Do You Need Trickle Vents With Heat Recovery Systems?

Do You Need Trickle Vents With Heat Recovery Systems?

By Ruth MacEachern

Product Manager

All homes need to have adequate ventilation - it can help to prevent damp and mould caused by condensation, and can reduce the chances of contracting health issues caused or exacerbated by poor indoor air quality. This is an increasingly important matter for consideration as our homes become more air-tight and energy-efficient. There are several ways to achieve good ventilation, from the ‘natural’ ventilation provided by vents, to full mechanical ventilation with heat recovery systems.

Why do you need ventilation in the first place?

Good ventilation is needed for several reasons. Condensation is one of the leading causes of damp and mould, and the NHS says that it could increase the risks of respiratory problems, respiratory infections, allergies, or asthma, as well as affecting the immune system. Together with reducing the problems caused by damp, proper ventilation can also improve air quality and get rid of potentially harmful pollutants throughout the home. If left to build up, these can trigger asthma attacks in sufferers, as well as contributing to a range of other health problems.

What are trickle vents?

A trickle vent is a small opening, which is usually built into the frame of modern double glazing, around windows and sometimes other areas, such as patio doors. As the name suggests, the vent is designed to allow a trickle of air to pass through.. This helps provide ‘natural’ ventilation within a home. Some types of vent incorporate a sliding switch to increase or decrease the ventilation.

There can be issues with this sort of ventilation, however. It partly depends on air movement outside the house and often only provides minimal ventilation. This may not be enough for some properties, and houses relying on natural ventilation alone might still suffer from condensation and poor air quality.

Also, trickle vents may still allow draughts through, even when turned to a ‘closed’ position. Even the small gaps used for trickle vents will affect the home’s energy-efficiency to a certain degree, allowing some heat to dissipate.

What is a heat recovery system?

If natural or uncontrolled ventilation is not enough, there are other options, which use motors,, fans, filters and other mechanical elements to improve the flow of air through the building. Individual extractor fans can be placed in rooms that are prone to moisture or pollutants, such as bathrooms and kitchens. These can be great for expelling air from those rooms but do not always promote air-flow through the entire property.

Whole house ventilation systems are designed to deliver fresh, filtered air throughout the entire home. Some do this by extracting stale air away, with the resultant lack of pressure drawing air in from outside. Others do the opposite, drawing air from outside, which increases the pressure inside the house, forcing the stale air out. The most efficient systems use a combination, simultaneously drawing fresh air in through filters that take out pollutants while also extracting stale, moist air out of the house.

These balanced systems can also be combined with a heat exchange to create a complete mechanical ventilation and heat recovery system or MVHR. As the stale or moist air is drawn away, it passes through a heat exchange unit. This draws much of the heat out of the air before venting it out into the atmosphere. The fresh, filtered air coming in is also passed through the exchange and the heat is transferred to this input, recycling the heat back into the home.

So, do you still need trickle vents when installing a heat recovery system?

The short answer is no, you do not need trickle vents if you have a full mechanical ventilation and heat recovery system. A properly commissioned and installed MVHR system will meet the necessary building regulations relating to ventilation. It will also provide far better ventilation, with a constant flow of clean, filtered air, than uncontrolled ventilation systems using trickle vents, air bricks, windows, and doors.

It also allows you to improve the energy-efficiency of your home without compromising on air quality, potentially saving substantial sums in heating bills over the lifetime of the system.