The energy performance of a building is one of the key credits in the Code for Sustainable Homes assessment methodology. The 2016 zero carbon homes agenda is another key driver of improving the energy perfromance of new homes. The energy Savings Trust has publish a report “The 100mm Cavity Debate” discussing the predominant use of the cavity wall to achieve good insulation values and investigating potential alternatives.
The report seeks to investigate why cavity masonry construction is so predominant in mainstream housing; why the industry appears so keen to stick to the 100mm cavity; and what are the potential
routes to achieve the improved thermal performance that is necessary at higher levels of the Code for Sustainable Homes.
In 2008 participants were invited to express their opinions on five of the key issues, and suggest the type of construction they view as most appropriate in achieving better thermal performance. The technical and commercial rationale underpinning the suggested construction was described, and extensive further information about their choice was then entered into an accompanying matrix.
Four key industry experts were invited to comment, each specialising in a different type of construction – masonry, timber frame, light-gauge steel frame and alternative construction techniques. Of these, three provided input, with the timber frame expert failing to comment. Sadly this means that considerations of timber frame had to be omitted from this report.
The results of the survey indicate that externally insulated solid walls could potentially provide a suitable way of increasing thermal performance whilst utilising the existing skills base. These would gradually be replaced in turn by Modern Methods of Construction (MMC) systems, which offer further benefits in terms of build speed and economy, as well as greater quality control.
Other findings of this report include:
- Cavity wall construction can only achieve Code performance levels 4, 5 and 6 with the cavity width significantly increased. This is commercially viable on all but the most inflexible urban sites.
- Planners can support the process of creating truly sustainable communities by placing more emphasis on thermal performance and innovation in housing.
- A clear focus on build quality will be key in meeting the challenges of higher thermal performance in housing. As this relies heavily on the skills of the site team and independent quality assessors, it brings potential for major training programmes and expansion in employment.
