11 Jul 2019

Ask the expert – Ventilation

Christian Rehn of National Ventilation answers your questions about ventilation, explaining the benefits of installing effective ventilation in your self-build home. But with so much choice on the market, where should you begin?


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Why do I need to ventilate my property?

To make new build properties more energy efficient homes are insulated to high levels and are increasingly air tight to meet Building Regulations Part L – Conservation of fuel & power. But without modern ventilation you will end up with an airtight box resulting in stuffy, warm, poor quality indoor air and with condensation and mould forming both on the surface and within the fabric of the building.

By installing effective whole house ventilation you can combat condensation and mould by reducing humidity; filter out pollen and pollutants from outside air and introduce clean tempered air. This provides your home with good indoor air quality, making it a healthier place to live.

What type of ventilation should I install?

We recommend mechanical ventilation with heat recovery (MVHR) as the best solution for new builds as it is a controlled way of ventilating a whole property, and it saves energy by recovering heat that would otherwise have been lost. You can control humidity, CO2 and indoor air quality.

Is an MVHR unit expensive to run?

Not at all. Small- and medium-sized units only cost about £20 a year and larger units might cost up to £40 a year. An MVHR unit fitted with in-duct humidistat allows the system to run very efficiently since it mostly runs on trickle and only boosts when needed. In addition, the heat recovery aspect means you save money on heating as up to 90% of the heat in the room can be recovered.

Is MVHR noisy?

As long as MVHR has been designed, installed and commissioned correctly it won’t be noisy. When on trickle the MVHR is so quiet that it shouldn’t be heard. On boost it might be heard where it is sited, although boost is only necessary during showers/baths and cooking so it shouldn’t disturb anyone.

Do I need a ventilation system design?

Yes. MVHR systems need to be properly designed to ensure you buy a correctly sized unit. If an MVHR unit is oversized it won’t provide efficient ventilation for your home. If it is undersized you won’t be getting adequate levels of ventilation, which will lead to poor indoor air quality and problems with condensation and mould. When it comes to designing the system, if your contractor doesn’t have the knowledge and expertise to do this themselves, there are design services available, such as the free service National Ventilation offers.

Do I need bathroom and kitchen fans too?

No you don’t. MVHR is a whole house ventilation system meaning you won’t need a fan in the bathroom or kitchen. You don’t need trickle vents either. And you don’t even need to fit an extracting cooker hood, just a recirculating cooker hood.

Is maintenance required?

The only maintenance needed is a filter check every 6-12 months – MVHR systems have a filter indicator which lights up once a filter is dirty. Changing a filter is easy and just involves opening the flaps of the MVHR unit, pulling out the filter, changing it and closing it back up.

Further information....

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