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Understanding steel building insulation and energy code compliance

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Understanding steel building insulation and energy code compliance

Building energy efficiency codes are designed to optimize the efficiency of building systems, resulting in greater efficiency and lower operating costs. And recently, the requirements of generally accepted energy codes such as the International Energy Conservation Code (IECC) or the American Society of Heating and Air-Conditioning Engineers (ASHRAE) standard 90.1 have become more and more stringent.

Stricter codes pose many benefits for builders, designers and owners — the Department of Energy (DoE) estimates that the increased requirements of codes from 2012 to 2040 will save homes and businesses nearly $126 billion.

But it also poses challenges: As code requirements continue to mount, it becomes more and more important for builders, metal building distributors and insulation manufacturers to collaborate to create efficient, cost-effective and compliant steel building envelope solutions.

For general contractors and owners, this involves understanding the insulation compliance requirements for steel building systems in your area and identifying a suitable pathway to compliance. Then it requires talking to local building code officials, your metal building distributor and a reputable insulation manufacturer about which type of insulation method might work best for your application and price point.

Here is a visual guide to steel building insulation and energy code compliance, which general contractors and owners can use as an introduction to these complex topics.

What are the requirements for steel building compliance?

Your building must comply with the commercial energy codes in your area. While the specific codes vary from area to area, almost every state has adopted an iteration of the IECC or ASHRAE 90.1.

The relationship between the IECC code and the ASHRAE 90.1 standard

The IECC is a model energy code —applying to both residential and commercial buildings— upon which states and municipalities can base their local energy codes. It specifies energy requirements for a building’s lighting, HVAC system and thermal envelope. The IECC is updated every three years (i.e., 2009, 2012, 2015), with 2018 being the most recent version of the code.

The IECC follows ASHRAE 90.1 —which is also updated in three-year cycles— by two years, adopting and referring to the standard. In fact, although IECC is the code, it allows designers to use the previous version of ASHRAE 90.1 as a means of compliance (IECC 2018 C401.2). For example, IECC 2018 adopts and references the standards specified in ASHRAE 90.1 2016 — and allows designers the choice to comply with ASHRAE 90.1 2016 instead.

Newer versions of ASHRAE 90.1 and IECC could cut energy use by as much as 30% over other codes. And by 2040, the Building Energy Codes Programs (BECP) estimates they will reduce harmful carbon dioxide emissions by 841 million metric tons (MMT).

Compliance requirements vary by state and municipality

While most building energy codes are based off some iteration of ASHRAE 90.1 or the IECC, achieving compliance is not as simple as following the requirements of the latest release.

Code adoption varies state by state and municipality by municipality, which is why it’s important to involve your local building inspectors at the outset of any commercial building project. They’ll understand the code requirements in your area and guide you toward compliance.

Some states adopt a version of either ASHRAE 90.1 or IECC with no amendments, some have no statewide code and yet other states have created their own code that exceeds the requirements of both ASHRAE 90.1 or the IECC. And municipalities can adopt their own codes if they exceed the standards mandated by the state.

Here are a couple examples: Missouri has no statewide code meaning different jurisdictions have adopted different codes, Nebraska has adopted IECC 2009 and California has created its own, more stringent code (Title 24). And specific municipalities within a state can adopt their own code equal to or more stringent than the state’s.

For a general overview of code adoption throughout the country, check out this map from the U.S. Department of Energy (DoE). Or, for more information on the specific energy code compliance requirements in your area, go to energycodes.gov and select the ‘Status of State Energy Codes’ dropdown.

Three paths to energy code compliance

Both ASHRAE 90.1 and the IECC contain tables with the minimum R-value (a measure of the insulating power of a material) and maximum U-values (the heat resistance of the entire assembly) for metal building insulation in eight different climate zones. High R-values and low U-values are indicative of better insulating qualities.

But exactly following these charts (the prescriptive path) is but one of three paths to compliance allowed by the Department of Energy: Prescriptive, trade-off or performance.

Prescriptive: The most conservative path to compliance

The prescriptive approach to metal building envelope compliance entails following the information in the tables exactly, following the exact R-value system specified or another insulation system with an equivalent or better U-value (called U-value substitution).

While the prescriptive option is the most definitive of the three approaches —either you meet the specified insulation requirements, or you don’t— it offers less flexibility and tends to be the most conservative. Because of this, the prescriptive approach can sometimes result in higher material costs than other methods.

Trade-off: Trading decreased efficiency in one element for enhanced efficiency in another

The trade-off approach to compliance offers more flexibility than the prescriptive approach, allowing designers to trade better performance in one part of the thermal envelope (e.g., a lower U-value roof insulation system) for a lower performance in another part (e.g., a higher U-value wall insulation system).

The BECP created a free compliance software —ComCheck™— which designers can use to verify the compliance of their proposed insulation system. They simply have to select which code their municipality has adopted, input information about all the features of the envelope (insulation type and thickness, roof type, wall type, etc.) and the software will tell you whether or not you’re meeting the requirements of the code.

While the trade-off approach allows you to mix and match elements from the same code, you can’t design some elements of your building according to the requirements of IECC and others according to ASHRAE 90.1. You couldn’t, for instance, choose to design your mechanical system according to IECC and your thermal envelope according to the corresponding ASHRAE 90.1 release.

Performance: A holistic look at a building’s thermal envelope

The performance approach to compliance tends to be the most expensive, time-consuming and complex of the three options. It involves using a whole-building energy modeling software such as EnergyPlus™ from the DoE to prove that the proposed design is equal to or more efficient than the baseline requirements laid out in IECC or ASHRAE 90.1.

The performance approach offers even greater flexibility than the trade-off method, by taking a holistic look at the energy needs of the entire building as a system. But it requires much more legwork on the part of the architect or designer —and even an energy consultant in some cases— including an annual energy analysis to simulate energy usage in comparison to the standard.

For more information about the paths to compliance, check out the Building Energy Codes Resource Guide from the BECP.

Which compliance approach is best for your project?

The path you choose will depend on the complexity of your building, the budget you have for compliance and personal preference. Work with your local building code officials to determine your compliance approach and then consult with your insulation provider to determine the best path for your building.

Generally, though, using the ComCheck™ trade-off approach is best fit for most applications — offering greater flexibility than the prescriptive path without the complexity of the performance approach. The performance approach is the most expensive but may be necessary for larger projects or where unusual energy-saving features are incorporated (e.g., solar panels or fuel cells).

Your insulation manufacturing representative can help you choose the best compliance approach —and insulation system— for the codes and climate in your area. For instance, we work closely with Therm-All and our representative, Eddie Read, helps us design compliant insulation systems for our clients.

Insulation that complies with high R-value metal building envelope requirements

Whatever compliance path you choose, there are three common high R-value insulation systems to consider for metal building roof and wall assemblies: Bag and sag insulation, long tab banded insulation and liner systems.

Bag and sag insulation: Least expensive and easiest to install

The bag and sag method of installation involves draping insulation loosely above the purlins, so that it sags slightly. You then fill the cavity you’ve created between each purlin with unfaced insulation. Above that, you install another layer of insulation.

Together, each layer of insulation helps achieve the higher R-values required by newer energy codes. And although bag and sag insulation is the least expensive of these three high R-value methods, it is the least aesthetically pleasing.

Long tab banded insulation: The best value and look for the price

Also referred to as a filled cavity system (FC) in ASHRAE 90.1, long tab banded insulation generally provides the best value of these three common types. It isn’t much harder to install than the bag and sag, but provides a much better appearance inside the building.

Metal banding placed perpendicular to the purlins holds up the assembly. Then a layer of faced insulation is rolled out between each purlin, and another layer of unfaced insulation is rolled on top of and perpendicular of the purlins.

Liner systems: Lower U-values and OSHA-approved fall protection

Liner systems consist of a metal banding to hold the assembly up, a heavy-duty moisture barrier, a layer of unfaced insulation between each purlins and a second layer of unfaced insulation running perpendicular to the purlins.

Liner systems tend to be the most expensive and difficult to install of the three types, but they can generally achieve lower U-values. They can be also specified with OSHA-approved fall protection for the installers — a key consideration on government projects. Liner systems tend to be proprietary, such as OptiLiner® from Therm-All.

To determine which compliance path or insulation system is best for your building, rely on the experts. Work closely with your metal building distributor, your insulation manufacturer and, of course, your local building officials to determine the best path to compliance for your application. From there, you can work with them to determine the insulation method that not only achieves compliance but is also best suited for your application and budget.

At Searcy Building Systems, we partner with Therm-All —the leading provider of insulation for metal buildings— to ensure each of our clients’ buildings complies with the relevant building energy codes. Our combined expertise, along with the guidance of local building code officials, allows general contractors to be confident that Searcy Building Systems will meet or exceed their client’s expectations.

Start a conversation with one of our experienced metal building consultants about how we can help design a compliant, high-performing building for your client’s applications.