Ceiling extractor, fittings and gotchas enquiry

30 Jul 2013
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United Kingdom
Hi there,

Thanks to some helpful fellows in a previous thread, I now know what I want to install, and roughly how to do it. If anyone could shed some light on the end questions, I'd be very appreciative.

I'm going to install an in-line exhaust fan in my loft, using flexible 100mm ducting; I'll vent the air though a hole I'll be making in the soffit fascia (composed of PVC over wood). I was planning on sealing the vents to the fascia using a neutral-cure silicon sealant - probably the same with the bathroom vent. I'm planning on getting:

Fan: http://www.screwfix.com/p/vent-axia-acm100t-in-line-extractor-fan/53730

External vent: http://www.screwfix.com/p/manrose-square-white-100mm-flap-vent/18561

Ducting: http://www.screwfix.com/p/manrose-pvc-white-1m-x-100mm-ducting-hose/17297

Bathroom internal vent: I'm not yet sure.

My concerns are:

1) I was going to install this about 300mm from the corner furthest from the door, rather than above the shower, so that it's furthest from the source of fresh air. This means a shorter ducting run, as that is also against the outside wall. Aside from being more cramped on installation (now much space in the eaves), is that what most people do? It's a small bathroom, at 3 x 3m.

2) Do people normally affix a block to a rafter, and then the fan to the block? I assume one raises it slightly so that the exit duct angles downwards.

3) How do people snugly affix the flexible ducting to the exit and entry vents? I assume it doesn't simply click in. Do I need to affix a mount of some kind on the opposite side of the vent?

4) Should flexible ducting be installed as stretched as possible rather than bunched, to make the airway edges smoother (and I assume quieter)?

5) Most ducting is listed as 100/102mm, does it make a difference to a 100mm exit vent, or most fans?

5) I was going use duct tape and rockwool to insulate the plastic ducting; I notice that Manrose do an insulated aluminium flexible duct, but they only sell 10m and it's £55! I don't think it's worth it, but I might be wrong.

Sorry, this has been a bit of an essay.
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You've planned this project well!
1) That position is fine
2) If the fan is fitted directly to anything, check for vibration drone - maybe pack with foam. A downwards angled outlet is good!
3) Use Duck tape and cable ties - for aluminium ducting use a large hose clip (jubilee type)
4) Avoid ducting loops where condensate may collect - the straighter the run the better but noise won't be an issue
5) Either ducting will be fine here
6) Insulate if you like, does no harm - but it probably won't make any difference for this run.
John :)
Ali ducting is for kitchen use as it`s heat resistant.
For quieter running I hang unit from rafters via couple of springs, reduces vibration.
I prefer to mount closest to moisture source, ie above shower.
You can get fan with vent kit which has all you need in one pack.
You could use twin inlets with Y joint to fan to pull air from each side of the room.
Hi chaps, thank you for the replies! Good information, and genius tip about suspending via springs - I'll do that. :)

Oh so there's no set way of affixing the duct to the vent? I was curious how one fixes the end to a flat vent face. Does duct tape from the inside of the duct to the outside of the fascia not lose. Adhesion after a while?

Edit: It looks like you can get ducting wall plates with spigots. I can put one of those on the inside of the fascia, then whack some mastic on the join. Sorted!
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Duct Tape no good it degrades with time, kit comes with cable ties, ducting is fitted around fan/outlets and cable tied.[You can use foil tape which is not affected by heat or moisture]

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