Client: Hodgkinson Design

Duration: 2 days

U-value target: 0.24 W/m2K

Air tightness target: no target 

Cost: £30/m2

Installation area: 150m2

Location: London, W5


Existing build-up specifications

  1. Tiles
  2. Battens
  3. Bitumin roofing felt/ Timber sarking boards/ Breather membrane
  4. 100mm existing rafters/ 150mm new rafters
  • 50mm ventilated air gap
  • 50mm rigid insulation board between rafters
  • 70mm insulated plasterboard below rafters
  1. Skim and finish

Proposed build-up specifications

  1. Tiles
  2. Battens
  3. Bitumin roofing felt/ Timber sarking boards/ Breather membrane
  4. 100mm existing rafters/ 150mm rafters
  • no air gap (Icynene is breatheable)
  • 100mm/150mm Icynene H2Foam Lite
  1. Vapour check plasterboard
  2. Skim and finish

The problem

Limited by the height of the existing roof structure the designer of this loft conversion was presented with challenging decisions. Maintaining ceiling heights whilst delivering an energy efficient structure would have been costly to achieve with conventional insulating materials as well as managing moisture vapour and ventilation with the different roofing membranes.   

The solution

To overcome these problems and ensure a complete, unbroken layer of insulation the client specified Icynene H2Foam Lite spray foam insulation. The unique properties of the 100% water blown, fully open cell foam mean that Icynene H2Foam Lite is BBA approved to be applied to any roofing underlay. The 100x expansion ensures a complete fill of all gaps with minimal effort.

The result

In two days London Insulation have been able to completely insulate the 150m2 timber/steel roof structure of this tricky loft conversion, leaving the client with a high quality, high performance air barrier and insulation.