What to do with MVHR for final airtest

[PNAmble]

searched but couldn’t find an answer to this 
 

 

Got our final air test next week and just wondering what the best strategy is re MVHR.  For Earlier Test (0.42) it wasn’t installed so we just taped up the penetrations. 
 

For this test can we just seal the outside ducts with an airtight membrane and tape?    
 

 

[Russdl]

Can you not disconnect it inside the house and then cover the inlet and exhaust pipes with a plastic bag and a bit of tape?

[Andehh]

That's all we did, plastic bag and duct tape!

[JohnMo]

We had an air test done pre plasterboard, fixed all leaks, then on the final air test the guy just put tape on the room terminals, test was no better than the first test. So don't do that. Do as others have said and isolate the mvhr from the outside world.

[Bonner]

+1 I just taped up the inlet and outlet terminals outside

[joe90]

  On 15/06/2024 at 07:02, Russdl said:

Can you not disconnect it inside the house and then cover the inlet and exhaust pipes with a plastic bag and a bit of tape?

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That’s what I did.

[Dave Jones]

  On 15/06/2024 at 07:22, JohnMo said:

We had an air test done pre plasterboard, fixed all leaks, then on the final air test the guy just put tape on the room terminals, test was no better than the first test. So don't do that. Do as others have said and isolate the mvhr from the outside world.

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no ceilings ?

[JohnMo]

  On 18/06/2024 at 06:13, Dave Jones said:

 

no ceilings ?

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Sorry you may need to expand, not sure what you are asking?

[Dave Jones]

  On 18/06/2024 at 06:26, JohnMo said:

Sorry you may need to expand, not sure what you are asking?

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that big gap under the roof trusses

[JohnMo]

All rooms are vaulted. Vapour and airtightness layer then 50mm service void and plasterboard, taped.

[Dave Jones]

you said air test pre-plasterboard ?

 

Would be hard with ceilings open to trusses no ?

[JohnMo]

  On 18/06/2024 at 06:39, Dave Jones said:

you said air test pre-plasterboard ?

 

Would be hard with ceilings open to trusses no ?

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It was just ready to plasterboard, all insulation, vapour and airtightness done, but with access to fix stuff. So service void battens on walls and ceilings etc. Holes through wall for mvhr were blanked off at the wall.

[PNAmble]

Thanks all. 

 

we also did a pre plasterboard (bare shell) 0.9, then a pre second fix test 0.42

 

We followed the advice re sealing the external MVHR ducts, it worked well enough, final result 0.47 ACPH.  Electrician had to re feed wires through a duct during second fix due to a fault so looks like we didn’t seal it as well as we’d previously.   
 

 

[Meabh]

Hi all - we have powder coated external MVHR vents in rendered walls. Did anyone find a good way to tape up the vents without pulling all the paint off? We've already had a bit of paint come off (mastic man on a ladder!). Thanks

[JohnMo]

  On 16/08/2024 at 08:29, Meabh said:

powder coated external MVHR vents

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If masking tape is pulling off the coating, they were badly done. I would strip the coating off and redo with a decent primer and top coat.

 

It may be easiest to take the inlet and outlet off the MVHR unit and bag and tape the ends there.

[MR10]

Used boot covers over the outlets and taped over those.