Air Test Experiences Please

[BTC Builder]

I'm approaching the end of my build and will be doing the air test soon. It's one of the last things to worry about so I'm naturally worried both ways, too high, too low. Too high can always be fixed with some CT1 somewhere so I'm not massively concerned with that.

 

I didn't even know that too low was a thing, but I've read that 3 or lower will require mechanical ventilation. I don't have this, any such product could only go on an external wall now and there's no budget for it. 

 

How likely is such a score? My build is a traditional cavity wall and rendered so window frames are tight, I drylined all around the bottom of the walls, I can't feel much of a draft through sockets. 

 

My sap assessor has told me I need "around a 5" to meet regs but as this is my first experience of an air test, I don't know what to expect. 

 

I'd love to hear the experiences of others one way or the other. Thanks 

 

Side note, the property will be fully carpeted and I'd have moved in by the time we do the test due to having to wait on the kitchen, which needs to go in before air test and then skirtings up to it, creating a bit of a delay.

[Mr Punter]

You will need mechanical ventilation in the kitchen, bathroom, WC and utility.  You also need trickle vents to all the habitable rooms.  The fans may need testing also.  What did Building Control put on their Plan Check report?

[Nickfromwales]

Do the windows have trickle vents? 
 

Have you fitted extractor fans? 

[BTC Builder]

Yes, extractor fans everywhere you'd except as per building regs drawing and trickle vents on every window 

[BTC Builder]

Just to clarify, when talking about mechanical ventilation, I was referring to MVHR, that's what I don't have, no infrastructure for it, no budget for it.

 

When I read the other day that mechanical ventilation will be required for 3 or lower, I assumed that was referring to MVHR as extractor fans are a given, surely no-one would build a house without extractor fans

[Nickfromwales]

3 minutes ago, BTC Builder said:

Yes, extractor fans everywhere you'd except as per building regs drawing and trickle vents on every window 

Ok, so just get the test done and see if there’s a problem.

 

Mechanical ventilation is just a powered fan, in whatever form that takes, so either push/pull like MVHR or single point extraction as per what you have.

[Oz07]

Nobody will make you have mvhr for a score less than 3. There's no mechanism for someone to make you. I've had places before with sub 3 scores and no mechanical ventilation. 

[Mr Punter]

8 minutes ago, Oz07 said:

Nobody will make you have mvhr for a score less than 3. There's no mechanism for someone to make you. I've had places before with sub 3 scores and no mechanical ventilation. 

 

Agreed I have heard this claim but cannot see it in the Building Regs.

[JohnMo]

12 minutes ago, Oz07 said:

Nobody will make you have mvhr for a score less than 3. There's no mechanism for someone to make you. I've had places before with sub 3 scores and no mechanical ventilation. 

Don't move to Scotland then - mandatory for better than 3 to achieve building sign off! The mechanism is building regs.

[ADLIan]

21 minutes ago, Oz07 said:

Nobody will make you have mvhr for a score less than 3. There's no mechanism for someone to make you. I've had places before with sub 3 scores and no mechanical ventilation. 

It's all in Appr Doc F in England.

 

Do you currently have background (trickle) vents and intermittent extract fans to 'wet' rooms? If your air pressure test comes in at less than 3 you will need to upgrade this to continuous extract or a mech vent system. Get the test done and see what the result is. If you get less than 3 I am sure there 'ways' of increasing this to above 3 (open a trickle vent???). Your testing guy may be able to offer some simple 'advice'!.

[BTC Builder]

8 minutes ago, ADLIan said:

It's all in Appr Doc F in England.

 

Do you currently have background (trickle) vents and intermittent extract fans to 'wet' rooms? If your air pressure test comes in at less than 3 you will need to upgrade this to continuous extract or a mech vent system. Get the test done and see what the result is. If you get less than 3 I am sure there 'ways' of increasing this to above 3 (open a trickle vent???). Your testing guy may be able to offer some simple 'advice'!.

Yes, got all that. It's all hypothetical at this point, but hopefully I'll have someone who will want to come up with a solution rather than someone who wants to tell the teacher so to speak.

 

Upgrading the extractor fans would be very difficult, impossible in most cases, as far as the bathrooms go as the ducting is now inaccessible, cables tiled in, etc

 

They're all above the 15 litres per second stipulation but what they are in reality, I don't know. 

 

[Nickfromwales]

1 hour ago, ADLIan said:

Your testing guy may be able to offer some simple 'advice'!.

Aka, ‘look the other way’, when a couple of windows are on night-latch vs fully shut. 

[saveasteading]

1 hour ago, Mr Punter said:

Agreed I have heard this claim but cannot see it in the Building Regs.

My thoughts exactly and I was going to have a read up later. So if anyone can point it out that would be helpful.

13 minutes ago, Nickfromwales said:

Aka, ‘look the other way’,

I  was once asked by the test guy 'what number are you looking for? It hadn't occurred to me before that I might want 3.1.

[Redbeard]

3 hours ago, BTC Builder said:

I can't feel much of a draft through sockets. 

If that means you can feel 'something of a draught' (at atmospheric pressure) from the sockets I think I'd be a bit worried about other areas. Who has it been built by? Yourself with a concentration on air-tightness, or a general builder with no specific air-tightness 'leanings'?

[BTC Builder]

15 minutes ago, Redbeard said:

If that means you can feel 'something of a draught' (at atmospheric pressure) from the sockets I think I'd be a bit worried about other areas. Who has it been built by? Yourself with a concentration on air-tightness, or a general builder with no specific air-tightness 'leanings'?

It was done by me with a high attention to detail. I should clarify, there's no draft whatsoever through fastened socket faces, perhaps "cold" is how I'd describe a couple that are just flapping currently