Mechanical ventilation with heat recovery

8.3.8Fixing and jointing of ductwork

MVHR ductwork and insulation shall be installed to a satisfactory standard. Issues to be taken into account include:

  1. fixing
  2. jointing.

Ductwork should be securely installed in a neat and workmanlike manner.


Parallel ductwork runs should be positioned to maintain a reasonably even gap.

To prevent condensate collecting, horizontal ductwork should be to a suitable outfall in accordance with the design, and installed to a true line to avoid localised dips.

Where ductwork passes through an external wall, it should be positioned to slope slightly outwards to prevent water entering the building.

Ductwork should be securely held in position by evenly spaced clips no more than 750mm apart, or in accordance with the ductwork manufacturer’s recommendations.

Ductwork should not be in direct contact with other surfaces, such as plasterboard ceilings, that may transfer noise to the home.


The method and materials used for jointing ductwork should be specified by the duct manufacturer, and be:

  • durable and airtight
  • securely fixed
  • sealed with purpose-designed connections in accordance with the manufacturer’s recommendations.

Where tapes and sealants are used, they should be suitable for the intended purpose and be recommended by the ductwork manufacturer. Issues to be taken into account in relation to the durability of the jointing method include:

  • thermal movement
  • moisture
  • temperature
  • compatibility with the duct material.

Tape should be installed in a neat and workmanlike manner, and surfaces should be dry and free from grease and dust before applying. Excess sealant should not extrude to the inside of the duct.