4 research outputs found
Energy-led retrofitting of solid wall dwellings: technical and user perspectives on airtightness
Purpose – Mechanical ventilation with heat recovery (MVHR) is increasingly being promoted in the UK as a means of reducing the CO2 emissions from dwellings, and installers report growing activity in the retrofit market. However, the airtightness of a dwelling is a crucially important factor governing the achievement of CO2 reductions, and the purpose of this paper is to understand the technical implications of airtightness levels in an experimental dwelling, purpose built to typical 1930s standards, at the same time as gaining the users’ perspectives on airtightness and ventilation in their homes.
Design/methodology/approach – In-depth interviews were carried out with 20 households to collect information on their retrofit and improvement strategies, attitudes to energy saving and their living practices as they impinge on ventilation. The experimental house was sealed in a series of interventions, leading to successive reductions in the air permeability as measured by a 50?Pa pressurisation test. The behaviour of a whole-house MVHR system installed in the experimental house, was simulated using IES Virtual Environment, using a range of air permeability values corresponding to those achieved in the retrofit upgrading process.
Findings – In the house considered, air permeability must be reduced below 5?m3/m2h for MVHR to make an overall energy and CO2 saving. However, to achieve this required a level of disruption that, on the basis of the views expressed, would be unlikely to be tolerated by owners of solid wall dwellings.
Originality/value – The paper is the first to combine results from a user-centred approach to exploring the existing practices of householders with a simulation of the energy and CO2 performance at different levels of airtightness of an experimental house in which MVHR has been installed
Energy-led retrofitting of solid wall dwellings - technical and user perspectives on airtightness
Mechanical ventilation with heat recovery (MVHR) is increasingly being promoted in
the UK as a means of reducing the CO2 emissions from dwellings, and installers report
growing activity in the retrofit market. In parallel with a survey of householder
preferences and practices, the behaviour of a whole-house MVHR system installed in
an experimental house, purpose built to typical 1930s standards, has been simulated.
The range of air permeability values corresponded to those achieved in a retrofit
upgrading process carried out on the house. In the house considered, air permeability,
as measured in a 50 Pa pressurisation test, must be reduced below 5 m3/m2.h for
MVHR to make an overall energy and CO2 saving. This required a level of disruption
that would be unlikely to be tolerated by owners of solid wall dwellings
Energy-led domestic retrofit: impact of the intervention sequence
Interviews conducted with householders reveal that energy efficiency is often a lesser motivation than other factors for undertaking home improvement work. Homeowners' approach to refurbishment is typically staged over several years, not as a whole house retrofit. As the operational performance of an individual emission-reducing technology typically depends on what other measures are already in place, the retrofit intervention sequence can potentially affect the overall performance of the dwelling. The impact of the intervention sequence on a semi-detached 1930s house is investigated with dynamic thermal modelling, using five sequences based on different homeowner personas developed from qualitative interviews. The results show that, whilst a whole house retrofit would reduce cumulative CO2 emissions over 25 years by 54%, the sequences actually implemented by the individual households result in significantly smaller reductions of between 42% and 24%. This variation in operational performance due to the intervention sequence means that there is a variable return on the investment for a particular technology and, significantly, that different sequences will yield different cumulative emission reductions. This has significant consequences for policies providing financial incentives for energy-led retrofit, particularly to include the intervention sequence and timing
Refurbishing the UK's 'hard to treat' dwelling stock: understanding challenges and constraints
Project CALEBRE (Consumer Appealing Low Energy technologies for Building
REtrofitting) is a four year £2 million E.ON/RCUK funded project that is investigating
technologies and developing solutions for the UK’s solid-wall houses to offer energy
demand reduction, energy efficient heat generation and energy management
combined with user appeal. Understanding how technical solutions can be aligned
with householder lifestyles is central to the CALEBRE project. The technologies
include: vacuum glazing to achieve exceptionally low U-values whilst being capable
of retrofit in existing window frames; advanced gas and electric air source heat
pumps that operate at the temperatures needed for integration with existing domestic
radiator systems; innovative surface materials for buffering moisture, humidity and
temperature; retrofit mechanical ventilation with heat recovery (MVHR) to manage
ventilation and its associated heat loss. The technologies are being trialled in
facilities that include the University of Nottingham E.ON 2016 House, a highly
instrumented replica construction of a1930s dwelling. Alongside development and
trialling, business case modelling of technologies is being conducted to establish
mass roll-out strategies, as well as modelling to identify bespoke packages of
measures for house refurbishment. This paper introduces Project CALEBRE, its
content and scope, and reports some of its initial findings to highlight the challenges
and constraints involved in the process of refurbishing the UK’s domestic stock