Mechanical Ventilation and Heat Recovery for Low Carbon Retrofitting in Dwellings

Abstract

The ventilation heat loss in a typical unimproved UK dwelling is approximately equal to the conduction loss; therefore draught-proofing measures should form part of any energy refurbishment package. This will improve the building's air permeability but risks incurring additional energy costs associated with the need to provide controlled ventilation to maintain indoor air quality. This paper aims to determine the point at which the air permeability of the building improves the energy performance by enough to justify the increase in energy associated with the installation of mechanical ventilation with heat recovery (MVHR). A 1930's style semi-detached house, representative of a large proportion of solid wall dwellings in the UK, has been improved by a package of measures including MVHR. The building air tightness plays a critical role in reducing the building energy consumption and CO 2 emissions.

Determining of the role of ventilation in residential energy demand reduction using a heat-balance approach

“…The impact of wall insulation was particularly high in two houses, H30 (30% reduction) and H39 (64% reduction), which are both detached properties with solid wall construction. Similar figures were found by Banfill et al (2011b), suggesting a 60% to 20 71% potential reduction was possible by applying retrofit measures to a solid wall house. The difference in the potential reduction between these two solid wall houses might be partially attributed to larger impact of ventilation on H30, tempering the impact of the insulation.…”

Performance evaluation of a mechanically ventilated heat recovery (MVHR) system as part of a series of UK residential energy retrofit measures

“…A Mechanically Ventilated Heat Recovery (MVHR) system is one solution, and can help to maintain a good standard of air quality. It has been suggested that two key measures are required to reduce dwelling space heating demand, namely increased airtightness and installation of an MVHR system (Banfill 2011a). Energy savings are achieved due to a decrease in infiltration levels, in conjunction with an elevated base air temperature obtained via the preheating of supply air using recovered heat from the extracted air.…”

“…This showed theoretically that an energy saving could be realised in the test house when the MVHR system was in operation. This could be plausible, as work undertaken by (Banfill 2011a) relating to the E.On House suggests that a building airtightness level of 7 m 3 /m 2 .h at 50Pa is required in this property to realise a reduction in overall heat loss when MVHR is in use. The relevant value at the time of testing was 4.74 m 3 /m 2 .h at 50Pa, which could potentially result in a lower HLC.…”

Quantifying energy demand reduction considering householder willingness to apply measures

“…The interview findings suggest that householders need more information regarding their ventilation practices and their impact on energy consumption. Although there are energy benefits from the application of mechanical ventilation systems (Banfill, Sophie A Simpson, Gillott and White, 2011), this work suggests that changing ventilation practices in existing homes will be challenging, particularly when a significant investment from the householder is required.…”