Building Regulations, trickle vents, and what it means for replacement timber windows and doors.

We are going to look at changes to the Building Regulations, trickle vents, and what it means for replacement timber windows and doors, particularly timber windows and doors fitted in period homes.

What are the changes to the Building Regulations?

This blog relates to Approved Document F: Volume 1: Ventilation in Dwellings. It came into effect in June 2022. All work started after this date must comply with the revised regulations. The full document can be viewed and downloaded here.

Approved Document F (ADF) deals with various aspects of ventilation in buildings, but for the purposes of this article we are only looking at the two types of ventilation relating to windows: Purge ventilation and Background ventilation.

Purge ventilation – This is achieved by opening a window and door and is used to rid a room of a build-up of pollutants or water vapour, or to help with temperature control in hot weather.
ADF states that most replacement windows need to have an openable area at least 1/20th of the total floor area of the room. This is a fairly simple calculation and does not usually affect the look of the new window or door being installed, so we will leave purge ventilation there.

Background ventilation – This describes the ability of a property to “breath” and maintain good air quality inside the building. This is important for the health of occupants and also helps prevent the build-up of condensation and mould.

The changes to the Building Regulations essentially mean that most new window and door installations will require the inclusion of trickle ventilation. Trickle vents will usually be required in kitchens, toilets, bathrooms and all habitable rooms. They are not required in hallways and landings. Two-stage locking mechanisms, such as night-vents and adjustable sash locks, are no longer considered acceptable means of background ventilation.

How do these changes affect you?

Now we come to the important bit. You are looking for new timber windows and doors and, in all likelihood you live in a period home and want to retain its original character. Fitting trickle vents in your beautiful new timber windows and doors really goes against the grain here, right?

Well, yes, and no. There is no escaping the need to comply with the Building Regulations, but there are things that can be done to ensure the character of your home is retained as far as possible.

So, let’s work through some scenarios and see what options are available:

Do you really need trickle vents?

Let’s look in more detail and define when trickle vents are and are NOT required. As mentioned above, trickle vents MUST be installed:

• In all habitable rooms and kitchens;
• In toilets or bathrooms (with or without a bath or shower) even if that room has mechanical extract ventilation.

But, there are exceptions:

On elevations facing busy roads. There is no definition in the Building Regulations as to what constitutes a busy road, but, unfortunately, FENSA have taken a rather extreme interpretation of a busy road as being:

• Classified as an “A” road;
• In an urban setting;
• More than two lanes in any direction;
• Carries sustained heavy traffic.
  – Think homes directly adjoining the A3, North Circular, parts of the South circular /Westway etc., not a road that is used as a rat-run during school term times.
  – It may be that you could consult your local Building Control department and argue this point in order seek an exception, in which case, as long as you could prove to FENSA in writing that your home is exempt, this may negate the need for trickle vents on the elevation facing the road, but we are unable to confirm this here.

When a Mechanical Ventilation with Heat Recovery system (MVHR) is installed.

• This is a system that continually supplies clean air from outside and extracts the air from inside.
• An example of one such system is the “Fluxo”, by venti. It is a discrete system that is fitted in the wall at high level. It is easy to retro-fit and is very quiet during operation.
• A unit fitted in each room would eliminate the need to fit a trickle vent in that room.
• The benefit of this system is that it supplies constant, clean air, without adding a cold draft. It is also rated to a noise reduction of 36dB, so it is useful in areas where noise reduction is important.
• More information can be found here.

In Conservation areas

• It may be possible to avoid fitting a trickle vent if your home is within a conservation area. However, the installation still needs to be registered with FENSA and they will need written confirmation from the conservation officer that a trickle vent is not required. In this case, it is best to seek this confirmation from the conservation officer before work commences.

In listed buildings

• Trickle vents are not usually required where windows or doors are being replaced in listed buildings, although they will be expected to be fitted where the work is part of larger building works, such as an extension /loft conversion etc.

If you can prove your home already meets the requirements of the Building regulations

• You can do this by carrying out Air Pressure Testing (Pulse test).
• In reality, all homes leak some air. Older, period homes, even ones that have had insulation fitted, will still most likely leak so much air that additional background ventilation would actually not be required. However, The Building Regulations and FENSA are unable to work on this assumption and proof must be provided. This is where a pulse test comes in.
• A pulse test is an operation performed by a specialist accredited company before and after the installation of new windows and doors, where the air leakage of your home is measured.
• If the amount of background ventilation is found to be adequate, additional trickle ventilation is not required. However, as the second test is completed after the installation of new windows and doors, there is then the question of what to do in the event of there being insufficient ventilation without the vents being fitted, and they may need to be retro-fitted, which will likely be costly.

Air bricks

• If there are two or more airbricks fitted in a room, trickle vents may not be required

What are your options then?

In most cases, unless you can satisfy one of the exceptions above, you will have to fit a trickle vent in your new timber windows and doors.

Whilst we at Woodland have tried to resist fitting vents for as long as we can, it is no longer realistically possible. We have therefore done whatever we can to incorporate trickle vents that will meet the requirements of the Building Regulations whilst remaining as discrete as possible.

These examples incorporate trickle vents, and, as you can see, the original character of the windows is retained, to a large degree.

Our position on trickle vents is that they are a necessary evil. Unfortunately, we have all seen in the news the devastating effects on health that poor ventilation and mould growth can have, particularly on the young. That said, it seems non-sensical that we are being told to install windows and doors with ever lower U-values (i.e. offering better insulation) and then being told we have to put a hole in them because the building has been sealed so well. In some ways, modern insulation is a victim of its own effectiveness. Probably the most effective solution, both in terms of aesthetics and outcome on air quality, is to fit a MVHR such as the Fluxo, but this comes at a cost. We will be happy to discuss this in more detail with you if you wish, just get in touch.