A change of Rules & Regulations for Trickle Vents

Tuesday, 19 July 2022

Here at Bill Butters Windows, we understand the importance of energy efficiency and ventilation. They are two aspects of window products that make a home comfortable and economical. Getting the balance right is often down to that often underappreciated part, the trickle vent. Now, the rules and regulations for trickle vents have been updated so we thought it would be useful to delve into this part of double glazed windows a bit further.

What are Trickle Vents?

You’ll find trickle vents in the upper part of a window frame or casement. Their purpose is to keep a degree of ventilation in a room, improving the air quality and reducing things like mould and condensation. They often appear as a small strip and may be permanently open or alternatively have an open / close function. They are vital in achieving a balance of ventilation and energy efficiency.

Updated Building Regulations

So, how do trickle vents tie in with the latest updates to the building regulations in England? Regulations have been amended in the parts regarding ventilation and energy efficiency, both areas in which trickle vents perform a role. These parts (F and L in the Building Regulations document), now include different requirements and guidelines.

Part F - Ventilation

This section of building regulations governs the ventilation requirements of both new build properties and any properties undergoing a change of use. In 2020, Public Health England and World Health Organisation guidelines rendered current standards out of date. As buildings have been made more energy efficient, they have become more airtight. In this way, it is vital to maintain minimum levels of ventilation.

What are the guidelines?

If replacement windows are being installed, they must maintain levels of background ventilation. This means that if existing windows have trickle vents, new windows must also have trickle vents that are no smaller and that are controllable. If no mechanical ventilation is present (like air con or other air management system) then any increased air tightness caused by replacement windows must be offset with background ventilation. Unless another ventilation system is evident, this should be in the form of trickle vents regardless of whether the previous windows included trickle vents.

• • • • Each standard, habitable room must provide a minimum of 8,000mm² of ventilation.
      • Kitchens should also provide a minimum of 8,000mm² of ventilation.
      • Bathrooms should provide a minimum of 4,000mm² of ventilation.
      • For homes which have mechanical ventilation such as air conditioning, the standard minimum background ventilation requirement is 4,000mm2.

These guidelines are applicable both to new homes and existing homes. Additional specifications state that:

• • • • Background ventilators should be at least 1700mm above floor level. This is intended to reduce cold draughts, but stay within reach to be easily controlled.
      • Trickle vents are intended to remain open.
      • Every room with an external wall should have background ventilation. Rooms that run in between two external facades should have background ventilation on both facades to allow cross ventilation.
      • High noise areas should be fitted with a noise attenuating background ventilator.
      • Different ventilation items should be installed at least 500mm apart. This includes trickle vents and extractor fans.

Part L - Energy Efficiency

The reason that homeowners replace windows is often for reasons of energy efficiency. And the reason that the guidelines on ventilation have been updated is because modern products have radically increased in performance in this area. The amends to Part L of building regulations apply to new homes and replacement windows. They refer to the ‘U-value’ of products. The number that the U-value indicates is the rate of transfer of heat through the product, in this case a window.

• • • • Windows replaced in existing homes should have a U-value of at least 1.4 W/m²K. For U-values, the lower the number the better. So double glazed or triple glazed products achieving a U-value of 1.2 are better performing than minimum requirements specify. We ensure that all our window and door products comply at least with the minimum requirements, as we want projects we’re involved in to be future proofed as much as possible.
      • Windows fitted in new homes should strive to a notional U-value of 1.2 W/m²K. This is the target, in order to move homes towards the government’s Future Home Standard by 2025. The absolute minimum U-value for new homes remains at 1.6 W/m²K and products must be sealed with air sealing tape around structural openings.

How Trickle Vents Help

Because of changes to both of these areas of building planning, trickle vents are becoming an increasingly important feature in high performing double glazed window products. Increased thermal efficiency is great for energy bills and a reduction of energy waste. However, it also means that air can be trapped and prevented from circulating. While improved temperature regulation increases comfort, air stagnation decreases it. So trickle vents are crucial in providing a balance to this. The structure of a trickle vent allows air to circulate from outside in, and vice versa, without creating a draught. In this way, the thermal performance of the window remains high, and the health of the building is maintained.

Aesthetics of Ventilation

For some projects, the visibility of standard trickle vent ventilation can cause concern. However, as the requirement for ventilation is so important, these features are increasingly incorporated into frames and casements, so they are far less visible. Background ventilation in aluminium, uPVC, sash and heritage windows is all less intrusive than you may have imagined. Indeed, for ventilation to be retrofitted is a challenging task that is visually obvious. So it’s important for you to ensure that replacement windows include sufficient ventilation on installation. This means that you will both comply with the updated building regulations document and also enjoy a more comfortable living environment.

At Bill Butters Windows, we strive for high performance in our window and door products. This means great energy efficiency, but also good building health. This is where integrated trickle vents are so important. To discuss your replacement window needs, contact us for a conversation. You’ll be surprised how easy it is to get a balance of thermal and ventilation performance.