The Vectaire Midi is a whole-house mechanical ventilation with heat recovery (MVHR) unit engineered for residential properties up to 170 m². Manufactured in the UK, it delivers up to 94% heat exchange efficiency — one of the highest in its class — while drawing as little as 2.2 W at minimum speed. Whether you are building new or retrofitting, the Midi provides continuous fresh, filtered air throughout your home, recovering the warmth from stale outgoing air before it is exhausted, keeping energy bills low and indoor air quality high all year round.
94%
Heat Exchange Efficiency
101 l/s
Max Airflow Capacity
Installer Note: Sufficient access for safe maintenance or removal following installation must be provided for this product. A minimum 200 mm clearance each side of the cabinet is required for access to the motors. This unit must be installed by a competent person and commissioned in accordance with Building Regulations Part F.
Compatibility: The Midi is available in universal handing (without humidistat) or with left/right drain humidistat versions. Check ductwork handing requirements before ordering. The humidistat handing direction is factory-set; confirm your layout before purchase.
SAP PCDB Listed — the Midi is fully listed on the SAP Product Characteristics Database, making it straightforward to use in energy calculations for Building Regulations compliance. Specifications available at vectaire.co.uk/downloads.
Key Features
Counter-Flow Heat Exchanger
The Midi uses a counter-flow heat exchanger that achieves up to 94% thermal efficiency — recovering warmth from stale exhaust air and transferring it to the incoming fresh supply without the two airstreams ever mixing. This dramatically reduces the heating energy needed to bring incoming air up to room temperature.
Automatic Summer Bypass
When outdoor temperatures are pleasant, the automatic summer bypass routes incoming air around the heat exchanger entirely, bringing cooler fresh air directly into the home. The bypass activates and deactivates automatically based on adjustable internal and external temperature setpoints — no manual intervention needed.
Integral Frost-Stat Protection
The integral frost-stat proportionally reduces the intake motor speed as outside temperatures fall between +3°C and −8°C, preventing ice formation on the heat exchanger core. This is a standard feature, protecting the unit and maintaining safe operation through UK winters without requiring an additional external controller.
Low Energy EC Brushless Motors
Fitted with electronically commutated (EC) brushless motors with forward curved impellers and direct drive, the Midi draws just 2.2 W at 20% speed and 120 W at full speed. The specific fan power (SFP) is as low as 0.50 W/l/s, comfortably meeting Building Regulations targets for energy-efficient ventilation.
Variable Speed Control
Each motor has independent variable speed adjustment for trickle, boost, and purge modes, set at installation to match the specific ductwork design. Boost speed can be triggered by a 230V switched live from a light switch, remote humidistat (DRH240), PIR sensor (PIRFF), thermostat (THM), or pull cord. The boost over-run timer is adjustable from 0 to 90 minutes.
Thermo-Acoustic Lining
The compact steel casing is lined with thermo-acoustic insulation, providing both noise attenuation and thermal performance. At 80% speed (79 l/s) the breakout sound pressure is just 29.9 dBA at 3 m, making the Midi suitable for installation in lofts, cupboards, or utility rooms adjacent to living spaces. The unit weighs 24 kg.
Flexible Installation
Designed for vertical installation in lofts or cupboards, with a wall fixing bracket supplied. The universal handing models (without humidistat) can be orientated left or right on site, giving installers flexibility. The unit can also accommodate 0-10V connections for BMS integration, CO₂ detectors, or home automation systems — factory-set options available.
Easy Filter Access & QR Diagnostics
Standard disposable G3 filters are easily accessible for routine maintenance. The unit records run-time and power outage counters downloadable via QR code, making service visits straightforward. Optional integral LCD or remote LCD commissioning units are available for accurate airflow balancing at installation.
Technical Specifications
| Max Airflow Capacity |
101 l/s (364 m³/hr) |
| Airflow at 50Pa |
95 l/s |
| Heat Exchange Efficiency (max) |
94% (SAP 10: Kitchen + 1 wet room) |
| Specific Fan Power (SFP) |
Down to 0.50 W/l/s |
| Total Power — 100% / 20% |
120 W / 2.2 W |
| Operating Current |
1.21 A |
| Airflow Speeds (l/s) |
101 / 79 / 58 / 36 / 14 (100–20%) |
| Breakout Sound Pressure @ 3m |
33.9 dBA @ 100% · 19.7 dBA @ 20% |
| Max Operating Temperature |
60°C |
| Frost-Stat Activation Range |
+3°C to −8°C (outside temperature) |
| Boost Over-Run Timer |
0–90 minutes (adjustable) |
| Remote Purge Timer (optional) |
0–250 minutes (factory preset: 15 min) |
| Filter Grade |
G3 (disposable, easily accessible) |
| Dimensions (W × H × D) |
600 × 555 × 382 mm (approx) |
| Weight |
24 kg |
| Duct Connection Diameter |
Ø125 mm (four spigots) |
| Casing |
Steel sheet, epoxy paint finish |
| Heat Exchanger Type |
Counter-flow |
| Motor Type |
EC brushless, direct drive, forward curved impellers |
| Supply Voltage |
230V AC |
| Warranty |
5 years (1 year parts & labour, 4 years parts only) |
| Certifications |
SAP PCDB Listed · CE Marked · ISO 9001:2015 · ISO 14001:2015 · EU RoHS · IEC60335-2-80 |
| Suitable For |
Any domestic wet room installation |
| Sound Testing Standard |
BS EN ISO 3743-1:2010 (independently tested) |
Models Available
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WHHR-Midi/BY — Bypass, universal handing
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WHHR-Midi/LBYH — Bypass, left drain, humidistat
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WHHR-Midi/RBYH — Bypass, right drain, humidistat
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Midi-BY+LCD — Bypass, universal, integral LCD commissioning unit
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Midi-BY+LCDLH — Bypass, integral LCD, left drain, humidistat
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Midi-BY+LCDRH — Bypass, integral LCD, right drain, humidistat
Frequently Asked Questions
What size property is the Vectaire Midi suitable for?
The Midi is rated for residential properties up to 170 m². With a maximum airflow of 101 l/s, it comfortably serves homes with a kitchen plus up to four or five additional wet rooms under SAP 10 calculations. For larger properties (up to 250 m²), the Vectaire Maxi is recommended; for properties up to 400 m², consider the Maxi Plus BY.
How does the summer bypass work on the Midi?
The automatic summer bypass monitors both internal and external temperatures continuously. When both reach adjustable setpoints — indicating warm, pleasant outdoor conditions — the bypass damper diverts incoming air around the heat exchanger, delivering cooler fresh air directly into the home. This prevents the home from being warmed unnecessarily in summer, without any manual switching by the occupant.
Can the Midi be integrated with a smart home or BMS?
Yes. The Midi supports 0-10V signal connections (factory-set) for integration with a Building Management System (BMS) for remote motor shut-off, a CO₂ detector for demand-controlled ventilation, or a home automation system. A relay output for an external pre-heater is also available. The optional holiday mode reduces fan speeds to 50% of trickle when the property is unoccupied.
How quiet is the Vectaire Midi in operation?
The Midi is one of the quieter units in its class. At 100% speed (101 l/s) the breakout sound pressure level is 33.9 dBA at 3 m; at 80% (79 l/s) this falls to 29.9 dBA. At typical trickle speeds the unit is virtually inaudible from an adjoining room. All acoustic data is independently tested to BS EN ISO 3743-1:2010. For very noise-sensitive installations, an optional acoustic top box is available from Vectaire.
Does the Midi comply with UK Building Regulations?
Yes. The Midi is SAP PCDB listed and complies with Building Regulations Part F (ventilation) and Part L (energy efficiency). The SFP of 0.50 W/l/s meets the enhanced energy-saving requirements. It is CE marked, EU RoHS compliant, and manufactured in the UK to ISO 9001:2015 quality and ISO 14001:2015 environmental standards.
How often do the Midi's filters need replacing?
The standard G3 disposable filters should typically be replaced every 6 to 12 months, depending on local air quality. Properties near busy roads or in urban areas may need more frequent changes. The filters are easily accessed from the front of the unit without tools. An annual service check is recommended to inspect the heat exchanger, verify balance, and replace filters — run-time counters are downloadable via QR code to assist maintenance planning.
