DIY Home Improvement Forum banner

Installed pvc pipe in house but later on there was moisture in area

460 Views 7 Replies 5 Participants Last post by  Datawise

I Installed a 1inch pvc pipe with cat5 inside from my house connecting to the garage. From the exterior of my home, i sealed the box with silicone and in the pvc pipe i had put duct seal putty inside to fill the gap of the pipe. In the inside of the house i had sealed around the 1inch pvc pipe with silicone then sealed around the pipe with foam insulation for more protection. Around the pipe is probably about 4 inches of spray foam. With the cat5 coming inside the house i had put silicone inside the 1inch pvc to stop cold air and bugs and all to come in. Then covered it back with the pink fibre glass insulation and vapour barrier.

But i had to then remove the underground pipe and cat5 as it needed to be relocated(dont really want to get into that part), but still leaving the exterior box attached.. While in the process of removing the cat5. I had noticed that it was kind of damp in the area where the foam insulation was and where the cat5 was coming in. That whole area was not spray foamed by the builder and all there was, was drywall layer and pink fibre glass insulation and vapour barrier before i drilled the hole. When i touched the drywall area it was cold from the outside. I had put a leak sensor in there as well to check the next day and it was going off saying it was wet area and all so it was definitely getting damp in that area.

My question are:

1. How do i prevent the area from getting damp? Should i spray foam the whole area? Did i fill the pvc pipe wrong? It seems the builder only spray foamed some parts and not every part of the house in the basement, seemed odd as its usually all spray foamed in other houses.

2. From the exterior box, filling the pipe with duct seal putty and from the inside the house, filling the hole with silicone so cold air doesnt get through a bad idea? Or is there a better way that everyone does?

My guesses are that its just cold and with the insulation there and all is making it damp. I might just be paranoid but it just doesnt seem right to have that area damp at all, the places i touched that didnt have spray foam also seemed damp to the touch but the fibre insulation didnt seem damp.
Thank you in advanced for your guys help.
See less See more
1 - 2 of 8 Posts
You probably violated the vapour barrier when you drilled the hole through the insulation.

A few different things need to happen:

1. The area around the conduit needs to be sealed to keep moisture and insects out;
2. The vapour barrier needs to be sealed around the conduit so it is 100% in-tact with the rest of the envelope;
3. The conduit penetration through the house / insulation needs to be sealed from air flow (looks like you did part of that with the duct seal; and
4. Your sealing needs to be separate around each cable to prevent air flow.

As a side note, your cables are not going to last long if they are not underground rated. Moisture will eat up the insulation and corrode the wires in short order.

See less See more
  • Like
Reactions: 1
2. The vapour barrier needs to be sealed around the conduit so it is 100% in-tact with the rest of the envelope;
- are you talking about the exterior wall where the box is?
I don't know where you live, so your vapour barrier may be in a different location. The vapour barrier is the plastic between the insulation and the drywall. If you pierce that plastic, you need to make it whole again by using approved "tuck tape" and secure the plastic around the conduit (so the plastic becomes part of the seal).

If you do not do this, you will get warm moist air from inside the home that travels along the outside edge of the conduit and meet with the cool exterior air and will condensate inside the wall.


1 - 2 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.