What Is a Single Room Heat Recovery Unit?
Also known as an SRHRU or “through-the-wall MVHR”, it’s a compact ventilation system designed for one room.
It doesn’t just blow air in and out like a fan. Instead, it recycles the warmth from the outgoing air and passes it to the fresh air coming in.
Think of it as a set of mechanical lungs for your room — breathing out stale, humid air, breathing in fresh, filtered air, and keeping hold of the warmth you’ve already paid for.
Who Benefits from an SRHRU?
Homeowners
- Stops condensation and mould in their tracks.
- Makes the air feel cleaner — especially handy for hay fever or asthma sufferers.
- Takes pressure off the heating system, cutting energy use.
Builders & Developers
- Helps meet Part L (energy efficiency) and Part F (ventilation) regs without awkward redesigns.
- Can nudge SAP scores and EPC ratings higher, which buyers notice.
Commercial Spaces
- Great for small offices, salons, and clinics.
- Better air = better concentration and happier clients.
How It Works – The Two-Stage Heat Recovery Cycle
The principle’s simple but brilliant. Most SRHRUs work in a 70-second cycle:
- Exhaust phase – The unit pulls out warm, stale air. As it passes through the ceramic core, that core soaks up the heat like a sponge.
- Intake phase – The fan reverses, drawing in cooler outside air through the now-warm ceramic core, so it enters the room already heated.
You barely notice it happening, but the room feels fresher.
Good units also include decent filters (G3 or G4) to catch dust and pollen before it gets inside. The smarter ones have humidity or CO₂ sensors so they can speed up automatically after a shower or when a few people pile into the room.
At a Glance – Benefits and Applications
Benefit |
Description |
Best For |
Improved Air Quality |
Replaces stale indoor air with fresh, filtered air |
Bedrooms, living rooms, home offices |
Mould & Condensation Control |
Removes excess humidity before it condenses |
Bathrooms, kitchens, utility rooms |
Energy Savings |
Recovers up to 90% of heat from extracted air |
Older properties, airtight new builds |
Regulatory Compliance |
Meets Part L & Part F standards |
New builds, extensions, major refurbishments |
Choosing the Right Unit
Step 1 – Match airflow to room size
We always start with the room’s volume (L × W × H) and multiply by the recommended air changes per hour (ACH). Bathrooms need more air changes than bedrooms, so calculations upfront avoid buying a unit that can’t keep up.
Step 2 – Compare key features
- Heat recovery efficiency – Aim for 85–90%+ if you want real savings.
- Noise levels – Bedrooms need sub-25 dB operation; you want a whisper, not a whine.
- Filter grade – G3 or higher if allergies are a concern.
- Controls – Humidity/CO₂ sensors make them set-and-forget.
Feature Comparison by Model Type
Feature |
Basic |
Mid-Range |
Premium |
Heat Efficiency |
Up to 75% |
Up to 85% |
Up to 93% |
Noise (Low) |
25–30 dB |
20–25 dB |
<20 dB |
Filter |
G2 (dust) |
G3 (dust & pollen) |
G4+ (fine particles, spores) |
Controls |
Manual |
Remote + speeds |
Smart app + sensors |
Best For |
Toilets, utility rooms |
Bathrooms, kitchens |
Bedrooms, living rooms, allergy sufferers |
Why They’re Essential for Airtight Homes
We’re building homes tighter than ever to save energy, which is great — until you trap all the moisture and pollutants inside.
Without ventilation, kitchens get steamy, bathrooms grow mould patches, and indoor air quality tanks. An SRHRU gives that air somewhere to go while pulling in fresh air without throwing heat out the window.
Installation and Maintenance Tips
- Start with wet rooms or any space with a condensation problem.
- Clean or swap the filters regularly; it takes minutes and keeps performance high.
- In big spaces, install two units in sync — one drawing in, one pushing out — for balanced airflow.
Final Takeaway
A single room heat recovery unit isn’t just about ticking a building regs box. It’s about making a room feel fresher, keeping heating bills in check, and protecting your home from damp.
We’ve seen them transform problem rooms in days — no more misty windows, no musty smell, just a healthier space to live or work in.
If you want help choosing the right model, Heat Recovery Direct can guide you from selection to installation so you get the full benefit — and the best SAP score possible.
Contact us today to start breathing easier.