BC question on trickle vents and stoves with external air supply

[gcm]

My question concerns window ventilation BC compliance rules for fitting windows to a living room in an existing property with a woodstove.   It may be basic and obvious for the pros but as a householder I am unsure.  Safety is fundamental but so is prospective BC signoff of the windows.

The planning baseline for this living room space was an open fireplace, chimney + hearth airbrick and five windows with trickle vents (1996/7 approved plans), Egress door in room (not a requirement but it's there)

Since then an inset wood stove has replaced the open fireplace under an installer self-certification.  As part of this an optional external air supply tube was added to the end wall behind fireplace to provide direct external ventilation for stove combustion air.  This is beyond stove install minimum compliance regulations which relies on room air to a greater extent without getting into that here.  The stove install is believed compliant as of its install date - hearth, CO detector, stove space vents, liner etc.  Works well - way better than the open fire - no longer extracts all the centrally heated air from the house to heat the county.

Proposed window change and trickle vent issue now
 

It is proposed to replace all the windows in the room.  3 of the 5 are candidates for fixed lights as they are never opened but they could lose their trickle vents in this implementation scenario as not all suppliers in play offer the combination.

Over both changes (external air supply and trickle vents) - we are still likely to be "up" from the baseline in room ventilation but this may not be the only factor in determining BC compliance for the windows - as the direction of travel is "less than existing" viewed in isolation looking at the windows.

There do not appear to be any relevant fire egress considerations as the room has doors to main building doors nearby and a direct egress door in the room itself

There are two other opening windows in the room which are keeping their opening sashes and trickle vents regardless of scenario.

Any thoughts on this combination is appreciated. Whether the proposed scenario is valid or help on the rule it likely fails on so I can look at the most cost/energy efficient solution. 

Specifying opening lights for tiny and light well windows - which have pretty much never been opened in 20 years or had their trickle vents touched is to be avoided if a compliant design without either is possible.

 

Thank you

 

Graham

[Jml]

Does not answer your question, but for replacement windows my understanding is that if you get a FENSA supplier, then there is no need to involve BC directly, which may make things easier.

[ProDave]

I don't think the fire is the issue. It's simply providing the required room ventilation depending on it's size.

 

If you employ a FENSA supplier to self certify you do not even need to notify BC.

[gcm]

It has spurred me to think about it as background ventilation calc 23x8000mm2 existing background and for the room 5x 8k and reread the rules again.
A simple retrofit fail on 7.3 - if they already have them then they must have them again at the same size. Not very helpful and it might also fail on "not worse than" depending upon the view taken on the other added ventilation and my hopeful sounding offset.

Regarding Fensa - some of my suppliers want me to go LA BC route (as seemingly not members of and indeed sceptical of self cert).  Not sure if this is the province of those using rogue sub-contractors or some of these and also those confident in their work vs BC.  If I do go that way it may be worth tying them to some holdback to the BC signoff of installation matters if they are not providing it en passant.
 

Thank you for your thoughts