Shed wall insulation usually starts with good intentions — and ends with itchy arms, blown budgets, or half-finished wall cavities.
Most DIYers struggle with the same questions: what’s affordable, what’s easy to install, and what actually holds up over time.
That’s exactly why we put this insulation comparison together.
In this article, we break down three popular shed wall insulation options — fiberglass, Rockwool, and spray foam — and compare them based on real-world cost, installation, and performance.
We also have a Free Shed Insulation Guide that walks through insulation as a complete system (walls and ceiling), that you can reference as you go.
What This Article Covers
- Real-world pros and cons of fiberglass, Rockwool, and spray foam for shed walls
- Cost comparison based on actual material coverage
-
R-value comparison of each insulation option
- Which option we ultimately chose, and why
The Three Shed Wall Insulation Options Tested
We compared three popular options side-by-side in the same shed wall cavities:
- Fiberglass (R-13)
- Rockwool (R-15)
- Spray foam (Great Stuff and Stanley Kit)
Let's look at how they stacked up.
1. Fiberglass Insulation (R-13)
Fiberglass is the most common shed wall insulation — and the cheapest.
We used standard R-13 fiberglass batts, sized for 2×4 walls. Installation is straightforward: cut to length, press into the cavity, and keep the batt flush with the stud face.
Pros of Fiberglass
- Lowest upfront cost
- Easy to find at any home improvement store
- Simple to cut and install
Cons of Fiberglass
- More prone to mold
- Easy to over-compress (which reduces R-value)
- Gaps around wiring are common
Fiberglass can work well, but only when installed carefully and paired with a solid strategy to mitigate moisture.
2. Rockwool Insulation (R-15)
Rockwool is becoming increasingly popular for shed builds, and after testing it, we see why.
The batts are dense, rigid, and friction-fit tightly into the wall cavity. We installed two 48-inch batts per bay with minimal cutting.
Unlike fiberglass, Rockwool doesn’t itch, doesn’t slump, and is far more forgiving during installation.
Pros of Rockwool
- Higher R-value than fiberglass (R-15)
- Naturally moisture resistant
- Better sound dampening
- Easier to work with (no itching or slivers)
Cons of Rockwool
- Costs roughly twice as much as fiberglass
Even with the higher price, Rockwool holds its shape, resists moisture, and maintains performance over time. Totally worth it.
3. Spray Foam Insulation (Great Stuff & Stanley Kits)
Spray foam insulation sounds great on paper: air sealing, high performance, and no batts to cut — just spray and you're done. But not so fast...
We tested two popular options — Great Stuff and a Stanley kit — and what we discovered was surprising.
Spray Foam Test Results (All Cons)
- Coverage was far less than advertised (two cans barely filled half of one wall bay).
- Foam thickness averaged only 1 to 1½ inches.
- Application consistency was difficult.
Even with careful spraying and proper surface prep (including wetting the sheathing), both kits struggled to deliver consistent coverage.
Cost Reality Check: A Huge Difference
When broken down by 32 square feet:
- Fiberglass: $18
- Rockwool: $40
- Great Stuff spray foam: $120
- Stanley spray foam: $150
At those prices, spray foam is simply not practical for most sheds.
Shed Wall Insulation R-Value Comparison
R-value measures how well insulation resists heat flow. The higher the R-value, the better the insulation performs.
Here's how the wall insulation types compare:
- Fiberglass: R-13
- Rockwool: R-15
- Great Stuff spray foam (2 in.): ~R-8
- Stanley spray foam (2 in.): ~R-12
R-values can vary widely by region. If you're in a colder climate, you may need higher R-value in your shed.
Which Shed Wall Insulation Did We Choose?
After comparing performance, cost, moisture resistance, and ease of install, we crowned our winner:
Rockwool Insulation.
Here's why:
- It's mold resistant
- No fiberglass itch
- Higher R-value
- It cuts easily and friction-fits into place
For a shed being converted into an office, workshop, or studio, those advantages outweigh the higher upfront cost.
Watch our Shed Wall Insulation Comparison Video on YouTube to see why we decided on Rockwool.
One Critical Shed Insulation Step Most People Skip
Before you get started on your shed wall insulation, take a step back and analyze your shed's ventilation.
Ventilation (which affects your ceiling insulation setup), should always be addressed first.
If you haven’t already, read our article on shed ceiling insulation before finalizing your wall insulation choices.
FAQs: Common Shed Wall Insulation Questions
Can I use fiberglass in a shed?
Yes. Fiberglass is budget-friendly and works well when installed carefully and kept dry.
Is Rockwool worth it?
Absolutely. It’s easier to work with, resists moisture, and holds performance over time.
Are spray foam cans good for insulating stud bays?
No. They’re expensive, inconsistent, and better suited for sealing small gaps — not full wall cavities.
Should I insulate my shed if it’s only used for storage?
It's usually not worth it. Instead, we recommend sealing gaps and using a quality heater for occasional heat.
Conclusion: Choosing the Best Shed Wall Insulation
When it comes to shed wall insulation, there’s no one-size-fits-all, but there are clear tradeoffs.
- Fiberglass is the most budget-friendly option and can work well when installed carefully. But it’s less forgiving if moisture or air leaks become an issue.
- Rockwool costs more upfront, but it’s easier to install, resists moisture, and holds its performance over time. This is why it’s our top choice for shed insulation.
- DIY spray foam kits promise convenience, but once you look at real-world coverage and cost, they’re hard to justify for most shed projects.
Insulating shed walls is absolutely something a DIYer can tackle. With the right insulation plan and attention to detail, you can dramatically improve comfort in your shed, and avoid common mistakes.
To learn more, our Free Shed Insulation Guide is a great reference on wall insulation options and ceiling insulation strategy, with real-world examples and resources.
And if you're in the planning phase of your DIY shed, check out Premium Shed Build Plans for a complete step-by-step guide, including the ideal framing and ventilation setups for insulation.
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