Metal Roofing Insulation: How-To’s + Tips

6 minutes Read

Level Edge Construction

Metal roofing is known for being a show-stopping roofing material. It’s quickly rising in popularity among home and business owners because it’s:

• Durable (lasting 50+ years) 
• Weather-resistant
• Aesthetically pleasing
• Low-maintenance
• Energy-efficient

Even though metal roofing is naturally energy efficient, the best way to ensure maximum efficiency is to install the proper insulation underneath your metal roof. Get the most out of your investment, and follow the tips below on metal roof insulation!

Why Your Metal Roof Needs Insulation

You’re probably familiar with the fact that your house and attic need insulation to keep temperatures regulated. But why would a metal roof need insulation? Well, believe it or not, almost all roofing structures need insulation, regardless of the material. Metal roofs are no different.

Insulation provides two main benefits:

• Energy conservation ⚡
• Reduced noise pollution ????

Insulation helps keep the temperature in your home regulated so that it stays warm in the winter and cool in the summer. Proper insulation is vital to keep energy bills low, reduce condensation buildup, and prevent ice dams.

Metal roofs are sometimes thought to be noisier than other roofing materials during rainstorms. While the actual difference is very minimal and oftentimes not noticeable at all, proper insulation will ensure noise levels stay low on your metal roof.

3 Most Common Metal Roof Insulation Options

Okay, so you need insulation for your metal roof. But what kind should you choose? There are many types of insulation, but spray foam, fiberglass batts, and rigid board insulation are the most common roof insulation options.

Let’s take a closer look at the differences between each option, including price ranges and pros and cons.

1) Spray Foam: Best for Existing Roofs

Spray foam insulation is mixed with water and is quite literally sprayed on with high-pressure spray machinery. When it interacts with the oxygen, the water dries up, and the polyurethane foam expands, hardens, and cures within mere minutes. The end result is thick, firm foam (not soft, squishy foam like foam soap).

✅ Spray Foam Pros:

• Great for insulating awkward or tricky areas since it’s self-adhering.
• Can be installed on old roofs without the need for a total re-roof.
• Easy to work with and successful at preventing condensation and pest infestations.

❌ Spray Foam Cons:

• Not suitable for DIY installations, so it should be left to a professional contractor.

Spray foam comes in both closed-cell and open-cell applications. Open-cell is less expensive (44-65 cents per board foot) but isn’t as effective, so it should only be used in regions with mild weather. Closed-cell is a little more expensive ($1-$1.50 per board food), but it’s more effective at dealing with extreme temperatures.

2) Fiberglass Batts: Lowest Upfront Cost

Fiberglass batts are probably what first comes to mind when you think of “insulation.” Also called batt and roll insulation, this type is incredibly popular due to its low upfront cost of 12-60 cents per square foot.

The material is made up of fine, thread-like glass formations that are woven together. The threads are mixed with other materials, forming a thick insulating pad. It’s commonly seen in a pink or yellow color, and you can unroll the sheets to install them.

✅ Fiberglass Batts Pros:

• Affordable and easy to install.
• It can be cut to the size you need.
• It can be placed underneath an existing roof in the attic.

❌ Fiberglass Batts Cons:

• You must wear protective gear when installing because the micro-pieces of glass can damage your hands, eyes, and lungs.

3) Rigid Board Insulation: Best Performing

Rigid board insulation is made from polystyrene or polyurethane, and it comes in panels of various sizes. It’s a more condensed, firm board compared to fiberglass batts. This insulation is very effective for roofs, walls, and foundations.

✅ Rigid Board Pros:

• This insulation offers maximum thermal resistance when the sheets are caulked together.
• Since the material is thinner and denser, there are usually fewer gaps between sheets, which improves energy performance.

❌ Rigid Board Cons:

• Rigid board insulation is the most expensive option at $4-$7 per square foot.
• Requires a professional installation to ensure the joints are sealed properly.

How to Install Insulation on a New Roof

Installing new roof insulation is easiest during an existing roof replacement project. During a re-roof, your installation team will follow these steps using rigid foam insulation (or the other insulation of your choice):

• Install the plywood roof deck, which acts as structural sheathing.
• Lay the ice and water shield (roofing felt) to protect against moisture.
• Install rigid foam insulation over the entire roof surface. The sheets should be right next to each other but not overlapping.
• Use duct tape or caulk to seal the seams between insulation sheets.
• Install the metal roofing panels over the insulation.

Please, for your safety, don’t attempt a total roof replacement by yourself unless you used to be a professional roofing contractor. ????

How to Apply Insulation to an Existing Metal Roof

So, you already have a metal roof in place, but you want to improve your insulation. Thankfully, you can still add insulation without replacing your entire roof. You’ll need to use spray foam or fiberglass batts for this project.

• Go into your attic and look for the plywood underside of your roof.
• Place fiberglass batts into any gaps between the sheathing and purlins. (Purlins are small horizontal wooden frames.)
• Fiberglass insulation is less effective if packed too tightly, so it should only be installed if it can fit loosely into places.
• Alternatively, you can spray foam insulation into gapped areas.

A professional contractor should always handle spray foam and fiberglass insulation! If you want to DIY this project, opt for rigid foam sheets instead. It’ll cost more upfront, but you can cut the sheets to size and fasten them with staples. Just keep in mind that they likely won’t be as effective if they aren’t installed by a professional.

Leave Metal Roofing to the Experts!

We hope this metal roof insulation guide taught you a thing or two about the importance of roof insulation and the options you have. If you’re thinking of getting a new metal roof, be sure to contact the professionals here at Level Edge Roofing! Not all roofing contractors have the expertise to properly install metal roofs, but the Level Edge team does.

We’ll make sure your new metal roof is properly insulated during the roof replacement process. Reach out today for a free consultation!

Written by
Level Edge Construction