How to improve air tightness on a new home?

Doozergirl

coffeehound said:

Doozergirl said:

coffeehound said:

Close the trickle vents as a starting point!

If the House has trickle vents, they are there to be used and the house isn't designed to be airtight.  

My contention would then be: why worry about a 0.6 m3/h.m2 leak rate above the nominal ideal if the homeowner is then expected to live with holes drilled in the window frames in every room?

They shouldn't worry about it unless they're prepared to make significant investment and start undoing a brand new house.  

We need ventilation.  

stuart45

I live in an old cottage which has it's own Eco system. My wife goes round the single glazed windows with a J cloth every day, and the furniture beetles drink up the rest of the moisture.

ccbrowning

Doozergirl said:

ccbrowning said:

This is a very modern home with underfloor heating across both floors and a GSHP, so I am hoping it was designed to not get damp, too. Don't recall seeing an extractor fan (current place has one), but who knows.

There is absolutely no question that it has extraction.  

Living in a house produces moisture.  From you breathing and sweating, from your washing and cooking.  In an airtight house, what do you think would happen to your shower steam if there is no ventilation?  All houses need ventilation.  

'Normal' houses are a bit leaky, but in order to meet building regulations, they have to have trickle vents in the windows and mechanical extraction to outside from any room with a tap.   

An airtight house doesn't work like that, it has expensive mechanical ventilation from one singular hole in the house wall that runs constantly, bringing fresh air in and extracting from rooms with taps via a ducting system that runs through the house.    

If you try to make your house airtight by blocking your ventilation, you will end up with a mouldy house.  

I mean I know it has extractors in the bathrooms and kitchen. However, my current home has a whole-house one on the top floor that is continually pulling air out. It'd be surprised if there isn't one, it just wasn't so obvious.

Doozergirl

ccbrowning said:

Doozergirl said:

ccbrowning said:

This is a very modern home with underfloor heating across both floors and a GSHP, so I am hoping it was designed to not get damp, too. Don't recall seeing an extractor fan (current place has one), but who knows.

There is absolutely no question that it has extraction.  

Living in a house produces moisture.  From you breathing and sweating, from your washing and cooking.  In an airtight house, what do you think would happen to your shower steam if there is no ventilation?  All houses need ventilation.  

'Normal' houses are a bit leaky, but in order to meet building regulations, they have to have trickle vents in the windows and mechanical extraction to outside from any room with a tap.   

An airtight house doesn't work like that, it has expensive mechanical ventilation from one singular hole in the house wall that runs constantly, bringing fresh air in and extracting from rooms with taps via a ducting system that runs through the house.    

If you try to make your house airtight by blocking your ventilation, you will end up with a mouldy house.  

I mean I know it has extractors in the bathrooms and kitchen. However, my current home has a whole-house one on the top floor that is continually pulling air out. It'd be surprised if there isn't one, it just wasn't so obvious.

You'd be surprised if there isn't one, but I'm not sure what kind of system you're talking about.  

ccbrowning

Doozergirl said:

You'd be surprised if there isn't one, but I'm not sure what kind of system you're talking about.  

Hi, something like this: https://nuaire.co.uk/product-list-page/drimaster-eco-range

Doozergirl

ccbrowning said:

Doozergirl said:

You'd be surprised if there isn't one, but I'm not sure what kind of system you're talking about.  

Hi, something like this: https://nuaire.co.uk/product-list-page/drimaster-eco-range

That's pushing air in, not out.  I understand though.  

Mistral001

This is just crazy.  The OP risks making their house an unhealthy house.  Expelled air that is constantly being rebreathed is bad enough but it will create a breeding place for all sorts of nasties that love lots of moist warm air.  The only fresh air will be air that comes in once an external door is opened and closed when someone comes out or in.  

coffeehound

Mistral001 said:

This is just crazy.  The OP risks making their house an unhealthy house.  Expelled air that is constantly being rebreathed is bad enough but it will create a breeding place for all sorts of nasties that love lots of moist warm air.  The only fresh air will be air that comes in once an external door is opened and closed when someone comes out or in.  

I love this place:  when I suggest keeping trickle vents closed most of the time, there are howls of disagreement.  Then when I suggest opening a window so that extractor fans can work effectively, I get someone saying no, there's plenty of passive ventilation into a home so that's not necessary!

Anyway, with energy prices going up, I think there will be closer scrutiny of this, since it is nuts having vents open all the time letting heat blow straight outside.  This idea of 'trickle vents good, leaky house bad' is weird: they are the same thing via different paths.

This quote even suggests that no further ventilation is required where leak rates are above 3, though presumably asumes point-of-use extraction in wet areas

In the UK the Maximum Air Permeability is 10 m3h-1m-2. However, as a general rule new dwellings should achieve an Air Permeability of 5 m3h-1m-2 or less. A test between 3 – 5 m3h-1m-2 would usually be acceptable by building control and your SAP assessor. A reading of less than 3 m3h-1m-2 might mean the building is too airtight. This could lead to condensation and mould, and therefore would need to be accompanied by an adequate ventilation system. 

Anyway I wasn't suggesting no ventilation, just use extractors as required (with a window open somewhere), control the usual moisture sources where possible, and change the air as required by opening a window for a brief period.