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Intumescent/non-combustible sleeving/ducting in timber-framed buildings.

Farmboy
PE magazine have run the article 'Wiring Timber-Frame Buildings' (a typical construction example shown in the attachment), which seems similar to those alluded to by ES1st (in their BP Guide 5, Fire Safety).


When installing wall fans in timber-framed buildings, one option is to use intumescent sleeving (such as shown in the attachment) for flexible ducting (but seems quite expensive at approx £60 for a standard 100mm ducting up to 500mm). Another option is use non-combustible/metal ducting (as suggested in BPG5). However, does anyone know of a supplier for such metal ducting (fire rated or proven for such use)? When I ask wholesalers and fan manufacturers, they all seem bemused (with some saying they don't think anyone bothers to use them), and as yet a google search reveals little help.


F
attachments.zip
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  • 0

    Zoomup:

    Hopefully plastic cased ventilation fans are made of a non-flammable material. Also hopefully the fan motor has a thermal cut-out device embedded into its windings. Hopefully we fuse the fan according to the maker's instructions, often 3 Amps. maximum. Hopefully the thermal wall insulation in the wooden framed homes is flame retardant. Statistics show that fan fires are prevalent. Possibly they are positioned incorrectly like over a hot cooker and a buildup of grease occurs within the fan. Personally I have never found a big black molten plastic blob on the floor under a wall extractor fan, but I suppose that it does happen. I have found brown marks inside the fan timer module where the large Voltage dropper resistor gets hot, and even a charred circuit board, but no evidence of fire.


    I imagine that a conventional cheap flexible metal wall sleeve duct will contain a fire for a period of time. The danger might be from a fan catching fire and igniting interior floor coverings or furniture in a timber or brick built house.


    Some makes of extractor fan have GS approval. To what extent that covers fire safety I would have to research.

    https://www.vent-axia.com/range/basics-slim-line-range


    Z.




    Apparently it's not just fans themselves catching fire that's the problem, it's also that if there's a fire in a room when the fan is running, it can suck the flames into the pipe, so if plastic melt it and get into the wall void etc.


    I'll do as mentioned and contact ventilation supplies co's and see what's available, flexible or otherwise that's fire rated.


    The PE article mentioned that building regulations regarding timber framed buildings are being reviewed and may change later in the year, so liaise with building standards for further advice.


    F

Reply
  • 0

    Zoomup:

    Hopefully plastic cased ventilation fans are made of a non-flammable material. Also hopefully the fan motor has a thermal cut-out device embedded into its windings. Hopefully we fuse the fan according to the maker's instructions, often 3 Amps. maximum. Hopefully the thermal wall insulation in the wooden framed homes is flame retardant. Statistics show that fan fires are prevalent. Possibly they are positioned incorrectly like over a hot cooker and a buildup of grease occurs within the fan. Personally I have never found a big black molten plastic blob on the floor under a wall extractor fan, but I suppose that it does happen. I have found brown marks inside the fan timer module where the large Voltage dropper resistor gets hot, and even a charred circuit board, but no evidence of fire.


    I imagine that a conventional cheap flexible metal wall sleeve duct will contain a fire for a period of time. The danger might be from a fan catching fire and igniting interior floor coverings or furniture in a timber or brick built house.


    Some makes of extractor fan have GS approval. To what extent that covers fire safety I would have to research.

    https://www.vent-axia.com/range/basics-slim-line-range


    Z.




    Apparently it's not just fans themselves catching fire that's the problem, it's also that if there's a fire in a room when the fan is running, it can suck the flames into the pipe, so if plastic melt it and get into the wall void etc.


    I'll do as mentioned and contact ventilation supplies co's and see what's available, flexible or otherwise that's fire rated.


    The PE article mentioned that building regulations regarding timber framed buildings are being reviewed and may change later in the year, so liaise with building standards for further advice.


    F

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