Condensation risk: comparison of steady-state and transient methods

Accurate assessment of both surface and interstitial condensation risk is important not only to reduce the damaging effect of moisture within the structure of buildings, but also to provide a healthy environment free from mould growth. The current British Standard (BS EN ISO 13788: 2002) contains an assessment procedure based on the assumption of a steady-state heat flow through the building envelope, neglecting the transient nature of the problem. This paper compares and evaluates numerical results of the condensation risk calculation under both steady-state and transient conditions using the existing numerical codes. Significant differences are apparent between the predictions of the simple (steady-state) and complex (transient) methods for all construction details modelled

Reviewing past environments in a historic house using building simulation

This paper reviews different heatingregimes applied to the same space,using building simulation. Theconstruction of a computer simulationmodel to investigate past and presentenvironments in a historic house libraryis described. The model simulated fourhypothetical scenarios, based on realdata. The simulation outputs werereviewed in terms of the risk ofphysical and chemical deterioration,and their relationship with an existingnational standard for archives. Thepossibility of simulating pastenvironments to investigate naturalageing is also discussed

An initial evaluation of a biohygrothermal model for the purpose of assessing the risk mould growth in UK dwellings

Moulds are organisms that may be found in both the indoor and outdoor environment. Moulds play an important rolebreaking down and digesting organic material, but, if they are significantly present in the indoor environment they mayaffect the health of the occupants. A relative humidity of 80% at wall surfaces is frequently stated as the decisivecriterion for mould growth and methods used to assess the risk of mould growth are often based on steady stateconditions. However, considering the dynamic conditions typically found in the indoor environment, a betterunderstanding of the conditions required for mould to grow would seem desirable. This paper presents initialexploratory work to evaluate and assess ‘WUFI-bio’ - ‘biohygrothermal’ software that predicts the likelihood of mould growth under transient conditions. Model predictions are compared with large monitored data set from 1,388 UKdwellings before and after insulation and new heating systems are installed (‘Warm Front’), the suitability of thissoftware as a tool to predict mould growth will ultimately be assessed. This paper presents some initial, exploratorywork

Post occupancy evaluation of buildings in a zero carbon city

This paper presents a methodology to monitor the performance of buildings in a Zero Carbon City from the occupant perspective. Masdar City in Abu Dhabi is hailed as the World's pioneering Zero Carbon Zero Waste city. The initial phase of construction is complete and the first students have moved into the residential quarters of the Masdar Institute of Science and Technology (MIST) in September 2010. Although the study monitors both Carbon and Waste, this paper outlines a Post Occupancy Evaluation (POE) to assess the resident's satisfaction and building performance at MIST. The research focuses on the role that user behaviour and satisfaction plays on energy efficiency. It is hoped that such an approach will allow building performance to be normalized for user behaviour and to examine how best to commission, explain and handover complex low energy developments to new residents. It is hoped that the residents' reaction and adaptation to the first Zero Carbon Zero Waste city will provide valuable insights that can be applied to future low energy developments

What moderates the attainment gap? The effects of social identity incompatibility and practical incompatibility on the performance of students who are or are not Black, Asian or Minority Ethnic

A successful journey through higher education is, for many, a once in a lifetime opportunity for social mobility. Unfortunately, one notable feature of higher education systems is that students from some backgrounds do not achieve the same academic attainments as do others. The current study tests the role of one particular set of processes: social identity (in)compatibility on academic performance. Participants were recruited at two time points from a pool of first year undergraduates at a modern London University (N=215) of which 40.1% were classed as Black, Asian or Minority Ethnic (BAME), 57.1% as non-BAME and 2.8% did not provide this information. A prospective design was employed: Alongside demographic data, measures at the start of the academic year consisted of measures of student and ethnic identity, and both practical and identity incompatibility. At the end of the academic year, average marks achieved were gained for each student from the university’s registry system. Results indicate that BAME students had equal levels of student identity to non-BAME students, but higher levels of ethnic identity. They also typically experienced higher levels of both practical and identity incompatibility. Finally, BAME students had lower attainment than did non-BAME students. Both practical and identity incompatibility appeared to moderate this effect. However, contrary to predictions, it was only under conditions of low and medium levels of incompatibility that BAME students attained lower marks than their non-BAME peers. The theoretical and practical implications of these findings are discussed

Variation of Thermochromic Glazing Systems Transition Temperature, Hysteresis Gradient and Width Effect on Energy Efficiency

Due to increasing pressure to reduce the energy demand in buildings, thermochromic thin film based glazing has become a recognized potential solution due to the intrinsic ability to modulate the solar heat gain of a window as a function of the materials temperature. These “intelligent” glazings have been investigated for several years, and it has been found that, through variation of synthetic route, the thermochromic properties (transition temperature, hysteresis gradient and width) can be altered; however, less attention has been applied to how such alterations affect the overall energy savings attributed to the materials. In this study the building simulation software EnergyPlus TM has been used to model a series of idealized thermochromic spectra in a series of different environments to evaluate their energy saving potential against both clear glass systems and industry standards. The idealized spectra are used to see what effect each of the materials thermochromic properties and therefore elucidate which are the most important with respect to the energy saving properties. It was found that the best thermochromic materials were those with a narrow sharp hysteresis and a low transition temperature and result in an increase in energy saving between 30%–45% across the different environments compared to clear glass systems

The effect of transition hysteresis width in thermochromic glazing systems

Thermochromic glazing theoretically has the potential to lead to a large reduction in energy demand in modern buildings by allowing the transmission of visible light for day lighting whilst reducing unwanted solar gain during the cooling season, but allowing useful solar gain in the heating season. In this study building simulation is used to examine the effect of the thermochromic transition hysteresis width on the energy demand characteristics of a model system in a variety of climates. The results are also compared against current industry standard glazing products. The results suggest that in a warm climate with a low transition temperature and hysteresis width energy demand can be reduced by up to 54% compared to standard double glazing

Performance of internal wall insulation systems - experimental test for the validation of a hygrothermal simulation tool

In the UK, transient models of heat, air and moisture transport (HAMT) are common tools used by building practitioners to better understand moisture movement within building elements and construction systems. Enforced by BS 5250:2011, hygrothermal simulations are also used for condensation risk analysis and to estimate the likelihood of mould growth and fabric decay. This paper describes the methodology applied in the validation of a hygrothermal-modelling tool used in the evaluation of internal wall insulation. Wall assemblies typically constructed for internal insulation were exposed to transient boundary conditions derived from vapour pressure profiles and their response to step changes and fluctuations were analysed. The wall assemblies were constructed using one wall substrate (aerated clay blocks and gypsum plaster) and eight commonly used internal insulation systems. Relative humidity and temperature levels measured at the interface between the wall substrate and each insulation system were used to assess the hygrothermal performance of each insulation system. As a result, the wall assemblies were clustered in three subgroups; dense capillaryactive insulation, lightweight vapour-permeable insulation and synthetic vapour-closed insulation, and the hygrothermal performance of the proposed clusters compared with the results provided by the simulation tool. It was found that simulated assemblies have similar hygrothermal performance as those monitored