External Insulation for London Semis

June 2012: South Kenton and Preston Park Residents Association (SKPPRA) recently obtained a grant from the Local Energy Assessment Fund (LEAF) to externally insulate a pair of semi-detached houses on the estate to show residents how this will make the houses warmer and easier to heat. Under the ‘warmhouse’ project two houses in Wembley were clad in external wall insulation and a series of detailed reports of the project have been published and are available to download from the ‘warmhouse’ website, which will provide some valuable learning for the roll out of the Green Deal in London.

Some points of interest:

  • Detailed photographic records of the retrofit are posted in the first document, setting out the level of work undertaken to externally insulate these two homes.
  • The second report provides a useful ‘scope of works’ document, which sets out the requirements of the insulation project to the contractor – a helpful template to any other similar project being considered.
  • The fourth report highlights that, via a survey of local residents applying for to have their homes insulated, annual gas bills are shown to range from just over £400 to just under £1400 (presumably down to occupation levels rather than energy efficiency levels of the various homes?) with the majority of gas bills between £850 to £1100.
  • The average annual gas consumption across residents submitting information is 21,500kWh of gas (hot water and space heating)
  • Actual energy consumption modelling over the year hasn’t been undertaken(the project timeline most didn’t allow for this) and page 33 of this fourth report sets out a modelled indicative spread of space heating (only) consumption over the year
  • Page 34 of the report then provides an indicative idea of how space heating consumption will be reduced as a result of the using external insulating walls, suggesting a >50% reduction in energy use in the home
  • However, the FAQs set out however that “Utility bills and monthly gas readings will be required after the work is done so that the effect of the insulation on your energy consumption is recorded. As part of the preparation work a forecast will be made of the effect of the insulation on your heating energy consumption and the monthly gas readings will help to assess the accuracy of the forecast computer model.”
  • Unfortunately,  the project will not undertake a full fabric approach, the FAQs saying  “No your windows will not be replaced – the grant is for the external insulation only”, but it’s possible the homes were already double-glazed…? However, it’s not immediately clear if this is the case with the two homes insulated
  • Both external (and internal) wall insulation – and also replacement glazing (see Annex 1 of the Government’s recent response to the Green Deal and ECO consultation on the full list of qualifying measures) – will be subsidised under the forthcoming £1.3 bn a year Energy Company Obligation (ECO) scheme, which starts in October 2012
  • It will be interesting to see how the houses perform in their new insulated state, and hence post-occupancy evaluation reports from the project will be of great value.
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