Building Services Engineering Research & Technology

Large wind turbines are usually installed in areas where wind speed distributions have been observed long enough to make sure of their high efficiency. However, micro-wind turbines are mostly used in areas where wind conditions are not necessarily favourable for efficient power production. Therefore, micro-wind turbines require specific designs to work effectively in low and turbulent wind resource areas. However, because this is not the case, more experimental results are being published in recent years that report under-achieving micro-wind turbines. In the present article, a similar under-achievement is reported. The experience gained from the wind energy project undertaken at Napier University is reported, as well as the analysis of the wind speed data collected at the facility and at Edinburgh Airport, some 16 km away from it.

Practical applications: A micro-wind energy system can be one of the most promising technological solutions for producing electricity in residential applications for remote consumers as well as in urban areas provided that the problems reported in the literature are successfully tackled. The currently reported research project identifies such problems associated with micro-wind turbines, stemming from their use in urban areas on roofs of buildings. Thus, this will contribute both to the understanding of micro-wind turbines and to their possible improvements in the coming years.

The construction, operation and demolition of buildings represent one of the most damaging human activities in the global environment nowadays and water use and conservation is one of the most representative environmental loads to be considered. Brazil, unlike some other countries, has not yet implemented its own body building environmental assessment. The development of an environmental assessment system requires the identification of the most important topics to be considered in each theme for each country or region, due to local environmental agenda. This article presents a summary of the main topics concerning water conservation considered in some international environmental building assessment systems and presents a proposal of topics to take into account in a Brazilian assessment system.

Practical application: The civil construction industry is not only one of the biggest sectors in the economy but is also one of the greatest polluters. Along with standardisation, it is also necessary to establish measures to attract significantly higher levels in different topics related to sustainable construction. New mechanisms that allow users to recognise the difference between buildings with different sustainable performance levels need to be developed. This article will be used as a base for the development of a Brazilian system of assessment and rating for building environmental performance and sustainability in terms of water use and conservation.

The performance assessment as to water consumption in WC cisterns has contributed to the development of flushing system technologies, which allow smaller flushing volumes. The purpose of this work is to assess the performance of the the low water consumption requirement of WC cisterns with dual flushing system (6/3 L), when compared to 6 L flushing volume WC cisterns in multifamily buildings. The research methodology consisted of a case study in a multifamily residential building with submetering system, by monitoring the total water consumption and the two flushing systems using water meters installed in WC cisterns. By means of a mathematical model, a comparison of the design flowrate in the main branch was carried out considering the two types of WC cisterns. The results indicated that the water consumption in the 6 L WC cistern was 20% in relation to the total domestic consumption, whereas the water consumption observed in the dual-flush WC cistern (6/3 L) was 16%. The dual flushing system (6/3 L) presented about 18% consumption reduction impact as compared to the 6 L system. The design flowrate values in the main branch, obtained by the mathematical model, were 0.35 L/s for systems with 6 L WC cistern and 0.34 L/s with dual-flush WC cistern (6/3 L), that is, a reduction of ~3%.

Practical application: The knowledge of the performance in field of dual-flush WC cistern contributes to industry to improve this system and to users to aid their choice of technologies aimed at water conservation, and so assisting to the development of sustainable buildings.

Whilst considerable research has been carried out on the process of moisture transmission through porous building materials under a concentration gradient with isothermal conditions, limited experimental data are available on the influence of temperature gradients on moisture transfer rates. Such thermodiffusion can be predicted from irreversible thermodynamics, however, its significance to concentration-driven transfer in materials has not been definitively established. Models for the prediction of moisture movement in building structures generally neglect such effects, and rely on moisture transport properties based on isothermal measurements. This paper describes an investigation to determine the significance of non-isothermal effects on the total moisture transfer through building materials. The investigation concluded that the vapour pressure gradient is the critical driving potential for moisture transfer, whilst thermodiffusion is not significant.

Practical application: Building professionals can be confident that the use of vapour permeabilities of building materials measured under isothermal conditions are satisfactory for the prediction of moisture transport through building envelopes under temperature gradients: no correction for thermodiffusion effects is necessary.

This paper investigates the thermal comfort level of an office room through various windows-door opening arrangements in hot and humid climate. To determine the windows-door opening performance, 14 opening configurations have been considered and the combination of opening arrangements was carried out in an air-conditioned office at UPM, Malaysia. After conducting objective measurement for each condition, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) were calculated. The concentrations of carbon dioxide (CO₂) were also monitored. Subjective survey involved questions on the thermal environmental perception and indoor air quality for office occupants for this study. Objective data analysis showed that in most of conditions office had thermal conditions falling within the comfort zone of ASHRAE standard 55, and in all of conditions neutral temperatures are higher than ASHRAE standard requirements. Subjective results revealed that staff has higher thermal comfort level as compared to what PMV has predicted.

Practical application: It is believed that the results in this paper will contribute to knowledge that international standards are not applicable in hot and humid climate. Fanger equations would give the results for European conditions, people in hot- humid climate have some cultural preferences that are different from the Europeans hence modifying these equations and standards for this climate are necessary. In terms of the use of climatic control to modify the indoor environment it is found that when the occupants have the freedom to modify the environment, and make necessary adjustment, they always use windows-door opening arrangements to compensate for the less comfortable thermal condition and increase air movement.

Research findings about maintenance costs of chiller plants — a ubiquitous installation in large buildings, are rare. The study reported in this paper was conducted through inspection of 40 maintenance contracts, their associated monthly service reports and payment records, and interviews with the contract administrators. Routine maintenance cost was found to dominate among the maintenance resources. Repair maintenance work accounts for a less, but significant portion. The cost incurred for emergency maintenance work is minimal and condition analysis is seldom applied. Large chiller plants, by virtue of their scale, can economise on their maintenance cost. Total maintenance cost varies with plant age following a `bell-shape' pattern, with relatively less expenditure for new and old plants whereas that incurred for middle-aged plants spreads over a wide range. Factors that potentially affect the cost relation between preventive maintenance and corrective maintenance have been identified. Apart from investigating their effects clearer, future work is needed to explore how to improve the practice of recording plant faults, which are crucial performance data to reflect whether the costs spent on maintenance are value-for-money.

Practical application: The study has revealed the significance of various maintenance cost elements and the empirical cost relation between preventive maintenance and corrective maintenance. The effects of plant capacity, age of plant, operation period and heat rejection method on maintenance cost have also been analysed. Understanding the influence of these factors can help practitioners prepare maintenance budgets and perform benchmarking exercises. Besides, the lack of proper record of plant faults, as identified, is a barrier, which needs to be overcome before evaluating the value of maintenance service.

Heating degree days are widely used in building energy management for weather normalization of energy use. Degree days are normally calculated at Meteorological Office weather stations sited some distance from the building of interest and this can introduce errors between the degree days used in the calculations and the actual degree days at the building. This paper analyses the major sources of errors in the degree days derived from a newly available data set of Met. Office stations supplied by the British Atmospheric Data Survey (BADC) and compares these errors against those from other available data sets. The BADC data set consists of hourly temperatures for 242 weather stations in the UK from January 2001 until November 2007 and has been converted to monthly degree days for the analysis. The errors have been analysed in terms of measurement and recording errors, errors due to altitude and errors due to spatial separation between weather station and building. The largest error is due to spatial separation between building and weather station. It is therefore important to use data sets with high numbers of weather stations. The data set used in this analysis has been made available on the internet at http:// www.eci.ox.ac.uk/research/energy/degreedays.php and consists of daily, weekly and monthly degree days for over 200 UK weather stations at a range of building base temperatures for the years 1987—2006. Also included is the 20-year mean for the 55 stations with unbroken records for benchmarking purposes.

Practical application: The paper discusses how errors arise in degree day data when using Met. Office weather stations sited some distance from the building of interest. The paper discusses both the method and the extent of reductions in errors that are possible by using spatially rich weather station degree day data sets. The paper makes the data set used — the best for UK degree day monitoring of buildings — available through a website, daily, weekly and monthly, over a range of building base temperatures, back to 1986.

This study examined acceptable noise level of a construction site office in Hong Kong by analysing responses obtained from interviews of 77 occupants. The equivalent continuous noise level L_eq measured in the office was chosen as an indicator and correlated with the occupant acceptance recorded on a visual analogue assessment scale and a dichotomous assessment scale. With the use of a logistic regression model, this acceptance was found to be significantly influenced by the working experience and age of occupants, which were in turn highly correlated. Satisfactory noise levels within the office have been evaluated by comparing acceptance responses given by the occupants at different L_eq. The proposed criterion of aural comfort was further identified by the survey samples and a conclusion was drawn: an indoor environment with an equivalent continuous noise level L_eq of 65 dBA would be deemed acceptable for a construction site office.

Practical applications: This study reported the occupant acceptable noise level in construction site offices was more adaptable to a noisy environment than a general office because the occupant acceptance would be significantly influenced by the outdoor noise level, working experience and occupant age. The construction site office with an equivalent continuous noise level of 65 dBA would be recommended as a design criterion for construction site offices as it can balance the cost of acoustical treatment and the satisfaction of occupants.