Domestic ventilation by Johnson and Starley

Stan Bell, sales director at Johnson and Starley, explains the benefits of using a whole house heat recovery system for managing ventilation of houses.

Domestic ventilation requirements have increased due to improved insulation standards and the drive towards low energy housing over recent years.

Houses of today are essentially sealed boxes and therefore, effective ventilation needs to be considered as without it, results can be damaging both to the buildings and its occupants.

If the house is tightly sealed and insulated, air within it will become saturated with water vapour and create an uncomfortable atmosphere for the occupants.

As air in the house cools it will release the water vapour which condenses on to colder surfaces.

This condensation can have damaging effects on the building fabric, such as mould growth, that can be lead to costly repairs.

To prevent condensation occurring, the relative humidity of the air must be kept below 70 per cent and there are two basic methods of achieving this.

The first is to increase the air temperature and this would give the air the capacity to hold more water vapour.

However, already high fuel costs would increase and the water vapour would condense during the night when the heating is turned down or off.

The second method is to ventilate, diluting moisture laden air by using fresh air with a lower relative humidity.

The overriding message from Stan is that when you insulate, you must ventilate.

There are many types of ventilation so selecting the most effective method can be a challenge.

For example, the use of low cost extract fans sited in wet rooms, or the use of a whole house central extract systems can be considered.

Either system could prove effective as they extract air from the wet rooms, and create a negative pressure internally which in turn draws in fresh air through trickle vents.

Johnson and Starley's central extract ventilation systems support Part F of the building regulations and also the Good Practice Guide 268 for domestic ventilation.

However, when they extract to the outside they also remove heat from the property.

This disadvantage can be overcome through the use of a heat recovery system that uses the heat to warm fresh incoming air which is then supplied back in to the property.

A system of this type effectively removes all stale air from a house and replenishes it with fresh air.

Heat recovery systems meet Part F of the building regulations requirements, significantly reducing energy consumption and carbon emissions.

Whole House Heat Recovery systems manufactured by Johnson and Starley include the SAP Appendix Q listed LE range which have a white or steel effect finish, and an optional slimline cooker canopy.

Models incorporate EC fans for highly energy efficient operation and lower running costs, consuming around half the power of traditional AC fans.

During operation, stale and moist air is extracted from wet rooms through grilles or the cooker hood if fitted.

It is passed across an aluminum plate heat exchanger to remove the heat and the residue is exhausted to atmosphere.

Fresh filtered supply air is drawn across the heat exchanger, warmed by the retained heat and distributed through ceiling mounted grilles to dry rooms.

With a whole house heat recovery system, close control of operation is essential for optimum performance including the accurate management of supply/extract rates; over or under ventilated properties are not energy efficient.

The system can be specified with a balancing panel that is set by the installer during commissioning and provides variable control of fan speeds, enabling the exact amount of required air to be extracted.

The balancing panel can be set for normal and boost speeds and additional wall mounted controls for the occupiers can also be specified.

Using a heat recovery system means a property can be tightly sealed and insulated to a very high standard.

Once insulated, the building becomes energy efficient and the ventilation must then be managed by the heat recovery unit, to prevent over or under ventilation.

The air within the house is constantly replenished, therefore cooking smells etc are removed quickly and the inside environment is fresh at all times.

Johnson and Starley's range of heat recovery systems includes units for wall or loft siting, as well as models for fitting above a cooker hob.

A full survey and design service is also offered.

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