Barndominiums are the latest real estate phenomenon and seem to be appearing everywhere. From their beginnings in the rural Southern states, barndominiums are becoming more popular in colder Northern climates too.

Whether your barndominium is a steel or timber frame building there are several ways they can be successfully insulated to provide the spacious, but cozy, home you desire. Because of the way they are framed out, barndominium insulation can be installed to be very efficient.

So if you are considering building, or buying a barndominium, here’s how to go about insulating one.

The Money-Saving Budget Barndominium

Barndominiums are supposed to give you bang for your buck, a cost-effective solution to acquire the space you crave. In today’s hot housing market, square footage comes at a price.

So how can you keep costs down? Well, the answer to that question is fiberglass. It has the lowest installation cost of any insulation product.

Fitting Fiberglass Rolls on the Barndominium Walls

Use faced insulation with the vapor barrier on the inside of the building.

Seal the top and bottom of the walls to prevent air movement or bugs from getting in. A metal flashing on the exterior and a few cans of low-rise spray foam on the interior should make things nice and secure.

Make sure that the fiberglass is in contact with the external metal sheathing and properly vented to eliminate any condensation gaps where moisture can form.

Staple the fiberglass to the internal timber framing. If your barndominium does not have an internal timber frame for drywall that you can attach the fiberglass to, then it is probably not the right insulator for your project. 

Make sure the fiberglass rolls are fluffy and not compressed. Compression lowers the insulating value of fiberglass.

Top Tip: Whatever your budget, fiberglass is an excellent way to cut sound transmission between internal walls. Use R-13 faced or unfaced fiberglass insulation on a roll to fill the space between the internal wall studs.

You won’t be able to staple unfaced fiberglass so you will be relying upon a friction fit tight between the wall studs. Avoid using very long lengths of unfaced fiberglass in case gravity should compress it under its own weight.

If you cut it into a maximum of 6’ lengths then it should sit in the wall cavity quite comfortably.

Fiberglass For Barndominium Roof or Attic Insulation

Use rolls of unfaced R-30 fiberglass insulation inside any loft areas.

In the South, the minimum level will be R-49, while the building code states that further North up to R-60 will be required.

When building a new barndominium, install a layer of faced fiberglass between the purlins, then a continuous layer of unfaced fiberglass at 90° over the top before installing the roof panels.

It will be harder to retrofit the required depth on a vaulted cathedral ceiling, but not entirely impossible.

You will need a secondary frame to carry the insulation, usually steel banding, but fiberglass is pretty light, which is a big advantage in a lightweight steel-frame construction.

Top Tip: A feature of barndominium ceilings is that they are usually higher than those seen in more traditional homes. When hiring a scaffold to reach the ceiling level, make sure that you have adequate edge protection. It’s a long way to the concrete on the floor!

The Mid-Range Barndominium

Fiberglass might be a good choice if you have a vast area to cover, but another good choice, one that comes in at a price that is also quite competitive is foam board.

As long as the area between the foam board and the metal sheathing is adequately vented there should be no issues with condensation.

Polyiso or Styrofoam can be installed between the steel frame and sealed with low-rise spray foam to help deliver a solid air seal to the barndominium.

It will come in more expensive per square foot than fiberglass but it does have distinct advantages in that it won’t settle over time and is resistant to moisture and pests.

Four inches of polyiso will give you R-20 over the long term, accounting for off-gassing with age, and will last the lifetime of the building.

Top Tip: When choosing a foam board interlocking panels give a better seal. If gluing panels together make sure the adhesive is suitable for foam board as some can melt polyurethane, polyiso, and Styrofoam. Always check the manufacturer’s instructions, or test on a small offcut before use!

The Upscale Barnstorming Barndominium

So what’s the premium way to insulate a barndominium? Between the metal sheathing and the internal timber framing, there is sometimes almost eight inches of space to play with.

This is ideal for feeding all of your pipework and electrical conduits right around the building, but it’s also a great space to fill with open or closed-cell spray foam.

Installing Spray-Foam in Your Barndominium

The advantage of spray foam is that it will give you a great R-value and will happily adhere directly to the metal sheathing of your barndominium.

Spray foam will also provide you with a fantastic air barrier, whether you are in the South and want to keep that hot air out for ten months of the year, or you are further up the climate charts and want to keep those polar vortexes at bay.

In Texas, arguably the birthplace of the barndominium, a four-inch depth of open-cell spray foam is standard on the walls, with closed-cell spray foam on exposed ceilings i.e. in the garage, because it gives a better finish.

Coupled with the right HVAC and dehumidifier, Southern ‘barndos’ can be kept very comfortable all year round.

While there are several DIY options for spray foam these days, there are also plenty of contractors who specialize in this work.

Check references or reviews online before you hire or buy your own spray product.

Spray foam mixes at the nozzle, so be sure to keep equipment clean and follow the manufacturer’s instructions.

Top Tip: While it is easy enough to spray foam across large areas of wall, care must be taken around door and window openings. It’s easy to miss those small areas below windowsills or above door headers. 

All of those spaces that are hard to see, check them twice, but respray with a light touch so as not to over-expand and cause damage to the windows!

Installing Flash and Batt in Your Barndominium

This method might be a way of saving money on spray foam while reaping the benefits of the superior air seal that it can deliver.

Installing an inch of spray foam over the metal sheathing will likely serve to close any small gaps between panels, fixings, and penetrations.

Following the drying and hardening off of the spray foam, fit an unfaced insulation batt such as mineral wool, or wood fiber in the timber framing.

Top Tip: If you spray foam the steel panels before installing the timber framing it means you can keep the timber, plumbing, and electrical conduits clean when they are installed afterward. Spray foam sticks to everything, so make sure anything you don’t want to be covered with foam is properly protected before you start work!

Premium Barndominium Insulation

Possibly the best insulation product to consider when building a barndominium, especially in Northern climate zones, would be the sandwich panel.

These are dual-faced panels that have expanded foam between two sheets of metal, the panels are interlocking and fixed directly to the steel frame of the building.

Sandwich panels are most commonly used in the construction of industrial-scale buildings, so a large-scale steel-framed barndominium is the perfect building for them.

The polyiso or polyurethane insulating interior foam comes in widths from two to eight inches and can be manufactured in many sizes, from 4’ x 4’ to 4’ x 50’ and in a wide range of finishes too.

Top Tip: Make sure you have the detailing right between wall and roof junctions to ensure no break in the continuous thermal envelope of the building. On a door blower test, this is where you will find most problems, so check the seal inside and out!

What Insulation Not to Use in a Barndominium

The key thing to remember is that whatever insulation system you employ in your barndominium, you only want to do this job once, so make sure it’s done properly.

Some insulation products are easier to install than others, which makes quality checking simple, while others might need specialist equipment to ensure conformity.

The biggest enemy in a metal-clad construction is condensation. Pay attention to venting in an unconditioned attic or wall space and where you install your vapor barrier.

Top Tip: A thermal imaging camera can offer a quick way to discover gaps, or thinner areas where spray foam has not been adequately installed. If spray foam needs a top-up, always use more of the same product. Different products, using different chemicals, could cause problems, one degrading the other.


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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