Peter Tregenza

Quality of life and building design in residential and nursing homes for older people

Older people living in residential and nursing care homes spend a large proportion of their time within the boundaries of the home, and may depend on the environment to compensate for their physical or cognitive frailties. Regulations and guidelines on the design of care buildings have accumulated over time with little knowledge of their impact on the quality of life of building users. The Design in Caring Environments Study (DICE ) collected cross-sectional data on building design and quality of life in 38 care homes in and near Sheffield, Yorkshire. Quality of life was assessed using methods which included all residents regardless of their frailty, and staff morale was also assessed. The physical environment was measured on 11 user-related domains using a new tool, the Sheffield Care Environment Assessment Matrix (SCEAM). Significant positive associations were found between several aspects of the built environment and the residents’ quality of life. There was evidence that a focus on safety and health requirements could be creating risk-averse environments which act against quality of life, particularly for the least frail residents. Staff morale was associated with attributes of a noninstitutional environment for residents rather than with the facilities provided for the staff. The new tool for assessing building design has potential applications in further research and for care providers.

Mean daylight illuminance in rooms facing sunlit streets

The illuminance from windows that are shaded from direct sunlight can depend strongly on reflected light from the ground and from other buildings, while the sky component can be insignificant. The paper describes a method for estimating the mean illuminance on the working plane and on other room surfaces using, as data, solar normal illuminance and diffuse horizontal illuminance. These can be either computed or measured values. The method calculates direct illuminance on a window from sunlight and skylight, from ground reflected light andalso the illuminance from inter-reflection between facades. A split-flux technique is used to determine window direct internal illuminance and the internal inter-reflection, the light entering the window being divided into 3 components. The paper gives a worked example and typical values of window transmittance with louvres, canopies and light shelves.

The Sensitivity of Room Daylight to Sky Brightness

The fundamental equation of daylighting links the daylight illuminance of a surface with the sky luminance distribution. The key element in the equation is the ‘daylight coefficient’ function. This indicates the sensitivity of illuminance to changes in the sky luminance distribution. Examples are given for mean and point illuminances in a room.

Glazing daylight transmittances: a field survey of windows in urban areas

Abstract The effect of urban air pollution on glazing daylight transmittance was investigated by measuring the percentage loss in glazing transmittance of a number of windows throughout a large city in the UK. A total of 430 windows in a range of building types and locations were used to create the database for this window survey. The measurements were taken under overcast sky conditions to minimise errors that could occur during periods of rapidly changing sky luminance. In addition, two adjacent photocells were used so that simultaneous comparative measurements were taken. In general it was observed that the loss in transmittance for a vertical window did not usually exceed 10%. The factors that most significantly reduced glazing daylight transmittance were (i) the function/use of the building or the rooms within, (ii) the inclination of the window and (iii) the shading of the window by overhangs. It is, therefore, suggested that future daylight design guidelines should include these factors.

Discomfort glare and time of day

There are strong reasons to suspect that glare sensation varies with the time of day. This study was designed to test whether such a relationship exists. Thirty subjects were exposed to an artificial light source four times of the day. The source luminance was progressively increased and subjects were required to give glare sensation votes corresponding to the level of visual discomfort experienced. Glare indices were calculated for every reported glare sensation vote, and the results were statistically analysed. The findings indicated a tendency towards greater tolerance to luminance increases in artificial lighting as the day progresses. This trend was found not to be statistically related to the possible confounding variable of learning, providing evidence of an effect of time of day on glare sensation.

Temporal variables and personal factors in glare sensation

Previous laboratory experiments have provided evidence of an effect of time of day on glare sensation. During the tests, temporal variables and personal factors were also measured to analyse their influence on levels of visual discomfort as the day progresses. The results revealed statistically significant and practically relevant tendencies towards greater tolerance to source luminance from artificial lighting at all times of day for earlier chronotypes and for participants not having ingested caffeine. No conclusive evidence was found for the effect of fatigue, sky condition and prior light exposure on glare sensation throughout the day. These findings suggest that temporal variables and personal factors should be measured in conjunction with visual discomfort levels to explore the causes of the wide individual differences commonly associated with the subjective evaluation of glare sensation.

The Influence of Building Design on the Quality of Life of Older People

Design in Caring Environments is a study of residential care buildings for older people carried out by architects and psychologists from the Universities of Sheffield and Loughborough. The study is a search for evidence that building design influences the quality of life of residents and the quality of care given by staff. Thirty eight care homes were observed and analysed in terms of their physical and environmental provision in parallel with an assessment of the quality of life of a sample of the residents in each home. The research finds that building design does appear to have an impact on quality of life both positively and negatively. There are indications that a risk-averse culture leads to a diminished lifestyle, and that physically supportive environments are life enhancing. The implications for the design of residential buildings are the subject of this paper.

Opinion: Climate-based daylight modelling or daylight factor?

Discussion about daylighting seems to be dominated by one question: In a daylighting standard, should criteria based on computer modelling replace the use of daylight factors? To ask this is meaningless until a more fundamental question is answered: What is the purpose of the standard? Is it to ensure sufficient natural light to maintain the health of building users? Or to minimise energy use? Or to provide an environment that brings satisfaction to users? Or to obtain their optimum work output? We know from the research evidence that what people need and enjoy from windows goes far beyond the scope of any single measure of illuminance. Essential now is focussed discussion both on the aims of regulation and on the means. There are many methods of disseminating good design practice, and a mandatory standard is not necessarily the most effective. Like a good law, a standard must, if it is to be enforceable, have an evident and beneficial purpose, have a clearly defined scope – where it applies and where it does not, and set out requirements that are few in number, robust, meaningful and easy to test. Consider the analogous example of road traffic. The research evidence on the occurrence of accidents is comprehensive. There are empirical functions that give the probability of a driver recognising a hazard in a given time, and others that predict driver behaviour and the subsequent path of the vehicle. But no matter how useful these are to the design engineer, they do not meet the requirements for enforceability. Instead we have speed limits. They are clear, simple and obviously correlate with the accident rate. Installing a 30mph sign in a hazardous area will not keep every vehicle’s speed within that limit but will significantly reduce the accident rate. What, in daylighting standards, is the equivalent of the speed limit? What is simple to specify and test yet has an evident relationship with daylight in a room? The obvious answer is a purely geometrical measure such as the ratio of window area to room surface area and to the fraction of visible sky. But that describes precisely the average daylight factor. It is an irony that daylighting practice, which has long used a measure that correlates with user experience much better than does working plane illuminance, should focus on illuminance when lighting theory as a whole is seeking more relevant measures. I think that daylight factors, or measures very similar to them, have a long-term use wherever simple figures are required. But that is not my main point. There is an opportunity being missed: Simulation of daylight is not leading the exploration into new and non-numerical measures of lighting and it should be. It provides the power to look at patterns of luminance that vary with time, or at extreme values, or at the behaviour of complex control systems, and more. It is a tool to be used creatively.

Attenuation of diffuse daylight due to dust deposition on glazing in a tropical urban environment

Transmittance of diffuse daylight by horizontal and vertical glazing was measured in a model placed in an exposed outdoor environment in Singapore for 41 weeks. Correction factors for sensor location were developed, and associations between transmittance and rainfall, wind speed and wind directional frequency were analysed. The paper discusses the interplay of forces for adhesion, resuspension and cleaning.

Reduction of glazing transmittance by atmospheric pollutants

Glazing transmittance was measured in approximately 500 windows in urban buildings in Sheffield, UK. In addition, laboratory measurements were made of transmittance reduction due to dirt deposited on glass samples on a test rig exposed over a 2-year period. The overall results were that actual glazing transmittances differed significantly from values given in current codes of practice, and that exposure to precipitation, glazing slope and room use are major determinants of glazing transmittance. Where glazing is exposed to rain, deposited dirt on the outside of windows tends to build up in 2-3 months to a level that then remains relatively constant. Typically, the final reduction of transmittance is 4-8% for commercial buildings in clean environments. We suggest values to be used in daylighting calculations.