Retained window to EWI, thin jamb (section) [Version ID #142]

Author details

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Detail summary

EWI detail to an existing window, to be retained, where existing window is hard up against the inside edge of existing window jamb. This detail proposes Phenolic foam to be used in foam based EWI systems or in woodfibre systems where existing window jamb and head is too narrow for standard 40mm woodfibre reveal boards.

Technical description

Section detail. EWI to existing retained window, perpendicular cill profile.

Where existing position of windows is to be retained when EWI is installed, window reveals must be insulated to prevent cold bridge. Phenolic foam to be used in foam based EWI systems or in woodfibre systems where existing window jamb and head is too narrow for standard 40mm woodfibre reveal boards.

Care should be taken during the installation to ensure the continuity of insulation and air-tightness at the junction between window, existing wall and external wall insulation.

Parts list

  • External Wall Insulation (Woodfibre) System With Rendered Finish

    For use on solid and hard to treat cavity walls. Composite woodfibre board. UdiTherm SK back board, Diffutherm NF (T&G, renderable) top board. \ Fixed mechanically to substrate in accordance with manufacturers recommendations. \ Base Coat - levelling on substrate: 90% contact required around edge of boards between board and substrate to prevent thermal bypass. If substrate is very uneven, use base-coat material around edge of board to achieve contact. \ Thermal conductivity: 0.045W/m2K. GWP 0.

    Unger \ \ Reference: UdiFRONT. \ Render: UDI Perl

  • Insulation to retained window within EWI (Thin - Phenolic)

    Phenolic foam where existing window jamb and head too narrow for standard 40mm woodfibre reveal boards. \ Thickness 20mm. \ Thermal conductivity: 0.023W/mK. \ Finish: rendered as adjacent EWI. Render stops required at junction with window head/jamb to manufacturers standard.

    Kingspan Insulation Ltd \ \ reference: Kooltherm® K5 External Wall Board

  • Extended aluminium Sill with upstand.

    Create extended window sill over depth of EWI to match existing window. Pack insulation beneath cill to prevent cold bridge at existing cill reveal and use basecoat to fix as directed by manufacturer.

    As external wall insulation system manufacturer


  1. Admin - 2015-04-29 16:27:00

    PDF and DWG file updated to latest revision. Amendments to formatting. EWI accessories added to parts list.

  2. Admin - 2015-03-30 12:19:39

    Preview image and detail pdf updated.

  3. Admin - 2015-03-27 15:36:42

    Air seal tape and cill details added to parts list

  4. Admin - 2015-03-25 13:21:09

    General re-formatting. Technical description updated with additional clauses and notes. Parts list updated with suppliers codes.

  5. Admin - 2015-03-10 11:50:16 [Displayed version]

    First version

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