The Glazpart Bi-fold vent has a unique low-profile louvred canopy design combined with a low profile vent to allow both the internal vent and louvered grille clip in easily to sit between the open concertinaed door leaves.

Moulded from high quality virgin ASA the vents are highly temperature and colour stable when compared to PVC.

The vent is designed for compliance to the building regulations with the independently tested equivalent area, it sits in a 16mm rout and in many cases, can be located directly into the door leaf or frame, removing the need for expensive additional “knock on” or extended profiles. With an EQA of 2700EA a 3-panel door meets the background ventilation regulations for the room.

The tried and tested clip design sits perfectly in the low-profile chassis allowing the split closure plates to direct the air away from occupants.

The internal closure plates of the Bi-Fold Door Vent clip onto a uniquely designed low prolife chassis which in turn clips within the aluminium profile, so you only have the height of the lids protruding above the profile. The chassis will be suppled in either white or black dependant on the colour of the patented closure plates with their innovative vertical closure plates.

The external section has a new louvered design, to give the minimum amount of protrusion from the face of the profile. The louvred flyscreen will sit beneath the reveal giving additional protection from the elements.

Note: The louvre grille is not designed for fitting to window profiles especially with the trend for low profile (sightlines) which will struggle to accept a 16 mm rout.

Consideration should be made as to the location of the installation and in extreme and highly exposed locations other solutions may need to be considered.

Glazpart’ s bi-fold door vent achieves an equivalent area of 2700 EA each vent. Therefore, with a typical installation having three leaves, this will achieve 8100EA satisfying the room’s background ventilation requirements under the building regulations (Part F & L).

If the installation has to only two leaves, additional background ventilation would need to be installed to assure compliance.

Glazpart support CAB in its theoretical research into the limited reports of moisture entering aluminium window profiles, of which there could be many possible root causes. To date, Glazpart has not experienced any feedback where the fitting of a trickle vent to an aluminium window has been linked to moisture damage.

What is clear, is that the potential worst case scenario for this theory, is the use of an open ended, undrained “knock on or add on” profile where, if there is a moisture build up inside, it might flow along and eventually down in between the frame and the reveal, with the moisture’s surface tension, capillary action and gravity taking over, potentially leading to moisture damage.

If a trickle vent is fitted in the frame or sash, there are moisture pathways in, to remove the moisture from the external profiles and should these extend through into the internal profile, any potential build up would be removed.

The possible surface condensation on the internal face of the internal profile which get reported back by homeowners (especially in the winter months) could be reduced by damming either side of the trickle vent rout with the introduction of the correct waterproof, insulating foam which would localise this still theoretical issue.

Glazpart will continue to support research into any issues regarding trickle ventilation and work with the industry’s technical experts to ensure safe, functional and compliant products.

Following the recent changes in building regulations (Approved Documents – Part’s F & L) especially for domestic applications such as domestic windows and bi-fold doors. This has introduced a requirement for a routered slot for these applications when using aluminium profiles.

This has reignited the ongoing debate relating to the theory that fitting a tricklevent has a technical concern of cold bridging, due to the higher thermal conductivity of aluminium profiles.

“The theory is – and I want to emphasise that at this point it remains a theory – is the trickle vent cut-outs, allow air to circulate around the external permitter of the window frame between the frame profile and the structure.” 

“The challenge is that moisture damage often takes a long time to be visible. The reports of moisture-related callbacks from our members are increasing, and there are patterns, with more complaints in winter when homes have more moisture build up and the outside is cold.”

Dale Pegler – Technical Director CAB (Council for Aluminium in Buildings)

Working with our Glazpartner CAB we support their ongoing research to prove or disprove the theory and identify if this is a root cause.

CAB have recommended that it should be “best practice” when fitting any manufacturers tricklevents through aluminium window profiles. IF the internal profile is not already foam filled that a “dam” constituting a foam seal at either end should be introduced.

The schematic below demonstrates the potential issue when a cooler internal profile cell, encounters the warmer, higher humidity air of the room in which it is fitted, generally more in winter. through the more conductive aluminium.

“The positive here, is that the solution doesn’t need to be expensive or complex. It may be simply about sealing the trickle vent so that cold air can’t escape down the profile channels or an adaptation of drainage”

Dale Pegler – Technical Director CAB (Council for Aluminium in Buildings)

Today, we are working with our technical Glazpartner Soudal, experts in foam applications for the UK fenestration market, to find a solution should this theory be proven.

Schematic from CAB