Retrofit design

Window replacement guidance (subject to detailed design considerations).

DESCRIPTION
Replacement of some windows
TARGET U-VALUE: 0.8-1.5 W/m2K
RELEVANT STANDARDS
Building Regulations Part L1B, Approved Document 7 Materials and Workmanship
INTERFACE WITH OTHER ELEMENTS
•Windows to be installed, with insulated cavity closers.
PRODUCTS
•uPVC windows
•Compressible filler tape: IsoChemie Win2Wal 64 mm wide or equivalent performance and approved
•Airtightness tape: ProClima SOLSL80 Contega Solido SL 80mm wide or equivalent performance and approved
•Trickle vents Glidevale Acoustic Energy Saver Humidity Sensitive Trickle Ventilator or equivalent.
WORK SPECIFICATION

PRE-INSTALLATION WORK
Window sizes to be confirmed by manufacturer considering detailing and including external cills
PREPARATION
1.Original windows to be removed and surround cleaned to take new window.
INSTALLATION
2.Install insulated cavity closers
3.Apply compressible filler Win2Wall to all edges of window frame.
4.Install window as per details and to manufacturers’ recommendations.
5.Install air tightness tape over window frame and surround.
6.Plaster in the air tightness tape internally and finish appropriately externally.
SUPPORTING GUIDANCE
CONTINUOUS INSULATION TO REDUCE THERMAL BRIDGES
Thermal bridges between the wall and window are minimised by positioning the window in line with the insulation layer. Where this is not possible the insulation should be installed up to the window.
AIRTIGHT CONSTRUCTION
The airtightness tape provides an airtight seal between the wall and window internally. The compressible filler seals the gap between window and wall/ reveal by adapting to the unevenness of the structure. It prevents ingress of rain while not trapping vapour in the structure, which could condense. Together these two elements provide an airtight solution associated with minimal risk of condensation.

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