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National Self Build and Renovation Centre visit

By Roger Lovegrove

The energy group was triggered into arranging this visit because of the Heritage Foundation’s new Design Standards appear to prevent any heritage area house being clad in external insulation. There are about 7,500 pre-war houses in Letchworth that have solid brick walls with no cavity.

22 local residents were coached to Swindon for what turned out to be a very interesting and useful day.

The visit was very illuminating, being a useful mix of focused presentations, guided tours, one on one sessions and free to roam time amongst 400 exhibits and 3 full size houses.

Before cladding walls inside or out it is probably more cost effective to :

1          Insulate the roof with up to 400mm of insulation (yes, 16inches!!).

2          Make the house draft proof  and confirm with fan pressure testing.  Including the letter box and those vent fans but also the window frames and door seals etc).


3          Fit triple glazing.

4          Insulate flooring.

5          Install heat recovery systems

Only the first 2 have a 10 year or less payback time.

Cladding issue Points learnt:

Internal cladding has intrinsic problems because the dew point for condensation moves to the inside of the solid brickwork making for problems with moisture between the brickwork and insulation.  Always consult an expert before installing internal insulation.

External cladding has problems for different reasons.  (The dew point is always outside the brickwork.) The HF, with its ‘Scheme of Management’ and its new ‘Design Standards’  has very strict rules on external cladding. These include:

Semi’s – must do both houses,  Terraced and groups – must do whole terrace / group at the same time.

As neighbouring houses invariably have different owners (eg NHDC, NHH and freeholders etc) this makes it almost impossible to contemplate external cladding.

Any cladding must replicate the architectural detail of the original house. This includes brick string courses, window heads, cill detailing, cornicing and decorative plaques. In conversation, the HF would prefer no external cladding in the heritage area and would only accept such cladding if and only if a very high degree of replication is achieved.  This would include the above, plus detail in the window and door reveals and moving all the windows outwards into the insulation.

Letchworth has a number of renovation problems, including having a very restrictive dual planning system thanks to Ebenezer Howard and the early garden city movement. The NSBRC was able to focus the presentations and guided tours around our particular problems and eco aspirations. As a result our team of home owners – all with pre-war houses – was able to get a focused, up to date view of the latest technologies, identify manufacturers and come away inspired to get going!  The condensation problems with internal wall insulation, in particular, made our team re-think their insulation solutions.

The mix of free parking, free entry, well organised domestic arrangements, excellent presentations and guided tours, by real experts amongst unique displays including 3 full sized houses makes for a fantastic opportunity for anyone planning a new build or renovation. It is particularly useful to see renovation problems for real , full size and in typical situations rather than in a book.  Any organisation involved in self build or renovation will greatly benefit from the unique offer by the NSBRC to combine focused presentations by experts in their field, guided tours and one on one sessions.

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