Trickle Vents in Timber and Composite Windows

UK Building Regulations – Part F

For a “normal” home, regardless of whether it’s a newbuild or an existing property, “background ventilation” is a really important requirement. With our class 4 airtight windows, we always recommend looking into mechanical ventilation and heat recovery systems. But we do understand a full-house ventilation system isn’t feasible in a lot of cases. Therefore, it’s useful to understand where you’ll likely need trickle vents in your new windows:

When replacing windows, there is an exception to that table, which involves a “not technically feasible” argument. Basically, if a window is too small to be physically able to provide the required number of trickle vents, you should simply have as much ventilation as is feasibly possible.

Visible Hood Vents

The most common type of trickle vent you’ll see has a hood sticking out on the outside and a plastic contraption on the inside that be opened and closed to let air through. These are a very simple idea: long holes are cut straight through the frame of the window; that hood and plastic part will cover up the gap.

Generally, we try to avoid giving this type of vent to customers – they’re a little unsightly and there’s normally a better alternative…

Invisible Vents

…such as these! For outward opening windows, and most outward opening doors, we recommend aiming for this type of trickle vent.

Invisible trickle vents don’t change the appearance of the window from the outside – there’s no way of knowing how many or where they’re placed and the overall appearance of the product isn’t spoilt by a hood sticking out.

On the inside, you’ll see a completely flush plate against the side of the window frame. For the most part, we tend to recommend these stay closed: there’s a very simple Danish recommendation that keeps homes supplied with fresh air, regardless of whether trickle vents are installed:

• In the morning, windows in all rooms should be opened to bring fresh air into the home. 20-30mins should be sufficient
• During the day, try to air occupied rooms 3 or 4 times for 10-15mins

The 2nd bullet point might initially sound a bit awkward, but remember their advice assumes an average sized family are living in the house. If each person opens a window during or after taking a shower, and windows are opened during or after cooking, this easily creates a lot of fresh air exchange.

STM trickle vents

Unik Funkis trickle vents

Mechanical Ventilation and Heat Recovery

We mentioned this very briefly at the start, and we maintain, if possible practically and financially, this is the best route to go. When high-performance windows are installed, it doesn’t make much sense to immediately cut a few holes through them to give them more ventilation. On the other hand, the more airtight your windows are, the more efficient an MVHR system will be.

Since trickle vents and MVHR systems do the same job, you should avoid having both at the same time. So, if you feel it’s time to replace your windows, you should be consider whether a mechanical heat recovery system is feasible before you confirm the window order.

As this article is mainly about trickle vents, we won’t go into this any further, but we’ve written about it before in relation to airtightness and new-build regulations.

How to Measure Windows and Doors for a Quick Ballpark Quote

The Most Requested RAL Classic Colours

Interesting Design Ideas For Your Home Using Danish Windows

Winterproof Your Home Using High Performance Windows