Fixing a hole where the rain gets in. (new AC pipe into PassivHaus)

[puntloos]

One of our passivhaus rooms is unexpectedly getting warmer than we hoped, and as such we will have to add one more fan coil unit. The challenge is that the aircon team isn't really well versed in passivhaus, so I'm trying to find a guide on how to drill a hole into a passivhaus wall and then sealing up the gaps left by having a hole with a pipe. 

 

To my understanding so far I have:

- Pro Clima Tescon Sprimer Spray Primer

- Orcon F

- Passive Purple Airtight Liquid Vapour Control Membrane Spray

- Contega Solido SL tape or (and?) Tescon No 1 tape

 

And steps:

 

1/ Drill, clean drill site. 

2/ Fix aircon pipe in place

3/ Fill large gaps with filler (orcon F?) 

4/ Apply Primer

5/ Purple membrane spray (2 layers)

6/ Cure for 48 hours

7/ Tape with the Shingling method

8/ Rainscreen cladding somehow? To protect the tape?

9/ Perhaps finish for visuals? 

 

Is the above correct? I'm especially fuzzy what it looks like when an outdoor wall (with its render?) has a bunch of tape stuck to it? Or is there some way to eg apply render over all this?

[Redbeard]

Hi. You say 

On 04/08/2025 at 17:37, puntloos said:

(with its render?)

Is the wall in question rendered, or was that added as an extra variable? I would do 1 and 2 as you suggest, and

add 2(a) remove render for approx 100mm diameter.

Fill BIG gaps (should there be any, given a 'clean' hole?) with mortar.

Allow to dry

Prime area and pipe with air-tightness tape primer.

Leave to dry tacky

Apply one of the 'fluffy' a/t tapes designed to be plastered/rendered onto. (Pavafix Win or (?) Pro Clima Contega (?may have changed its name?). Lap the tape onto the pipe just a tiny bit less than the depth of the render.

Apply render.

 

Alternatively use an EPDM grommet but I have not yet refined the thought-process for ensuring that the EPDM square stays stuck to the wall. You'd still need 'fluff tape' over the EPDM anyway, so maybe this is a non-option.

 

Your mention of render is not repeated in your 'steps', so I may have got the wrong end of the stick.

Out of interest what do you mean by taping 

On 04/08/2025 at 17:37, puntloos said:

with the Shingling method

 

 

I am guessing:

 

Bottom piece of tape

Tape 2 above overlaps by say 15mm

Tape 3 ditto

Etc.

 

That sort of thing?

[Nickfromwales]

Firstly, the info needed is the hole size, the dia of the thing going through the hole, and then the size/area/diameter of whatever it is that's getting affixed to the external rendered wall.

 

Externally you just need to be weatherproof, and the only airtightness needs addressing at the AT layer internally; usually doing a job like this retrospectively commands the use of FM330 foam as the means to the end, as it insulates, is weathertight, and is airtight, plus it conforms to the gaps and voids left to complete the task.

 

I've made a LOT of houses airtight, and then we've had the client "reconsider some options I gave them from day dot....." and then I've had to make new penetration(s) through a plastered, painted, AT wall, so I am quite familiar with doing this tbh. Just needs an eye on it or any 3rd party you entrust this to.