In the seventh of the series of blog posts regarding retrofitting homes to be more sustainable, PJH are looking at ventilation comparisons (natural, mechanical and MVHR). Beginning with an introduction and facts regarding ventilation, pros and cons, costs required space and additional considerations.
Ventilation Comparison Introduction
There are three main types of ventilation that are designed to move air in and around your home; natural, mechanical and mechanical ventilation heat recovery (MVHR). Natural ventilation comes in the forms of trickle vents and air bricks, designed to be a natural way for humidity to escape and fresh air to be introduced. Mechanical ventilation comes in the form of extractors, like bathroom fans, cooking hob hoods etc. These are usually manually operated and are designed to extract moisture and excess warm air from a room when they are in use. Mechanical ventilation heat recovery operates through a series of ducting around the dwelling in order to pull warm, moisture filled air out of rooms and transferring the heat with fresh outside air through a heat exchanger in in order to recover the heat and reduce heat loss. This air is then circulated into rooms like reception rooms and bedrooms that require the warmer purified air.
MVHR can be retrofitted into existing homes that have the available space within floor joists or loft space in order to benefit from such a system. This would be entirely dependent on the individual dwelling but there are a number of systems available and ducting solutions for retrofitting.
It is important that a dwelling tries to achieve maximum air tightness for an MVHR system to be most effective as it controls the air that leaves the dwelling and utilises the heat as it does. Sealing cracks and air leakage channels enable a more effective MVHR system, with this it can circulate and redistribute hot and cool air more efficiently. This will in turn reduce heating demand due to the ability for the MVHR to redistribute heat.
Pros and Cons of MVHR
Ventilation Comparison: Associated costs
An efficient MVHR system will reduce the heating demand within a dwelling by redistributing the heating gained in areas like a bathroom or kitchen or south facing rooms into the colder areas. This system can vary in price, depending on the size of the dwelling and extent of measures required to increase air tightness, however Checkatrade (2023) estimates it to cost around £6,500 to retrofit for an average 3-bedroom house, including ducting and installation.
Required space for a MVHR system
The required space for a MVHR system again varies on the size of the dwelling it is installed in. However it can be expected that the unit for extraction/filtration/heat exchange can vary in size from a under counter fridge to freestanding fridge/freezer, an example of the main unit can be seen below. Space saving options available with some companies when space is limited. Low profile ducting is also available to be able to be fitted within existing floor/ceiling joist zones.
Requirement for ventilation as per updated building regulations
As per the Building Regulations Approved Document F, the updated regulations regarding ventilation which took effect from 15th June 2022 requires properties to allow for consideration of the ventilation. Whole dwelling ventilation needs to be considered which can be delivered through natural ventilation, mechanical ventilation or a combination of both. Natural ventilation within window systems would be trickle vents to ensure the input of fresh air to dilute, disperse and remove water vapour and pollutants not removed by mechanical extraction.
Conclusion
To conclude the ventilation comparison and overview, the new requirements for ventilation means that some form is needed within the different spaces of a dwelling. The most efficient method for ventilating a property is MVHR, whilst being the more expensive option to retrofit out of the three main methods, it provides the best way to improve a dwelling’s energy efficiency due to the heat recovery. Used in conjunction with other retrofit measures, it can provide a dwelling with additional cost savings with the ability to maintain a comfortable internal environment through the reuse of otherwise wasted heat/cool air. Has the ability to be retrofitted in a number of dwelling types as long as there is adequate space for the ducting within the floor/ceiling joists or loft space.
Ask us for advice
If you have a project in its infancy and want to have an informal chat regarding your options, feel free to contact us, we are always happy to provide friendly and knowledgeable advice. Get in touch on 0161 460 0382 or email the team at enquiry@pjhas.co.uk
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