A metal building must meet all the same building code requirements as a building constructed from any other material. However, the Energy Code singles out metal buildings as a separate category in numerous places. Most notably, the insulation requirements are different for metal buildings. Metal is an excellent conductor, meaning: NOT a good insulator unlike wood. Metal buildings without proper insulation can quickly become too hot or too cold. Occupants or sensitive contents could be endangered or damaged from exposure to extreme temperatures. Plus, huge amounts of energy can be used trying to keep an uninsulated metal building comfortable.
Let’s take a look at what the model Energy Code is and how it affects your new metal building.
What’s in this guide?
The Energy Code
The Energy codes were developed in the 1970’s in response to the energy crisis and continue to be developed, usually recommending increasingly higher energy-conservation standards. Because these codes are made into law across the nation, residential and commercial buildings are projected to save about $40 billion dollars per year in energy costs over the next 30 years.
What is the Energy Code?
The main model code (a standard code that is developed for states to adopt with or without modifications) is the International Energy Conservation Code (IECC). The IECC sets forth requirements for building design, materials, and performance related to energy efficiency. Many of the IECC standards come from the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE). In 2009, the congress mandated that all states must comply, at a minimum, with the ASHRAE Energy Standard for Buildings (section 90.1).
What does the Code Cover?
Codes cover every aspect of your building that affects energy use—walls, roofs, windows and doors, insulation, heating and air conditioning systems, power and lighting systems, water heating systems, ventilation, and even air leakage—all have standards that must be met.
There is almost no getting out of meeting IECC requirements. Your building must meet the energy codes in nearly every circumstance, including:
- New buildings,
- Additions to existing buildings,
- Alterations to existing buildings
- Replacement of portions of existing buildings, and
- Changes in space conditioning (example: unheated area to be heated)
In the codes, regional climates are separated into zones (0-8, with 8 being the coldest). Your zone and what type of building determine the energy performance requirements you must meet.
Can I Deviate from the Code?
The IECC lists mandatory requirements. But they do offer different ways of meeting those requirements. For instance, your building can be designed to meet energy requirements by either:
- Building exactly per the code (or better),
- Trading off higher performance in one area for lower performance in another,
- Using a computer simulation to show that the alternative design meets the standard, or
- Demonstrating that a system meets the standard by building and testing a model of it.
To get a building permit, you will need to prove that your building meets the energy code requirements in one or more of these ways.
There are also “green” codes that have been adopted in some areas. They provide even more stringent certification guidelines than the IECC. Most of these codes or standards are voluntary. Some have been written by code-writing agencies, like the U.S. Green Building Council (USGBC) and the International Code Council (ICC).
There is also a growing number of independent standards. Organizations that want to take energy efficiency and environmental and community responsibility even more seriously offer voluntary certifications for meeting their rigid certifications. The Passive House Institute and the WELL Building Standard are two of many.
Types of Building Uses
The building code defines buildings by their end use, like barn, factory, or home. For energy-use purposes, buildings are defined by whether or not they are heated. A building space can be:
- Conditioned: heated and cooled to human comfort levels
- Semiheated: not heated to comfort levels and not cooled at all. IECC uses the term “low energy,”
- Unconditioned: not heated or cooled at all, or
- Ventilated: not heated or cooled but outside air can move freely through the inside space.
Many buildings, including homes, contain more than one type of space. The walls and roofs that surround these spaces are called the “building envelope.” The building envelope is especially important when you are building a metal building.
As we mentioned before, metal is not a good insulator and a lot of energy can be wasted heating and cooling metal building envelopes. So, proper insulation becomes critical. In fact, insulation requirements are the main difference between IECC requirements for metal buildings and those constructed of other materials. Mostly, IECC requirements reference ASHRAE 90.1 specifications.
R and U Values
To understand what the codes are talking about, you need to understand two values: R and U. Most people are familiar with the R value. You see it on insulation. R is a number that tells how resistant the material is to letting heat pass through it—how well it insulates. R values are given to individual materials, like insulation or wood. The higher the number the better.
The U value measures how much heat or cold actually passes through a system. U values are given to a system that is usually made up of many materials, like windows or doors. The lower the number the better.
You might think these two sound an awful lot alike, and you would be right! They are, indeed, the reciprocal of each other. U = 1/R and R = 1/U. But you don’t need to know how to calculate them as long as you know that you want a lot of resistance (high R) and little transfer (low U).
Continuous Insulation (ci) and Linear Systems (ls)
Another insulation requirement that metal buildings often have to comply with is “continuous insulation.” Continuous insulation (ci) means that insulation covers the entire building envelope, including the structural components themselves. To do this, ci is usually installed on the exterior of the building.
Traditionally, insulation is placed between the studs and columns of a building and nothing covers the studs and columns themselves. Wood construction is a common example of this method of insulation. This approach works for wood because wood is a good insulator, and little heat is lost through wood members.
However, metal is not a good insulator. Heat can be rapidly lost or gained through the studs, columns and the roof/wall sheathing itself. So, these pieces must be covered in insulation.
The recommended method for insulating the building in order to cover these pieces is to wrap the entire structure, after it is framed, in insulation. Rigid foam board is often used to wrap the building when ci is required. CI does not necessarily replace the need for insulation between the columns.
Another method is called a Linear System (ls). LS is continuous insulation installed on the inside the building. It must be continuous over the structural members as well. Usually, LS is used to insulate roofs.
Insulation Requirements for Metal Buildings
Now that you understand the basics of the energy codes, let’s take a look at just how the code applies to metal buildings.
Metal buildings often (but not always) have higher R value and lower U value requirements than other building types. There are many, many components and systems that are covered in the IECC, but we’ll just take a look at some insulation requirements for building envelopes as an example.
Below, is the ASHRAE table for building envelopes in Climate Zone 7 (very cold). For a nonresidential building, the minimum insulation R value is 0, and a ci layer of R22 is required. The requirements for a steel framed building are about the same. Even though the total R values may be slightly lower than that for a steel-framed building (remember higher is better), the U value is lower. This means that the total system for a metal building must lose less heat than the steel framed building. This works because all of the insulation covers the entire building, not just the spaces between columns.
Meeting Code Requirements
Once the insulation-performance level is determined, there are a few ways a building can be insulated to meet them. Various types and ratings of insulation can be combined in different ways to achieve the ratings required. The methods include:
- Continuous insulation (ci or ls),
- Single compressed layer,
- Single layer in cavity, and
- Double layer in cavity.
A building designer will check the tables in the code to see what level of insulation is needed and what combination of insulations can reach the requirement. This process must be done for every part of the building that is covered under the IECC and ASHRAE 90.1. Yes, every window, door, vent, wall, roof, etc. must be checked to make sure it meets energy requirements. Fortunately, there are computer programs that help with these tasks. The U.S. Department of Energy offers REScheck (residential) and COMcheck (commercial) software applications that check a design for compliance with IECC, ASHRAE 90.1 and any state-specific requirements.
So, as you work with your building designer or engineer on your metal building, expect that the energy code requirements will need special attention. Your building may require more or different insulation than you are used to seeing in a building. But it will all be worth it when your new building is comfortable and functionable.