What stage of build to put passive purple/blower

[health mechanic]

Have decided that will be going mvhr on my 2 storey wrap around extension built with blocks and standard joists. New block and beam floor with old suspended timber. Roof slates going on, windows and sliders 9 weeks away. About 20% of external perimeter is old cavity walls with 75mm.  So to get flush walls battening 25mm internal Wall where old meet new. 

 

Builders has already battened walls, and outside where cladding. First fix electrical and plumbing awaiting. 

 

Should the passive purple/blower be put on directly onto walls and take battening off, or as awaiting first fix plaster and board and then apply.

 

Also is it worth filling where ground floor joist meet inner leaf, or no pint as will be sealing above that.

 

Has anyone used it fir vcl under cladding and does it matter if applied after battens put in or before.

 

Picture below of 1 of the rooms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Iceverge]

Sorry, I'm a bit confused about this. 

 

Do you have more plans and pictures to help please. 

 

Is the picture above the first floor or ground floor? 

 

Is the wall being battened an external wall or internal? 

 

Purple passive and other airtight paint is expensive, much cheaper to use a membrane or a parge coat where you can. It's of limited benefit to apply until you're absolutely sure you've filled every hole you could poke a pencil through first. 

 

My advice is to make a DIY blower fan once the windows and doors are in. 

 

The get some Illbruck FM330 and fill all the big gaps. 

 

Then use a sand cement parge coat to do all the flat surfaces that might leak like un rendered blocks. 

 

Then spare the airtight paint for the junctions and hard to reach areas. 

 

[ProDave]

Sorry I would say airtight membrane on all the walls with all joints taped BEFORE the battens go on.  then all your services are inside the sealed envelope.

 

You need a lot of detailing at those joist ends going into the wall, and a set of basic rules to ALL trades along the lines of DO NOT drill or otherwise penetrate the airtight layer without first discussing it with you and agreeing it is necessary and there is a plan for how to seal up whatever is passing through the airtight layer. 

[health mechanic]

Thanks for comments.

 

 

 

 

 

 

 

Photo is of ground floor

 

 

 

 

 

 

 

See below plans

 

 

 

 

 

 

 

 



 

 

Edited March 26, 2023 by health mechanic

[Dave Jones]

do you have the windows, doors and 1st floor ceilings in ?

 

It's going to leak like a sieve around those joists....

 

 

[health mechanic]

Windows are 8 weeks away

 

Roof almost slated.

 

In regards to the floor joist...surely if it's airtight above subdeck floor to wall junction it's should be okay....as the area is being vented from vents?

 

 

 

 

 

 

[Sparrowhawk]

8 hours ago, Dave Jones said:

It's going to leak like a sieve around those joists....

Are joist ends a good place to use passive purple (other brands available)? It seems it'd be much easier than taping round them.