IWI to new triple/double glazed window. [Version ID #79]

Author details

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Detail summary

IWI perimeter detail to head and base of new window in an existing window position. Where windows sit outside the internal wall insulation, it is necessary to insulate the reveals to prevent a cold bridge.

Technical description

Section detail. IWI, perimeter, to window to be replaced.


Cills and framing : Remove existing internal cills and framing to window.

Plaster : Where existing plaster is gypsum-based, or where space is required, remove existing plaster finish.

Parts list

  • Insulated Dry-Lining Board to window jambs and head

    Phenolic Foam Thermal Plasterboard with integral vapour control layer (plasterboard thickness: 12mm, insulation: 17mm thickness). Tapered edge. \ U-value: 0.21W/m2k. GWP<5. \ Adhesive scored bonding coat to ensure no air-gap to rear of board. Taped and filled joints. Prepared for plaster skim coat finish.

    Kingspan Insulation Ltd \ Kooltherm® K17 Insulated Plasterboard

  • Rigid insulation below cill.

    Rigid insulation board. Thickness: 15-24mm (to suit window frame/ opening). \ U-value: 0.023W/m2k

    Kingspan Insulation Ltd \ Kooltherm® K3 Floorboard

  • Softwood Window Board to Sill

    Subject to contractor. Half-round edge. European redwood. Class 2 to BS 1186-3. Natural finish. No preservative treatment. FSC certified. Fixed with lost nail heads at 30mm centres.

    Contractor choice.

  • Internal Wall Insulation System (95mm)

    Earthwool Eco batt insulation. Thickness 95mm\ Target u-value: 0.3W/m2k. Thermal conductivity: 0.033W/m2k/ 0.130W/mk. GWP<5. \ Fixing: In accordance with manufacturer's recommendations. Supports: EcoStuds - XPS and OSB uprights.

    Knauf \ ThermoShell Internal Wall Insulation System

  • Single-sided air seal tape

    Tape for junctions critical to air-tightness. 60mm (typical). \ Accesssories: ORCON F sealant and TESCON PRIMER RP (for use on rough/old surfaces to assist adhesion)

    Pro Clima \ http://www.greenbuildingstore.co.uk/page--pro-clima-airtightness-tapes-options.html \ TESCON VANA/ TESCON PROFIL (2 release tapes)

  • Intelligent membrane- Vapour Control Layer

    Intelligent breather membrane. \ Fixing: Laps And Edges: Sealed with vapour-tight adhesive tape. At junctions with party/patition walls, lap under insulated plasterboard. At floor and ceiling junctions ensure is appropriately sealed.

    Pro-clima \ Intello membrane


  1. Admin - 2015-04-30 09:57:30

    DWG and pdf file updated.

  2. Admin - 2015-04-30 09:54:26

    DWG file uploaded. general formatting amendments.

  3. Admin - 2015-03-30 12:06:52

    Preview image and detail pdf updated.

  4. Admin - 2015-03-29 11:06:25

    IW05b "insulated dry-lining board" replaced with "laminate plasterboard

  5. Admin - 2015-03-29 10:58:22

    Air-tight sealant added to parts list

  6. Admin - 2015-03-26 22:50:34

    General error removal. Parts list codes updated.

  7. Admin - 2015-03-26 22:28:06

    General re-formatting. Introduction and technical description revised and updated with approved document links, notes and BS codes. Parts list updated with suppliers information.

  8. Admin - 2015-03-16 16:15:50

    Version 3. Technical description updated to remove errors in installation sequence.

  9. Admin - 2015-03-16 16:09:34

    Version 2- Introduction updated. technical description expanded. Parts list updated codes.

  10. Admin - 2015-03-03 17:05:12 [Displayed version]

    First version

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