ᐅ Retrofit Installation of Split Inverter Air Conditioning System

Dear forum,

Perhaps I am already too late with my question, as I have already installed the air conditioning system and am now wondering if I made a serious mistake out of ignorance.

I live in a KfW 55 timber frame building, into which I installed a 5.3 kW (18,000 BTU) air conditioner. I simply made an opening from the living room into the garage and ran the line from there onto the roof, where the outdoor unit was mounted.

Now, of course, I have penetrated the vapor barrier, but I only ran a pipe from the interior to the exterior. A friend who is a carpenter told me that this was not good and that the hole in the vapor barrier could very well lead to moisture entering the insulation.

Most of the hole is filled by the pipe; however, some material was likely chiseled away around the edges, so it may no longer be properly sealed there.

Do I need to take action here, or is the risk negligible due to the size? If I do need to act, what would be the best approach? I have already made another opening because of water issues (drilling a well unfortunately did not work), and no attention was paid to sealing there either.

Thank you for your advice. Best regards

You definitely need to restore the airtightness.

Mycraft schrieb:

You definitely need to restore the airtightness.

Just to clarify my understanding: Is the airtightness issue between my garage and the house, meaning inside the installed pipe, or is it about the vapor barrier’s airtightness, so basically extending the vapor barrier and sealing it to the pipe from the outside?

Option 1: Simply fill the pipe completely with insulation material and apply sealant from the outside... this should be fairly easy.
Option 2: Open up the drywall, remove the OSB board behind it, without damaging the vapor barrier around the hole, and wrap a vapor retarder around the pipe... I think this would be a major effort, especially since the assembly is already attached to the wall — it might allow a little movement but certainly wouldn’t hold the pipe in position...

So... hopefully option 1.

Thanks so far.

There are adhesive collars for penetrations through the membrane. The electrician you trust should be able to get something like that for a small price from the wholesale supplier.

This way, the pipe is sealed airtight to the membrane. Now, should you just generously apply silicone to the pipe?

Option 2. To be on the safe side, you need to seal the pipe at the vapor barrier. This means you have to tape both the membrane and the pipe. Whether you use collars or vapor barrier tape is up to you. Without this, you will have a potential entry point for condensate to get into the wall framing and insulation, with all the consequences.

P.S. I am currently installing four air conditioning units at work and am considering adding two more at home to the ones I already have. It’s getting hotter here every year.

How can I best access it now? Does anyone have a good idea? I’d rather not dismantle everything again, as I would have to take down the entire system...