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How to Insulate a Shed: From Start to Finish

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This post on how to insulate a shed is sponsored by Arrow Fastener.

If you’re wondering how to insulate a shed, I’ve got you covered! I bought a 16′ x 26′ prefabricated she (which will become my “she shed” workshop) and decided to do as much of the interior work myself, including running the electrical (under the advice of a master electrician who helped me), along with the insulation. 

I’ve learned some things along the way that will be helpful if you’re wondering how to insulate a shed. Let’s jump into it right now! (And if you’d like to keep reading about getting your own “she shed,” read this helpful post on 10 Questions You MUST Ask Before Building a She Shed). 

Click here to save this project on Pinterest. 

How to Insulate a Shed - Thrift Diving

 

Watch This Project in Action!

Some people are visual learners. 🙂 Check out the video for this project!

 

 

Materials Need to Insulate a Shed

Below you will find the materials I used to insulate my shed. (Some of these links may be affiliate links).

 

 

What Type of Insulation Should You Use to Insulate a Shed?

Walk through the aisles of a big box store and you’ll see several brands, sizes, and R-values of insulation to buy to insulate your shed. But which one should you buy? 

For me, the choice was obvious. I wanted an insulation that was fire-proof, waterproof, soundproof, and wasn’t as itchy as the pink fiberglass insulation. And for all those reasons, I chose Rockwool insulation.

But regardless of the brand you choose, you’ll also need to choose the R-value for your shed based on its framing. My shed has 2×4 framing, which is 3.5″ deep, so an R-13 or R-15 fits perfectly at 3.5″ thickness. (The R-value is basically how well the insulation is able to resist heat; the bigger the number, the better job it does of resisting the transference of heat. But the size of your shed studs will determine what R-value you can use).

Keep in mind, though: Rockwool doesn’t have a vapor barrier attached, so you’ll need a big roll of 6-mil plastic sheeting to cover it to prevent moisture!

Most of the pink fiberglass stuff you can buy with that paper backing on it which is the vapor barrier.

Just be prepared for the extra work required when installing insulation that requires a vapor barrier. It’s challenging doing it as one person, like how I did it! 😉

 

 

Does a Shed Need Ventilation?

Before you go any further in insulating your shed, be sure to answer the important question about whether your shed needs ventilation.

This step confused me to no end because I couldn’t find a definitive answer on whether a shed needs ventilation or not. Here’s what I was able to gather:

Yes, a Shed Needs Ventilation if the Following is True:

If you are planning to heat and cool the interior of your shed, and you’re insulating your shed with fiberglass or Rockwool stone insulation, yes, your shed will need ventilation. Since you’re heating and cooling the interior of your shed, mixing interior conditioned heating and cooling with the elements could cause condensation. This is why the vapor barrier is important, to keep those elements separate. Also, though, with the ventilation, it keeps the warm air rising and out the ridge vent, while replacing the attic air above the insulation with cooler air from outside.

I also learned that if you’ve got a ridge vent (such as my shed does) at the peak of your shed roof, then soffit vents work best to keep that flow of fresh air.

The best resource I was able to find on the topic of ventilation was from Fine Homebuilding: A Crash Course in Roof Venting.

 

No, a Shed Does NOT Need Ventilation if the Following is True:

The only times when you wouldn’t need a ventilation system, from my understanding, is if you’re using spray foam to insulate the ceiling, if your shed won’t be insulated, and if you’re not planning to heat or cool the interior of your shed.

Be sure to do your own research and make the best decision based on how you plan to use the shed.

 

STEP 1: Measure the Space Between the Studs

Wouldn’t it be nice if every single stud was 16″ part, from stud to stud? Yeah–fat chance when it came to my prefabricated shed! Because all of my studs aren’t 16″ on center, I had to measure each stud bay and then cut each piece of insulation to fit the space. I made sure that each piece was 1/2″ to 3/4″ bigger and longer than my measurements.

 

 

STEP 2: Place the Insulation Between the Studs

Because the insulation is a bit larger than the stud bay, the insulation should fit snugly. Since each piece is only 48″ long, you’ll need to double up your insulation between the studs. You’ll likely have lots of trimming to do! Be sure to wear your dust mask, gloves, and eye protection. Some people have told me that rubbing baby powder on your skin prior to insulating your shed helps to keep the insulation off your skin and makes it way less itchy. Unfortunately, I didn’t have any baby powder and I bore the brunt of an itchy next every single night. LOL

 

How to Fit Insulation Around Electrical Boxes and Wires 

You’ll definitely have to fit the insulation around electrical boxes and wires, but it wasn’t too difficult.

For the boxes, use a tape measure or hold the insulation in place and place a cut mark carefully to indicate where you’ll need to trim. Be sure to measure your boxes so that you’ll know how deep to cut for each electrical box. 

 

 

 

For the electrical wires, place a slit in the back of the Rockwool insulation (without cutting all the way through), at the location where the wire is located, and gently wrap the Rockwool insulation around wiring. This allows the insulation to not disturb the wiring and prevents the wiring from not fitting properly.

 

 

 

For electrical wires, make a slit along the back of the insulation (after taking measurements to be sure your slit is perfectly aligned). Don’t cut all the way through. Bend the insulation slightly and place the electrical wires into the slit of the insulation. This will allow the wires to be buried safely in the insulation without getting in the way.

 

 

For any spaces between the studs that have light boxes or lots of electrical wires, cut out enough insulation in order to fit around the electrical and boxes so that the insulation will still fit. Watch the video tutorial for more help with this step.

 

STEP 3: Add Ventilation to Your Shed

I mentioned above about how to tell if your shed needs ventilation or not. It doesn’t have to be done at this step; it could be done sooner. This is when I added ventilation to my shed, though.

I decided on adding 2″ soffit vents spaced about every 24″ apart. I used soffit vents that have built-in insect screens ordered from Amazon. 

First, I drilled the holes with the hole saw attachment, added a bead of caulk around the edge of the soffit vent, and inserted the vent into the hole.

 

 

Installing Baffles for Ventilation

Hilarious, but for some time, I was calling these things “waffles.” HA! Nope, completely different.

Baffles are attached to the underside of a roof with staples to protect the fresh airflow coming in from the outside of the shed via the soffit vents. You don’t want your roof insulation blocking that air flow.

This is where the Arrow Fastener T50 heavy duty stapler (or the Arrow Fastener PT50 pneumatic stapler) comes in handy!

 

 

But first, I created some additional holes in the bays above the double top plate to allow for additional airflow. My shed isn’t built like a traditional construction on a new home, where there is an air gap between the overhang of the rafters or trusses.

My trusses stop at the edge of the double top plate, and the engineered wood wall meets the roof. Therefore, there really wasn’t a sufficient pathway of airflow. With these holes drilled at the same angle as the roof, the draft from the soffit vents should provide a good airflow! (At least, I hope!)

 

 

To keep the baffles in place, I used my Arrow Fastener T50 stapler with Arrow Fastener staples to attach it to the roof. 

 

 

Once the baffles were all in place, I used spray foam to seal around the cracks and gaps of the baffles so that air flow doesn’t escape through the sides. I want that airflow to continue up through the baffles to the ridge vent, where the hot air can escape in the summer and where cool air can flow in the winter.

 

 

STEP 4: Insulate the Shed Ceiling or Roof

For this step in insulating my shed, I chose R-30 insulation, which is a thicker insulation batt and will prevent more heat loss in the winter and will keep more heat out in the summer.

The ceiling batts are also a bigger pain in the butt to install, especially when doing it by yourself! Rockwool tends to be very crumbly so you have to carefully hoist over your shoulder and have a method of keeping it in place.

I found that stapling smaller sheets of plastic in place first and then sliding the thicker insulation batts into place worked incredibly well. It kept the batts in place until a larger sheet of plastic vapor barrier could cover the entire ceiling.

 

 

Insulating Around Recessed Lights

If your shed will have recessed lights such as mine, make sure they’re IC rated, which means “Insulation Contact” is allowed. Recessed lights can get hot with traditional bulbs and you don’t want to start a fire (by the way, Rockwool is fire-proof, but still….you don’t want to install the wrong can).

Many people are switching to LED lights, including the kind of lights that can simply be cut into the drywall after it’s been hung, and plopping them in that way.

(My light inserts will be LED, but the cans are traditional recessed cans).

Regardless, make sure the cans (if you install them) are rated “IC”.

STEP 5: Install a 6-mil Vapor Barrier

Not all insulation will require this step because many insulations have the vapor barrier built in (which is the paper backing on fiberglass insulation). Rockwool, however, requires a minimum of a 6-mil vapor barrier, which is a huge sheet of plastic that will cover the stone insulation’s walls and ceiling.

Here are the rules for using a 6-mil vapor barrier. Be sure to:

  • Overlap all your seams by several inches, and staple on the studs.
  • Cut out the plastic over the windows and electrical boxes.
  • Tape all seams with Tuck Tape so there are no gaps or airflow through the vapor barrier.

 

 

STEP 6: Cover All the Staples and Openings with Tuck Tape

As mentioned above, you don’t want to mix any of your conditioned space that will be heated and cooled with any air behind the vapor barrier in your walls or ceiling. 

To prevent this, tape around the electrical boxes, recessed lights, and any staples, including any holes or tears in the plastic, around electrical boxes, recessed lights, etc.

 

 

I’ll admit that I likely “over” taped, but I would rather have over-taped than to not tape enough. By the time I was done, it looked like I walked onto the set of Showtime’s Dexter New Blood. HA!

Around my workbench, that was the hardest because of the 2x4s. In fact, I did over-tape in this area because later, when the drywallers came to install the drywall, I ended up having to remove some of the tape that extended past where the 1/2″ drywall would be so that the tape wasn’t exposed. Not a biggie, but just be mindful of not using too many staples in places where staples may not be needed, especially if you’re using large sheets of plastic that can stretch across the width without needing to overlap another piece.

 

 

Save Money…Spent Time

Installing your own insulation in your shed isn’t impossible, but definitely plan to take longer than you think it will! I thought it would literally take no more than a week, but due to the unfamiliarity with the project, along with running into issues related to figuring out ventilation requirements (not to mention working alone), it took much longer than expected.

You will save money by installing your own insulation, but expect to spend time instead.

Total cost for the insulation was just under $1,400, not including the batts, foam, soffits, etc. I didn’t add up those expenses, but add another hundred or two, and the total cost to do my own insulation was about $1,500 – $1,600.

I had received a quote for about $2,300 for spray foam walls and a fiberglass insulated ceiling. I chose not to do spray foam because I didn’t want to breathe in any off-gassing for years to come.

Did I save money??

Meh–a little bit. But I did get what I wanted, which was Rockwool. It was a lot of work, though, especially with the added step of the vapor barrier. But I couldn’t be happier that I got what I wanted, and that I did it myself!

If your shed is smaller than my 16’x26′ shed, it will take less time and money, but you’ll feel just as proud. 😉

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