Warm Roof Construction and Part L Compliance

Posted by: Wholebuild

Meeting approved Document L of the Building Regulations (the practical guidance on ways of complying with energy efficiency requirements through the conservation of fuel and power) may require significant changes to the design, specification and construction detailing of warm roofs, especially where U-Values are concerned.

Warm roofs are constructed to improve a roof’s thermal efficiency by eradicating heat loss and to make more use of available space in lofts, attics and other roof spaces.

What is Warm Roof Construction
In previous decades, roofs would have been built with little attention paid to ventilation and insulation. As a result, heat gain and loss during summer and winter months meant that buildings either over heated or cooled requiring excessive air conditioning or heating to maintain a more ambient temperature all year round. It was common to find moisture within the roof structure, leading to condensation, damp and rotting of joists and subsequent breakdown of the roof structure.

In warm roof construction, insulation is installed across the top of the rafters (unlike cold roof construction where the insulation is placed between the rafters). This creates a void of warm air between the ceiling and the joist, retaining heat within the property with the result that heating requirements and resultant heating costs can be significantly reduced.

Warm roofs are generally cheaper to build than the ‘cold roofs’. Cold roofs have issues with thermal bridging and reduced thermal efficiency with the increased specification of ventilation solutions at the junctions of the rafters and the external face of the roof structure.

What do I need to construct a warm roof?

  • Floor Joists – such as the innovative EcoJoist
  • Joist Hangers
  • Insulation
  • Counter battens
  • Breathable Membrane
  • Roofing battens
  • Fixtures such as:
    InSkews the strong and durable fixing for pitched warm roof construction
  • Roof tiles such as the innovative high performance Envirotile

For more information on warm or cold roofs, please contact a member of the Wholebuild team on 01892 882 540.

Image of warm roof construction ‘sandwich’ provided by Helifix.

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Information Updated on: 20 November 2012