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Prescriptive vs. Performance Building Codes

 

A general understanding of building codes helps all parties involved in design and construction understand the specific requirements involved in compliance, preventing errors, delays, cost overruns and most importantly, ensure public safety. In this episode, Arnold Corbin and Mark Klos from CENTRIA explain how to meet energy building codes using insulated metal panels and the two paths for compliance: prescriptive and performance building codes.

 

Lexi:

Hello everyone and welcome to another episode of Metal Minutes by Cornerstone Building Brands. My name is Lexi Edwards and I'll be your host today. With me, I've got Arnold Corbin and Mark Kloss, representing the Building Envelope Solutions segment of our business. Today, we'll be spotlighting insulated metal panels and discussing how they can help meet energy building codes. How are you two today?

Arnold:

Never better.

Mark:

Fine.

Lexi:

All right. So, before we start out, can we get a little bit of background on your experience within the company and the industry?

Arnold:

I guess I'll lead off first. This is Arnold Corbin, I'm the Technical Sales Manager for Metl-Span, and also do support our Centria brand, and will be transitioning more into a support role for all of commercial for Cornerstone. You know, my background, I've had almost 20 years of experience with the insulated panel business. Before that I had 10 years for architectural metals, primarily with standing seam roof, and the prior 10 to 15 years before that was pre-engineered metal buildings and general construction.

Mark:

Mark Kloss. My title is director of R & D for the Commercial division and, like Arnold, had a long-storied past in both insulated metal panels for both Centria and Cornerstone companies. Before that, single skin companies, roofing, engineering, structural engineering, you name it. So we've, we've both been around the block a few times and hopefully we're, we're qualified to talk about this.

Lexi:

All right, great. So let's dive in to the background of energy building codes and discuss how insulated metal panels can help meet those energy building codes.

Arnold:

That's a great question. I think the main thing is you need to start off with the fundamentals of what the building codes are, and there's a little bit of confusion with that. And depending where you are is a lot of confusion. The one that people kind of most see is the IECC, which is International Energy Conservation Code. And ASHRAE 90.7. ASHRAE is the American Society of Heating and Refrigeration and Air-conditioning Engineers. And that helps develop the, what I call the guide that are used for a lot of codes. Some State municipalities, go ahead and adopt that as the code, but then the International Energy Conservation Code is really based upon ASHRAE. So the ASHRAE really is a guide code, and then people will decide to elect if they want to use that code or the IECC, or in some cases may develop their own code separate from that.

Arnold:

But almost in all cases, the ASHRAE is the fundamental basis of all codes we're using in North America right now. A little more in-depth on that, the codes actually are normally updated every three years. We use the terminology of code cycle. And so typically the code cycles between ASHRAE and IECC actually offset each other. And right now the current or most current ASHRAE code is from 2019 and the IECC is 2018. So basically you're going to see the new code coming out for ASHRAE in 2022 and a new code for IECC in 2021.

Lexi:

So as these are updated, does that mean that existing buildings that might have met the previous code could now be out of code?

Arnold:

Typically they don't go retroactive on the codes on that. And then some of the codes changes right now are very incremental and very small, in some cases, past codes have been focused on very heavily on the insulation value of the building, but the newer codes are focused on air leakage and thermal bridging of the building. So they, really can't get that much more efficient for actually the thermal performance of walls on that, so they're starting to look at where you may get areas of leakage or thermal conduction through the buildings, for example, at corners, windows, doors intersection between roof and wall details or roof to foundation. So there's a big emphasis on that. And also the installation is becoming a major focus on it, no matter how well your building is designed and how good the engineer or designers were on that, if it's not properly executed, it still leaks, and you will lose a specific amount of thermal performance out of the building.

Mark:

I agree with that since ‘75, when the first ASHRAE came out, it was it focused on just improving some of the fundamentals of how much insulation is in the wall, as Arnold said and such, as we evolved through in the last couple of cycles that ASHRAE 90 was out, it focused on execution and details because you could have small deficiencies in an insulation could really magnify what it actually, the net effect of that insulation is. So you could put R13 in your wall. And if you left out a big space, so you were insulating your house, the net effect of putting in all that insulation is zero, because of the way that the insulation works and the way you calculate it. So it's just like water going through a sieve. It seeks the largest hole. So now the codes, whether it be the consensus codes of IECC or the standards of ASHRAE, as Arnold had said, is focused on execution and details. And a lot of that is one thing. So the codes necessarily need the function and focus on that.

Mark:

It's a challenging time for a lot of the multi-component wall assemblies that they have multiple people trying to execute to a specification and how well they execute now is going to be judged either during construction or after the fact as that building was put into place.

Arnold:

Probably a good question to ask is, “How do you determine how much insulation do you need in your building?”.

Lexi:

Okay. So, from what I understand, the building products have to meet a certain code, but then the installation of those products also have to be done in a certain way that also meet the codes?

Arnold:

Yes, and basically the way ASHRAE and IECC break down the North America, they break it down into eight zones. Those were primarily based on temperature, but then they have a sub series on there that are based on amount of moisture. So is it a Marine environment? Is it a dry environment? Is it a moist environment or is it a warm, humid climate? So they break it down in different parts of the country on that. And that's what is used as our guide for how much insulation we need for our building.

Mark:

And directly to your question, the code language used to be just qualitative as to how well you executed these numbers, say, it said R13, it says, provide an air barrier all joints shall be sealed with caulking. Now there's testing that has quantitative numbers of how much air leakage you may have and meet the requirements of the code. So that's what both Arnold and I are getting at. It really switched from qualitative to quantitative on a lot of these execution-type specific figures in that code, mandated language, sorry for the run on there.

Lexi:

Yeah. Okay. That makes sense. Let's talk about the actual paths for compliance. So there are prescriptive and performance building codes, correct?

Arnold:

Yes. And those are actually how you comply with the code on that. And so the way that the code there's really two different tables people work from on that. And again, it's broken by the various zones. And whether if it's a Marine environment, in some cases on that. The first table they use on that, and this is out of the IECC is C 402.1.3, and the title is ideal on that- it’s the Opaque Thermal Envelope Insulation Component; and we really want to focus on component requirements for R-value. And that's the one people are most familiar with. And the way it looks at it, it looks at the performance of individual components on that in a specific wall assembly. And this is the one thing that's been used for many years, in a lot of cases, it's misused when it gets to insulated panels.

Lexi:

Okay. Is that the prescriptive way of doing it?

Arnold:

That is the prescriptive way, that's correct. And our construction market is very mature on that and people are used to seeing R’s. A lot of people don't understand the U-values. And again, the prescriptive code on this, we're looking at specific performance of the components on that, not the whole assembly. This is a functional way of using some very basic or probably some of the most common in assemblies that have been used in the past for building construction on that. But it doesn't necessarily recognize there's more types and different types of materials out there. I got to think through how I want to present this: To a certain extent, the prescriptive code does limit the options designers have for building a building. And again, not to limit the design flexibility or to limit new products that may be coming into the marketplace, they developed the next table, which is C 402.1.4: Opaque Thermal Assembly and they’re going to focus on assembly on that.

Arnold:

And so, again, it started looking at the whole assembly on that, not just individual elements, and that's where insulated panels typically live in for code compliance. And that's reported as a U-value.

Mark, you want to comment on the difference between U and R values?

Mark:

Yes, I may. When we talk about the U-value, that's an engineering term that's actually used to calculate heat loss. The problem with that is for the consumer and even for the design professional, the architect, is that it's a number less than one. So it's cumbersome for them to work with. In typical human nature, you like to see numbers, you want to compare a 10 to 8, you want to compare 20 to 10. You don't want to compare 0.01 to 0.03. So the R is really a manifestation of just consumer usage for the regular working man usage of looking at a whole number instead of a fractional number. And it is by definition, the inverse of the U-value. But as Arnold pointed out from an engineering point of view, or from a calculation point of view, when you look at the code and what requirements there are that U-value of the assembly is how IMP goes to market because we test the entire assembly. And then we report that as a large scale test, as the functionality in thermal transmittance of that panel assembly, multiple panels joined together, tested for heat loss.

Arnold:

This is a prime example of bigger is better. You know, we're actually trying to reduce heat flow through the wall, but the on the marketing side, the bigger the number, the better we're going to be, that kind of mentality on that.

Lexi:

Okay. So working on the prescriptive way of being in compliance, you want to look at both the U values and the R values or one over the other?

Arnold:

Normally you just pick one over the other. And of course, your most effective way of looking at the assembly on that is that U value. Again, you're looking at the whole assembly on that, not individual components, because what can happen sometimes with prescriptive designs on there, if somebody changes the stud spacing or the girt spacing, whatever it is on there, those values can change significantly on that due to thermal bridging. And so some of the items that are reported out there are based on very limited variability of the assembly. Mark, you want to comment more on that?

Mark:

Yeah, a lot of it has to do with the end user. So if you have a building code official on a residential project, it's mandated that the insulation that goes in, in that same prescriptive section will be marked. So that's why when you buy insulation in the store, very large, very conspicuously, you'll see R 13 or you'll see R 10 on that foam board because he's coming around, looking at those numbers, seeing if those match what's required for, as Arnold pointed out, that climate zone- that installation. On the commercial side, moreover than not, you're entering it in a program called Comcheck and you're entering into the U values for each wall. Each wall you're putting in building a building, it totals them all up, and there's a compliance document that goes to the plans reviewer. So it’s really broken up on the U versus R primarily along the lines of a residential type installation or commercial type installation. That's the way it should be broken up.

Lexi:

So it's very situational then.

Mark:

Mm-hmm (affirmative).

Lexi:

Okay. So, the prescriptive codes, so the prescriptive way of being in compliance, you basically have to meet a certain level of compliance for each part of a building, right? So your walls, your windows and your roof, they all have to meet a certain compliance, correct?

Arnold:

That's correct. And it's one thing, that is really, probably not the best way of looking at the assembly of a building, because it looks at individual elements. It's not looking at the whole building in total. And so the thought is, if you have an area that's underperforming, you overcompensate another area of the building on that to take care of that, that weakness in the thermal envelope. And so what we believe we're going to see in the future, we're going to be looking at whole, build and modeling. So we're not going to look at overcompensating. We're going to look at improving underperforming details to get an overall better performance of the building.

Lexi:

Okay. So then that would be the way of being in compliance via a performance code, then?

Arnold:

That would be toward the performance code. Mark, I may let you talk to them more about that because it's basically the envelope trade off methods what I was talking about. So they look at individual components and overcompensate on that were, where performance starts to look at the whole assembly, but even at that point, we're not looking at the whole building.

Mark:

Yeah, no, it's a good point. It still hasn't become so complex that, as Arnold mentioned, that you look at the interface between a window and the opaque wall. The prescriptive requirements say you must have this requirement for the opaque portion of the wall, this much for the glaze portion and the intersection between those two are really outside the scope of the code, is the way it's been done now for 20-30 years. As we move forward into the performance side, you have two different levels. You have the trade off with just the envelope where, as Arnold mentioned, you could have better windows to reduce the opaque value- it's usually not the case. You add insulation to the roof, you can put less in the wall, maybe because you have a better opportunity to do that, is the net effect of energy loss you're looking at.

Mark:

But the true performance code is one that's completely modeled not just talking about what Cornerstone supplies, through Centria and Metl-Span, which is building envelope products, it also is the mechanical system, the hot water heating, your plugs and light, everything that that uses energy in that building on the performance side is really modeled and traded against some mandatory minimums. So if you look at it in the broadest sense, I could have all type of occupancy sensors and other things to try to turn off my computers, turned on my lighting, set back my heating and all of that can be traded as well against other less efficient objects in there.

Mark:

So we talk about very large, publicly owned structures. We do, stadiums, hospitals, airports, any of the like, whether it's a partial public funding. A lot of those are modeled at the extreme end of the performance side, looking at every aspect and how much that, a lot of times products that we supply in the envelope with great trade offs, the IMP products can provide more than efficient, more than the basic requirements for efficiency the envelope and allows them then to look at more glass area or less efficient things inside that building because we're a great item to trade off with.

Arnold:

To kind of build a little more on that thought, also we're a fairly easily installed product. So it's easy for us to maintain the thermal envelope and continuity in the air barriers around the building, so that's one thing we really bring to the table. We have high levels of performance, but relatively simple to install. So it's easy to avoid making mistakes in installation.

Lexi:

That was a really good way of explaining it. So I think you had mentioned at one point that the performance pathway is kind of the way that we're moving towards, just because that it's looked at from a complete building standpoint or is the prescriptive way still being used?

Arnold:

Oh, absolutely it is. I get it. We have a very mature construction market. We keep doing things because we've always done it that way. In some cases we perceived them to perform well when in all actuality, when you look at the actual performance are really down. So it's an education process with designers and code officials. I was at an industry meeting not too long ago. And one of the people that were in a meeting and said, "it's a good thing the code officials don't know the code." And so we've seen a kind of a slow adopting or understanding of the changes that are going on the codes and the limitations of our current products. But right now there's a lot of people still out there using prescriptive codes for design of their buildings.

Lexi:

Okay. So is there a reason that, I mean, I know that you said that, just doing it the way that it's always been done, but is there a time that you would prefer to use one way over another or is it just preference?

Arnold:

Well, if you're using a traditional construction method, you know, your steel studs or wood studs within field installation, you could very well use that. And it's still a very common and valid assembly method for buildings out there. But again, there's a lot of different trades involved with lots of components that have to come together that are installed by at least two or three trades. So yes, it can still be used on that. If that's your preferred method of construction. Yes, you can do that. But then again, you still get into verification that was properly installed with commissioning of the building or air barrier testing of the building.

Lexi:

So the performance pathway, it allows the building designer to optimize various parts of the building. Can this save time or money or any type of operating expenses?

Arnold:

And the answer is yes, to all three. A lot of people focus on the cost of construction and really the majority of the cost of ownership is the maintenance and operation of the building after construction. So a lot of people focus too much of their time on the, to get a built version, or let me restate that. Too many owners focus on the construction cost and not necessarily the operational cost of the building. And in almost all cases, operational costs will always outweigh the cost of building the building over the long-term ownership. Mark, you want to restate that?

Mark:

No, I think that you get to the right point there that sometimes it's a matter of just complexity. So let's say that you wanted to have a lot of glass area. You wanted to have a large glass facade, and you looked at the prescriptive method and that would be such a penalty, but then you look at the fact that you could gain energy through those windows. You can shade it so you don't overtax your cooling system. And if you start bringing in those other factors that are more complex, that in the end could all be a net advantage, the orientation of the building, the proportions of the building, all these things that when you look at a performance standpoint you can look at the energy savings that you don't have to have the lighting, the lights on as much, instead of just the heat loss through that glass. So in those types of larger energy trade-offs, the only way to justify that, which usually ends up in net positive is to use the performance method.

Arnold:

Yeah. And then there's really kind of two costs of ownership that people were working on. First is construction, which is the predominant thing people focus on and then there's a cost of ownership. In almost all cases the cost of ownership will far outweigh the cost of the actual construction of the building. So spending a little more time, a little more money in detail on building a thermally efficient building will always pay for itself in the long-term.

Lexi:

That's great stuff. Is there anything else that we haven't covered yet about how to meet building codes using insulated metal panels?

Mark:

I think the only thing, if you want to touch on is the single component versus multi-component, as you touched on earlier, but as verifications are more needed, and it gets more complex with air leakage and such that this one stop shop entity, this single component entity with the confidence that usually you can install it right. That maybe we want to do a little bit of a salesmanship on what the IMP provides.

Arnold:

Okay. One of the beauties of an insulated panel system is that it's a one step process. So provide your thermal moisture and vapor barriers all in one component, including your exterior finishes. The finishes in some cases are warranted up to 40 years. And to add even more to the value, we also have integrated details such as windows, corners, and intersections into other foam panels, components such as roofing. And so it's a simple one step method on that to achieve a very high performing thermal envelope.

Lexi:

Okay. Well, any last point that you would like our listeners to know?

Arnold:

Yeah. The only thing I may add on here is, and I think it's important to understand that that energy codes vary widely across the country and in Canada also. And there are some States that have no state codes at all, they leave it up to what they call home rules. So it's up to the local jurisdictions to develop codes. There may be state codes that are out there- but that's the minimum code on there. So if there's certain cities on there that want to go to a higher standard, they can do that or adopt a more current code, they're allowed to do that. And so it's really, really important to understand where your building's being built and to understand what code you need to comply to. You can literally go walk across the border into another town and have a totally different code. So it's really important to understand that that concept- know where you're at.

Mark:

Exactly.

Lexi:

Great. Well, thank you guys so much for joining us today. This has been a lot of great information.

Arnold:

Thank you. And enjoyed the conversation.

 

 

 

 

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