The Shocking Truth About Extractor Fans!

Picking the right extractor fan can be tricky—price, power, noise, and aesthetics all play a role. But beware of the datasheet! Some fans may look the same, but as we see in this video, looks don't always equal performance.

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Time Stamps ⏱
00:00 Choosing the right extractor fan can be challenging
01:12 Don't focus solely on the fan
02:13 Key design elements need to be analysed
02:45 Fan performance in typical installations
03:35 Noise doesn't equal airflow!
03:50 We need to study the fan curves
05:11 Good luck working this one out!
05:33 Gauging pressure drop
05:55 Flexible ducting can massively effect performance
06:50 Kitchens and utility rooms need higher ventilation rates
07:27 Gordon had to revisit his own installation!
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#ventilationsystem #extractor #ventilation

[mkg]

It was only a matter of time before you had an onlyfans episode.

[albertogarcien]

"A single 90° turn is equivalent to 60 straight meters" is the explanation i need to give most often to my clients as hvac engineer

[simonbeasley]

I bought a 12 year old house and there was a small amount of mould in the bathroom. The large housebuilder had fitted a mains ceiling fan on the opposite side of the wall to the bath. It made a noise but would not hold a single sheet of toilet paper up with its suction, I kid you not. Looked in the loft and "ducting" to a roof vent was made of various leftover bits including a flexible toilet connector taped together! Got a Manrose MF100T, put the vent right above the shower and it's been great. Now a flattened toilet roll tube can be held up by the fan, and that's on medium setting!

[mikepeter]

What lot of people fail to understand is that you can put hundred extractor in your romm, if there is no way for the air to enter from an other way, there will be no extraction because the room will be in depression and the air flow will stop.

[philross]

Guys... you guys have my subscription. You guys are the only ones i have found on youtube that actually get it, and understand the importance of a video WITH A TEST COURSE. The real people out here are interested in retaining the information, not just passively watching youtube videos and forgetting about it a week later.

[Lucozade.sport]

Very few people want to pay for adequate ventilation in my experience. I've known people who had fairly large and expensive 'luxury' bathrooms installed, but want to use the cheapest fan possible - using the existing ducting or core hole to save a few quid. If there's a loft space above, its fairly easy to install a 4 or 5 inch inline fan and extract via a soffit in many cases. If the fan is mounted above the insulation, they can be extremely quiet - all you hear is the sound of air air being pulled through the inlet grille.
If you use a 5" grille, 5" ducting and have the fan set to the lower speed, it can be almost silent, but still retains a very good extraction rate.

Having to core a hole through a wall, get up a ladder outside to mount a grille, run sensible dusting etc can take up the best part of a day in some cases. Including the cost of an adequate fan, insulated ducting, install an accessible isolator etc. may well cost £400, but is generally money well spent IMO.

When a customer says they want to use the existing fan in their nice newly fitted bathroom - just because it seems to work and saves some money I despair!

If a fan wont even hold a single sheet of toilet paper to the ceiling/wall inlet, then you know its not going to perform very well!

Humidistat fans can cause grief in certain properties. We retrofitted one in a basement in Kensington and would run constantly no matter what humidity sensitivity it was set to - purely as the basement had high humidity all year round due to damp issues.

[ypyp]

So refreshing, simple yet with enough technical background to justify the conclusions being reached. Thank you

[TheStigma]

I think it is important to note that the different performance of fans is not just due to quality differences. The type of fan design usually matters the most. There are different fundamental designs optimized for high flow, high pressure, or a bit of both - but you inherrently can't be great at both. The design of fanblades is a very well explored science, so don't let marketing persuade you that some expensive fancy fan has the best of both worlds. This is a design tradeoff you have to maks - so use the appropriate type for the spesific situation.

High flow fans typically have fewer, larger and more spaced blades with deep angling to scoop up a lot of air, but they work best if you are venting sirectly to the outside with no or minimal ducting. They drop in performance very quickly if there are restrictions and might even stall out completely if used inappropriately.
High pressure fans have many, dense, shallow-angle blades to maximize pressure (ie. how well it can force air to move against restrictions, like long ducting or filters). While every fan will lose performance with long and winding ducting, these will suffer least.

Personally I would go for a model with an adjustable hygrostat (humidity meter/controller). These sensors are cheap and shouldnt add much cost, but it can can save both noise and energy by running on minimum or even turning off when the room is already dry. Remember that in the winter you are venting out the heat in the house, so you don't want excessive venting when its not needed.
Having a "boost" button that temporarily runs the fan full speed can be nice if you want to get rid of toilet stinks quickly. Thats also a common feature.

[guffermeister]

Good job we are all fans of the channel. I'll get me coat.

[skfalpink]

I gave up on standard extractors and instead fitted two in-line fans in the loft. They simply amazing, and have (especially in the bathroom) completely eliminated shower condensation.

[Brian]

I ended up simply installing a PIR unit onto my envirovent 100 and it drastically improved the extraction process overall, stink humidity etc with a run on timer, along with ensuring a 10mm gap under the door.

[barryfoster]

In my opinion, it's actually best to go for a Heat Recovery Fan which is on all the time. Many have a boost feature which you can activate while you're in the bathroom.

[robcarver]

Re condensation and cold walls. Our new-build when we moved in suffered from numerous problems that should have been picked up by the building inspector (NHBC).
One major problem was the dry lining stuck to the inner block-work with dab and dot. The top of the inner side of the plasterboard was open to the roof space. This rendered the cavity wall insulation almost useless as the heat was just insulated by the thickness of the plasterboard. When I eventually realised what the problem was I had to drill a line of holes round the top of the outside walls in each room and squirt expanding foam in to fill the gap.
In the bathroom I increased the under door gap and fitted grills above the door to improve airflow. The extractor fan now performs really well.
This made a tremendous difference to the amount of condensation on the bathroom wall and noticeably improved comfort in the rest of the house.
And no, I wouldn’t waste my time involving building control, they didnt want to know about the NHBC failings.

[robertwilliams]

When I fit inline fans and ducting, I put the fan as close to the outside vent as I can. Less pressure to push against and let the power of atmospheric pressure fill the slight vacuum behind.

[chillstar]

I added 3 flow switches when I rebuilt our bathroom. 1 on the cold feed of the shower, bath and toilet which triggers the fan, 1 to the hot feed to the shower & bath (also triggers the fan, added as redundancy).
These are connected to the fan where a lighting circuit would normally be connected to trigger the fan, so it's using the built-in timer that keeps the fan on after the water stops flowing.
Lastly, there's one on the hot feed of the shower (triggers the lights in the shower cubicle. This has a custom built electronic timer that keeps the lights on for 6 minutes after the water flow stops).

There's a sink in the bathroom, but I intentionally put the flow switches after the sink in the water circuit as there's no need for the fan to come on when just brushing teeth or washing hands.

With this setup, the fan only comes on when the shower or bath is running, or if the toilet is flushed. It then stays on for 10 minutes or so after the water flow stops.

If we ever need to force the fan to come on, we just turn the bath or shower tap on for a second.
If we ever need to force the fan off, we just use the fan switch outside the bathroom.

We also have a movement sensor that's controlling the lighting, with a 5 minute delay before it turns off.

Simple setup that works a treat and has been reliable for over 10 years.

[einseitig]

This is excellent information.
Having just bought a new build house I am en garde so to speak.
Thanks.

[Kegels_gti_V]

We had the silent serie for Some years, 3-4.. and we reduced& stopped mould grow in the bathroom.

but we still had mould grow in the bedroom.
So i changed the silent serie for a vent axia multihome, that Provides us from fresh air 24/7! No more mould in the bedroom since we ventilate 24/7.. 🤞🏻

[AaaaandAction]

Pity you didn’t highlight the effect of sagging on those flexible ducts. At some point on its way to the outside air the moisture in the shower air condenses out and forms a puddle in the sag. The additional weight increases the sag and sooner or later the gallon of water leaks out onto your plasterboard ceiling.
I had a new house where the extractor wasn’t working and tracing the problem in the loft had me lifting the sag and pouring a bucket load of water out of the eaves outlet.
Changed it to an immediate rise at the extractor and solid pipe sloped towards the eaves and wrapped in quilt. Also a condensate catcher with 20mm drain at the ceiling position.

Much under-appreciated problem!

[joopterwijn]

Nice presentation, however I mis the notice of the supply of air in a (bath)room. If you want to suck out moist air, you need to to supply fresh air. Next if you live in a area with lots of bugs like 🦟, take a vent with a filter or beter with flow-shutters etc.

[chris-non-voter]

I use a slow extractor fan to gently move floor level cool air out of the room to improve the warmth in the room. I have an ASHP that moves warm air around my flat. The fan helps put cooler air back towards the heater.