IWI to retained window with insulated reveal board

Detail summary

Detail for internal wall insulation to an existing window, to be retained, with a thin jamb profile, requiring a slimmer reveal board to provide continuous thermal insulation.

Target Values

• Cill: 0.045 W/mK.
• Lintel: 0.059 W/mK.
• Wall U-Value: 0.3 W/m²K

Technical description

Section detail. IWI to flush eaves with retained window, thin jamb.

Suggested Installation Sequence:

Before starting work: Remove existing internal cills and any additional internal framing to window. Scabble surface to perforate paint (create lots of small holes with appropriate tool) and remove all wall-paper etc. Re-fix/renew all removed once insulation complete. Plaster: Where existing plaster is gypsum-based, or where space is required, remove existing plaster finish.

Before installation: Remove all timber fixtures: Skirting, Picture Rails, Dado Rails etc. Remove curtain rails. Remove electrical socket/ telephone/cable socket outlets. Re-fix/renew all removed once insulation complete.

Installation:

1. Remove existing wall finishes and plaster as required.
2. Fit internal wall insulation.
3. Fit air-seal tape to window reveal.
4. Fit reveal insulation.
5. Finish with plaster and timber cill.

Reference Specification:

Refer to approved document C (resistance to contaminants and moisture) with reference to the condition of internal walls before application on IWI.

Documents L1b of Part L (conservation of fuel and power) should be referred when working on existing dwellings, with particular attention to sections 5 and 6 regarding material alterations. Document L2b should be referred to with existing buildings other than dwellings.

Replacement window installation to BS 8213-4. PVC-U windows installation standard: to BS 8213-4

All Expanded polystyrene insulation (EPS): To BS EN 13163. All fixings manufactured in accordance with BS1210. Mineral wool (MW): To BS EN 13162; reaction to fire rating to: BS EN 13501-1.

Rigid insulation: where used Phenolic foam (PF): To BS EN 13166.

All vapour control layers/ air tightness layer to durability requirements of EN 13984.

Notes

Care should be taken to ensure air-tightness. Seal all service penetrations through IWI and existing wall. Lap and tape all membranes around edges of IWI system.

All insulation to be continuous to avoid thermal bridging.

Parts list

• Laminate plasterboard [IW05b]

  Phenolic Foam Thermal Plasterboard with integral vapour control layer

  • Plasterboard thickness: 12.5mm.
  • Insulation thickness: 17mm.
  • Edge profile: Tapered edge.
  • Thermal conductivity: 0.21W/m2k.
  • GWP<5.
  • Fixing: Adhesive scored bonding coat to ensure no air-gap to rear of board.
  • Joints: Taped and filled joints.
  • Finish: Prepared for plaster skim coat finish.
  Contacts:

  Kingspan Insulation Ltd:
  Web: http://www.kingspaninsulation.co.uk/
  Product Reference: Kooltherm® K18 Insulated Plasterboard

• Rigid insulation below cill [IW05b]

  Rigid thermoset phenolic insulation board.

  • Insulation Thickness: 15-24mm (to suit window frame/ opening).
  • Thermal performance: : 0.023W/m.k
  Contacts:

  Kingspan Insulation Ltd:
  Web: http://www.kingspaninsulation.co.uk/
  Product Reference: Kooltherm® K3 Floorboard

• Softwood Window Board to Sill [IW05b]

  • Manufacturer: Subject to contractor.
  • Type: Half-round edge.
  • Species: European redwood.
  • Class: Class 2 to BS 1186-3.
  • Finish as delivered: Natural finish.
  • Treatment: Not required.
  • Certification: FSC certified.
  • Fixing: Lost nail heads at 30mm centres.
  Contacts:

  Contractor's choice.

• Internal Wall Insulation System (95mm) [IW02a]

  Water repellent glass mineral wool slab to BS EN 13162.

  • Thickness 95mm.
  • Target u-value: 0.3W/m2k.
  • Thermal conductivity: 0.033W/m2k/ 0.130W/mk.
  • GWP<5.
  • Fixing and supports: In accordance with manufacturer's recommendations.
  Contacts:

  Knauf insulation Ltd.
  Product Reference: ThermoShell Internal Wall Insulation System (Requires: EcoStud for solid wall uprights.)

• Single-sided air seal tape [DP09a]

  Tape for junctions critical to air-tightness.

  • Location: see detail drawings - generally critical junctions for air-tightness. Size: 60mm (Single sided).
  • Accessories: ORCON F sealant and TESCON PRIMER RP (for use on rough/old surfaces to assist adhesion)
  Contacts:

  Back to Earth: Tel: 01392 861763.
  Web: http://www.backtoearth.co.uk/
  Product reference: TESCON VANA/ TESCON PROFIL single sided tapes

• Vapour Control Layer [IW02a]

  Intelligent breather membrane.

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

  Options for intelligent membrane

  • Pro-clima. Reference: Intello membrane
  • Knauf Insulation Ltd.Thermoshell Vapour Control layer.

• Insulated supports IWI system [IW02a]

  Vertical supports for IWI batts. Thermally engineered composite of high performance extruded polystyrene bonded to Oriented Strand Board 3 (OSB 3)supports to IWI sheets. Expanded polystyrene insulation (EPS): To BS EN 13163.

  Contacts:

  Knauf insulation Ltd.
  Reference: EcoStud for Solid walls.(Used in conjunction with Earthwool EcoBatt.)

• Single layer plasterboard backings [IW02a]

  Plasterboard backings. Nail fixed.

  • Manufacturer: Contractors choice.
  • Plasterboard: wallboard
  • Thickness: 15mm.
  • Edge profile:Tapered.
  • Fixing: Nail fixed to Manufacturers recommendations.
  Contacts:

  Contractor's choice

• Two coat Board finish Plaster [IW02a]

  • Manufacturer: Contractors choice.
  • Extent: whole system.
  • Plaster: Gypsum bonding plaster
  • Surface preparation: Tape joints.
  • Undercoat thickness: As manufacturers recommendations.
  • Final coat: Gypsum finish plaster.
  • Final coat thickness: 2-3mm applied one coat.
  • Finish: Smooth.
  Contacts:

  Contractor’s choice.