Choosing ventilation systems demands consideration of all the facts

Chris Yates, managing director of Johnson & Starley Limited explains what housebuilders need to look at when planning for ventilation in a development.

For years ventilation was a topic not worthy of too much discussion – as long as a window could be opened wide, then the issue could be considered, “dealt with.” If there was any mechanical ventilation, it may well have been no more than a simple mechanical extract fan inset into a kitchen window and operated by a pull cord. Later, electronically operated extract fans demonstrated a higher level of sophistication – but not much serious thought was given to the most appropriate form of ventilation for the dwelling. How things have changed.

The need to provide proper and fit for purpose ventilation has been brought about by changes and advances in the new build market and in building refurb. Not only have construction methods improved, but materials have become more technically advanced, so the new home has become a far more tightly sealed unit. Alongside this change, there has been the never ending drive towards greater energy efficiency spurred on by global environmental concerns. Homes now have much higher levels of insulation both in the loft and between the walls with grants readily available. Furthermore, Parts F and L of the Building Regulations have demanded additional responsibilities and the drive is to develop properties where carbon emissions are controlled and energy consumption is reduced – all within a comfortable and healthy living environment.

But tighter buildings where air cannot circulate has potential detrimental side effects, not least of which is the risk of condensation build up. This can lead to longer term problems of mould and spores leading to potential health risks to occupiers caused by stale and air contamination. In the longer term, there is also a risk not just of damage to furnishings but to the structural elements of the house itself.

How to balance any requirements for ventilation with the more traditional need for a highly efficient heating system is a challenge that housebuilders are now having to consider – and indeed are already doing so. The advent of renewable heating technology alongside traditional fossil fuels and how best to ventilate throws another factor into the equation. Therefore, heating and ventilation can no longer be considered separately and a ventilation strategy is needed that is based upon a number of factors. These include the house type and structure, its specification and price, levels of accommodation, lifestyle of the potential occupants, its heating requirements and its running costs.

The easiest option when specifying ventilation for residential properties – forgetting just opening the windows and letting heat out/noise and pollution in – remains the installation of extract fans in bathrooms, kitchens, en-suites and utility rooms. While certainly an advantage in terms of upfront costs, this type of solution simply does not provide the sophistication of ventilation that can be achieved in the 21st century and does not take advantage of the benefits of the technology that is now available.

Today the emphasis is very much on recovering heat energy used in the home and recirculating it. Therefore a system that actually takes indoor stale out and replaces it with outdoor air, then cleans it and pre-warms it before recirculating it within the property is very attractive. These latest state of the art MVHR systems will significantly reduce energy consumption/ carbon emissions and are becoming increasingly specified for upmarket developments. They can also be used with smart home automation systems as part of a completely integrated living environment.

With whole house heat recovery, stale air is extracted from wet rooms – even through cooker hoods in kitchens – and passed across a heat exchanger to remove the heat and the residue is exhausted to atmosphere. Fresh, filtered air is drawn across the heat exchanger to be warmed by the retained heat. This warmed air is then distributed back into the property. The streams are kept separate to avoid any cross contamination and the result is a cleaner and healthier living environment.

MVHR may be the optimum approach in terms of sophistication and energy efficiency, but extract systems alone still provide a viable approach. Central extract systems may be the next level down in terms of efficiency, but the better specified systems will nevertheless incorporate highly energy efficient EC fans. These systems also extract stale air from “wet” rooms and exhaust it to the outside atmosphere with fresh air replenishment through trickle vents. Different sizes of systems are available for large dwellings, smaller houses and apartments. They can be conveniently located out of the way in a roof space or cupboard with ducts fed into the individual rooms as required.

With both these types of ventilation system, an often overlooked fact is that close control of their operation is absolutely essential for optimum performance. Heat recovery and central extract systems can be specified with a balancing panel that is set by the installer during commissioning and provides infinitely variable control – not just stepped control – of fan speeds. This results in exactly the required amount of air being extracted. Over or under ventilated properties are simply not energy efficient. Once the balancing panel is set, additional wall mounted controls for the occupiers can also be specified.

Positive pressure ventilation systems are also available as whole house systems for wall or roof mounting. They introduce a constant flow of filtered, tempered air into the home with the system creating positive pressure that forces stale air to escape through the fabric of the building.

An overlooked fact about open flued heating appliances is that they encourage ventilation of a property. The air required for the combustion process is drawn in from the occupied space and the moisture laden gases vent to the atmosphere. Not only that, but today’s warm air heating systems also frequently offer optional electronic air filtration that can remove airborne particulate down to one micron circulating around the house.

The choice of ventilation strategies is very wide but today’s housebuilders are in position to provide solutions that take all legislative, environmental, budgetary and lifestyle considerations into account. Discussing requirements at an early stage with the many organisations and consultants with long standing expertise in this field is the way forward.