Building Services Engineering Research & Technology

The sound transmission loss of a stiffened window was investigated using a coupled finite element and boundary element method. This approach allowed the window to have arbitrary elastic boundary conditions and the stiffeners to be located at arbitrary positions inside the window. The in-plane deformation of the window was also taken into account. The natural frequencies predicted by the present approach showed good agreement with earlier published results. The prediction method was subsequently applied to parametric studies examining the effects of stiffeners on the sound transmission loss of a window. The results showed that the stiffeners (or their locations) notably influenced the window’s sound transmission loss values, thereby demonstrating the possibility of using stiffeners to improve the sound insulation of a practical window.

Practical applications : This study provides an approach that can be used to predict the sound insulation of a window with arbitrary elastic boundary conditions and with any-shape stiffeners lying anywhere inside the window. This approach can also be used to guide the design of windows (or other plate-like building structures) with better sound insulation.

Energy efficient new and retrofit building construction relies heavily on the use of thermal insulation. A focus on the environmental performance of current construction materials with regards to both embodied energy and energy in-use has resulted in a growing interest in the use of natural fibre insulation materials. The results of heat flow meter thermal conductivity tests on a range of straw samples of different densities are presented. The innovative use of straw in the development of a prefabricated straw-bale panel and the results of guarded hot-box testing are presented. In common with most building materials, there is a degree of uncertainty in the thermal conductivity due to the influences of temperature, moisture content and density; however, from evaluation of a range of the literature and experimental data, a value of 0.064 W/m·K is proposed as a representative design value for straw bales at the densities used in building construction. Computer simulation and experimental testing suggest that the overall heat transfer coefficient (U-value) for the complete prefabricated panel is approximately 0.178 W/m²·K. This article also briefly discusses the use of this innovative unit in a highly instrumented test building constructed at the University of Bath.

Practical application : Knowledge of the thermal properties of building materials is necessary for evaluation of energy performance of the building envelope and appraisal of retrofit fabric improvements. The presentation of robust data for the thermal properties of straw will be of interest to designers developing projects employing this natural fibre insulation material.

Building drainage demands are assumed random and intermittent. The existing Hunter-based models have been developed to aid in the sizing of pipes for instantaneous demands but not to predict the occurrence and duration of such demands. This paper proposes a time series model to determine the occurrence and duration of drainage demand, which are greater than some predefined flow rates due to a number of appliances that discharge randomly and intermittently with variable flow rates. While the duration is resolved using the time series data for simultaneous demands, the occurrence together with the time-dependent flow rate is quantified via Monte Carlo simulation based on occupant usage patterns and appliance discharge profiles derived from appliance flushes at the base of the main vertical stack. The applicability of this model is demonstrated with example discharges from a number of water closet (WC) cisterns with reduced flush volume.

Practical application: This study will help designers determine the duration and occurrence of drainage demand due to a number of appliances that discharge randomly and intermittently with variable flow rates.

Water-saving facilities were constructed in response to the sustainability and global issues all over the world. However, the performance of drainage systems must be ensured as the volume of flush water is reduced. Otherwise, it might cause sanitary problems to indoor environments and interrupt building functions. According to the methodology of investigation and observation, this paper categorized parameters that dominate the solid transportation performance of main drains. An empirical experiment was executed to clarify the quantitative influence of these parameters. A calculation model for estimating the boundary condition of main drain design is conducted. Furthermore, an estimation interface is validated and proposed as an assessment tool for practical application.

Practical implication: This paper offers an evaluation tool by statistic methodology to ensure solid transportation performance. An estimating model and regulation proposal of solid transportation in main drains of buildings that can guide the designer and engineer to confirm the performance of drainage system is validated and proved to be practicable. Furthermore, this research conducted an estimation interface to validate the solid transportation performance, which can offer an assessment tool for practical application. The results can contribute to building code guidelines and lead to new technical development of building drainage systems.

This article presents the results of water sorption properties investigation and thermal conductivity measurements of expanded polystyrene thermal insulation materials with different mass densities. The sorption behaviour of the expanded polystyrene materials was achieved in a Climacell 111 type climatic chamber, after drying in a Venticell 111 type desiccator apparatus. The relative humidity varied from 25% to 90% at 293 K for 240 min. The thermal conductivity of each sample was determined using a Holometrix 2000 (HLS) heat flow meter. In this article, the sorption isotherms, sorption kinetics, thermal conductivities and the prediction of changes in function of water content of four pure expanded polystyrene (30, 100, 150, 200 and grey) slabs with different densities (14, 17.5, 23.7 and 27.5 kg/m³) and one expanded polystyrene mixed with graphite are given (grey expanded polystyrene).

Practical application: The thermal conductivity as well as the moisture content are key thermal transport properties of building materials. The role of insulating materials in the building energy and moisture balance is more significant when compared with the other materials of the building structures. The laboratory measurements of these values of the insulating materials are very important either for the manufacturers or the contractors. The available bibliographic data for these materials are strongly incomplete and somewhere out of date.

The overall assessment of an intensive green roof located in a sub-tropical region has been undertaken. The results showed a fairly good agreement between the published and measured solar radiation data and also confirmed July and January as the hottest and coldest periods, respectively, for the region. The soil was established as a silt type with good planting medium properties for green roofs. The overall thermal performance showed that the green roof provided an average temperature reduction of 3.3℃ (i.e. 50% temperature reduction) through the roof in July. Equally, its performance was remarkable during the coldest period of January. A maximum differential temperature of 15.5℃ was achieved with the soil contributing to 24% of the temperature difference through the roof. Further studies are, however, needed to cover a wider area of influence such as effects of different types of construction materials, plants, locations and soil. In view of the limitation of the theoretical model, it would also be useful to consider some of the factors which were either neglected or assumed to be constant in any future comparative studies.

An experimental heat pump utilizing wastewater discharged from the common bathroom in a SPA center as a heat source was built. In this article, the field measured operating performance of the wastewater source heat pump is reported. An analysis based on the collected field data under various operating conditions is included. It was shown that the temperature of wastewater greatly affected the evaporating temperature and the coefficient of performance of the wastewater source heat pump. Circulating wastewater from the bottom to the top of the wastewater storage tank could weaken even out the vertical wastewater temperature distribution inside the wastewater storage tank and improve the coefficient of performance and compressor suction pressure of the wastewater source heat pump accordingly. The daily averaged coefficient of performance of the wastewater source heat pump was monitored for over an entire month. It was shown that the measured coefficient of performance gradually reduced, suggesting the need for regular cleaning of the heat exchangers used in a wastewater source heat pump system. In addition, the recorded maximum transporting capacity of the wastewater pipe reduced by 16.9% over the 1 month operation and by 20.1% after ∼5 months due to the bio-fouling build-up. Finally, an analysis comparing the economics of operating a wastewater source heat pump system with that of operating conventional water heating systems is presented.

Practical application: The use of heat pump to recover heat from wastewater is significant to energy conservation and environmental protection. A number of researches and projects on wastewater source heat pumps using urban sewage or treated sewage as a heat source have been carried out. However, field measured results on a heat pump, which recovered heat from waste bath water, was not previously reported. As the quality of waste bath water was different from that of sewage in terms of temperature, amount, and the degree of cleanliness, the experiences on designing and operating urban sewage source heat pumps previously obtained could not be used as a full reference for designing a waste bath water source heat pump. In this article, field experiment work of designing and operating a heat pump which used waste bath water as a heat source for hot water heating is presented, and the results can be used as a key reference for designing and operating waste bath water source heat pump systems in the future.