Heat, cool and ventilate with one system
Most UK homes solve comfort with a patchwork: radiators for winter, a portable unit wheeled out in summer, and a window cracked open for fresh air. Three problems, three half-fixes. There's a tidier way — and it's been proven in homes around the world for decades.
What is small-duct high-velocity?
Small-duct high-velocity (SDHV) does exactly what it says: it moves conditioned air through slim 50–63mm ducts at higher velocity than a conventional system. A single compact air handler — tucked in a loft or cupboard — heats or cools the air, and discreet outlets deliver it gently into each room. Custom Comfort is our SDHV system, designed and installed by Custom Comfort.
The clever bit: aspiration
Rather than dumping a big slug of air into a room, SDHV outlets release a small, faster jet that gently draws the room's own air into the stream — a process called aspiration. The result is thorough, even mixing: no hot ceilings and cold floors, no draughty blast, just steady comfort. In practice that means less than a 2°C difference from room to room and floor to ceiling.
Why one system beats three
- It heats and cools. The same system keeps you warm in winter and cool in summer — pairing naturally with an efficient air-source heat pump.
- It ventilates. Built-in filtration, plus optional heat-recovery ventilation (MVHR), brings in fresh, filtered air and removes up to ~30% more humidity than a typical system — great for allergies and condensation.
- It's hidden. No radiators eating your walls, no wall-mounted cassettes, no rows of outdoor boxes. You get your rooms back.
- It's whisper-quiet. Sound-attenuating ducts isolate noise and vibration, so you feel the comfort without hearing the system.
- It suits real homes. Because the ducts are so slim, SDHV retrofits into existing and even period properties with far less disruption than traditional ducting.
How it compares
| Feature | Custom Comfort (SDHV) | Radiators + portable AC |
|---|---|---|
| Heats | Yes | Yes (radiators) |
| Cools | Yes — whole home | One room only |
| Ventilates / filters air | Yes | No |
| Visible kit | Hidden ducts & small outlets | Radiators + a portable unit & hose |
| Even temperatures | <2°C variance | Hot and cold spots |
One system. Three jobs. Hidden away.
See what Custom Comfort would look like in your home — free estimate in 60 seconds, or a callback from our team.
Get a fixed price Request a callbackFrequently asked questions
Is small-duct high-velocity any good for UK homes?
Very — its slim, hidden ducts make it ideal for the UK's older, awkward-to-duct housing stock, and it pairs perfectly with heat pumps for low-carbon heating and cooling.
Is it noisy?
No. The supply ducts are sound-attenuating, so the system runs whisper-quiet with even, draught-free air.
Can I keep my boiler?
Often yes — Custom Comfort can work alongside existing heat sources or pair with a heat pump. Our team will design the right setup for your home.
Does it improve air quality?
Yes — filtration and optional heat-recovery ventilation bring in fresh, filtered air and help control humidity, which is good news for allergies and condensation.