Air Vents Discharging Externally

[Mr Blobby]

I've just noticed our M and E spec includes "automatic air vents to be installed at the highest point to discharge externally" in the same section as the heating/cooling flow and return that services the single MVHR heat exchanger in the loft.  House is passive build hence I am trying to keep external penetrations to a minimum. 

 

Obviously I have limited knowledge about all this but am suprised to see automatic air vents discharching externally.  What do the M and E consultants mean and do I need to vent externally?

Edited June 12, 2022 by Mr Blobby

[Russdl]

That doesn’t sound right. If you’re having MVHR and you’re building to passive stands then you don’t want “automatic air vents discharging externally” that will kind of defeat the object. 

[JohnMo]

This is all it needs, 

 

https://www.screwfix.com/p/bottle-air-vent-15mm/34359?tc=TA5&ds_kid=92700055281954514&ds_rl=1249404&gclid=Cj0KCQjwwJuVBhCAARIsAOPwGASEU9pcMfS0jV7msoGiH8MQI8Z0lWWqvgrLvrNS4x4WH42gipahiZsaAiwEEALw_wcB&gclsrc=aw.ds

 

No idea where they get the need for external venting.

 

I would check to see what else they are putting through the external wall.

[MikeSharp01]

It may be that they have thought through passive stack cooling for you! We have electrically operated roof lights at the top of the house and windows, at ground level, which can open (with suitable security / rodent protection) to create a cooling cross flow through the house when / if it overheats in the summer when MVHR is in bypass anyway.

[joth]

54 minutes ago, MikeSharp01 said:

It may be that they have thought through passive stack cooling for you! We have electrically operated roof lights at the top of the house and windows, at ground level, which can open (with suitable security / rodent protection) to create a cooling cross flow through the house when / if it overheats in the summer when MVHR is in bypass anyway.

 

This was my first thought too, but you need to ensure it seals well (airtight) when closed.   We have a passive house certified skylight high up in the vaulted roof that I use as an automatic air vent. It works excellently for night time cooling.

 

However I think @JohnMo is on point here - this is about automatically discharging air from the water circuit to the heat exchange.  Is it possible "externally" means to release air externalize it from  the water pipes?  There's absolutely no need for a heating system AAV to vent outside the building.