MVHR Installation

Installing an MVHR system has never been so easy

By Penny Jones, Product & Marketing Manager, Domus Ventilation

Mechanical Ventilation with Heat Recovery (MVHR) systems have become highly popular in residential new builds.  They improve indoor air quality, making for a more comfortable and healthier home environment, and can provide up to 50% savings on energy bills due to the reduced heating demand.

Whilst it was common practice to install MVHR units in lofts, most units are now wall mounted within the heated envelope of the property, usually in a cupboard.  This has made installation far easier and further contributed to their widespread use.  But just how easy is an MVHR system to install?  Clearly, it will depend on the make and model, but most MVHR systems are now very straightforward to fit.  Based on our Domus Ventilation HRXE MVHR range, which is suited small to medium size residential properties, and Domus ducting, here we show just how simple it can be.

  1. Identify the location of the MVHR unit

MVHR Installation
A clear working space is required around the MVHR unit

A clear working space is required around the installed unit to allow the cover to be removed and provide sufficient access for maintenance such as filter change.

Allow a minimum of 350mm in front of the unit. The fan must be installed indoors, on a suitable wall away from direct sources of frost, heat and water spray or moisture generation.

2. Identify extract / supply areas

The MVHR unit is designed to extract air from all wet rooms e.g. bathroom, kitchen, utility room (with sink).

Supply air should be to all habitable rooms e.g. bedrooms and lounge.

  1. Install ducting

Round or flat channel rigid duct should be used and held in place with a support strap every 750mm. Alternatively, semi-rigid Radial ducting systems are a great way of reducing install time on site. Ducting must be installed in such a way that resistance to airflow is minimised, with bends kept to a minimum. A minimum distance of 300mm between the MVHR appliance and any bends in ductwork is recommended.

A clear working space is required around the MVHR unit

  1. Seal ducting

Seal ducting joints with silicone type sealant such as DDSEAL.

  1. Fit insulation to ducting

Install ducting insulation on the outside of the external air inlet duct and the air outlet duct from the unit, to prevent condensation.

The Domus Thermal system is easy to fit and actually exceeds the Government’s Domestic Ventilation Compliance Guide standard for ducting insulation.

  1. Install grilles

Extract / input grilles should be valves which are adjustable for commissioning. External grilles are to have a minimum free area of 12,250 mm2.

A clear working space is required around the MVHR unit

  1. Fix the mounting bracket for MVHR Unit

Fix the mounting bracket to a solid wall, ensuring the interlock side is at the top.  If it’s not practical to use a solid wall, the MVHR unit should be fixed to a stud partition with a 25mm minimum thickness MDF panel solidly fixed behind the plasterboard.

  1. Wall mount the MVHR unit and connect to power supply

Install the unit on the wall by ensuring the bracket fixed to the rear of the unit interlocks over the wall mounted bracket. The HRXE unit, measuring just 507mm (h) x 356mm (d), is highly compact and can be easily installed in cupboards.

The cable from the mains power supply should be connected to a fixed wiring installation, via a fused isolator, in accordance with current IEE wiring regulations. For good EMC engineering practice, any sensor cables or switched live cables should not be placed within 50mm of other cables or on the same metal cable tray as other cables. The unit must be earthed.

A clear working space is required around the MVHR unit

  1. Connect condensate drain

If the condensation pipe is fitted in an unheated space the pipe should be insulated.

  1. Check filters prior to commissioning

Prior to commissioning, take the protective film off the filters and replace. Ensure they are dust and debris free.

A clear working space is required around the MVHR unit

  1. Commissioning

A calibrated moving vane anemometer and hood are required to carry out commissioning. Adjustment valves should be locked in place to prevent further adjustment.

  1. Post Commissioning

The clear panel covering the control has an adhesive panel which should be exposed and sealed post commissioning to prevent tampering.

As simple as that!  One happy installer, one happy developer and one soon to be happy home owner.

A clear working space is required around the MVHR unit

When you consider we spend around 90% of our time indoors and around 16 hours a day on average at home, the quality of the air we breathe in our home environment matters.  An MVHR system dramatically improves that indoor air quality, removing stale damp air and replacing it with fresh, filtered air.  Furthermore, in high pollution zones a filter can be added to the system to filter out PM2.5 and NOx, which are the key polluters and represent a danger to our health.

Domus Ventilation is a manufacturer of market-leading ventilation systems that save energy and improve indoor air quality.

For further information on the Domus Ventilation HRX range of MVHR appliances, please go to or call on 03443 715523.

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