A garage ceiling can be insulated using several types of insulation materials. If you’re having a hard time wrapping your head around which ones, rest assured, you’ve come to the right place. In this article, we compared 14 different materials based on their thermal characteristics. 

So not only will you find the most insulating materials, but you’ll also find those that are most compatible with the insulation method that you may want to carry out at home. 

How to Choose the Best Insulation Material for a Garage Ceiling 

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To figure out which insulation materials are best for a garage ceiling, we looked at 14 different materials based on the following 5 thermal characteristics:

• Thermal conductivity (K-value)

• Thermal resistance (R-value)

• Diffusivity

• Effusivity

• Thermal lag (in hours)

Before we get ahead of ourselves, here’s a list of the best garage insulation materials:

Now, let’s take a closer look at the different insulation material values:

R-Value (for an 8-inch thickness)

An R-value stands for a material’s thermal resistance coefficient and is based on two factors:

• Thickness

• Thermal conductivity

A material’s thermal conductivity is quantified by a numerical value, and the lower that value is, the better the material’s insulation properties are. However, thermal resistance, measured by the R-value is quite the opposite: the higher the R-value, the better the insulation performance.

Thermal Diffusivity and Effusivity

Thermal diffusivity and effusivity are significant thermal properties to consider when choosing an insulation material meant for a garage ceiling. By selecting a material with decent thermal properties, you’re in turn ensuring that your garage is efficiently insulation and safeguarded.

Thermal diffusivity

Thermal diffusivity is a material’s capacity to transmit heat through conduction. An excellent thermal diffusivity is typically indicated by a value below 0.2, whereas a value exceeding 1 is considered exceptionally poor. 

Thermal effusivity

As for thermal effusivity, it indicates a material’s ability to transmit heat through radiation. The lower the effusivity coefficient, the better the insulation material is.

As such, a value above 1,000 suggests poor insulation capabilities in a material, while a value below 35 indicates excellent insulation properties.

Thermal Lag

Thermal lag refers to the time period (delay) during which an insulation material can inhibit heat transfer.

What are the best materials to insulate a garage ceiling?

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Polyurethane made from the latest technology and extruded polystyrene are, without a doubt, the best materials to insulate a garage ceiling. However, if you’re looking to solely use eco-friendly materials in your home, cork is your best bet. 

Learn more about the best garage ceiling insulation materials down below.

Polyurethane panel or polystyrene panel? 

It all depends on the quality of the polyurethane material. If you come across polyurethane with a thermal conductivity of 0.026 rather than 0.035, it indicates that it’s a cutting-edge polyurethane technology; it’s more efficient than a polystyrene panel.

Otherwise, polystyrene will be a way better insulation material. Moreso because you can choose extruded polystyrene, or even better yet, expanded polystyrene. 

Polystyrene and polyurethane panels have the added bonus of being aesthetically pleasing, while also cutting back on drywall use.

Rockwool 

Mineral wools are far from the most efficient insulation, but they do have one significant advantage: their flexibility.

It isn’t uncommon to see piping snaking through a garage ceiling. Therefore, rockwool is the perfect material. Since it’s very malleable, it can easily be slipped between pipes. 

As a result, you won’t need to install drop ceiling tiles to properly insulate your garage, which turns into significant space gain.

Vapour barrier 

A vapour barrier is a must if your garage happens to be below a living space. Typically, the vapour barrier will be a part of the living space's flooring insulation system. 

Cork

As we’ve already mentioned in the first part of the article: cork is an excellent insulation material for green homes. It ranks just below polyurethane and polystyrene.

However, cork has two issues:

• Requires installing drop ceiling tiles

• Isn’t made for winter

Therefore, if your garage ceiling is rather low, cork may not be the best insulation material. Generally speaking, in Quebec, where winters are quite harsh, cork doesn’t typically hold its own. 

As a matter of fact, while it does have an exceptional thermal lag in terms of heat, its thermal conductivity and resistance (R-value) are deemed average. 

How to DIY a Garage Ceiling Insulation

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There are three methods used to install insulation material on a garage ceiling:

• Glue/screws

• Drop ceiling (drop tiles or self-supporting membrane)

• Spray

You can base your decision on:

• Your preferred method

• The height of your garage

• The insulation material you’ve selected

For example, should you decide to opt for a spray-in method, polyurethane is your only option. Whereas, with a drop ceiling, you can use mineral wools, polystyrene, or polyurethane. 

However, using the glue/screw method, for which the polystyrene panels are typically preferred, you’ll lose a significant amount of height in your garage.  

Concrete Garage Ceiling Insulation Tips 

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Favour the following three insulation materials: 

• Polyurethane insulation panels

• Extruded polystyrene insulation panels

• Cork

If you’re not comfortable using the glue/screw installation method, note that a concrete garage ceiling can be insulated using spray polyurethane foam.