Aug 062016
 

I haven’t made a time-lapse movie in a while.

I made this one on Thursday afternoon working in the basement. It’s important because I can finally show you what is going into those walls.

In this first video you can see me struggle to get the top-plate in above the 2X4 stud wall I built and then start insulating behind it.

I framed the interior wall on May 10th.

I framed the interior wall on May 10th.

That was the first wall I’d ever built. Our Rescue Contractor (He Who Fixed The Structural Issues Left Us By Another Contractor) taught me to build the wall flat on the floor, then lift it into place and attach it to another 2X4 attached to the ceiling (called the top-plate). I did that three months ago and then got distracted by more urgent tasks.

In the meantime, the electrical team (Leanne, her Dad and Golden Ears Electric) went ahead and roughed-in the wiring. That made it more difficult to get the top-plate up there.

Notice the stripes of sealing foam I had already added around the edges of the exterior sheathing. That was a tip from Walter.

Here is a play-by-play:

-James slides top-plate into position and balances it on a board so he can screw it up unassisted (he is screwing stuff up unassisted a lot lately)

-James notices that a wire is on the wrong side so he pulls out the top-plate and tries again.

-James notices that another wire is on the wrong side so he pulls out the top-plate and tries again.

-James puts two screws through the top-plate into every ceiling joist, careful to avoid the wires running through the joists.

-James uses a flashlight to confirm that yes, he put a screw right through one of the wires running through a joist.

-James curses, marks the damaged wire, and considers how to apologize to Leanne who is going to have to replace that wire.

-James uses a hammer to bash the top and bottom of the stud wall into place under the top-plate because he didn’t leave that 1/4 inch space that contractors always say you should leave.

-James grabs some Roxul batts from the huge pile that was taken out of the attic and has been cluttering up the basement for months and starts fitting it into the spaces in the exterior 2X6 stud wall.

-the battery dies.

We’re finding it very helpful to have short-term goals to work toward. A big one lately is the spray foam. That’s the kind where the people in space-suits show up with a van and hoses. We’re planning to fill the rafters under the roof with about 5 inches of 2-pound spray-foam insulation and there are a number of things we have to do before that can happen.

In the basement, the spray foam is going only into the rim joists–sometimes called box joists–which are the spaces at the top of the basement walls between the ceiling joists. It’s very difficult to seal and insulate those spaces, so spray foam is a good idea in there.

The walls, however, are easy to insulate so you can save money on that expensive (and not so environmentally-friendly) spray foam.

Shout-out to Monte Paulsen again because I am finally following through with his advice for an inexpensive super-insulated wall.

The building code requires new construction to have 2X6 stud walls instead of 2X4s. That means a thicker wall that can be insulated better. Roxul batts that fit 2X6 walls have an insulation value of 22 (R22).

However, the building code is only a minimum standard. Once you have your 2X6 wall and the structural engineer has signed-off, you can make your walls thicker. It’s easy!

More than simply adding insulation, you can interrupt the heat transferred through the wood studs in your wall. This is called thermal bridging and I am obsessed with eliminating it.

With Monte’s idea of adding a 2-inch thick sheet of styrofoam between and then building another wall inside it, the heat can’t use the studs as a bridge. On the inside of the interior wall, a sheet of plastic keeps the moisture in the warm interior air from getting into your walls. Over that goes your gypsum drywall.

Since the Rescue Contractor and engineer have already made sure the house is structurally sound, I’m free to fumble around learning how to build walls without worry. (I like to think the Rescue Contractor is very busy and has faith in me and those are the reasons he didn’t return my texts when I wrote to ask if I can publish his company’s name.)

And space? Yes, we will lose about 6 inches of space around the exterior walls, but after a week we won’t notice anymore.

In the second time-lapse, taken after I plugged my phone in, the sun goes down as I gleefully insulate.

There are two parts to this wall: the concrete and above the concrete (AKA the pony wall).

The concrete has almost no insulation value (and, if you remember, I didn’t consult with Monte in time to know we could put Terrafoam rigid insulation under the footings–a nagging regret.) On the outside, under the ground level, is 2 inches of EPS styrofoam with an R-value of 8. Above the ground the concrete is bare until the shingles start.

The basement wall below the ground will be insulated like this:

2″ Exterior styrofoam (insulation value R8)
Concrete (R0)
2″ Interior styrofoam (R8)
Roxul batt in 2X4 stud wall (R14)
Total: R30

In the wall space above the concrete foundation–the pony wall–there are three types of insulation. There are Roxul batts in the 2X6 stud wall, Roxul boards and styrofoam. Roxul board is the product I told you about which fits perfectly in this unexpected inch-and-a-half space between the 2X6s and the styrofoam. The white EPS styrofoam is much, much cheaper than the higher density blue or pink rigid foam insulation you have seen around. It has a lower R-value, but is less carbon-intensive to produce. Finally, the interior stud wall will be insulated with more Roxul batts.

Looking at insulation value above ground we get this:
Roxul batt insulation in the 2X6 wall (R22)
Roxul board (R6)
Standard EPS white styrofoam (R8)
More Roxul batts (R14)

That makes for a total insulation value of R50 when the wall is finished. The shingles outside might even add a little more.

Incidentally, you can buy all these insulation types at your local building supply

Inside Plastifab's local facility. Photo taken without permission (I hope they don't mind!)

Inside Plastifab’s local facility.

store, but I went straight to Plastifab for the EPS styrofoam. I bought a lot of that stuff!

Ask the Rescue Contractor how much I have been looking forward to insulating those walls. Every time he added another 2X6 to a wall to make it stronger, I would whine about thermal bridging.

That’s why I pushed through dinner and, at 9pm, Leanne showed up with some sushi leftover from her dinner meeting.

I don’t know if you can tell in the video, but she forgave me for damaging her wire.

Afterthought: watching me cut up that styrofoam into little pieces to fit it between the studs, I think you can see how much more sense it would make to insulate the pony wall and add the styrofoam in big sheets before building the interior wall. The building inspector is going to let us do that with the rest of the walls instead of insisting all the electrical work is done before inspection. Thank heavens for flexible officials!

  2 Responses to “Super Thick Wall”

  1. Good job taking care of the thermal bridging. I guess it’s not practical to insulate the concrete on the outside above ground. I regret not doing a better job of insulation when we finished our basement 11 years ago.

    • Nice to hear from you, John. We have agreed not to change the exterior look of the house to retain its heritage character, so exterior insulation of that ribbon of concrete you mention was not possible. Lots of options are available for homes which don’t have such limitations. As you know, insulating the outside of your house is a very effective way to do it.

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