Ventilation

There is much concern today about energy efficiency and achieving a net-zero greenhouse gas rating to achieve carbon neutral homes.

However, with the increase of insulation and addition of extensive building sealants, the goal has been to achieve full “air tightness” of the building envelope (refers to external walls, roof and ground level floors). We are now finding that this optimum solution creates some problems that can be resolved with ventilation.

To achieve adequate ventilation of buildings, mainly for providing fresh air intake and oxygen with a release of stale air and carbon dioxide to the outside. This flow also helps with condensation and damp issues including odours and smells.

The most simple form of providing ventilation is done by opening a window. It is advised, principally in bedrooms, to open a window for at least ten minutes every morning. 

In the UK, trickle vents (a slight air filter gap at the top of windows - sometimes called window ventilators) have been the preferred method of ventilation and has become the current, acceptable standard of providing ventilation to rooms.

Unfortunately, trickle vents tend to be kept open all the time or left closed. They are also weak areas of thermal resistance as they are mainly built from thin plastic with no insulation qualities.

Asides from ideas to help improve natural ventilation through the house, we will discuss alternate means of ventilation.

Traditionally, we have mechanical ventilation exhaust fans within extract cooking hoods above stove tops and within bathrooms. These typically remove air but what about fresh air intake and what can be done further in other rooms of the house?

A supply ventilation system will provide fresh air but we need to consider removal of air as well as supply. Keep in mind that the supply of fresh outside air, depending on the time of year, may bring in cold air thus weakening our attempts at insulation and heating of the house. A balanced ventilation system ensures the flow of incoming air while expelling air to the outside. To ensure that outside air enters the house at a more comfortable temperature, ‘heat’ or ‘energy’ recovery systems help to precondition the incoming air to warm it up before the air enters the rooms.

One natural system that has been used is a gravity or stack effect for ventilation. This uses a central duct with side openings whereby hot stale air can enter and naturally travels up and rises through the duct to a top opening (such as windows or vents) leading to the outside. A downside of this method is that you lose heated air in the colder months so it is not very energy efficient. This system, traditionally, has its openings open all of the time, but one way that this can be remedied is by having mechanical openings and closures to the internal and/or external openings.

There are other natural ventilation systems that can be used but let’s look at more modern mechanical systems which can be installed throughout the whole house. Two most widely used methods are ERV and HRV systems.

A heat recovery ventilator (HRV) is another option, particularly in cold climates. It exchanges heat between the incoming and outgoing air streams, helping to maintain indoor temperatures.

Energy recovery ventilator (ERV) systems are similar to HRV systems but they also transfer moisture between the incoming and outgoing air streams. In addition to recovering heat, ERVs help regulate humidity levels inside the home, making them ideal for humid climates where moisture control is important. Both these systems help exchange indoor and outdoor air while minimising energy loss.

Larger buildings tend to favour ducted systems to distribute fresh air throughout the building. This can include central ventilation systems that distribute air through ductwork or decentralised systems that supply air through individual room ventilators.

Asides from ducting, the use of air purifiers with HEPA filters can be an additional means to remove indoor pollutants and allergens. While not a direct means of ventilation, they can complement ventilation strategies by improving indoor air quality.

In damp areas, consider using a dehumidifier, such as in basements or under ground floor crawl spaces, to control humidity levels and prevent mould growth. Excessive moisture can compromise indoor air quality and the effectiveness of the insulation.

Please bear in mind, that proper maintenance of mechanical systems, vents, filters and ductwork to ensure that they are kept clean and free of obstructions. Regular maintenance helps optimise the performance of ventilation systems, to achieve peak efficiency, and maintain optimal indoor air quality.

Proper inspection of the building envelope (inside and outside) will address any leaks or inefficiencies in the building envelope thus minimising the need for excessive ventilation and reduce energy losses.

In designing a ventilation system, factors such as climate, building design, energy efficiency goals and budget will affect your preferred choice.

It would be wise to consult a professional services company who can provide recommendations tailored to your lifestyle and your home's requirements.