Designing for Centralised MVHR

Mechanical Ventilation with Heat Recovery (MVHR) is becoming a standard feature in high-performance homes. By supplying filtered fresh air and extracting stale air while recovering up to 90% of the heat energy, it creates healthier indoor environments and reduces energy bills.

But the benefits only come if MVHR is properly integrated from the design phase. Retrofitting ductwork, plant space, or airtightness details at the end of a project can be messy, expensive, and compromise performance.

Why Early Planning Matters

• Efficiency — poorly thought-out duct routes increase resistance and energy use.
• Comfort — incorrect grille placement can lead to draughts, noise, or uneven airflow.
• Cost — adding bulkheads or altering layouts late in the build inflates costs.
• Compliance — Passive House or airtightness targets require coordination from the beginning.

Key Design Phase Requirements

1. Plant Space for the Unit

• Allocate a dedicated location such as a laundry or hallway cupboard for the MVHR unit.
• Ensure the unit is accessible for filter changes (usually every 6–12 months).
• Consider acoustics — even quiet units are best kept away from bedrooms.
• Allow clearance around the unit for servicing — requirements vary by model.

2. Ductwork Planning

Centralised MVHR requires a network of supply and extract ducts. Getting this right early makes all the difference.

• Plan main distribution runs in ceiling voids, dropped bulkheads, or service cavities within the thermal envelope of the build.
• Avoid sharp bends — every 90° bend adds pressure loss and reduces efficiency.
• Coordinate with electrical and plumbing layouts to avoid conflicts at ceiling cutouts.
• Insulate ducts passing through unconditioned spaces such as roof voids.

3. Fresh Air Intake and Exhaust Placement

• If using separate grilles, plan for at least 1.5–2 metres separation to avoid recirculating exhaust air.
• Place intakes away from sources of pollution such as driveways, chimneys, and flues.
• Consider prevailing wind and sun exposure when deciding orientation.
• Avoid taking fresh air from the roof even if exhaust can exit there.

4. Room-by-Room Ventilation Strategy

MVHR works best when supply and extract points are carefully distributed.

• Supply air: living rooms, bedrooms, studies — the “dry” areas.
• Extract air: kitchens, bathrooms, laundries, toilets — the “wet” areas.
• Air naturally flows under doors and through hallways from supply to extract zones.
• Supply and extract volumes must be balanced to avoid pressurising the home.

Early design work should include airflow calculations, ensuring each room gets the correct volume based on occupancy and use.

5. Airtightness and Building Envelope

The success of MVHR relies heavily on airtightness. While a lower ACH (air changes per hour) improves heat recovery efficiency, MVHR systems will still supply fresh filtered air in leakier homes.

• Plan for airtight service penetrations using tapes, membranes, and grommets.
• Schedule blower door tests during construction to find and fix leaks before finishes.
• Ensure duct penetrations through the airtight layer are fully sealed.

6. Integration with Other Building Services

MVHR does not replace heating and cooling — it can help to balance and smooth the background temperature.

• High-performance homes often require smaller air conditioning systems.
• Consider boost switches in kitchens and bathrooms, and humidity controls.
• Some systems allow for CO&sub2; sensors and smart home integration.
• MVHR can often replace exhaust fans in wet areas entirely.

7. Maintenance and Homeowner Usability

• Filters should be quick and easy to swap without tools.
• Provide access hatches to key ductwork for occasional cleaning.
• Plan for homeowner handover, including filter schedules and basic troubleshooting.
• Choose a location that will remain accessible for the lifetime of the system.

Design Checklist

Conclusion

Centralised MVHR is not just a ventilation upgrade — it’s part of the home’s overall performance strategy. By designing with it from day one, you avoid compromises, reduce costs, and deliver a healthier, more efficient home that lives up to the promise of high-performance building.

At HiPer Haus, we partner with builders, designers, and homeowners throughout the design and construction process — from concept layouts to final commissioning — to make sure MVHR systems perform exactly as they should.