Understanding the interactions between occupants, heating systems and building fabric in the context of retrofit of social housing
Jenny Love, UCL
(above animation: visualisation of data collected while monitoring occupant presence, radiators and temperatures of 2 rooms in a real dwelling)
Effects to be investigated
There is evidence that retrofitting dwellings does not save as much energy as our models predict. Reasons normally given include modelling error, installation error and occupant behavioural change. I am investigating the latter of these, focussing particularly on three variables and their relationships to each other: occupant use of space, heating behaviour and individual room internal temperatures – before and after retrofit. Theory and qualitative findings suggest that occupants use more rooms after [some types of] retrofit, maintain their dwelling at a higher temperature, and in some cases increase their demand for space heating. I am investigating this quantitatively and qualitatively.
I am carrying out research via a longitudinal mixed methods case study approach, to follow the process of retrofit from both a physical variables point of view and the occupant point of view. The sector I am concentrating on is social housing, since this is where potential comfort-taking could be argued to be the largest.
I am tracking a CESP scheme in the midlands, where council properties are undergoing addition of external wall insulation and in some cases new glazing and boilers. I have 13 case studies, and am undertaking quantitative and qualitative research. The main two research periods are February 2011 (before the retrofit) and February 2012 (after the retrofit), with some additional interviews in September 2012.
Quantitative: Sensors to measure internal temperature and humidity of every room, which radiators and other heat sources are being used when, and occupant use of space.
Qualitative: 3 sets of semi-structured interviews are being carried out with occupants, covering both pre and post retrofit periods. As well as covering heating behaviour, temperature and use of space (the quantitative variables), the interviews go broader and cover lifestyle, attitudes towards cold, the CESP program and other topics.
I am interested in the extent to which people heat the spaces they use and do not use, and how this changes following retrofit. At the moment I am working on visualising temperature fields and occupancy patterns. Before this, I carried out some modelling about the potential energy implications of comfort taking: see the conference paper at http://www.lolo.ac.uk/projectoutputs/view/type/phd/idprojects/50
Interesting findings so far
Having completed the pre-retrofit part of the fieldwork and undertaken some analysis, here are some examples of insights currently emerging:
– More use of whole-house central heating than I expected – either all the radiators are on or none of them are. Therefore in some cases a large proportion of time where a room is heated but not occupied.
– Lack of communication to the occupants about what the energy efficiency measures are supposed to do.
– Heating behaviour unlike that which we assume in models: for example, in the cases studies thermostats are not used to control the temperature in the dwelling.
– Not much distinction in lifestyle between weekdays and weekends, again unlike we assume in models.
– One occupant trapped in a cycle of illness partly caused by mould, therefore having to stay in the house and not work, therefore not having much money to heat the house yet having to spend a lot of time in the cold house, therefore not getting better.
Wider context of PhD
The PhD is part of a project joint between UCL and EDF R&D, called “People, Energy and Buildings”. It is so named because it aims to advance our understanding of the complex interactions between these three entities.
Although the sample size in the PhD is small and thus the findings cannot automatically be extrapolated to the UK fuel-poor population, it is hoped that insights gained from this new approach of monitoring behavioural variables directly instead of extrapolating them from discrepancies in engineering model predictions will increase our understanding of how occupants react to retrofit.
(below: visualisation of a susbpace of space heating energy use scenarios, given different heating behavioural variables. Traditional models of retrofit assume no behaviour change but this modelling work shows the potential effects on energy use of such change. The graphs show that if retrofit measures are not done well and there is behaviour change, energy use can increase (middle column), but it measures are significant, energy use becomes robust to variability in heating behaviour (left hand column).
Mapping the impact of changes in occupant heating behaviour on space heating energy use as a result of UK domestic retrofit
Modelling exercise presented at Retrofit 2012, Salford.
What can be learned from the process and results of modelling thermal mass in dwellings?
This is my masters dissertation, completed in September 2010
Presentation to heat pump industry of IEA Annex 37: well-performing heat pumps
Work I undertook for DECC in 2012
Retrofit results: disentangling the role of the occupants and the building fabric
Presentation at NEF, October 2013
Comfort taking, rebound and backfire
Presentation given at PEB:D3 workshop
Report (progress/mini project/consultation reports)
Report for the social landlord whose estate was monitored as part of this PhD project
Anonymised and available for other social landlords and any other interested partied
Understanding the interactions between occupants, heating systems and building fabric in the context of energy efficient building fabric retrofit in social housing
Thesis submitted for the degree of doctor of philosophy