Ventilation

Ventilation is a much underestimated element of modern housebuilding — but will play a crucial role in how much you enjoy your new home. Our guide explains what you need to know.

Put simply, ventilation is the removal of ‘stale’ air from inside a building and its replacement with ‘fresh’ air from out­side. Adequate ventilation is essential in your home to maintain a healthy environment but also to prevent the build-up of excess levels of humidity and to provide air for fuel-burning appliances. A good ventilation system will help remove cooking smells, allergens and other irritants, such as tobacco smoke, and make your home a considerably more pleas­ant, healthy and comfortable place to live.

Buildings are ventilated through a com­bina­tion of air infiltration and purpose-provid­ed ventilation. Infiltration is the uncontrollable air exchange between inside and outside a build­ing through a range of air leakage paths in the building structure i.e. drafts. Purpose-provided ventilation is the controllable air exchange by means of a range of natural and/or mechan­ical devices such as trickle vents in windows and electric extract fans. The current aim of the Building Regulations is to minimise uncon­trol­lable infiltration ven­ti­lation in favour of con­trol­lable ventilation in order to help improve energy efficiency.

The right ventilation solution for your project will depend largely on the amount you are prepared to spend, how much system main­te­nance you consider acceptable and the level of importance you place on energy efficiency. You also need to consider whether you want to filter, warm or cool incoming replacement air to give a more controllable indoor climate. Aesthetics is another con­sideration: some people hate the sight of trickle ventilators in windows and the noise of individual extract fans in bathrooms, both of which can be eliminated with a whole-house system. In some areas noise pollution will be a factor and there are ventilation options that reduce this problem.

For households with allergy sufferers a system with electrostatic filters can bring great benefits. If you are building a new house, it will also depend on how airtight and energy efficient the building is, as this will be a big factor in determining the efficiency of features such as heat recovery. These systems can be highly effective but require the property to be relatively airtight and so are best suited to new builds, especially construction systems that tend to be inherently airtight such as timber frame, structural insulated panels and insulated concrete formwork.

If you are on a tight budget the least cost option is probably going to be individual extract fans in wet areas and passive vents (trickle ventilators or airbricks with sliding hit and miss vents), or a positive input ventilation system (PIV). If you are building an eco house with a very low heat requirement then your choice is likely to lie between a passive stack system that uses no direct electricity, a PIV system, or a heat recovery ventilation system (HRV). If you want to be even more ecological, you could opt for a mechanical system that preheats the incoming fresh air via solar panels: when the heat is not required it is diverted to the hot water cylinder.

You may also wish to consider other factors such as whether you want to combine your ventilation with an air conditioning and/or a heating system. If you don’t want to see trickle vents in all of your windows, then you should consider an HRV system, a PIV system or a mechanical whole-house system that operates continuously. If you would like to control allergens, a mechanical system with controlled (filtered) air intake is the best option.

Whichever system you opt for you must include purge (formerly rapid) ventilation, either through natural means (such as open­ing windows to each room) or where there are no windows, a mechanical fan. You might also wish to provide extraction above the kitchen hob. This can be incorporated into a whole-house system but it is generally consid­ered best to keep this separate due to the high levels of grease and moisture prod­uced in kitchens. Kitchen extractors can be ducted to the outside, or can filter out cook­ing smells and return the cleaned air back into the kitchen.

house ventilation