in line fans, recommendations appreciated

Dave the spark · Mar 28, 2017

Evenin' all,

Looking for recommendations for an in line fan. Want to install 2 of these in my loft to replace the ceiling extract fans currently in place. I don't want to spend too much but want something that will be effective.

Also, would anyone recommend venting out through a roof tile, rather than through the soffit as it's currently set up?

We have been getting excessive condensation in our loft, akin to rainfall on a bad day. The house is only 5 years old and i think the builder hasn't properly vented the loft space. My plan is to improve the extract fan ventilation and have more vent tiles installed on the roof.

Andy78 · Mar 28, 2017

Axial fans in ceilings have very limited capability, but I'm guessing that is what has been fitted in your new build house, as I see a lot of that.
I have recently been fitting Manrose mixflo 100 fans where the situations suits. They have three extract flow settings, up to 68l/s, and are extremely quiet whilst still being at the lower end of cost for a quality inline fan.

Octopus · Mar 28, 2017

Given the choice, I always recommend inline fans.

Avoid the £25 units from the sheds etc as they are no good unless the vent run is less than 1 metre.

On new installs I tend to use this unit:

SL TD160T In Line Extractor Fan Kit with Timer - https://www.tlc-direct.co.uk/Products/SLTDK160T.html

and no pesky 3A fuse required plus never yet had a unit fail!

For upgrades I tend to use these:

4 inch Inline Extractor Fan + Timer - Manrose CFD200T - https://www.tlc-direct.co.uk/Products/MRCFD200T.html

If the run is long, lay some 100mm loft insulation over the pipe to reduce condensation AND raise the height of the fan so the vent runs away to the sofix.

Dave the spark · Mar 28, 2017

Thanks guys, looks like the manrose fans are what I should be looking at in terms of performance for price.

Would you recommend venting through the roof? We have black mould forming on the seam of wall and ceiling in the bathroom and it looks to me to be where the flexi duct sits in the loft just before it drops in to the soffit vent. I think there could be a build up of condensation in the ducting which is cooling that part of the ceiling.

I'm pretty unhappy about the whole situation, I'm going to contact the NHBC for advice as the house is under a 10 year warranty and we shouldn't have to pay out for a problem not of our own making.

Wilko · Mar 28, 2017

Hi - IMHO roof tile outlets are more effective due to the natural upwards flow of warm air and 'safer', in that the exhaust is much less likely to be drawn back into the roof space (through soffit vents) or the house (through open window or trickle vent). But they are harder to do and cost more.
FWIW I was thinking about this while up in a loft trying not to get electroluxed with open twisted cable joins and condensation dripping around me. My memory of physics is condensation is the result of warm (moist) air contacting a cold surface (does your condensation form on the sarking/felt and drip down?). Anyway, if you just ventilate then you bring in cold air, but you could try this as it may help a bit. If it was truely a simple fix then dew would never form on your car etc. Unfortunately the fact there is a big temp difference with thick insulation on the ceiling means there is going to be potential for condensation nearby. If there is no effective vapour barrier beneath the insulation then we are just feeding it with moisture from cooking, showering and breathing etc. So my next thought is to properly seal the roof space from the rooms below. This means a vapour barrier /dpm under the insulation, all pipe and cable entry's sealed etc. These are just thoughts and hopefully will trigger more discussion

PEG · Mar 28, 2017

Dave the spark said:
Evenin' all,

Looking for recommendations for an in line fan. Want to install 2 of these in my loft to replace the ceiling extract fans currently in place. I don't want to spend too much but want something that will be effective.

Also, would anyone recommend venting out through a roof tile, rather than through the soffit as it's currently set up?

We have been getting excessive condensation in our loft, akin to rainfall on a bad day. The house is only 5 years old and i think the builder hasn't properly vented the loft space. My plan is to improve the extract fan ventilation and have more vent tiles installed on the roof.

Hi,what roof construction is it? Underlay type,dry verge ridges or traditional mortar?

Has the loft got insulation,and is there any water entering the loft by other means?

Any header tanks,vents or similar?

Cheers,i love these remote detective thrillers

Octopus · Mar 28, 2017

Back to the OP - do you have the window open when you use the fan? and is there a sufficient gap under the floor to ensure a good flow of air into the bathroom?

You don't want to be drawing cold air into a steamy room and if there's no flow under the door the fan won't be much good!

Also - best not to have the vent pipe sitting directly on the plasterboard, except at the point it goes "down" - surely you must have a decent layer of insulation up there!

PEG · Mar 28, 2017

Also,let me save you the worry,regarding NHBC,they will not help you,as they exist for the summary and intangible benefit of the builder/developer...NOT you.

I know this,as one of their representatives,told me exactly that,whilst i was stood,ankle deep in human excrement,in the back garden of a large,expensive 5 bedroom detached property,one Christmas,2 months after it's first owner moved in...

The Bio-filter had been installed by three blind mice,overseen by the least useful wise monkey

SparkyChick · Mar 28, 2017

I've been in quite a few lofts recently that have had bad condensation problems. The common factor was a thick layer of itchy poo on the floor of the loft. We have the same problem at home, and it started when additional itchy poo was added to improve the energy rating.

Having done quite a bit of reading around it, the best solution I could find was to install insulating boards in the rafters with a 50mm gap between the felt and the insulation, followed up by a moisture proof membrane. And then either removal or serious reduction in itchy poo on the floor to allow the loft space temperature to equalise whilst still being well insulated from the outside world.

I initially thought more ventilation would fix it, but in reading around, the general consensus from apparent experts was not.

Andy78 · Mar 28, 2017

I once attended a less than ten year old three floor "town house" style building. An axial fan had been installed in the ceiling of the bathroom on the middle floor. The rigid ducting extended five vertical metres through the top floor and loft before another 5 metres of floppy, looping, flexible ducting leading eventually to a tile vent.
The fan had burnt out and the owners wanted it swapping for another similar axial fan, but one that wouldn't leak water through it like the old one.
When I told them that these fans are designed to extract no more than two horizontal metres they wouldn't have it. "Well the builders wouldn't have designed it like this if it wouldn't work"
New builds. You couldn't pay me to buy one.

Electric Magic · Mar 28, 2017

The Manrose MF100T is a great fan. The Aventa AV100T is almost as good (50 litres a second and 27 decibels) and quite a lot cheaper.

Dave the spark · Mar 28, 2017

Christ, that's a lot to take in!

Thanks for the replies, i thought a simple fix would be to add more air flow to the loft space. As i know nothing about the roof type or installing membranes and insulating board i think I'll employ to opinion of a good roofer. Still fancy the in line fans though

Toneyz · Mar 28, 2017

Axial fans unless direct through wall have little effect there is too much resistance and burns out the fan use insulated duct reduces condensation ridged where possible the Manrose in line fan I also would recommend

SparkyChick · Mar 28, 2017

Dave the spark said:
Christ, that's a lot to take in!

Thanks for the replies, i thought a simple fix would be to add more air flow to the loft space. As i know nothing about the roof type or installing membranes and insulating board i think I'll employ to opinion of a good roofer. Still fancy the in line fans though

Do some research, I found it a nightmare finding info, but got the impression there are companies out there that specialise in fixing it or at the very least offering professional advice.