some critical general propositions related to the phenomenon of instability. A set of four principal strategies for an engineering design philosophy are then proposed. It is suggested that any method of stability control in structural systems must incorporate one or more of these strategies. The author works at the Scottish Laboratory of the UK Building Research Establishment.

Building on expansive clays : Berkovitch, I Civ Engng, London, April 1983, P37–38

Joint research by the UK Building Research establishment and the Jordanian Building Research Centre has shown that damage to buildings can occur, as the result of swelling and shrinkage of clay under foundations, as the moisture content varied. Normally foundations are placed upon the bedrock beneath the clay, but because areas are being built upon where the bedrock is very deep, various types of foundations have been developed for use on the superficial clays. Several investigations in Jordan have shown that most cracking occurred on single-storey buildings where low foundation loading associated with a change in the moisture content. All movement in the building can be prevented by providing foundations at least 3M deep on deposits of the most expansive clays or by developing small diameter piles and beam foundations. Movements can be minimised by the use of sealed paving around buildings to prevent seasonal changes in moisture content. There should be no trees at distances nearer than half their height. Buildings could also be designed to tolerate movements of the foundation, allowing sufficient flexibility in pipes. (TRRL)

Affordable sanitation for poorer countries

In many parts of the world the need for improved sanitation is paramount for obvious health reasons, but research must always bear in mind the need for methods which the people in such countries can afford and are able to put into practice. Work by the UK Building Research Establishment on this subject is described here, with special reference to the development of the double-chambered pit latrine, of which several thousand have been built throughout Southern Africa.

Quality control on the site

Quality standards in site construction often leave much to be desired. To discover more about the factors which in practice affect the standards achieved, the UK Building Research Establishment made a special study of 27 sites. It revealed how personalities are sometimes more important than apparent functions.

The thermal properties of lightweight concretes

The thermal properties of lightweight concretes used for implementing UK Building Regulations are compared with those used in Europe and the USA. When corrected to the same moisture content, UK standard values for concretes are much the same as those used elsewhere, but thermal properties assigned to blockwork differ because other countries take account of mortar joints, and standard moisture contents vary. Some UK problems are discussed, including that of scrutinising claims for thermal conductivity values which are lower than would be expected, the difficulty of obtaining data for hollow blocks, and the difficulty of meeting UK Building Regulations with traditional double leaf masonry walls.

Packaged heat pumps for housing

A sensible use of both financial and energy resources might be to develop heat pumps for specific heating functions. This article describes experimental work on two types at the UK Building Research Establishment. One is a single packaged air-to-air unit for individual room heating; the other recovers heat from waste water for the bulk of domestic hot water needs. The problems encountered and some possible future developments are discussed.

Energy conservation tests with simulated occupancy

Whether testing the heating systems or the role of factors like house insulation, it is difficult to relate experimental results to ‘real’ situations. Occupiers' reactions vary, and the vagaries of the weather at different periods can also confuse the picture. An experiment at the UK Building Research Establishment uses two identical houses at the same location, both unoccupied and both controlled with a micro-processor, to simulate automatically occupier's behaviour in great detail— drawing curtains at night, running hot water, dining, watching TV and so on.

Reducing demands for potable water

Industry may be the biggest user of water, but this largely involves untreated and relatively cheap supplies, whereas the public water supply system is costly to install and maintain. Domestic demands on this treated water are significant and this article describes work at the UK Building Research Establishment on possible economies in this area, particularly in relation to the w.-c., where the scope for savings is considerable.

An eye on the building weather

The future work of CIB groups dealing with climatological matters is being reviewed following the completion of many initial tasks. The former co-ordinator of CIB work on the collection and presentation of climatological information for the building industry here records (1) the progress that was achieved Mr. Lacy, who worked at the UK Building Research Establishment, has now retired.

The light switch in buildings

The paper reviews recent work at the UK Building Research Establishment aimed at deciding if there is a significant potential for saving energy used for lighting in buildings. This necessarily involves examining the ways in which building occupants use their switching facilities and hence their lighting. The savings which might accrue from automating lighting controls are discussed, with particular reference to daylight linking, and suggestions made for more sophisticated methods of manual switching.

Interaction of walls, floors and roofs

The specification of more realistic overall loads for structures makes it necessary to have detailed data on the behaviour of whole structures and the interaction of their elements. The author, who is head of the Components Division, UK Building Research Establishment and co-ordinator of CIB working commission W 18 on timber structures, discusses the considerations involved with special reference to timber-framed houses.

74.154 A new approach to predicting the thermal environment in buildings at the early design stage: Milbank, N. O. UK Building Research Establishment. Current paper 2/74 (1974) 8 pp

74.154 A new approach to predicting the thermal environment in buildings at the early design stage: Milbank, N. O. UK Building Research Establishment. Current paper 2/74 (1974) 8 pp

Building defects: anatomy of a major failure

Abstract Because the collapse of a school roof in London last June took place at night, a constructional failure avoided becoming also a human tragedy. But the technical shock waves persist. A special investigation by the UK's Building Research Establishment at the request of the Department of Education and Science highlighted the detailing of the prestressed concrete roof beams, the bearing of the nibs on the edge beams, the subsequent behaviour of the concrete and the continuity reinforcement, and the structural cross-tying of the building.

Building with soil-cement bricks

An experimental building constructed of bricks made from a silty sand with 5 per cent cement is still in use as a store at the UK Building Research Establishment. Faults have developed over the years, but the following report suggests that this type of brick could find many uses in reasonably sheltered surroundings provided care is taken to ensure the exclusion of excessive quantities of water.

Electrical supplies for construction sites

For permanent electrical installations, well-established principles exist for the initial design and the planning of lighting, heating and power-supply requirements; but these aspects are often neglected for electrical supplies for construction work. The result can be an inadequate initial supply and a dangerous improvisation at various stages as building proceeds. This article describes a unified system of equipment developed at the UK Building Research Station for use on sites.