The Perfect Wall House Build

Perfect Wall Review – Building a 500 Years Lifespan Timber Frame Wall with ‘Outsulation’.

Matt Risinger shares insights on a house he constructed in 2015, introducing a concept back then that is still unknown to many builders and designers today – OUTSULATION.

This wall system involves applying insulation to the exterior of the timber frame, just like putting on a coat. Interestingly, if installed and maintained correctly, the wall can last for up to 500 years, making it an incredibly durable option. Join Matt as he takes us on a tour of this “Perfect Wall” system, which promises outstanding efficiency, indoor air quality, and comfort, and can be built anywhere in the USA.

Matt built this house in Austin, Texas, utilizing the “Perfect Wall” system developed by Joe Lstiburek & Building Science Corporation. Architecture by Rauser Design. Construction by Risinger Homes.

Video Transcript:

Today we’re talking about the perfect wall system for a house, what it is, and a few reasons why I like it. I want to talk to you today about the perfect wall system. You know, this was developed by Joe Lstiburek and the really smart people at Building Science Corporation, and this system can be utilized anywhere in the U.S. It’s really off-the-shelf building materials and systems, but utilized in a different way.

The house behind me, we just finished it, has been built with this concept. This was designed by Rouser Architecture and the talented architects there. Let me tell you about the concept first though. Basically, we start with a very standard wood framing package. Almost every house in America has wood framing, and this house is no different. Two by fours on 16-inch centers, very normal stuff. But from there, we get a little bit different.

The Perfect Wall?

This house has no insulation, no inside insulation. This house is using the concept of everything on the outside of the framing package. We’re basically treating this house like a piece of furniture, just the same as you would your baby grand piano in your living room. All the systems are outboard of the framing. So once we finished framing this house, again, very conventionally, then we put all the insulation, the weather barrier, everything on the outside of the house.

Matt Risinger The Perfect House Wall 1

Let me walk you through a cross-section of the wall here. As I mentioned, two-by-four construction. After the two by fours, this is where it differs a little bit. We didn’t frame the house with any overhangs to start with, so that we had a nice easy box. We used a peel-and-stick exterior weather barrier. This is actually Carlisle CCW 705 on the outside of this house. And because we didn’t have any overhangs, we’re able to take that peel-and-stick from the foundation to the ridge and all the way back down continuously, no breaks. That 705 peel-and-stick is now acting as a vapor, a water, and an air barrier, and it’s doing a perfect job of those because there are no breaks in the system.

Peel and stick weather barrier

So then, after we finished with the peel-and-stick, we added our insulation, and really, this is ‘outsulation’, not insulation. We’re all on the outside of the house. We’ve got four inches in the walls of Polyiso with a silver facing. This is made by Carlisle. And we’ve got six inches in the roof. We did it in two layers so we could stagger the seams and really get a nice, continuous, thick blanket. This is akin to putting a sweater on the house.

we added our insulation, and really, this is ‘outsulation’, not insulation.

Matt Risinger – The Build Show Network

On top of that insulation, we’ve got a one-by or baton that we’ve screwed all the way back to the framing. And then we’re attaching our metal skin on top of that. We’ve got a metal corrugated siding and a metal galvalume roof on this house. Really, both of those are going to be extremely durable.

There are four things I like about this system. Of course, number one is durability. They talked about this being a 500-year house or a 500-year wall. If we did have a leak in the future, although we’ve taken extreme measures to make sure we don’t have one, it would be really easy for that leak to dry up and not cause any rot. We’d also be able to tell very easily if we had a problem. And ultimately, because we had no insulation, we didn’t need to put sheetrock in, so we have nothing to stop a drying process if there were a leak.

As part of that durability, the exterior skin was a big part of that. We’ve got all metal on the outside, so you really have many, many decades of durability on the outside of this house with no maintenance. All that metal is pre-painted, so there’s nothing that needs painting on the outside.

The next thing I really like about this concept is extreme efficiency. Because we’ve got that great thermal blanket on the outside of this house, we have no thermal bridging. This house is extremely airtight and very efficient. We’ve got a HERS rating of 40 on this house, and it would be really easy to add a little bit of solar and get to a Net Zero in this house. Very, very tight construction.

The next thing I like about this concept is easy upgradability. You know, we went with the pier and beam foundation on this house, which is a little unusual here in the South, but a pier and beam allows us to crawl under the house and access anything we might need to. And lastly, the thing that always gets left out of the equation is the extreme comfort that comes from it. We’ve got a super airtight shell, we’ve got no thermal bridging on that outsulation [outer insulation], and so as a result, my house stays very comfortable. It can coast for long periods without having to use the HVAC system.

I can manage the humidity on the inside of the house with my very small dehumidifier, and of course, I can manage the indoor air quality because I’m not worried about infiltration in the house. For more information on the perfect wall concept, visit my blog at I’ve done a ton of blog posts. I’ll also have a link in the description to a couple of videos that I’ve done on this concept. Hey, join me on Twitter and Instagram. We’ll see you next time.

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