The Ultimate Guide to Insulating a Metal Building

Metal Building Insulation (MBI)

Today’s building codes have changed the way we insulate metal building structures. Insulation is no longer an afterthought. Choosing the right insulation system can have a major impact on reducing energy consumption and creating a good working environment.

Building owners and architects have finally discovered that with the benefits of system construction, the standing seam metal roof, and low-cost fiberglass insulation, metal building systems can create highly affordable, low-maintenance, and energy-efficient structures. In this guide we will discuss the most popular ways to insulate a metal building today and how they can transform your jobsite.

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fully insulated metal building


The right insulation system can develop a metal building’s long-term structural integrity and add years to its lifespan. Here are just some of the benefits of finding the right insulation system for your metal building:

  • Added insulation value
  • Managed interior climate control
  • Reduced heat loss and heat gain
  • Increased sound absorption
  • Decreased condensation
  • Improved air barrier with various facings
person on top of Simple Saver Liner Systems Fall protection while working


Insulating a metal building properly does more than conserve energy, it promotes comfortable living and profitable savings. Learn the many ways you can benefit from metal building insulation.


By reducing the heat flow into and out of a metal building structure, metal building insulation provides a building envelope that enables the heating and cooling system to reliably control the interior building temperature.


For years, metal building insulation‘s primary job was to reduce condensation that was created with temperature differentiation between inside and outside temperatures. This is still the case, however, insulation is also helping to reduce thermal bridging that can create heat loss and condensation.

Perm ratings: the perm rating measures the facing’s ability to reduce or eliminate moisture transmission, reinforcing that fiberglass performs better.


With extra interior padding, metal building insulation keeps sound inside, resulting in happy neighbors and improved sound quality within the building’s interior. This is especially beneficial if you’re working with loud machinery.


Create long-lasting durability with structural solutions that protect your building’s longevity. To find the best metal building wall insulation system for your building, consider the wide range of system solutions and their distinct benefits.


Fiberglass is the most popular insulation solution for metal building systems because it provides the lowest installed cost per R-value. With various facing solutions, the fiberglass insulation will result in a durable and attractive finish.

Advantages: easy to install, eco-friendly, causes less stress on equipment.

Disadvantages: PPE required in order to avoid exposure to carcinogens.


Traditional-faced fiberglass insulation is installed between the outside face of the girts and the exterior metal wall panel. Standard metal building blanket insulation is easily retrofit and very user-friendly when installing. For standard applications, the R-Value ranges from R-7 to R-19.

Advantages: easy to install, low installation cost, provides an approved air barrier.

Disadvantages: thermal bridging at each girt location reduces the effective R-Value.


There are two different metal building wall insulation products that will fill the girt wall cavity. In both cases, the installer will first apply thermal break tape to the outside face of the girts prior to installing the wall panels. These filled cavity systems can stop air leaks and critters in their tracks, preserving air quality within your metal building.

Advantages: low installation cost, easy to install.

Disadvantages: can interrupt the purlins.


After the wall panels are installed, the unfaced insulation is installed between the girts and are held up by insulation hangers. After that process is complete and the insulation is installed, a fabric liner system is placed over the girts and the insulation.

Advantages: works well in new and retrofit situations, meets most energy codes, easy to install, provides a high-quality vapor/air barrier, attractive white finish. Coordination between the insulation provider and the building manufacturer is required.

Disadvantages: Installation process is complex, harder to access purlins for electrical, maintenance and HVAC services.


Polyisocyanurate insulation is a continuous insulation solution for metal building systems. If left exposed (or covered with a liner panel thinner than 22 gage), it is required that the product have a class A fire rating.

Advantages: continuous insulation, reduces thermal bridging, durable facings are available, and meets most building codes.

Disadvantages: expensive solution, special lengths are typically required, join conditions need to be addressed, coordination with building manufacturers is required in regards to trims and building lines.


Although this form of metal building wall insulation is not available through IDI Distributors, it has become increasingly more popular with metal building systems in recent years.

Advantages: Attractive finish on interior and exterior, with right equipment easy to install, is a continuous insulation solution. Coordination between the insulation provider and the building manufacturer is required.

Disadvantages: expensive, special equipment is required for installation.


With this solution the faced insulation needs to be equal to or slightly greater than the depth of the wall girts. When insulating your metal building, it is important to fill any excess cavity space to reduce the risk of condensation.

Advantages: low-cost method to meet higher energy codes, wall panels are quickly installed as insulation is installed after the wall panels. Coordination between the insulation provider and the building manufacturer is required.

Disadvantages:  insulation width needs to be the same as the girt spacing.


Over the past several years, spray foam has become an effective option for metal building wall insulation. We have seen spray foam mostly in smaller buildings. IDI recommends that building owners check with the building supplier to understand if the spray foam may affect any warranties. Learn more about getting started with spray foam insulation.

Spray foam systems are installed directly to the inside of metal wall panels. The installer needs to prep the metal panel and assure that the surface is ready to accept the spray foam. Closed cell spray foam is typically used, however open cell can be used in some applications. A fire rated coating needs to be installed to the spray foam if left exposed.

Advantages: easy to install,  provides rigidity to the building (closed cell).

Disadvantages: may void building manufacturers warranties, more expensive than fiberglass.

Looking for more hands-on training and information for getting started on providing metal building insulation?

Contact IDI for Training Opportunities


Properly insulating the roof of a metal building can be essential for its living and working conditions. If not correctly installed, condensation and water damage can begin to erode the building materials and could potentially lead to roof collapse.

Meet building codes easily and protect the structure of your building by finding the most suitable solution for your insulation needs. Metal building roof insulation systems can make all the difference when it comes to saving money and prolonging a structure’s lifespan. When looking at how to insulate a metal building ceiling, keep the following types of insulation in mind:


This is the traditional method of insulating metal building roof systems. However, due to increased stringency in the energy codes, a single layer system does not meet the requirements for conditioned space in most of the US.

The single layer system is typically R-10, R-13, R-16, or R-19 (only up to R-13 is recommended with a screw down roof system). The single layer faced fiberglass blanket insulation is installed perpendicular and over the roof purlins (facing side toward the inside of the building), the roof system is then installed directly over the insulation. This system used either 2-3” tabs (which are stapled together) or 1-6” tab (that is overlapped or tape tabbed).

Advantages: low cost, easy to install, traditional method, good appearance.

Disadvantages: will not meet most energy codes, R-value loss due to thermal bridging.


This is a low cost solution to provide a high R roof system. Warning: this system does not meet most energy codes due to inconsistent sag and thermal bridging, caused by the roof purlins.

The first lay of faced insulation is installed perpendicular and over top of the roof purlins.  Installers need to make sure to add in sufficient sag for the second layer. The second layer of unfaced material is then installed over top of the first layer between each purlin. The roof system is then installed over the metal building roof insulation.

Advantages: easy to install, low cost.

Disadvantages: poor performing insulation values due to thermal bridging at the purlins, does not meet most energy codes for conditioned space.


For buildings that need a high-R value solution in the roof, this metal building roof insulation system is ideal. The first layer of faced insulation is installed between the purlins and over top of metal support banding (approx 30” o/c). The second layer of unfaced insulation is installed perpendicular to and over the first layer. Once the insulation is properly installed, the metal roof is then installed directly over the second layer of insulation.

Advantages: low cost solution for high-R value required projects (R-30 to R-38), various facing available, installation from roof deck, other trades still have easy access to the bottom flange of the roof purlins. Works well with flange bracing. Coordination between the insulation provider and the building manufacturer is required.

Disadvantages: bracing interferences (purlin channel bracing, and sag angle bracing) are difficult to work around.


Fabric liner systems have become a very popular solution to meeting energy code requirements and delivering a well insulated metal building envelope.

The fabric liner system is installed below the roof purlins, and is supported with metal banding.  Most liner systems do provide “leading edge” fall protection for the workers once it is installed.  Once the fabric liner system is installed, the first layer of unfaced fiberglass insulation is installed between the purlins and directly over the liner system. The second layer of unfaced fiberglass insulation is installed perpendicular to and over top of the roof purlins and first layer of insulation. The metal roof is then installed over the second layer of insulation.

Advantages: meets or exceeds building energy codes, provides an excellent air/vapor barrier, attractive finish, and reduces thermal bridging by filing the purlin cavity, works well in retro-fit situations, works well with purlin channel bracing and sag angles. Coordination between the insulation provider and the building manufacturer is required.

Disadvantages: difficult to install the first time.


Rigid board insulation is a good continuous insulation solution for metal building roof systems.  If left exposed, the material needs to have a class A fire rating.

Advantages: easy to install, continuous insulation, reduces thermal bridging.

Disadvantages: higher costs, special conditions on the joints.

The rigid board is typically installed over the roof purlins with the roof panel being installed directly over the rigid board. Things to consider:

  • Make sure that the rigid board endlaps terminate at a purlin connection.
  • It’s a good practice to tape the outside joints of the rigid board to secure the board and provide a vapor barrier.
  • Check with the building manufacturer to see if bearing plates will be needed for the standing seam roof clip attachment.


The science behind reflective insulation can work in the right situation. The situation being solar heat gain, or rooms with lots of windows, skylights and light penetrating in. If heat absorption is the concern, a Sol-R-Eclipse insulation product is the right choice of metal building insulation products.

  • Reflective insulation provides a radiant barrier composed of high-grade aluminum that maximizes the reflection of unwanted heating.
  • Sol-R-Eclipse systems have vinyl facing reinforced for easy installation and long-term durability.
  • Our selection is available with white and silver facings.


Spray foam insulation can be used with a screw down roof system, but spray foam is not recommended to be used with standing seam roof systems. In most cases, a closed cell spray foam is used, therefore increasing the rigidity of the roof system. This is a problem as standing seam roof systems are designed to expand and contract.


Insulated metal panels (not sold by IDI) are more popular on the walls, but are available as roof panels. Coordination with the building manufacturer is critical due to loading (weight), and trim conditions.

Advantages: consistent R-Value, attractive interior finish.

Disadvantages: cost, special equipment needed for installation.


IDI is a full supplier of all metal building insulation products.  Here is a list of the products and services we provide:

  • Energy code expertise.
  • Expert job take-off and cut sheets.
  • Coordination of High-R systems.
  • Standard blanket insulation. IDI has access to standard blanket insulation.
  • 11 different facings. Each facing has different properties to fit the building environment.
  • Three different fabric liner systems. Simple Saver, MB Safety Liner, and Energy Craft.
  • Multiple options for rigid board insulation. Thermax, OX Board, R-Max.
  • Spray foam. IDI does not install spray foam, however, we have contracts with thousands of insulation contractors that can.


Have a question on anything insulation, pricing, or want to place an order? With hundreds of products and countless services, our experts will help walk you through the process of getting ready for your next project. Get in contact with our team today for help and guidance on the right products and best techniques for you and your business.