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Regulate, Moderate, Insulate – Safeguard Your Metal Building with Proper Insulation

Almost everyone knows that insulation moderates interior temperatures in a steel building. It keeps warm air inside during cold winter months and prevents heat from penetrating your structure in the summer. But for a steel building, it’s even more important. Insulation creates a barrier in the roof system and walls that prevents condensation – more than an annoyance, condensation can compromise the look, lifespan, and stability of your steel building.

In many areas, local building codes require that your steel building be insulated. Buildings without heat or air conditioning can usually pass inspections without insulation, but for just about every other kind of steel building, some kind of insulation is going to be required.

The experienced team at Great Western will help you make the right choice. But consider several things when choosing insulation.

Choosing the right kind of insulation is important – several factors are involved:

  • Your region’s climate
  • Your skill at application of the insulation
  • The use of the building
  • Of course, budget!


Standard Steel Building Insulation Packages

The most common is 3-6” (3″ on the walls, 6″ on the roof) fiberglass compression insulation.

Compression insulation is by far the most used insulation for steel buildings. It comes in thicknesses ranging from 3 to 6 inches and is usually faced with a white vinyl vapor barrier. The quality of the vapor barrier varies, WMP-VR/VRR is the most affordable and most common in the industry. At Great Western we supply WMP-50 as a standard, this vapor barrier allows less moisture transfer than the VR/R product. Ask your Great Western representative for product specifics.

This insulation system is called a compression system because it is sandwiched between the roof or wall panel and the secondary structural system (girts or purlins). The insulation is placed with the vapor barrier towards the inside of the structure and the bare fiberglass pressed against the panel.

Fiberglass Insulation Pros and Cons
  • Affordability
  • Ease of Installation
  • Excellent Moisture Control
  • Adds Aesthetic Appeal
  • Brightens Interior of Building
  • 6” Thickness Can Cause Oil-Canning Effect
  • R-Value Loss in Compressed Areas
  • Will Not Pass All Energy Codes
  • Max R-Value of R-19

Fiberglass Compression Insulation Specs

Fiberglass Manufacturer: Owens Corning

Facing/Vapor Barrier Manufacturer: Lamtec

Facing Type: WMP-VR or WMP-50 (Standard)

Thickness: 3 – 6” Faced

R-Value: R-10 – R-19

Facing Reinforcing: Tri-Directional Polyester

Facing Film: Metallized Polyester/Polypropylene

Light Reflectance: 85% (White)


Sag and Bag Metal Building Insulation Systems

Sag and Bag insulation systems are dual layer insulation systems. Typically only found on roof systems they are very similar to the standard compression system.

Sag and Bag uses standard 3-6” compression insulation that sags between the roof purlins. An extra layer of non-faced fiberglass in any thickness is rolled parallel to the purlins within the ‘sag.’ The thicker the ‘bag’ the more sag will be required. With Liner Systems becoming more and more affordable, sag and bag is not as popular as it used to be.

Vapor Barrier Pros and Cons
  • Higher R Values
  • Affordability
  • Passes Most Energy Codes
  • Difficult Installation
  • R-Value Loss at Roof Purlin
  • Provides Zero Fall Protection
  • Erectors Prefer Other Insulation Systems

Sag and Bag Insulation Specs

Fiberglass Manufacturer: Owens Corning

Facing/Vapor Barrier Manufacturer: Lamtec

Facing Type: WMP-VR or WMP-50 (Standard)

Thickness: 3 – 6” Faced

R-Value: R-10 – R-19

Facing Reinforcing: Tri-Directional Polyester

Facing Film: Metallized Polyester/Polypropylene

Light Reflectance: 85% (White)


Liner Systems

A powerful insulation system growing in popularity.

Fiberglass liner systems are becoming more and more popular with building authorities, the International Code Council, Erectors and building owners alike. Liner systems are at the cutting edge of Metal Building Insulation Systems. Capable of meeting OSHA standards for both active and passive fall protection and some of the highest R-Values available for steel building systems.

A continuous liner is installed on the underside of the roof purlin or the inside flange of the girt. For roof systems, a steel banding which provides the fall protection is used to hold the liner up, a similar system is used for the walls. The Cavity of the girt or purlin is then filled with pre-cut fiberglass and a top layer of fiberglass is rolled over the top of the purlin or girt to provide a thermal block and additional R-Value. Roof Panels are then installed over the insulation.

Fiberglass Liner Insulation Pros and Cons
  • R-Values up To R-50
  • Easily Meets All US Energy Codes
  • Fall Protection = Safety for Your Workers
  • Beautiful Finished Look
  • Less Expensive than Insulated Panels
  • Custom Fabricated For Each Building
  • Less Affordable than Other Fiberglass Insulation Systems
  • Adds to Engineering and Fabrication Time

Liner Insulation Specs

Fiberglass Manufacturer: Owens Corning

Facing/Vapor Barrier Manufacturer: Bay Insulation

Facing Type: Banded Fabric .02 perm factor

Thickness: Up to 12”

R-Value: Up to R-49

U-Factor: .037 to .029 W/ SS Roof and Thermal Blocks

Facing Reinforcing: .Tri-Directional Polyester and Steel Banding

Facing Film: Polyethylene

Light Reflectance: 85% (White)


Vapor Barrier Only System

Low R Value Moisture Protection

For buildings that are not going to be climate controlled in any significant way but still need to deal with moisture and condensation we offer a felt backing to our standard roof and wall panels. This felt acts as a thermal block and reduces heat transfer from the panel to the structural framing.


Vapor Barrier Pros and Cons
  • Excellent Moisture Control
  • Easy Installation
  • Affordable
  • Looks Great
  • Washable
  • No R-Value
  • No Noise Reduction From Wind or Rain

Insulated Steel Panels

Insulated panels are perhaps the easiest to insulation package to install.

They’re also the most energy efficient and the most expensive. Available in ribbed, stucco and flat exterior finishes, insulated panels are preferred by many builders and architects.

This system is incredibly simple, providing an interior liner panel, up to 8” of polyurethane foam insulation and the exterior panel in a single unit. Insulated panels are typically a tongue and groove configuration that conceals all fasteners. These panels can be purchased through Great Western or you can send us the panel specifications if you have a vendor you prefer.

Insulated Metal Panels Pros and Cons
  • Fast and Simple Installation
  • Fire Ratings Available
  • Numerous Finishes and Profiles Available
  • Meets All US Energy Codes

  • High Monetary Investment
  • Shipping Requirements