IWI to retained window with insulated reveal board [Version ID #244]

Detail summary

IWI detail for perimeter IWI to an existing window to be retained in a facade with a thin jamb profile, requiring a thin reveal board detail to provide continuous thermal envelope.

VALUES:

Cill: 0.045 W/mK. \ Lintel: 0.059 W/mK. \ Target wall U-Value: 0.3 W/m²K

Technical description

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

SUGGESTED INSTALLATION SEQUENCE:

Preparation: 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.

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.

Before starting work undertake study of form and condition of existing walls and likely resistance to penetrating damp; log requirement of any repairs and/ or additional works to both internal and external condition necessary before installation of new system -e.g. re-pointing or repairs to external render. Internally: Before starting work carry out study of form and condition of the existing walls; draw up schedule of fixtures, finishes and fittings to be removed/relocated in order to install the internal wall insulation system. Attention to be paid to mechanical and electrical services (e.g. radiators, light switches). Refer to detail drawings for treatment of potential cold bridges (e.g. window reveals). All timbers: Before starting work carry out inspection of any structural timbers which enter the wall to be insulated (e.g. floor joists). Report any signs of damp or rot to contract administrator immediately. Record current condition of timbers and moisture content for future reference.

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

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

Please refer to Approved documents: B (fire safety): B1 section 1 (material alterations)/ B2 section 3 (internal fire spread), and Appendix A (material properties). Doc L: Section 5 and 6 of L1B; including all relevant amendments. Ensure existing joists meet requirements in Approved document A (structural) before starting works.

Parts list

• Insulated Dry-Lining Board- Jamb & head [IW05b]

  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.

  Contacts:

  Kingspan Insulation Ltd \ Kooltherm® K17 Insulated Plasterboard

• Rigid insulation below cill [IW05b]

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

  Contacts:

  Kingspan Insulation Ltd \ Kooltherm® K3 Floorboard

• Softwood Window Board to Sill [IW05b]

  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.

  Contacts:

  Contractor choice.

• Internal Wall Insulation System (95mm) [IW02]

  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.

  Contacts:

  Knauf \ ThermoShell Internal Wall Insulation System

• Single-sided air seal tape [DP09a]

  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)

  Contacts:

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

• Vapour Control Layer [IW02]

  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.

  Contacts:

  Pro-clima \ Intello membrane

• EcoStud insulated supports IWI system [IW02]

  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. \ http://www.encon.co.uk/sites/default/files/products/downloads/datasheet-ecostud.pdf \ Reference: EcoStud for Solid walls. (Used in conjunction with Earthwool EcoBatt.)

• M20A Single layer plasterboard & backings [IW02]

  Wallboard, 15mm thickness. Nail fixed as IWI system manufacturers recommendations. Knauf multi-purpose sealant/ taped joints. Beads and stops for plaster in Stainless steel on all external angles and stop ends.

  Contacts:

  Contractors choice OR Knauf Moistureshield/ Wallboard/ Denseshield.

• M20A two coat board finish plaster [IW02]

  Applied to whole system including insulated reveal boards. \ Two coat (undercoat plus finish) plaster system. \ Gypsum bonding plaster undercoat to manufacturers recommendations. Final coat: finish plaster, 2-3mm applied one-coat, smooth.

  Contacts:

  Contractor’s choice.