Quick we need more foam!

Today, we’ll write about something lighter and shorter.  We finally got around to insulating the basement some more.

To recap from where we left off several month ago, the basement has 6″ of EPS insulation below the slab, as well as a 20 mil Stago Wrap as a vapor barrier.  See “Building a Bullet Proof Slab” for a review http://wp.me/p1F8Cx-3q.

On the walls, we used a Superiorwall system which included a combination of XPS and EPS foams as insulation.  See “How to Build a Basement in 3.5 Hours” http://wp.me/p1F8Cx-4w.  We also added more EPS to the outside to beef up the R-value and break some thermal bridges, see “Outsulation” http://wp.me/p1F8Cx-4w.

Now that you have thoroughly studied our foundation, we can move on the to next step of adding yet more foam to this house.  I know XPS and EPS aren’t the more sustainable insulation products to use but cut us some slack here.  We are beginners and need to work with something forgiving.

So, the next step is to complete our continuous thermal envelop by laying foam on the basement floor.

Here’s a before picture

Basement Before

As you can see, the StagoWrap is still sticking out of the concrete.

Salvado and his crew from Leon Home Improvement came to help us out today.

XPS in the stud cavities

They cut small pieces of XPS and filled the stud cavities with it, detached the Stago from the walls and laid them flat on the concrete.

Continuous Insulation

Then, they cut a piece of 1″ XPS to fit along a wall and butt it up against the foam in the wall cavities, creating a thin, cleaning caulking joint.

XPS Floor

A few hours later, the floor insulation was done and the continuous insulation was completed.  They moved on to insulating the walls with EPS foam.

Cutting EPS

EPS Foam Insulation

EPS is easy to work with.  Just cut it to size and jam into the space.

Eric and I decided to get our hands dirty too.

Caulking around spray foam

This penetration already had been sprayed around the pipe.  We decided to caulk around the foam joints as suggested by Sam at 475, then tape around the whole thing.

Wire Penetration sealed and taped

MiniSplit Penetration (Before)

MiniSplit Penetration (After)

I think all these steps are truly a “belts and suspenders” way to seal things.  I can see how spray foam might not create an extremely good seal.  When we trimmed back the bulging foam, sometimes we see voids or areas with only a very thin layer of foam.  Additionally, I think another reason is longevity, I am not sure if I trust the foam to hold that penetration for the rest of the building’s useful life.  The caulk adds another insurance policy between the different materials, i.e. foam and OSB or foam and PVC tubing, etc.  The tape is probably the final coverall.  475 folks, I know you are reading this, tell us what you think?

I have to say, I am not sure how I feel about doing a 3 step sealing process for 1 inch holes, there maybe larger gaps between my SIPs or other building members that I can’t even see.  I guess sealing penetrations are probably the low hanging fruit in a way, mainly because you know where the holes are.  Other potential places of air infiltration, say between SIPs or seams may be difficult to find visually.






7 responses to this post.

  1. Can’t wait to get back in the house and be part of this new way of home building.

    Performance Painters


  2. Posted by floris475 on 2012/01/23 at 1:41 pm

    Floris from foursevenfive.com chiming in. Yes a three step process might be a little bit much, but well worth it for a durable airtight layer – the house should stand and perform for 30-50-100 year….A few tips, but will blog about this soon too –

    Maximum number of pipes, cables etc in one hole – ONE – so you can seal it, as you can see the taping of the Romex cable was pretty simple.
    Make the hole large enough for the pipe to fit and stuff fibrous insulation (sheepswool, cotton, fiberglass) in there.
    Don’t put holes/pipes to close together or to close to a stud/wall – it will make it impossible to seal them.
    If you put a gasket on the duct/pipe/cable while installing it, the seal will be easy to make.
    If you seal it post installation, the TESCON No.1 will be able to form well around the pipe (inside – airtight and outside – windtight/waterproof), as long as you have room.

    Don’t trust foam – it won’t expand in the way you want it to, and thus leave gaps and leak air…


    • Hi Floris,

      I think a durable air-tight layer is really important. “Durable” being the operative word here. Sprayfoam is one of those things that I think people rely on as a cure-all for insulation and air-tightness. The problem is it really isn’t durable and I agree that it won’t expand the way you want it to.

      Thanks for the tips! Tescon No.1 really stretches and forms well around pipe/wire. Something I discovered through trial and error is I cut a piece of Tescon no1 sort of half way through (imagine a half-gasket), I put the wire in the cut, using the two flaps to tape and wrap around the wire and OSB. I do the same thing on the other side of the wire. This makes a much cleaner seal than just using one piece of tape.


  3. […] spaces in-between the cables/pipes. This is explained quite well by Roger Lin at the bottom of this blog post of the Arlington Passive House. Furthermore shrinkage of the foam or movement of the cables will […]


  4. […] spaces in-between the cables/pipes. This is explained quite well by Roger Lin at the bottom of this blog post of the Arlington Passive House. Furthermore shrinkage of the foam or movement of the cables will […]


  5. In my county, I also use Expanded Polystyrene for the building. That is cool.


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