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Installing modern insulation in a Grade II listed roof

20 Dec 11 The owner of the Grade II listed Old Manse building found the only practical way to improve the insulation of the extensive roof area was to use Walltite spray foam insulation applied directly to the timber sarking boards.

Quick to apply, the Walltite has immediately reduced a recurrent condensation problem while the improved U-value of the roof area should give a noticeable improvement in the temperature within the house.

The dramatic Manse has recently been extended, and the roof of the main building was replaced at the same time as the extension (consisting of a round tower structure) was completed.  When the new roof was installed, conventional insulation was fitted between the rafters but this did not solve the condensation problem.

The owner of the house had previously used Walltite to solve a similar problem in a workshop where the corrugated sheet metal roof had proved a condensation nightmare.  As the product cured the problem in this challenging situation, it was a natural step for him to specify Walltite for his home.

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Situated in the Scottish Borders, the roof is exposed to external temperatures that can reach lows of minus 200c.  The condensation problem was caused when moisture froze on the underside of the sarking.   The effect of this freezing was to draw more moisture through the tiles.  As the frozen surface thawed, moisture dripped down onto the insulation, and ultimately the ceilings, below. The application of Walltite cured the condensation problem by eliminating cold surfaces:  all the surfaces are now at a temperature above the dew point.

The house is an old structure with irregular surfaces and a unique shape.  The Walltite spray-applied product was ideal as it moulds itself to the contours of the building and can be used on any substrate material. 

The depth of foam applied can be increased to further improve the thermal insulation.  In this instance, 50mm of Walltite was applied to the entire roof – some 120 sq m.

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