Developing performance-based standards for external timber cladding

This paper reviews the background to, and development of, new British Standards for external timber cladding. The standards are being produced because timber has become a widely used external cladding material in the UK and this has highlighted that existing standards on the topic are inadequate. When fully published, the BS 8605 series will offer performance-based specifications and guidance on the main issues affecting external timber cladding. The standards involve multi-compliant performance measures; several technical conflicts had to be addressed

Moisture conditions in external timber cladding : field trials and their design implications

This thesis describes the development of technical guidance on timber facade design. The study involved a state-of-the-art review; an exposure trial of external cladding made from Sitka spruce (Picea sitchensis) and the production of construction details and associated information. It was undertaken because timber is an increasingly common cladding material in the UK, being used on low-rise residential buildings and for medium-rise and non-domestic buildings. The risks have, therefore, increased but this is not reflected in published guidance. Sitka spruce was used due to its availability in the UK and its similarity to Norway spruce (P. abies) which is widely used for cladding in Scandinavia. The exposure trial indicated that the moisture content range in timber facades is wider than accepted. The minimum moisture content of around 10% appears to be similar for all types of timber cladding and all species. The maximum appears to vary between species according to their fibre saturation point and is influenced by construction detailing and workmanship. A preliminary model of these interactions is proposed. From a theoretical standpoint, the moisture conditions observed in the trial mean that the (commonly quoted) mean moisture content is all but irrelevant. The mode is a more representative statistic as in most cases the data are skewed towards the fibre saturation point for the species concerned. Most detailing combinations had a moisture content near to the fibre saturation point throughout the winter. Sitka spruce is, therefore, only suitable as external cladding in the UK if preservative treated. Around 40 construction details were produced. They integrate, for the first time, all of the performance requirements applicable to low- and medium-rise timber facades in the UK. The work's key benefit is that the guidance arising from this study rationalises and improves facade design. Further research is, however, needed to validate the moisture content model and extend it to other timber species.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Moisture conditions in external timber cladding: field trials and their design implications

This thesis describes the development of technical guidance on timber facade design. The study involved a state-of-the-art review; an exposure trial of external cladding made from Sitka spruce (Picea sitchensis) and the production of construction details and associated information. It was undertaken because timber is an increasingly common cladding material in the UK, being used on low-rise residential buildings and for medium-rise and non-domestic buildings. The risks have, therefore, increased but this is not reflected in published guidance. Sitka spruce was used due to its availability in the UK and its similarity to Norway spruce (P. abies) which is widely used for cladding in Scandinavia. The exposure trial indicated that the moisture content range in timber facades is wider than accepted. The minimum moisture content of around 10% appears to be similar for all types of timber cladding and all species. The maximum appears to vary between species according to their fibre saturation point and is influenced by construction detailing and workmanship. A preliminary model of these interactions is proposed.From a theoretical standpoint, the moisture conditions observed in the trial mean that the (commonly quoted) mean moisture content is all but irrelevant. The mode is a more representative statistic as in most cases the data are skewed towards the fibre saturation point for the species concerned. Most detailing combinations had a moisture content near to the fibre saturation point throughout the winter. Sitka spruce is, therefore, only suitable as external cladding in the UK if preservative treated.Around 40 construction details were produced. They integrate, for the first time, all of the performance requirements applicable to low- and medium-rise timber facades in the UK. The work’s key benefit is that the guidance arising from this study rationalises and improves facade design. Further research is, however, needed to validate the moisture content model and extend it to other timber species

The surface brightness and distance of Dwingeloo 1

The Tully-Fisher distance to the galaxy Dwingeloo 1, recently discovered very close to the Galactic Plane, is highly uncertain because of the range of possible foreground extinction values which have been suggested. We show that very high values of AB ($\sim 10$ magnitudes) or low values ($\sim 4$ magnitudes) are unreasonable since the intrinsic surface brightness implied for Dwingeloo 1 would be unrealistically high or low for a mid type disc galaxy. Obtaining 'normal' surface brightness values requires AB close to 6 magnitudes. We therefore concur with distance estimates which suggest values $\sim 3$ Mpc

An empirical determination of the dust mass absorption coefficient, κd, using the Herschel Reference Survey

We use the published photometry and spectroscopy of 22 galaxies in the Herschel Reference Survey to determine that the value of the dust mass absorption coefficient κ d at a wavelength of 500 μm is κ500 = (0.051 +0.070 −0.026) m^2 kg^-1. We do so by taking advantage of the fact that the dust-to-metals ratio in the interstellar medium of galaxies appears to be constant. We argue that our value for κd supersedes that of James et al. (2002) – who pioneered this approach for determining κd – because we take advantage of superior data, and account for a number of significant systematic effects that they did not consider. We comprehensively incorporate all methodological and observational contributions to establish the uncertainty on our value, which represents a marked improvement on the oft-quoted ‘order-of-magnitude’ uncertainty on κd . We find no evidence that the value of κd differs significantly between galaxies, or that it correlates with any other measured or derived galaxy properties. We note, however, that the availability of data limits our sample to relatively massive (10^9.7 < Mstar < 10&11.0 Msol ), high metallicity (8.61 < [12 + log 10 O/H] < 8.86) galaxies; future work will allow us to investigate a wider range of systems

Tidal influences on cluster dwarf evolution

Using N-Body/Treecode, SPH simulations, including a self regulating Star Formation-feedback model, the influence of cluster tidal forces on infalling dwarf irregulars is investigated. Results suggest that an encounter with the cluster potential can disrupt a rotating disk causing morphological transformation of the gaseous component, resulting in an enhancement of star formation rates (SFRs) of up to an order of magnitude

Prediction of absorption line statistics for a network of quasars behind the Virgo cluster

The origin of the absorption features seen in the spectra of distant QSOs is still unresolved. The authors present predictions of the numbers and strengths of absorption lines expected for a network of QSOs behind the Virgo cluster based on the two distinct extrinsic hypotheses, viz. absorption by very extensive galactic halos or by very numerous low surface brightness dwarfs. The results are compared in order to see how the two hypotheses can be distinguished by currently feasible observations