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Question of the Week – Aug 28, 2015

August 28, 2015

Thanks for tuning in to our Question of the Week series.

This week’s question comes from a builder who knows that one of the keys to executing an airtight building cost-effectively involves thinking carefully about penetrations.

The question:

“We are using a combination of Intello Plus on the interior with Prosoco R-Guard system on the exterior of a current house. It’s not officially a passive house but we are working for that level of air sealing. I bought a PHPP package from you that we used in design.

Our biggest challenge in our last house was the mass of penetrations for the electrical service panel. In that house we used a section of black pipe air sealed into the exterior barrier and then taped and foamed the wires inside the pipe. This worked well but I’m concerned of the durability.

I would like to find a more elegant solution to this and am considering ProClima penetration products but can’t figure out the best/right way to handle this. It seems like a location every house has to deal with but I’ve been surprised to have never seen it talked about. What am I missing?”

Our response:


Thanks for the question. Good to hear you are using the PHPP and that you are focusing on airsealing.

The electrical panel can be tricky, especially if it is located in a difficult spot.  We can suggest a few solutions:

1. Use a main panel outside and a subpanel inside – This avoids excessive penetrations of the airbarrier. Only one electrical wire in (+ cable + telephone) and then maybe 2 electrical wires out for exterior lights – and then one back in from the heat pump. But these would all be in different spots, and easy to seal. The power to the heatpump can come from the outside panel – As well as exterior outlets etc. 

2. Have the meter outside, and the main panel inside – You will have one wire in, and a wire out for the heat pump and any exterior outlets – though those could go at at a separate location – then your outside lights etc.

3. It is our recommendation to split wires as much as possible. You can use KAFLEX or KAFLEX Multi for small wires – and ROFLEX 20 for the big conduit (however it is sometimes not round so you might be better off taping it bit by bit – see here (at minute 1) for some nice tricks to do this easily.”

Habitat for Humanity in Washington DC has some interesting solutions for penetration sealing that they introduced in our 475 On-Site video this winter. They involve consolidating all wires into one PVC pipe, to combine and seal penetrations together. Begin watching the video below at 6:45 to see the explanation:

In summary:

The list can often go on when it comes to penetrations.  Looking to seal an electrical box?  Consider InstaaboxINSTAABOX from Pro Clima, or tape your romex cable with a bit of Contega HF adhesive caulk for the dimple.

Sealing holes from densepacking below a subfloor?  Use a tapered plug with some Tescon Vana tape.


Sealing a duct penetration?  Use Roflex gaskets for ducts from 2″ to 12″.

Installing Roflex gasket with TESCON tape at duct penetration. Credit: Eco Homes of Vermont

Installing Roflex gasket with TESCON tape at duct penetration. Credit: Eco Homes of Vermont

In a project in upstate New York, 475’s Floris has a dedicated area in his floor for new holes, so that he can – for example – get cable service installed later without having to do any gymnastics.
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Have questions about how to solve a challenging penetration puzzle?  Contact us, send your photos, we’re happy to show you tried and true methods for success.


Until next week…


To read the other posts in our Question of the Week series, click here.


**Please note that in republishing our question of the week, we sometimes edit the text of the original question and response in order to provide additional clarity to the issue.**
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One Response to Question of the Week – Aug 28, 2015

  1. Seamus Sheehy August 31, 2015 at 4:25 pm #

    If you get to build from scratch the following might help. I installed separate 40 mm ducts for each cable coming into the house and intend to heat shrink each cable and duct. Large sweeping bends are a must. Keeping all ducts inside the airtight membrane is the method I am using. Regards, Seamus

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