Kitchen Exhaust Ductwork 1

[ickey]

If internal lining is used in kitchen exhaust ductwork. Can the internal lining be faced with a perforated foil? or is only perforated metal acceptable? If a pervious lining such as melinex is used to seal the lining, is the melinex to go over the perforated metal/foil or inbetween the metal/foil and the insulation?

 

[DouginMB]

I can't imagine a building code in the world that would allow lined kitchen grease duct. The inside of the grease duct needs to be washable to eliminate the buildup of grease. Duct liner does not lend itself well to washing.

 

[imok2]

Take a look here:

http://www.kees.com/kitchen_hoods-5.htm

 

[lilliput1]

Imok2 the lining in your link if for the makeup air supply. Grease hood duct should not be lined. The grease hood duct from the ceiling to where it exits the building should be enclosed in a fire rated enclosure or approved fire barrier type insulation (see 3M) or be listed double wall grease duct (see Metalfab)except if the roof where the duct exits is right above the room/hood.

 

[ickey]

DouginMB: Australian Standard 1668 Part 1 allows for internal lining of kitchen exhaust ductwork if: # The material shall be deemed to be not combustible. # The materials shall have a temperature of fusion not less than 1000C # insu;ation materials shall have a temperature of fusion not less than 500C and if internal, shall be faced with perforated metal complying with the above aforementioned.

The only problem with this standard is it is for fire & smoke control and it is not clear if it also applies to kitchen exhaust ductwork that does not operate in fire mode (smoke control)

 

[remp]

Ickey,

I have had consultants in Sydney spec attenuators with milnex lining before for kitchen exhasut systems. However I have always managed to get away with out one with a slightly oversized DWDI centrif fan running at low speed. Im not sure about milnex lining, i have heard of it been used on Attenuators been exposed to atmosphere so it is probably waterproof, but this will only lead to a reduced Sound Insertion Loss of the attenuator. Putting it in a K/E system will lead to it getting clogged up even if the material does conform to fire codes etc...colgged up K/E duct is a fire hazard itself. Dont do it.

 

[paulkeating]

Billy's comments and all others notwithstanding ......

The perf foil goes OVER the melinex. The purpose of the foil is to keep the insulation in place - it is merely a "retainer". The retainer, if you'll forgive the label, is metal when you anticipate that the retainer will be subjected to hot air or fire (ie the smoke control bit you mentioned), and it can be foil (ie not so good in a fire) if the system is NOT to be run during fire mode.

As for the comments about grease build-up, well that's a slightly different question, and that is a function of cleaning and AS.1851.6 and so on. Take the extreme cases of (a) melinex-lined and insulated duct cleaned EVERY day, and (b) an uninsulated unlined bare duct never ever cleaned.

This is to illustrate that the lining per se is NOT the cause of the problem, but only a SECONDARY factor. The MAIN factor is the maintenance and cleaning regime.

Does that help? If you need more info or a further opinion, drop me a note at paul.keating@jlwilliams.com.au