Kelly: (00:01 )
Welcome to buildings and beyond

Robb: (00:09 )
The podcast that explores how we can create a more sustainable built environment

Kelly: (00:14 )
By focusing on efficiency, accessibility and health.

Robb: (00:18 )
I’m Robb Aldrich.

Kelly: (00:19 )
And I’m Kelly Westby.

Robb: (00:21 )
This week I’m talking with Bill Zoeller who is a senior vice president here at Steven Winter Associates. He and I have worked together for almost almost 20 years now and it’s been observed by several people that Bill and I really don’t have many conversations. We have many more arguments, but I think we’re both very well behaved in this episode. We’re talking about high performance envelopes, specifically high performance walls. I mean designing building good envelopes has changed a lot over the past couple of decades. So we dig into this, the reasons for this a little bit and specifically talk about some high performance wall systems.

Robb: (01:03 )
Thanks for being here, Bill.

Bill: (01:05 )
Thanks Robb. My pleasure.

Robb: (01:07 )
So I talked to you about doing an session on envelopes, a podcast episode on envelopes, which is a huge topic, but the way envelopes are designed and built now is so drastically different and continues to change a lot with new materials, with new techniques, new details. I wanted to dig into that topic a little bit and we ended up deciding to talk about walls because that’s what came up first because every building has walls. So big picture, why are envelopes and enclosures so different now?

Bill: (01:48 )
Well, in order to look at why they’re different now, I think we need to look at the context of where they were and where they were is really the impetus for why they changed and where they were a bunch of years ago, let’s say 10, 15, 20 years ago. If someone was building your basic house pretty much anywhere in the country it was framed with two by four walls, add ore 13 bad insulation, jammed into the stud cavities without much care or Thought of how good or neat or quality the job was. Essentially no care at all to any sort of air sealing between the inside and the outside. So basically you had you know, a frame wall cavity with a little bit of insulation in it and a lot of air blowing through it. Well, it wasn’t very good. And when the energy codes changed to improve the performance,

Robb: (02:46 )
Or actually came into being in lots of places

Bill: (02:49 )
Or came into being in lots of places, they incorporated some attributes that caused some changes to occur. For instance if we have your basic r-13 wall with bad insulation and no air sealing capability, what you’ve got is a little bit of thermal insulation that’s stopping the flow of heat from inside to outside a little bit. But all the air is blowing around it. So even if I have installation in the cavities, the outside air is blowing through the insulation via infiltration and really bypassing the thermal installation altogether. Then, the building codes increased a little bit. And we ended up with two by six walls, r-19 or r-20 insulation in that same space. And we started to employ some air sealing measures. It became known that air infiltration into buildings was one of the largest causes of heat loss and comfort issues and so on in buildings. So the next reasonable response is, well, let’s tighten up the buildings.

Robb: (04:06 )
But there wasn’t yet a durability concern.

Bill: (04:12 )
The building science was not really a known quantity when we started to do that. You know, like anything else, when we start employing new measures and new aspects of anything, there’s always unintended consequences and we certainly found them. In this case, the unintended consequences have to do with the second law of thermal dynamics. And usually when I start this conversation, I start with the first law of thermodynamics, which is basically in a nutshell that energy can’t be created or destroyed. The reason I start with the first law is because I really want to talk about the second law, but if I do that, people always say, well, what the heck’s the first law? So we got that out of the way, right? And the second law of thermodynamics is really the main issue with high performance wall assemblies and why theyre causing problems and why they can cause problems. And that’s that it’s the law of entropy, which basically means that any system of energy in an isolated chamber, or setting, wants to morph towards basically chaos. So if I have heat on one side of the wall and cold on the other side of the wall, what the energy wants to do is basically e