# Airtightness and Trickle Vents



## markd (10 Dec 2013)

Does anyone know the reason that trickle vents can't be used on very airtight buildings? 

In Scotland you can't use trickle vents if your house is tighter than 5m3/m2/h. I think this might be different in England though. Other than the fact that you would need 'bigger' trickle vents I can't see any reason why you should be made to install MVHR if you inadvertently build tight.

Thoughts would be much appreciated.


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## Leo (10 Dec 2013)

Welcome to AAM Markd,

Please note AAM is an Irish site, so regs here differ to those in England / Scotland.

I'm no expert, (others on here are) but you do need to provide sufficient ventilation to maintain a healthy environment. I'd imagine sufficient trickle vents to achieve this may make it impossible to meet those air tightness levels.


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## lowCO2design (10 Dec 2013)

markd said:


> Does anyone know the reason that trickle vents can't be used on very airtight buildings?


yes its in part F of the building regs 
have you considered DCMEV by Aeroco or similar 

show us where in the Scottish regs they relax this vent issue?

why are you anti mvhr? did you not budget for it?


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## markd (10 Dec 2013)

Thanks for that.

Had a look at the Part F that you attached. It seems as though both the English and Irish regs allow trickle vents to be used <5m3/m2/h, by increasing the equivilent area. Scotland doesn't allow this for some bizzare reason - they think it will cause condensation and IAQ problems...where is the research that shows this though.

At the moment if you target 5 and acheive 2 after testing, they will probably ask you to fit MEV, its costly madness. Sorry couldn't attach link to the regs as I've not made enough posts yet!

I'm not anti-MVHR, it's just not always the right answer, I think.


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## lowCO2design (12 Dec 2013)

mark 
assuming your building a house 
have you carried out a provision BER? (to allow you to review options to achieve compliance with part L)


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## lowCO2design (12 Dec 2013)

markd said:


> Thanks for that.
> 
> Had a look at the Part F that you attached. It seems as though both the English and Irish regs allow trickle vents to be used <5m3/m2/h, by increasing the equivilent area. Scotland doesn't allow this for some bizzare reason - they think it will cause condensation and IAQ problems...where is the research that shows this though.
> 
> ...


why is it madness?
& when do yo think it IS the right answer?


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## Lanni (16 Dec 2013)

To comply with Part F, you must increase the trickle ventilation area by 40% if the airtightness level is less than 5m3/m2/hr. If you are looking at less than 3m3/m2/hour, I would definitely recommend MVHR.
It is always better to have planned all this at the start by checking drawing compliance using the DEAP software.


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