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Home / Method Statements / Construction Method Statements / HVAC Building Construction Method Statements / Duct Works / Method Statement For HVAC Ductwork Insulation And Acoustic Lining

Method Statement For HVAC Ductwork Insulation And Acoustic Lining



This method statement covers on site installation of insulation for pre-fabricated duct-work systems manufactured from hot dipped galvanized steel sheet to S.M.A.C.N.A.


2.1    This method statement is to define the method to be used to ensure that insulation and acoustic lining for prefabricated ducting, bracketing, and in line equipment installation and final connections and workmanship are correct and acceptable, and conforming to the contract documents and General Specifications

2.2    Material to be submitted for review by the Client- see latest Revision of the Material Procurement Schedule.


3.1    Construction Manager

3.2    Mechanical Engineer/Superintendent

3.3    Warehouse Controller

3.4       Quality Controller



  • All materials, drawings and other documentation relevant to a particular section of works will be checked by the Construction Department prior to the commence of work
  • Before commencing any construction works, pre-inspections will be carried out on all materials prior to them leaving the storage area.
  • Prior to the commencement of any construction works, areas and access will be inspected by the Construction Team to ensure that they are in a suitable condition for construction works to commence.


  • Mechanical Superintendent will instruct tradesmen regarding the execution of the works and will distribute all necessary approved construction drawings of the latest revision.  The supervisor will also check that tools and equipment available are in compliance with the contract requirements.
  • Supervisor will requisition approved materials for the specific installation to be carried out and adhere to the following guide lines for insulation and acoustic lining.
  • On receiving the approved materials, checks will be made by the Construction Supervisor to ensure that slabs are free from damage and ingress of moisture.
  • Care will be taken in the preparation of the under surface before any adhesive is applied, all the duct-work is to be clean and free from moisture.
  • For acoustic lining, the lining will be secured using 100% coverage of adhesive, and fixed using mechanical fasteners.  Fasteners will be at 400mm centers and not more than 50mm from the edges of the lining.
  • Ductwork acoustic linings will be William’s CFC free punf. foam  and will be applied with insulation adhesive and metallic fasteners. Site Supervisor will ensure that seams and joints are thoroughly sealed to eliminate possible fiber entertainment in the duct due to air velocities, and provide continuous sheet metal edge protectors at entering and leaving edges of lined duct section.
  • Sectional ductwork will be joined together after internal insulation or acoustic lining – Longtitudal seams shall be joined by means of the Pittsburgh lock system and traverse by mating flanges spot welded to ductwork.
  • Contractors Drawings will clearly indicate which sections of prefabricated ductwork are to be installed within one meter of electric heaters, and fire dampers.  If these sections are internally lined they will be sheathed with sheath metal to form a “double skin”  in accordance with the contract document.
  • If applicable, acoustic lining associated with exhaust ductwork from kitchens services, food preparation areas and similar areas shall be sealed with a impervious material such as polyethylene telephthalate or similar in accordance with the manufacturer’s recommendations.


  • Ductwork that is to be externally lagged will be identified on the approved contractors drawings and issued to the on site supervisor.
  • Surface areas of ductwork will be inspected to ensure that they are not wet or damp.
  • An independent section of insulation will be applied to each adjacent section of the ducting, ensuring corners have adequate backing foil with a minimum 75 mm overlap to achieve an acceptable vapor barrier.
  • Joints will then be sealed with 150mm wide adhesive tape horizontally and vertical.
  • Care shall be taken during the installation of the insulation that adhesive is applied with 150mm brush widths at 300mm intervals.  Insulation will be fixed with pins clips to prevent sagging, and tie cords or bands may be used at 900mm centers until adhesive sets.
  • Special care will be taken that perforations cause by pins and or clips or similar are correctly vapor sealed.
  • Supervisor to ensure that where insulation passes through a fire barrier sleeve all gaps are caulked with approved fire resistant material.
  • Flexible connections will be wrapped with insulation overlapped and secured to ductwork shoes and plenums by the use of metal bands.
  • High density fiber glass board complete with vapor barrier ‘or’ equivalent material shall be used on bracket/hangers for the external insulated ductwork.

Supervisor to ensure that all completed insulation works referred to in this method statement will look neat and tidy and that there is adequate spacing to allow access for dampers and in line equipment operation and ease of maintenance.

The Supervisor in charge and the QC officer shall continuously monitor the activities to ensure that all components indicated on the approved drawings have been installed and that the installation is in accordance with the contract requirements and manufacturers recommendation.

All completed installation works equipment will be protected to avoid damage until final completion/handover in accordance with the approved procedure.



Insulation Checklist.


  • Particular Technical Specifications
  • Shop Drawings