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How to Insulate an Existing Metal Building.png

How to Insulate An Existing Metal Building

Insulating a metal building such as a detached garage is quite different from insulating a typical concrete structure. It’s a well-known fact that metals have unique properties, and some metals may heat up faster than traditional building materials commonly used in existing metal buildings.

These unique aspects of metal buildings and metal structures make insulating such structures a challenging job. Many people have no idea when they face the question of how to insulate an existing metal building. 

This article will shed light on how to insulate an existing metal building and will tell you about the best way to insulate an existing metal building. We will discuss several methods to insulate a metal building, such as radiant barrier insulation and fibreglass insulation. We will also explain the advantages and disadvantages of insulating an existing metal building. 

Table of Contents

Why Insulate an Existing Metal Building?

You may or may not need insulation depending on the intended use of the building. Insulation is a must-have if you want comfort and energy-saving and will also help maintain temperature, reduce moisture, and absorb sound. 

Although, insulating a metal building may also have some unintended consequences. One of the main drawbacks of insulation is that it usually involves flammable materials prone to fire. 

Metal buildings on their own cannot ignite. Still, suppose the insulation uses flammable material. In that case, it may not be the best choice if you intend to use your metal building for storing flammable materials, as your risk of accidental fire will increase dramatically in this scenario.

Almost all types of insulation have several components that usually include radiant barrier, vapour barrier, panels, etc. The main aim of insulation is to cover all walls, roofs, seams, and joints to reduce dampness, moisture, or condensation. Continue reading till the end to learn how to insulate an existing metal building.

Ways to Insulate a Metal Building

ways to insulate a metal building
Insulating a Metal Building

One can choose from a wide range of insulation materials available to insulate an existing metal building, such as radiant barrier insulation, foam insulation, and fibreglass insulation.

Each insulation material has its pros and cons. Here we will discuss two types of insulation, i.e., spray foam insulation and fibreglass sheets, in detail. These two are the most common materials used for insulating metal buildings.

Installing Spray Foam Insulation

Spray foam insulation is one of the most accessible and most convenient insulation methods that can be installed by the building owner himself also if they choose to do so. This type of insulation works best if the metal panels are already attached to the building frame, and you can also use this method if you don’t want to install radiant barriers. 

Installing Fibreglass Sheets

Fibreglass sheets have been used as an insulation material for almost a century now and offer some advantages over other insulation methods. Still, they are not the best choice if you want to insulate a metal building due to several reasons that are listed below:

  • Rolled fibreglass sheets usually come in 15 to 24 inches wide rolls. At the same time, frame studs on a metal building are spaced 4 to 5 feet apart, which leads to spacing issues in metal buildings due to differences between fibreglass sheet sizes and frame studs, need for additional tape, gaps, and peeling.

  • Fibreglass is known to collect and retain moisture, making it more prone to mould growth.

Professional Installation Costs

Professional installation costs vary greatly depending on the cost of materials, location of the building, size of the area to be insulated, and labour costs. It’s usually quite challenging to give a ballpark figure for insulating a metal building as almost all the costs involved are variable. Steel and stud provides cost-effective installation service for their customers.

While on average, insulation will cost you from $1.5 to $4.5 per square foot. If you decide to go for the cheapest insulation materials, it is also possible to install insulation for around $1 per square foot. 

A 40×60 metal structure can thus be insulated for as little as $2,400 or as high as $10,800, depending on the type of material used and labour cost. 

Prep: How to Attach to a Metal

metal building frame steelandstud
Metal Building Frame

Now we will show how to install insulation on a metal structure. For this article, we have decided to show the process for installing radiant barrier insulation, which is among the best and most common types of insulation for a metal building. 

You will first need to remove the exterior panels to put the insulation directly on the building’s metal frame. 


  • Choose the Best Way To Attach the Insulation: You can choose several methods to attach the insulation. Self-drilling screws, self-tapping screws, and adhesive tapes are among the most used methods for attaching insulation to a metal building. In the case of radiant barrier insulation, self-drilling and self-tapping screws are used.  
  • Fasteners: Using self-drilling screws: People usually use either self-drilling screws for installing radiant barrier insulation as they are easy to use and eliminate the need for drilling in metal sheets.
 Self-drilling screw
 Self-drilling Screw

Self-drilling screws are pretty easy to use and can be used by anyone without a drilling machine or other tools. 

Pre-assemble and paint your fasteners: This step is optional but is highly recommended to give your insulation a more professional and aesthetically appealing look. 

You need to pre-assemble the fasteners and locking washers and then arrange them in a row using a cardboard or foam board, as shown in the image below:

insulate Metal Building
Locking washers

Prepare for the transitions in the corners:  You can use 2.5″ self-drilling screws to tighten wood pieces into the corners to create a hard corner that will be later used for installing the insulation in the corner. You will also need something hard in the corners of the building to screw the insulation into. This is usually known as a “hard corner,” as shown in the image below:

self drilling in wooden pieces
Self-drilling in Wooden Pieces

The gables and between the walls & roof: Now, the next step is to install similar hard corners using pieces of wood on the gables, between the walls & roof, as shown in the image below:

steelandstud metal building insulation

Mark up the metal frame as a guide before you get started: You will also need to mark up the metal frame as a guide before you start as this will ease the job considerably, and you will know where exactly to fix screws, fasteners and insulation sheets. 

We will assume for this example that you are using insulation material with a width of 48″. The first piece needs to go along with the ground, right at the bottom of the walls.

You need to measure 48″ from the floor and mark the metal using a sharpie as shown in the image below:

48" Metal Frame

For the second run, we’d advise you to have at least a 4″ overlap, so you need to measure 44″(48″-4″= 44″) and place the second mark on the metal using a sharpie.

The second mark will be 92″ from the ground (48’+44″= 92″) as shown in the image below:

92 inches from ground metal frame
92" from Ground Metal Frame

You can leave the corner bracing untouched if you don’t have any light fixtures or conduit. If you have light fixtures or conduits, it’s better to remove corner bracing.

Begin Your Installation

There are mainly two methods in use for installing insulation. The first one is known as a corner to corner method, and in this method, you can start doing the side walls first, beginning in one corner till the other corner, then doing the roof, and finally finish with the end walls, and gable ends. 

The second option is the wrap-around method, and you will need to go all the way down to one wall, make a 90-degree turn, and then continue going down on another wall until you have finished all the walls or terminate at a door or another corner. 

STEP 1-A The Walls: You need to use the floor of the building and the bottom part of the frame as your guide to starting the first run. Install the radiant barrier foil in such a way that the foil side is facing out of the building. You will need three people to finish this step, two to hold both the ends tight and one to fasten the screws. 

STEP 1-B The Corners: You should have 4-5″ left on the end when you reach the corners. It’s essential to use a flat blade like a dry blade or putty knife at corners for pushing the insulation deep into the corners, as corners are often the weak points in any insulation installation process. You must also use matching tape or paint to hide the screws used in the corners, as visible screws will affect the aesthetics of the metal building. 

STEP 2-A The Second Run: You will need to line up the insulation with the sharpie mark that you made at 92″ while marking up the metal frame. You can use the tape for lining up the insulation sheet with the tape edge pointing towards the bottom. 

STEP 2-B Prepping the Corner Bracing: If you have corner bracing in the metal building and want to go behind it, you will need to remove the two bottom screws of the brace (corner spacing is depicted using the red line in the first illustration). Now pull the bracing away from the wall at least 2″-4″. Run the insulation behind the corner brace around the wall, and fasten it to the wall using the screws or fasteners. 

STEP 3-The Roofline: You must try to keep a continuous new interior surface by connecting the walls to the bottom of the roofline, as shown in the image below:

Walls Connected to Bottom Roofline
Walls Connected to Bottom Roofline

STEP 4-Finish Up: Now, the final step is to finish the insulation process by taping all the seams and gaps in the insulation. You can also use extra tape to fix any exposed seams. 

Metal Building Size Chart

Here are Steel & Stud Most Popular Customized Sizes for metal buildings. We can also get them customized as per your requirements:

Metal Building Sizes Metal Building Sizes Metal Building Sizes Metal Building Sizes

Metal Buildings Delivery & Installation Across the USA:

Customer service representatives will contact you ahead of time to schedule your delivery date in your location. Steel and Stud offers metal buildings installation services in 48 US states, including:-

Frequently Asked Questions

What are the primary goals of insulating an existing metal building?

The main objectives of insulating an existing metal building are increasing energy efficiency, reducing condensation and moisture, and maintaining the temperature.

What are the other types of insulation?

Radiant barrier insulation, spray foam, and fibreglass are the most common insulation materials available for metal building insulation. If you live in a colder region, you can install radiant barrier insulation as it works best in a colder climate. 

Why You Shouldn’t Use Fiberglass Sheets For Metal Structures?

Fiberglass sheets are not a good choice for insulating a metal building as they often lead to spacing issues due to their sizes and are also prone to mould as they tend to collect and absorb moisture. 

Should I carry out the insulation myself or hire professionals to do it?

Installing insulation is a time-consuming process that requires a good amount of energy and DIY skills. If you want to save labour costs, you can adopt a DIY approach, but it’s almost always better to hire professionals. 

Hopefully, this article has helped you learn a lot about how to insulate a metal building, and now you can add insulation to your metal building. With a little bit of preparation, you can easily add insulation to an existing metal building.