EnviroVent Filterless Fans: The Extract Fan Built for Rental Property
Here is a thing that happens in rental property, over and over.
A landlord fits a decent bathroom fan. Two or three years pass. A tenant reports mould. We attend, take the cover off, and find a filter so packed with dust and lint that the fan is moving almost no air at all. The unit is fine. The motor runs. It has simply been slowly strangled, because nobody was ever going to take that cover off and clean a filter, and nobody did.
That is the problem EnviroVent's filterless fans are designed to remove — and it is why we specify them heavily across tenanted stock in Greater Manchester.
Quick answer: EnviroVent filterless extract fans are continuous-running, humidity-tracking wet-room fans designed without a filter, so there is no serviceable part to clog and no maintenance task for a tenant or landlord to forget. They run quietly at a low trickle rate and boost automatically when humidity rises. Supplied and fitted is £430 + VAT, which includes core drilling through the external wall, the ducting and terminal, the electrical connection and certification. Call 0161 706 1360 to arrange a survey.
Why the Filter Is the Weak Point
Every extract fan pulls air out of a damp, warm room. That air carries dust, lint from towels, hair, skin cells and aerosol residue from sprays and cleaning products. In a bathroom, it also carries a lot of moisture, which makes all of that stick.
On a filtered fan, that debris lands on the filter. That is the filter doing its job. The trouble is what happens next:
Nobody changes it. Not the tenant, who does not know it exists and has no obligation to. Not the landlord, who is not in the property. Not the letting agent, whose inspection checklist covers smoke alarms and condition, not fan filters.
Airflow drops gradually. There is no moment where the fan stops working. It just delivers less and less air, month by month, until it is doing nothing meaningful. It still hums when you switch the light on, so everyone assumes it works.
The failure is invisible until there is mould. By the time the problem is reported, moisture has been accumulating for a year or more, and the mould is established in the coldest bedroom rather than the bathroom where the fan is.
Then the fan gets blamed, or the tenant does. Neither is the cause. The maintenance model was wrong for the building.
For an owner-occupier who will pull a cover off once a year, a filtered fan is perfectly reasonable. For a rental property, a product whose performance depends on a maintenance task that will not happen is the wrong specification.
What a Filterless Fan Does Differently
EnviroVent's filterless designs approach it from the other end: build the fan so that debris does not accumulate where it matters, and there is nothing to service.
The characteristics that make them suit tenanted property:
Nothing to clog. No filter means no gradual airflow decline. The fan that is fitted today is broadly the fan you have in five years.
Continuous running. They run permanently at a low trickle rate rather than switching on with the light. That constant low-level air change is doing quiet work all day, which is what actually keeps a property's background humidity down.
Humidity tracking with automatic boost. When someone showers, the fan senses the rise in relative humidity and ramps up, extracting until the moisture has gone, then settles back down. It is not a fixed three-minute overrun, and it works in summer when nobody puts the bathroom light on.
It cannot be switched off. Wired permanently live with isolation for maintenance only, so a tenant who finds fans annoying cannot defeat it.
Very low running cost. A continuous fan at trickle speed draws a handful of watts — realistically well under £20 a year in electricity.
Quiet. At trickle speed, most people stop noticing them within a day or two.
Greenwood Airvac produce continuous-running humidity fans that work on the same control principle, and we fit a lot of those too — the comparison between the two is covered in our EnviroVent vs Greenwood Airvac guide.
Through-Wall Installation: What We Actually Do
Most of our fan installs go straight through an external wall rather than routing through a loft or ceiling void. It is the shortest, straightest, most reliable duct route available, and short and straight is what makes a fan work.
The job, in order:
1. Survey and position. The fan goes high on the external wall, ideally opposite or away from the door so air is drawn across the room rather than short-circuiting straight from the doorway. We check what is in the wall, where the joists and any services run, and confirm the external face is somewhere the discharge is acceptable — not into a covered passage, not next to a neighbour's window or an air intake, and clear of the ground.
2. Core drill through the wall. A diamond core drill, sized to the duct, taken through cleanly from inside to out. On a cavity wall this is the point where it matters who is doing the work: the sleeve has to be installed so it does not bridge the cavity and create a damp path. We use a proper telescopic wall liner for exactly that reason.
3. Set the fall. The duct through the wall is set with a slight fall to the outside so any condensation that forms in the sleeve runs out of the building rather than back into the fan and down the internal wall. A dead-level or inward-falling core is one of the most common causes of a damp stain appearing beneath a fan.
4. Fit the wall liner and external terminal. A proper external cowl or grille — one that actually passes air, with a functioning backdraught shutter. Fine fly mesh and stiff flaps choke airflow, and we see cheap grilles halve the delivered rate of a good fan.
5. Seal and make good. Mastic and mortar sealing at the external face so wind-driven rain cannot track in, and making good internally around the fan.
6. Electrical connection. Wired to a fused connection unit on a suitable circuit, with means of isolation for maintenance. Bathroom zones under BS 7671 govern what can be installed where — a fan sited in the zone above a shower is normally an SELV low-voltage unit with the transformer outside the zones. Adding a fan to an existing circuit in England is not notifiable under Part P, but it must comply with BS 7671 and you should receive a Minor Electrical Installation Works Certificate for the work. We issue one as standard.
7. Commission and measure. We measure the actual extract rate with an anemometer after installation and record it, rather than assuming the figure on the box. Required rates come from Approved Document F — see our Part F guide.
Where a through-wall route genuinely is not available — an internal bathroom in a flat, or a wall we cannot discharge through — we duct through the ceiling void or loft instead, in insulated rigid duct, terminating outside the building. Never into a loft, never into a soffit void.
Costs
| Work | Price | |---|---| | EnviroVent filterless fan, supplied and fitted | £430 + VAT | | Greenwood Airvac humidity fan, supplied and fitted | £330 + VAT |
What the price includes: the fan itself, core drilling through the external wall, the wall liner and ducting, the external terminal, the electrical connection, making good, commissioning and certification. It is the installed price, not a supply-only price with extras added afterwards.
Running cost is separate and negligible — a continuous fan at trickle speed draws only a few watts, which works out at roughly £8–£20 a year in electricity at typical rates.
Unusual wall construction, difficult access or a property needing new circuit work can move the price, and we confirm on survey before any work is booked. Portfolio work is priced on an agreed schedule of rates — see our portfolio compliance guidance.
Why Landlords Are Doing This Now
The volume of this work has changed sharply, and it is not because fans got better. It is regulatory.
The Renters' Rights Act came into force on 1 May 2026. Section 21 is gone, all tenancies are periodic, and penalties for non-compliance have risen to as much as £40,000. Alongside it sits the direction of travel on damp and mould: Awaab's Law took effect for social landlords on 27 October 2025 with binding timescales for investigating and remediating damp and mould hazards, and extension of those duties into the private rented sector is expected from 2027.
What that adds up to for a private landlord:
- A tenant reporting damp and mould can no longer be managed by ending the tenancy — Section 21 does not exist any more
- Damp and mould are Category 1 hazards under the Housing Health and Safety Rating System, and Greater Manchester councils have been visibly more active on enforcement since the Rochdale case
- "The tenant should open a window" has stopped functioning as a defence
- Evidence matters — a certificated ventilation installation with a measured extract rate is a materially stronger position than a history of mould washes
There is a straightforward electrical reason too. Sustained condensation corrodes terminals and accessories and produces the insulation resistance readings that turn a satisfactory inspection into an unsatisfactory one — see damp, moisture and electrical failures.
Frequently Asked Questions
Does a filterless fan really never need maintenance?
Nothing is truly maintenance-free, but there is no filter to replace and no serviceable consumable. In practice that means it keeps performing without anyone doing anything, which is the entire point in a rental property. A wipe of the external grille if it gets obstructed is about the extent of it.
Will it clear mould that is already there?
No — ventilation stops the condensation that causes mould, but existing growth has to be physically removed with a fungicidal wash. Fit the fan, clean the mould off properly, and it should not come back. Fitting the fan and leaving the mould in place just leaves you with dry mould.
Is running a fan continuously expensive?
No. At trickle speed these fans draw only a few watts. Realistic annual electricity cost is under £20 — considerably less than redecorating one mouldy bedroom.
Can it go through a cavity wall?
Yes, and most of ours do. The important detail is the telescopic wall liner, which carries the duct through without bridging the cavity and creating a damp path. This is one of the things that separates a proper installation from a hole with a pipe in it.
Will the tenant be able to turn it off?
Not casually. These fans are wired permanently live, with isolation provided for maintenance. Where a landlord has had recurring problems and suspects fans are being switched off, this on its own often resolves it.
How long does the installation take?
A through-wall install with core drilling, new ducting and electrical connection is typically two to three hours. A like-for-like swap onto sound existing ducting is under an hour. Both are achievable in a tenanted property, though a void is the easiest window — see void period compliance.
Can you do a whole portfolio?
Yes. Fan replacement programmes are some of the most cost-effective work we run for landlords and agents — quick per property, priced on a schedule of rates, and easily programmed alongside EICR and remedial visits so each property is attended once.
Arrange a Ventilation Survey
Manchester Compliance installs EnviroVent filterless fans and Greenwood Airvac humidity fans across Greater Manchester for landlords, letting agents, block managers and housing providers. Through-wall installation, correct ducting, measured on commissioning and fully certificated.
Call 0161 706 1360 Email: hello@manchestercompliance.co.uk
NICEIC approved. Covering Manchester, Salford, Stockport, Tameside, Oldham, Rochdale, Bury, Bolton, Wigan and Trafford.