How to Insulate a Metal Shed


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Metal sheds are a popular choice for storage. However, the metal sides and roof can get either very hot or very cold, depending on the weather. The inside temperature will be affected by this heat and cold.

This is why many people want to insulate their metal sheds, even if they are used just for storage. Nobody wants to find out that their yard chemicals have frozen over the winter and now pour out of the bottle in clumps.

You can insulate a metal storage shed with fiberglass batts, foam board, spray form insulation but you will need to frame the walls for most insulation types. Spay foam allows to to spay over the metal providing some insulation value.

What are the Options for Insulating a Metal Shed?

Fiberglass batts are the most popular way to insulate a metal shed. It can be purchased in handy rolls and is fairly inexpensive, but you do need to get the type with facing, which is more expensive. Fiberglas loses some of its insulating properties when it gets wet or damp. Once fiberglass insulation gets damp, it stays damp.

Sealing the seams completely with the proper tape is essential to prevent dampness from invading the fibers. Getting fiberglass with a facing that prevents moisture costs more but is worth it for your shed.

This insulation is pretty easy to install, even over the ceiling. The biggest problem is that it’s really not possible to install it unless you have studs, so if you buy a prefab shed, you’ll likely have to put in wooden studs to use this insulation. If you are ordering your shed built to order, you can ask the builder to put in a stud system for insulation purposes.

The installer needs to wear protective clothing such as long sleeves and use eye and breathing protection, as fibers tend to flake off and float around when the batts are handled. A similar option is mineral fiber. It comes in batts and resists moisture, but if it does get wet it tends to shrink. It also needs a stud system to be installed.

Solid foam board is another option. It features a high thermal resistance rating and is durable. It doesn’t require a stud frame, and can easily be cut to size to fit your space. You will need to make sure the seams are thoroughly taped.

You may also wish to use more than one layer. The foam board may be attached with some sort of fasteners, but there are non-solvent spray adhesives available that will work fine with the foam board. If you want two layers, installing the second layer with the adhesive won’t be a problem.

Check the ratings on the foam board when shopping, as some choices are neither fire- nor water-resistant. You may need to install a fire-retardant vapor barrier over the foam board if yours does not have these properties.

Closed-cell spray foam is a little more expensive than the solid foam sheets but it has the advantage of also acting as a moisture barrier, which offsets the extra cost. It can be applied easily all over the inside of the shed.

Applying it to the ceiling takes care of the condensation problem that may crop up. While you can’t just use a paint sprayer to apply the foam, the proper type of sprayer can be rented. Apply the foam evenly in one-inch layers, allowing each layer to dry before applying the next. You can get the foam as thick as you want where you want.

There is another kind of closed-cell foam that comes in rolls with a metallic reflective foil covering on both sides. The reflective foil on the siding side keeps the temperature outside from affecting the inside temperature as much and conversely keeps the inside temperature more consistent, as it keeps the warmth or coolness inside. It is also touted as being moisture-resistant and acts as a vapor barrier.

Blown-in cellulose is a fairly inexpensive method of insulating a shed. It’s made from old newsprint and other paper products that have been treated with chemicals to make it fire retardant. However, you must have interior walls to create a space for the insulation to be blown into.

Likewise, you must have some interior covering or a moisture barrier on the ceiling to hold the insulation. While it does have a higher R-value, or thermal resistance factor, than fiberglass, the factor is lower than for some other choices. In addition, it’s rather difficult to apply and needs a vapor barrier installed behind it, as it is not moisture resistant. Although it is treated to be fire-retardant, it is not fireproof. It is also not resistant to mold or rodents. For more information on insulating a shed read my article What’s the Best Insulation for a Shed? [Batt, rigid or loose fill?]

What is the Cheapest Way to Insulate a Metal Shed?

Fiberglass batts are usually the cheapest insulation for the shed, followed by blown cellulose. If you don’t have studs in your shed, you’ll need to add the cost of adding a stud system when figuring the cost of these types of insulation. There are other things you can do to keep your shed warmer, read my article How to Get Your Shed Ready for Winter for more tips.

How Much Does It Cost to Insulate a Metal Shed?

Average costs per square foot are as follows: Closed-cell spray foam – $7.50 per sq. ft., rigid foam board – $1.20 per sq. ft., mineral fiber – $0.55 per sq. ft., blown-in cellulose – $0.45 per sq. ft., and fiberglass batts – $0.40 per sq. ft. Of course, prices do vary from one area to another, and prices tend to rise and fall with the economy, so this is just to give you an idea of the price spread.

Can I Use Bubble Wrap Insulation in a Metal Shed?

While some sources state that bubble wrap makes good, cheap insulation, it actually does not provide much insulation. Some sources state that it can actually be dangerous if you plan on running electricity to your shed, as it catches fire easily. There is also some bubble wrap on the market that is faced with foil and is marketed as being good insulation.

It actually has such a low R-value (only 1.0 or 1.1) that it really has no use as insulation. The only job it does is acting as a radiant barrier. Some manufacturers even promoted it as serving as insulation and vapor and radon barriers under concrete.

Three of those manufacturers were said to have written apology letters later on. If you really want to use it, you will probably need several layers of it to do much good and have a fire-retardant barrier and interior walls installed as well.

Is Spray Foam Good for Metal Sheds?

Spray foam is great for insulating a shed. There are two types of spray foam: open cell and closed cell. The open cell kind is cheaper than the closed-cell version, due to air being able to get inside the cells. This makes it better at noise reduction. The closed-cell type is denser and is better able to withstand air and moisture penetration, making it act as a vapor barrier as well as insulation.

Another benefit that most people aren’t aware of is that the denseness of the dried foam actually can strengthen the shed structure. It spreads out when sprayed to fill in all the little nooks and crannies, so nothing is overlooked. It’s also easier to apply to ceilings than some other choices.

When searching for spray foam insulation, you’ll want to check out the fire ratings. Some foam products are fire resistant while others are not. This is especially important if you plan to have electricity in your shed.

Applying spray foam insulation is a little trickier than installing some of the other types. For one thing, you won’t be able to use any old paint sprayer to apply the foam. The foam is actually made of two chemical parts that must be kept separate until the actual application.

When the two chemicals meet and are exposed to air, the resulting mixture solidifies into a rigid foam. Fortunately, there are sprayers available for rental that have a tank for each substance and mix them properly when spraying.

Since the foam is very sticky until it dries and cannot be removed afterward, it is essential that you wear protective clothing or at least old clothes that you don’t mind getting ruined. Neither heat nor any kind of solvent can remove the foam, so be sure to have the shed cleared before you use it. If you already have the flooring installed, put down drop cloths to keep the foam from landing on the floor, especially when you’re spraying the ceiling.

The wet foam is also a skin irritant, so long sleeves and pants are a necessity. In addition, eye protection and a respirator are needed. If you’ve never worked with spray foam before, you might try spraying just a bit on a scrap board outside just to see how the spray comes out and how to handle the sprayer.

Spray the foam evenly back and forth over a manageable width, taking care to cover all the surfaces, then move on to the next section. Spray it to about an inch of thickness. Let it dry completely before adding coats. You can make it as thick as you want with additional coats.

While spray foam is more expensive than other types of insulation, its benefits make it a good choice to consider. With the fact that it also acts as a vapor barrier and its long life, the initial costs will probably be made up later.

Can Mold Grow on Spray Foam Insulation?

Spray foam insulation is good at preventing the growth of mold and mildew due to its moisture-prevention properties. The closed-cell type is especially good at preventing the penetration of moisture into your shed.

Can You Insulate Under a Metal Roof?

Insulation is vital under your metal shed roof. This is where moisture is most likely to condense. The easiest to install is the spray foam and the foam board. The spray foam covers thoroughly, and you won’t have to cram yourself right up to the roof in tight spaces to install it. Since the foam board can be installed with the right kind of adhesive spray, it has a lot of advantages over other types of insulation requiring a framework.

Be sure to check into the various types of foam board available. Depending on the material it’s made from, it can be fire and moisture-retardant. The cheaper types of foam board that aren’t moisture-resistant can deteriorate over time and would require moisture barriers to protect it.

How Do You Install Insulation in a Metal Shed?

Since spray foam and foam board have already been covered, we’ll discuss fiberglass batts. If your shed didn’t come with interior framing, you’ll have to install a framework to install the fiberglass.

You can install a wooden stud framework, attaching it to the existing framework of your shed, but there is another option. Steel framing is available and actually can cost less than wood. Metal studs don’t warp or split, and of course, they are resistant to fire, rot, insects and vermin. They are lightweight and easy to work with.

For tools, you’ll need straight-cut aviation metal snips, a drill with a two-inch extension for the bit, protective gloves and C-clamp locking pliers. Studs can be cut by snipping both sides with the metal snips, then scoring a line on the back. Bending the stud back and forth a few times will separate the pieces.

If your shed is large and you will have to cut a lot of studs, a circular saw fitted with a carborundum blade will make the job go more quickly. The best way to assemble the frame is to install the top and bottom tracks first, then the studs one at a time. The studs should be spaced to fit the batts.

When installing the batts, push them firmly between the studs. When cutting the length, leave a little extra so that the bottom will have a tight fit. If you get the kind with facing, that side should face the interior. If it doesn’t have facing, you’ll need to install a vapor barrier over it when you’re finished. For more information read my article Is a Metal Storage Shed a Good Option?

Conclusion

When deciding on shed insulation, the choices are much like those for a house. The main thing to consider is how well each type will handle the moisture problem that often plagues a metal shed, what with the extra condensation due to the temperature fluctuations of the metal. The decision process is often a balance of cost, using a product that protects all at once versus having to use two or more products, ease of installation, and any long-term savings due to lifespan.

 

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