How to improve air tightness on a new home?

ccbrowning

Hi

I am moving into a new home, one that is supposedly an 'eco' build. However, the EPC under 'Air tightness' has a rating of just 'good', with air permeability of 5.6 m3/h.m2 (as tested).  Any idea what the likely culprit(s) is/are going to be? I see some ideas on this page: Airtightness: What is it and Why Does it Matter? | Homebuilding However, we do not have a timber frame home, and it 'just' has double glazing, but no chimney etc. I assume if you had a test carried out yourself you would find out where the leakage is?

weeg

If you haven't yet moved in, I'd suggest you live in the house for a bit and see if you really do need to do anything. 5.6 is not bad. Most the the improvements are either really obvious - letter boxes etc, or a total nightmare, which would cost you more than you would save as remedial measures.

ccbrowning

weeg said:

If you haven't yet moved in, I'd suggest you live in the house for a bit and see if you really do need to do anything. 5.6 is not bad. Most the the improvements are either really obvious - letter boxes etc, or a total nightmare, which would cost you more than you would save as remedial measures.

I was just a bit concerned since my current home's EPC has a better rating in this area of 4.1 and honestly it feels drafty. Perhaps the whole testing of both houses was nonsensical. I'll see if I can identify any drafts when we move in...

coffeehound

Close the trickle vents as a starting point!

Doozergirl

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.  

rob7475

I don't get why you would want an airtight house. The moisure created by living in a house has to go somewhere. If the house is airtight with no fresh air entering the house to dilute the moist air, you end up with condensation issues.

Extractor fans work to a certain degree but they rely on being able to pull fresh air into the space to replace the moist air that's being extracted.

Doozergirl

rob7475 said:

I don't get why you would want an airtight house. The moisure created by living in a house has to go somewhere. If the house is airtight with no fresh air entering the house to dilute the moist air, you end up with condensation issues.

Extractor fans work to a certain degree but they rely on being able to pull fresh air into the space to replace the moist air that's being extracted.

I'd rephrase it to 'why would you want an airtight house that isn't designed as one'.  

You need properly managed ventilation in an airtight house, in the form of MVHR usually.   Ours is pretty airtight to the point that we can leave the door open in January and it doesn't impact the house very much as there's no through-flow of air, but if I turned off the MVHR, we'd very quickly have a humidity issue.  

ccbrowning

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.

Doozergirl

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.  

stuart45

Modern saying for new builds. 'build tight, ventilate right'. 

coffeehound

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?