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    RIBA NBS Specification

    RIBA NBS Specification

    The product information below is from the NBS Plus library of product clauses offered in NBS specification products.

    Specification is an essential part of the design process.  A badly written specification can cause major problems for every member of the project team, and can cost the client a great deal of money.  A well written specification can enhance project delivery and save money.

    The product information below is from the NBS Plus library of product clauses offered in NBS specification products. It has been created by NBS for Ventrolla. The clause is authored in NBS format and is intended for inclusion in product specifications. The clause can be copied and pasted into your project specification document. Please note that NBS product guidance is not a replacement for the manufacturer’s literature and it is recommended that Ventrolla be consulted before specifying.

    To find out more about producing specifications for building projects visit

    Specialist sash window renovation and performance upgrade

    Ventrolla's unique Perimeter Sealing System and Wood Repair System mean renovation rather than replacement, so that all the charm and original character of sash windows can be retained.

    Traditionally, a sash window requires a 3 mm gap around the sashes for functionality. Inevitably, this gap allows in draughts, dust and noise and is the source of annoying rattles. The installation into each window of the patented Ventrolla Perimeter Sealing System seals this gap and actually improves on the original by:

    • Eradicating rattles
    • Virtually eliminating draughts
    • Minimizing dust & dirt ingress
    • Increasing the energy efficiency
    • Reducing external noise

    All work is done from inside the building negating the need for expensive scaffolding. Windows are always left secure and weatherproof overnight.



    Guidance for Specialist sash window renovation and performance upgrade from Ventrolla

    More about Specialist sash window renovation and performance upgrade:

    Renovation and performance upgrade service:

    This service includes:

    • Staff beads, parting beads and sash cords removed and discarded
    • Sashes are eased by removing excess paint build-up, released and brought into the building
    • Adjustments made to ensure min 3 mm gap between upper sash face and parting bead face
    • Mid rail and lower rail of bottom sash routed to profile of pile carrier
    • Pile carriers fitted into the mid and bottom rails of lower sash and the new staff beads
    • Where specified, Ventrolla sash cord brake and detachable sash cord holder threaded on to each new sash cord. Sash edges routed to allow mounting of invisible Sash Removal System
    • Ventrolla parting bead snapped into the new U Section installed into the existing parting bead groove
    • Weatherfin pile weather-stripping size selected and inserted as appropriate to width of gaps to be sealed
    • Sash weights are adjusted to balance sashes
    • Sashes re-hung and checked to ensure easy sliding
    • New staff beads mitred or butt jointed and fitted by pinning, brass screw and cup, or easy release clips
    • Exposed bare wood is painted with white acrylic primer to BS 5082


    Perimeter sealing system performance:

    Air permeability: To BS EN 12207 Class 3 and BS 6375 (600 Pa), independently assessed by British Board of Agrément (test report number 2756).

    Draught strips: To BS 7386.

    Sound insulation: Independently tested and proven to fall within the 6 to 10 dB noise reduction range. Performance verified by Hanns Tucker Acoustic Engineers.



    Ventrolla Wood Repair:

    Ventrolla wood repairs are undertaken using Ventrolla VR90, formulated to give long lasting wood repairs beyond those normally carried out using conventional polyester wood fillers. VR90 is a two-part resin system and is designed to be used to impart the original strength to sash tenon joints, to fill large cavities in sills and to act as a powerful adhesive. It completely bonds with the parent wood and flexes when the wood contracts or expands. To achieve this bond, all decayed wood is removed exposing only sound wood. This is then stabilised using VR90 WS solution which penetrates the wood fibres to attain the permanent anchorage for the subsequently applied VR90 filler.



    Sash removal system:

    The Sash Removal System is a unique hidden method which allows the quick and easy removal of both top and bottom sashes internally. Staff beads can easily be detached from the window giving access to the bottom sash. Using the plastic cord holder, the sash cord can be unclipped from the window which allows the bottom sash to be completely removed. The parting beads can also be removed, allowing access to the top sash. The Ventrolla sash removal system allows all components of the window to be removed internally and brought into the building for convenient maintenance and painting, thereby avoiding the need for external scaffolding.


    Sill replacement:

    Replacement sills can be provided to match original profiles. The original bottom section of the box linings is removed and Sill trenches are cut, the outer and inner linings are spliced to facilitate a flush and water tight finish.



    A wide range of specialist locks and catches are available. 


    Further Information



    CPD information is available here Ventrolla from

    Additional information may be available for Ventrolla from

    To discuss your project and requirements please speak to our Commercial Sales Team on 0800378278 or