In April 2006 the Building Regulations were amended to include a section on Conservation of Energy and Fuel under Part L1B which was designed to compel homeowners to include insulation in walls, roofs and floors where existing insulation was nil or inadequate at such time as any renovation or repair work is carried out.

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The regulation concerning walls is that if an external wall has a U value – thermal efficiency – higher than 0.7 then insulation has to be used when removing, replacing or adding a layer to the wall unless a very good technical or economic reason makes this impossible to do. The target to try and achieve is 0.35 U value and an existing 9 inch solid wall is rated as 2.05 U value ie a 75% plus reduction in heat loss is being targeted.

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Therefore when replacing old render or pebbledash on the exterior of the wall or adding  a render for the first time a solid wall insulation system must be used at the same time . This can be external or internal but to comply with the Regulations internally is very disruptive and costly especially as the “whole of the wall ” must be covered with no thermal bridging allowed.

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Therefore it is far easier and ultimately cheaper to externally clad the wall from top to bottom in a layer of insulation before covering the insulation slabs in a weatherproof and maintenance free rendered or brick finish.

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These systems are all accredited and are checked and signed off by local Building Inspectors whilst the work is being carried out and the homeowner receives a Building Regs Completion Certificate at satisfactory completion of the work.

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The increasing relevance and popularity of external wall in sulation systems on solid wall homes doers have consequences on the external fittings and features of a property and the following are some considerations that need to be taken into account.

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On average the wall surface will be brought forward by around 65mm or 2.5 inches in old money. Most modern upvc window cills tend to extend 50mm from the wall surface so will need to be extended by around 50mm further to enable the cill to overhang the insulation depth and still shed water efficiently.

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Tiled cills and wooden cills can be similarly extended but stone cills are usually prohibitively expensive to replace on a like for like basis but can be over capped with upvc as a last resort if desired.

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Another alteration that can be needed are to roof lines that have insufficient soffit depth to allow the insulation to be tucked under them without water getting down the back of the insulation boards. Choices here are usually to either extend the roof tiles or more simply to fit an aluminium overtrim on top of the boards that acts like a roof cover and angles water away from the boards.

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The final most common alteration is to down pipes and waste pipes and both of these tasks are fairly straight forward. The exception being if the old rainwater goods are cast iron and usually are secured very close to the wall surface. Whereas upvc pipework is easy to remove and then re-position afterwards ,with cast iron this is not possible without shearing off the retaining plates and screws. In these circumstances it is best to relace with new pipework or if acceptable work around the pipework but avoiding creating any cold bridges.

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If you require further info or want to ask any questions on any of the above then please call on 08456 345 866

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