Billy Prewitt points out that applying a lagging adhesive to the cut edges of insulation can prove beneficial

Making sure ductwork delivers conditioned air free of debris is an important step in the process of installing air ducts. The process of cutting and installing insulation on the inside of ducts leaves raw edges that need to be sealed. If the insulation is not sealed properly, free-flying fibers are released into the duct’s air stream, out the vents, and into the occupied space. Applying a lagging adhesive to the cut edges of insulation locks down the loose fibers.

Lagging adhesives come in two main colours – black and white. Black adhesive not only seals the ductwork, but also blends in with the colour of the insulation, while white adhesive, when applied on an internally lined black insulation, makes it easy for the inspector and engineer to see that the edges are properly sealed. White has also been specified to coat the entire dark insulation surface for some hospital applications. The white coating, in this case, makes it easier to spot any build-up of dust and dirt in the duct system. Spraying or brushing the cut edges is the most common method of applying the adhesive.

It is important for the product to pass a freeze thaw cycle test to ensure product quality and stability. Mould and mildew resistance is always an important part of all products used inside any ductwork.

Another use for the white lagging adhesive is to seal the wrapped insulation on hot water and chilled water piping. The adhesive provides a vapour barrier, keeping moisture away from the metal piping.

Applying a lagging adhesive helps provide clean air to be distributed throughout the building and seals and protects water distribution piping.

The writer is Marketing Manager, Carlisle HVAC. He can be contacted at Billy.Prewitt@CarlisleHVAC.com