Andy Shea

Evaluation of the thermal performance of an innovative prefabricated natural plant fibre building system

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.

Non-homogeneous Thermal Properties of Bamboo

A Phyllostachys edulis (Moso Bamboo)sample’s density, heat capacity and thermal effusivity were obtained by a series of experiments. The porosity, thermal conductivity and thermal diffusivity were calculated. Based on these experimental values, this study discusses the Phyllostachys edulis sample’s microstructure characteristics and the causes of the variation of thermal properties along the radial direction.

Daylight transmission of atrium roofs under overcast and partly cloudy skies

This paper describes an experimental study of the effect of atrium roof form, internal structural obstructions and sky type (overcast and partly cloudy) upon the daylight levels in atrium buildings. Simultaneous daylight measurements were made in two identical atrium models under real skies. One atrium model had an A-frame glazed roof with obstructions created by white structural elements. The second model had a flat glass roof with no obstructions. For overcast skies it was found that applying the plan area obstruction correction factor to daylight levels usually underestimated the loss of light due to the obstructions, typically by 10-15%. For the partly cloudy sky the effects of roof shape and obstruction on atrium daylight levels were complex. The inclined glazed surfaces and structural elements could reflect the bright skylight either away from or into the atrium. Under some circumstances the presence of the obstructions in the roof increased the illuminance levels on north-and east-facing atrium surfaces (compared with the clear flat roof), while for south- and west-facing surfaces illuminance levels decreased.

Post-Occupancy Evaluation of a Mixed-Use Academic Office Building

The paper presents the results from a Building User Study (BUS) survey undertaken as part of the Technology Strategy Board’s (TSB) Building Performance Evaluation project. The results are from a mixed-used academic building on the University of Bath campus and are presented in relation to the design strategies used within the two distinct parts of the building, the new build and the refurbished, joined by an atrium. The summary indices from the BUS survey for both parts of the building are presented along with the results from twelve overall variables. The variables are then discussed in terms of the use and operation of the building in six sections: air quality; lighting characteristics; sources of noise; satisfaction with temperature; comfort, productivity and perceived health; and design and image to visitors. The paper concludes by highlighting potential changes to the redevelopment of buildings of this type in the future, many of which are more widely applicable.

Roof obstructions and daylight levels in atria: a model study under real skies

This paper describes an experimental study of the effect of atrium roof shape and atrium roof obstructions upon the daylight levels in atrium buildings. The work was carried out using physical models of atrium buildings under real sky conditions, and was divided into three stages. The first part of the study investigated the effect of the atrium roof on available daylight levels in the atrium. The second part examined how obstructions created by structural elements beneath the atrium roof influenced the roofs transmission characteristics. Finally, a comparison was made between the observed reductions in transmission and those predicted by applying the plan area obstruction created by the structural roof elements. It was concluded that for overcast skies the influence of atrium roof shape on transmission losses was small if the plan area roof obstructions were similar. Applying the plan area obstruction as a correction factor to daylight levels in the atrium usually underestimated the loss of light due to the obstructions. For overcast skies this underestimation was typically 10-15%. It was observed that as skies brightened the effects of roof shape and obstruction loss on atrium daylight levels became larger as the inclined glazed surfaces and structural elements either reflected away bright skylight and sunlight or reflected it into the atrium.

Heat of Sorption and Moisture Buffering Properties of Building Insulation Materials

Latent heat of sorption exchanges in hygroscopic materials can affect thermal comfort, and potentially the heating requirements of buildings, while moisture buffering regulates humidity levels, allowing for a healthy indoor air quality. In this study experiments were conducted to compare the moisture buffering performance of three hygroscopic natural fibre insulation (NFI) materials (hemp-lime, hemp fibre, sheep’s wool) alongside two more conventional materials (glass wool and gypsum plasterboard). Samples with a surface area of 200 × 200 mm were exposed to a cycle of step changes in relative humidity between 53 and 75 %, changing every 12 h in isothermal conditions. Their moisture buffering performance was then determined by their change in mass. Thermocouples were placed on the surface and 15 mm below the surface of each sample to record temperature changes. The hemp-lime sample showed the greatest moisture buffering capacity, around double that of the hemp fibre and sheep’s wool, which had similar performances. In comparison, the mineral wool and gypsum plasterboard samples showed negligible moisture buffering. Temperature changes were greater at 15 mm than at the surface, with the overall balance of heating and cooling approximately equal at dynamic equilibrium. The sheep’s wool saw the largest change in temperature, while the hemp-lime had a higher temperature difference over the whole cycle. These effects will clearly alter internal conditions and should be included in building simulations to determine their impact on energy use.

Thermal diffusivity measurement of Phyllostachys edulis (Moso bamboo) by the flash method

Abstract Thermal diffusivity (ThD) of Phyllostachys edulis (Moso bamboo) has been determined in three directions of the cylindrical coordinate system of the culm. A flash tube and an infrared camera system was utilised for this purpose. The results, calculated by the MATLAB programme, serve as a database for numerical simulation studies concerning the heat and moisture transfer behaviour of Moso bamboo. The porosity and complexity of cellular structure and interconnectivity are the essential parametres influencing the ThD of Moso bamboo.

Green composites for the built environment

Abstract Green composites used in construction are unlike natural fiber composites developed for automotive and other structural composites where particles or fibers are combined with a polymer matrix to form a composite material, often in the form of relatively thin sheets. Green composites for construction are designed to satisfy the requirements of low-energy, zero-carbon green buildings where walls and other structural building components are highly thermally insulating and breathable, ensuring effective climatic control. Coatings have also been developed for these materials which improve indoor air quality, impacting positively on the health of occupants.