Is MVHR suitable for my property? It is common in the Mechanical Ventilation with Heat Recovery (MVHR) industry to assume that an MVHR system wouldn't benefit a “draughty” property. Draughty here means the build has an actual fabric airtightness of 3 m3/(hr.m2) or higher.
This has led to MVHR systems only being considered in more airtight new builds or retrofits.
Research undertaken by the Passivhaus Trust now shows us that this is not necessarily correct. It proves that any property with a reasonable level of fabric air permeability will benefit from MVHR. Even in a draughty home, MVHR will significantly lower CO2 emissions. So is MVHR suitable for my property?
MVHR is a whole home ventilation system. It works by extracting the stale, moist, and polluted air from the inside of your home or other property. It then resupplies it with fresh, filtered air.
At the same time, the air travels through a heat exchanger. This transfers a large percentage of the heat energy from the extracted air to the incoming air, resulting in a more energy-efficient building when installed correctly.
This creates a more comfortable, condensation and mould-free environment year-round.
Read more about this in our previous article! What is MVHR?
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Ventilation in old buildings is important. This may seem odd as usually, we try to make older buildings more airtight, sealing holes and gaps. While this is important to stop cold air from getting in, airtight buildings have no air circulation which can create condensation and mould. This is why mechanical ventilation is important.
It is often said that older buildings do not benefit from MVHR, however, this is not the case. It may not be as efficient as it is in newer buildings but there are still benefits, such as:
In areas where air quality is a problem (pollen, air pollution), an MVHR system with adequate filtering can provide cleaner air to the property. The positioning of the air intake can also matter in this case.
MVHR will contribute to the reduction of humidity and condensation by providing constant ventilation. MVHR systems actively aid in dehumidification when the outside air is colder than the inside.
With the use of MVHR heat recovery systems, there will be no need for draughty window vents or loud bathroom fans.
If a property suffers from noise well installed MVHR systems with adequate insulation and silencing can provide a solution. Less opening of windows results in less noise ingress.
MVHR allows you to meet the EnerPHit standard for renovations/retrofits.
There are other factors to consider when renovating or retrofitting your property and installing MVHR.
Building fabric is one of these factors. Many old buildings will have trouble hiding ducting, and in some cases trouble running ducting to downstairs rooms at all.
Such properties can still benefit from MVHR, by removing air from upstairs wetrooms and adding fresh clean air to the living areas upstairs.
To meet the building regulations for new ventilation in new builds it is important to combine an airtight envelope with a high level of heating efficiency. Heat Recovery is key to achieving this goal.
MVHR is key to keeping a home healthy and comes with many benefits such as:
MVHR allows you to meet the Passivhaus standard for new builds.
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The more airtight a property starts before MVHR, the better. However, this does not mean that MVHR does not benefit “leakier” properties.
MVHR will still improve indoor air quality in a leakier property for example.
The efficiency however is much greater with an actual airtightness level of 3 m3/(hr.m2) or lower.
MVHR has all the benefits previously outlined, but what does that mean practically? What is MVHR like when we actually live with it?
Improved air quality means that your MVHR system filters out pollutants and particles in the air, meaning you breathe in less of the general city pollution or dust from living in the country. The lower dust level also means less housework, and no loud bathroom fans that activate whenever you switch on the lights at night.
Regardless of your property, the chances are MVHR will improve the energy efficiency of your property. Whether it is old or new, airtight or draughty, you could save money and have a healthier home by using MVHR.
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