I'm looking for advice and reassurance! We're planning to fit an air-air heat pump to replace the direct electric duct heater we presently use to heat our house, and to provide cooling in summer. It's a conventional split unit with internal units and an external condenser unit. To connect the internal and external units we will need to make 60mm holes for the refrigerant, condensation and power in a conduit.

I'm planning to make the holes in areas where there is warmcel insulation instead of straw bales, so as I remember the construction from inside to outside is:
- lime plaster (30mm or so)
- 15mm Savolit board
- Intello Plus membrane (connected to lime plaster over straw bales with mesh
product)
- muslin to contain Warmcel
- 450mm of blown-in Warmcel
- 25mm Savolit board
- lime render (40mm or so)

My thoughts are to drill from the inside, starting with a pilot hole. Are there likely to be any issues to watch out for?

My other worry is airtightness. The main airtightness barier is the internal lime plaster but there are places (such as these areas) where the airtightness barrier is the Intello PLus membrane and it is connected to the plaster with Pro Clima Contega PV tape. We used Dafa pipe and cable collars or Siga Rissan tape to seal penetrations. Lots of short lengths of Rissan around the MVHR ducts and around the incoming water pipe for example.

I'm not sure how best to seal a 60mm pipe containing several other pipes and a cable though, and in theory it should be sealed to the Intello Plus although sealing to the plaster seems a lot easier. Any thoughts on the best approach?

https://proclima.com/products/connections/window-sealing/contega-pv
https://www.siga.swiss/gb_en/products/rissan

Posted By: Nick ParsonsCan the duct stand at all proud?

I don't know. It depends how it mounts into the indoor unit. I'll see if I can find out, but it will probably take a couple of weeks.

I like the FM330 idea.

Posted By: Mike1For the drilling, I'd choose a 68mm cutter and line the hole with a short length of 68mm downpipe

Why use 68mm drainpipe as well as the 60mm conduit?

I'm not sure how to seal the ends of the pipe to the wall without access to the interior of the wall and not wanting any tape visible on the outside for aesthetic reasons? Or have I misunderstood something?

Posted By: djh

Posted By: Mike1For the drilling, I'd choose a 68mm cutter and line the hole with a short length of 68mm downpipe

Why use 68mm drainpipe as well as the 60mm conduit?

Instead of - both are easily obtainable. But if you already have 60mm cutter & pipe, no problem!

Posted By: djhI'm not sure how to seal the ends of the pipe to the wall without access to the interior of the wall and not wanting any tape visible on the outside for aesthetic reasons? Or have I misunderstood something?

On the outside, the only option is to trim back the render, seal against the Savolit & make good after, as Nick suggests. Inside you could liberally apply Orcon F, as I did here, if you don't want to do the same as outside. You'd obviously need to make the hole a little bigger:

''If you are going to do the above don't forget derating requirements of cables in insulation.''

Good shout. Also compatibility of FM330 with uPVC cable sheathing.

''But while checking that, I came across an interesting post: https://accablesolutions.com/blogs/our-news/why-using-expanding-polyurethane-foam-in-cable-ducts-is-a-bad-idea Some interesting products there!''. That's why I sugg'd: ''a less perfect alternative would be to get the cables etc. in, then flood the conduit with Illbruck FM330 air-tight foam.''

Go with my first idea then (2nd post on this thread, above)

<blockquote><cite>Posted By: Nick Parsons</cite>a less perfect alternative would be to get the cables etc. in, then flood the conduit with Illbruck FM330 air-tight foam.</blockquote>

Posted By: owlmanPenetrating the wall with ducting to carry the pipe and cables is the obvious solution and I cant comment on the PH sealing of that work, others are more experienced. However, directing and routing the pipes and cables etc both externally and internally may require equal thought given your wall structure. Do you have a plan, how many splits are there.

Everything will be clipped to internal (conventional) walls where necessary. There are two internal units. For one, the through-wall duct will be immediately behind the unit. External trunking will be used and the installer is aware of the peculiarities of securing to the render.

I think the installer is competent.

I think from your posts above that you aren't doing lots of smaller pipes separately, but just in case it's worth considering Pro Clima's Kaflex Multi grommets. https://proclima.com/products/connections/grommets/kaflex

They allow for up to 16 penetrations clustered together in close proximity, and would probably work well with the Intello Plus membrane.