A musty patch creeping behind the washer. Laundry that never quite smells clean. The humble culprit often hiding in plain sight is warm, damp air from a tumble dryer lingering indoors. Vent it outside and two things can shift fast: the mood in your home and the number on your energy bill.
Rain rattled the back door while a tumble dryer hummed in a small South London kitchen. Steam curled up the glass like someone had breathed on it and forgotten to wipe. The owner cracked a window and shrugged — laundry day, nothing to do about it. Thirty minutes later, the windows were slick, the room felt tropical, and a faint grey bloom had taken hold behind the bin.
So they drilled a neat circle through the wall, clipped on a white hose, and pointed the problem outdoors. The next wash day felt… lighter. Windows stayed clear. The bin corner stayed dry. The energy monitor dipped. The change felt almost cheeky.
What if that tiny piece of plastic and pipe is the quiet win your home’s been waiting for?
Why pushing dryer air outdoors changes the room — and the bill
Every load of washing sheds water, and a lot of it. A family cycle can release one to two litres of moisture into the air. Indoors, that moisture clings to cold surfaces, feeds mould spores, and leaves a film of damp that never quite leaves the paintwork.
Move that moisture outside and the indoor climate shifts. Air stays drier, so the room feels warmer at the same thermostat setting. Windows stop crying. Radiators don’t waste heat evaporating indoor damp. It’s the same laundry, only the by‑product goes where it belongs — into the open air.
Numbers help. A typical vented dryer shifts many cubic metres of humid air per hour; if that stays inside, you’re paying to heat and then re-heat wet air. With an external vent, the latent heat load leaves the building. Over a winter, that can cut back on dehumidifier hours and shave a little off gas or electricity. It won’t halve your bill, but it can take the edge off the pain and starve mould of its favourite snack.
A small tweak with outsized impact at home level
Picture a busy terrace house where laundry runs five times a week. When that dryer vents into the room — even via one of those plastic “indoor vent boxes” — the kitchen walls quietly sip moisture. Paint softens. Silicone darkens. A black crescent forms above the skirting. No one notices at first, then the smell arrives like a wet dog that refuses to leave.
Switching to a proper outside vent often calms everything down. One Hackney couple logged their humidity levels with a cheap digital meter and saw peaks drop from 72% to 55% during cycles after fitting a rigid duct and a louvred external grille. The mould patch by the socket stopped growing. Their dehumidifier ran fewer hours. Not a miracle, just physics doing what physics does.
There’s also the health story. Persistent damp pushes dust mites and mould spores into the air, which can be miserable for asthma and hay fever. Keep the moisture in the breeze outdoors and the house air stops feeling swampy. The quick win isn’t just fresher towels — it’s calmer lungs and fewer condensation streaks on winter mornings.
The simple how-to: from wall hole to warm, dry kitchen
Start with the right kit. You’ll need a 100 mm (4 inch) core drill hole through the external wall, a rigid or semi‑rigid duct of the same diameter, a vent hood with a back‑draught flap, two stainless steel clamps, and foil HVAC tape. The dryer end usually takes a short flexible connector; keep the rest rigid to reduce lint traps and airflow loss.
Plan the run short and straight. The ideal route is a single, slightly downward-sloping line from the dryer to the outside wall. Long snake-like hoses and tight bends choke airflow, lengthen drying times, and collect fluff. Keep screws out of the airflow if you can — they snag lint. Use foil tape on joints, not cloth duct tape, which dries out and peels.
Cut, fit, seal, test. Drill the core, slide the wall sleeve, then fix the external hood with sealant so rain can’t creep in. Indoors, connect the duct, snug the clamps, and tape every seam for an airtight path. Turn the dryer on air-only and hold a tissue at the outside grille. You want a firm flutter, not a faint quiver. *Dry laundry smells sweeter when the air in your home isn’t carrying yesterday’s damp.*
Pro tips, pitfalls, and a little straight talk
Think like air. Any restriction steals performance, so keep the duct smooth and the run as short as your layout allows. Where you need flexibility, use a short aluminium flex rather than a long plastic spring hose. Fit a vent hood with a weighted flap or gravity louvres to stop cold gusts and inquisitive insects.
Clean the lint path. Empty the lint filter every cycle, brush the flexible connector monthly, and sweep the rigid duct twice a year. Lint is flammable and also strangles airflow. Let’s be honest: nobody does that every day. Set a phone reminder for the first Sunday of the month and do it while the kettle boils. Your dryer will run hotter, faster, safer.
If you rent, ask first and consider a window plate kit rather than drilling. Heat pump dryers don’t need an external vent — they condense moisture into a tank — but they still like good room ventilation. Condenser models can benefit from a window kit on laundry day to purge stray humidity. Keep an eye on Building Regulations Part F for permanent changes and think about local rules in flats. Your future self will thank you for the tidy paperwork.
“We see a lot of mould that starts with everyday moisture, not floods,” says a London housing surveyor who specialises in damp reports. “Kitchens and utility rooms are repeat offenders. Get the water vapour out and half the battle is won.”
- Use a 100 mm rigid duct and keep bends gentle.
- Seal with foil tape, not fabric tape.
- Fit a hood with a back‑draught flap; skip fine mesh screens.
- Clean filters every load; sweep ducts twice yearly.
- If in doubt, hire a pro for the core drill — it’s a quick job.
What changes when the moisture leaves the building
Homes feel calmer when they’re not forever drying themselves from the inside. A dryer that vents outdoors won’t cure a leaky roof or a cracked gutter, but it removes a daily spike of damp that so many kitchens and utility rooms suffer. Your best friend in winter becomes a small piece of plastic that opens when warm air moves and shuts when the wind tries to sneak back in.
There’s a money angle people don’t always see. Drier air needs less heat to feel comfortable, so the thermostat stops its little climb to compensate for clammy rooms. Dehumidifiers rest more often. Drying times drop because the machine breathes properly. One small hole, a short line of pipe, and a mild nudge to the monthly bill — not a headline-grabbing number, just a quiet reduction that stays.
We’ve all had that moment when the room smells of wet towels and the windows look like a greenhouse. A neat outdoor vent flips that script. The bin corner stays clean, the window stays clear, and the laundry no longer hijacks the whole house. It’s a modest bit of DIY that feels oddly elegant. **Slash mould**, **cut bills**, and get back a little peace.
| Key points | Detail | Reader Interest |
|---|---|---|
| Move moisture outdoors | Each load can shed 1–2 litres of water; stop it lingering inside | Fewer mould patches, clearer windows, fresher rooms |
| Trim energy waste | Less latent heat indoors; dehumidifier and heating work less | Real-world savings across the winter, not just on paper |
| DIY in under two hours | Core drill, rigid duct, back‑draught hood, foil tape | Practical weekend fix with instant feedback |
FAQ :
- Can every tumble dryer be vented outside?Vented models are designed for it. Condenser and heat pump dryers don’t need a vent, though a window kit can still help purge room humidity on laundry day.
- What diameter duct should I use?Stick with 100 mm (4 inch) to match most outlets. Narrowing the duct slows airflow, lengthens cycles, and collects lint.
- Is a mesh screen on the outside hood a good idea?Skip fine mesh. It clogs with lint. Use a hood with a back‑draught flap or gravity louvres to block pests and gusts while keeping the exit clear.
- How often should I clean the vent and duct?Empty the lint filter every cycle. Brush the flexible connector monthly. Sweep the rigid duct every six months or sooner if you dry daily.
- What if I’m renting or can’t drill the wall?Use a sash or sliding-window plate kit and a short hose on laundry days. It’s not as perfect as a wall vent, but it pushes the damp outdoors where it belongs.
