David Allinson

Spatial mapping of building energy demand in Great Britain

Maps of energy demand from buildings in Great Britain have been created at 1 km square resolution. They reveal the spatial variation of demand for heat and electricity, of importance for energy distribution studies and particularly for bioenergy research given the significant distance‐based restrictions on the viability of bioenergy crops. Maps representing the spatial variation of energy demand for the year 2009 were created using publicly available sub‐national gas and electricity consumption data. A new statistical model based on census data was used to increase the spatial resolution. The energy demand was split into thermal energy (the heat energy required for space heating and hot water) and electricity used for purposes other than heating (nonheating electricity or NHE) and was determined separately for the domestic and nondomestic sectors. ‘Scenario factors,’ representing the fractional change at national level in the demand for heat and NHE, were derived from scenarios constructed by UKERC. These scenarios represent a range of pathways from the present day to 2050. The present work focused on the two cases of greatest relevance, the ‘low carbon’ and ‘additional policies’ scenarios, and factors for both were derived, for the demand types described, for every 5 years between 2000 and 2050. Approximately, future spatial energy demands can be obtained by applying the scenario factors to the base mapping data for 2009.

First evidence for the reliability of building co-heating tests

ABSTRACT This paper provides powerful evidence empirically demonstrating for the first time the reliability of the co-heating test. The test is widely used throughout Europe to measure the total heat transfer through the fabric of buildings and to calculate the heat-transfer coefficient (HTC; units W/K). A reliable test is essential to address the ‘performance gap’, where in-use energy performance is consistently, and often substantially, poorer than predicted. The co-heating test could meet this need, but its reliability requires confirmation. Seven teams independently conducted co-heating tests on the same detached house near Watford, UK. Despite differences in the weather and in the experimental and analytical approaches, the teams’ final reported HTC measurements were within ±10% of the mean. With further standardization it is likely to be possible to improve upon this reproducibility. Furthermore, uncertainty analysis based upon a 95% confidence interval resulted in an estimated uncertainty in HTC measurements of ±8%. This research addresses persistent doubts about the reliability of the co-heating test. Avenues to further improvement of the test are discussed. This work helps to enable the test’s wider adoption as a component of the regulatory process and thus improvements to standards of house construction.

Occupant behaviour modelling in domestic buildings: the case of household electrical appliances

This paper presents a new approach to bottom-up stochastic occupant behaviour modelling for predicting the use of household electrical appliances in domestic buildings. Three metrics relating to appliance occupant behaviours are defined: the number of switch-on events per day, the switch-on times and the duration of each appliance usage. The metrics were calculated for 1,076 appliances in 225 households from the UK Government’s Household Electricity Survey carried out in 2010–2011. The analysis shows that occupant behaviour varies substantially between households, across appliance types and over time. The new modelling approach improves on previous approaches by using a three-step process where the three-appliance occupant-behaviour metrics are simulated respectively using stochastic processes to capture daily variations in appliance occupant behaviour. It uses probability and cumulative density functions based on individual households and appliances which are shown to have advantages for modelling the variations in appliance occupant behaviours.

Heat and mass transport processes in building materials

Abstract: This chapter introduces heat and mass transport in terms of the fundamentals and their application in the field of materials and building physics. It is the scientific topic that underpins all aspects of energy efficiency and thermal comfort in terms of the materials that make up our buildings and occupied spaces. An overview of thermodynamics and the conservation laws are provided to serve as a refresher for some readers and as a basic introduction for others. The chapter then deals with heat transfer by providing explanations of the fundamental science and then applying this to topics that are relevant to material properties and their application in buildings. The introduction of mass to these materials (e.g. water) adjusts the thermal properties, which in turn can alter the driving potentials for mass transport, which affects the thermal properties, etc., hence the true situation in materials is fully transient and highly time dependent. It is essential to consider this for accurate analysis and understanding of fabric behaviour, or of the indoor environment behaviour in response to the fabric it is made of. It is also an essential approach for studying phenomena such as surface and interstitial condensation, mould growth, as well as implications of changes to fabric (e.g. retrofit upgrades) and for thermal comfort. Therefore the next section in the chapter introduces mass transport where the approach is to, again, provide explanations of the fundamental science and then apply this to topics that are relevant to material properties and their application in buildings. Clearly mass transport is a subject in its own right, as is heat transfer. However, the chapter concludes by making the important point that in reality the two occur simultaneously and are inter-dependent, which leads on to the subject of hygrothermal behaviour.

Quantifying the effect of window opening on the measured heat loss of a test house

Opening windows is a common method for controlling air temperature, moisture, air quality and odours in dwellings. Opening a window in winter will increase the heat loss from a house, the additional heat loss will depend on the size of the window opening and the length of time for which the window is open. However, window opening behaviour is unpredictable, varying widely between different dwellings and occupants making it difficult to incorporate into predictions of energy consumption. This paper reports the results of an investigation to quantify the impact of window opening on the measured airtightness and total heat loss in a detached, timber framed test house built in the year 2000 to contemporary building standards, and located at Loughborough University. Blower door tests were used to measure the increase in ventilation caused by opening windows. The additional heat loss due to this ventilation was predicted using a simple model and then compared to the whole house heat loss as measured by a co-heating test. A linear relationship between window opening area and additional ventilation was found, independent of window location. This relationship was used to quantify the additional heat loss for a variety of window opening behaviours. The results show that window opening does not significantly increase heat loss rates in this particular house for all but the most extreme window opening behaviours. The implications of these results for different types of dwelling are discussed.

Toward quantitative aerial thermal infrared thermography for energy conservation in the built environment

The UK Home Energy Conservation Act puts a duty on local authorities to develop strategies to improve energy efficiency in all public and private sector housing in order to tackle fuel poverty and reduce carbon dioxide emissions. The City of Nottingham, UK turned to aerial Thermal InfraRed Thermography (TIRT) to try and identify households where energy savings can be made. In this paper, existing literature is reviewed to explain the limitations of aerial TIRT for energy conservation in the built environment and define the techniques required to overcome them. This includes the range of suitable meteorological conditions at the time of the survey, the use of ground truth data, the need to account for all radiation paths and losses when calculating roof surface temperature and the assumptions that must be made when calculating insulation levels. Atmospheric calibration, roof surface emissivity and sky view factor must also be determined by some means and approaches to these problems are reviewed from the wider literature. Error analysis and benchmarking are important if the technique is to be validated and these are discussed with reference to the literature. A methodology for determining the thickness of loft insulation for residential buildings in the city of Nottingham, UK using aerial TIRT data within a GIS software environment is proposed.