Is Foil Insulation Any Good?

You may well have heard plenty of opinions about foil insulation, covering a range of topics, terms, thoughts, and tips. However, there is one question that stands above the rest…

Is it any good?

And it’s no surprise that this is such an important question to ask. There is no point in wasting your time learning anything else about a product if it isn’t any good. So, we’d like to take a crack at answering this question for you. But before we go any further, let’s address the elephant in the room shall we?

As the UK’s leading manufacturer of multifoil insulation, it’s pretty obvious where we stand on the question of foil insulation. So aren’t we going to be too biased to answer this question properly?

That’s a fair question, and we understand why you might be skeptical. But here’s the thing. We truly believe in our products and what they can do for our customers. So we aren’t interested in trying to trick you into believing foil insulation is something it’s not. In fact, we freely admit that Foil Insulation isn’t going to be the best choice for everyone, and we don’t want to waste your time (and ours) if it isn’t the right fit for you.

Instead, we want to help people learn more about what our products can do, so that they can make the best choice for them when the time comes. And we believe the best way to do that is to be open, up-front, and informative about every aspect of foil insulation. That being said, let’s get back to the question at hand. Is foil insulation any good?

The short answer is yes.

But, since you’re already here, let’s go all in and dive into the long answer…

Radiant Barriers

At it’s core, a radiant barrier is a layer of reflective material designed to specifically reflect thermal radiation.

Generally, radiant barriers are extremely thin, often being made from a single layer of foil and measuring only millimetres in thickness.

The role of a radiant barrier is simple, to protect against radiative heat loss, which is why their reflective nature is so important.

Given that radiation is an element of heat loss that is far too often ignored in traditional insulation solutions; radiant barriers are often seen as a way to quickly provide a significant boost to the thermal performance of a structure.

However, this also means that they are rarely considered a “complete” solution in and of themselves. Rather, radiant barriers tend to be considered an additional product, one that is beneficial to include but is ultimately only part of a full solution.

Foil-Backed Insulation

Foil-Backed Insulation, Foil-Lined Insulation, Foil-Faced Insulation. There are plenty of names for this kind of product, but they all amount to the same thing.

A “traditional” insulation product (such as Mineral Wool or PIR Boards) with an integrated foil layer attached. In essence, this is meant to combine the benefits of a Radiant Barrier with the performance of a traditional insulation product.

There is a strong argument to be made that this isn’t so much it’s own type of insulation, but rather a combination of a Radiant Barrier with another kind of insulation. But we’ll leave it up to you to decide whether this is or isn’t it’s own type of Foil Insulation…

Distinct type of Foil Insulation or not, however, these products make a lot of sense on paper. After all, one of the biggest weaknesses of most traditional insulation products is their complete lack of protection against radiant heat loss. That weakness is very neatly countered by Radiant Barriers, with very few drawbacks.

Of course, the devil is in the details for innovations like this. We’ve seen some excellent implementations of this concept, but we’ve also seen plenty of the opposite too. But, as we mentioned earlier, we’ll dive into proper analysis of these products a little later on. For now, let’s take a look at our last type of Foil Insulation…

Multifoil Insulation

As the name suggests, multifoil insulation is made using multiple layers of foil, which are then combined with layers of wadding to create a product that brings the benefits of both materials together into a single, high-performance product.

This means that multifoil, much like foil-backed insulation, provides comprehensive thermal performance by protecting against all forms of heat loss in a single, high-performance product.

The foil layers of multifoil act as radiant barriers, protecting against heat loss through radiation. At the same time, the wadding layers act in the same way as “traditional insulation” providing high-quality protection against heat loss through conduction and convection.

The complexity of this combination design is both a benefit and a drawback for multifoil as a product; providing it the capacity to provide the kind of performance and range of benefits that would normally only be possible by using multiple products, but requiring a more complicated and technical manufacturing process as a result.

However, before we dive too deeply into the strengths and weaknesses of multifoil as a product type, let’s return to the question at hand…

But Are They Any Good?

Now that we’ve taken the time to clarify exactly what we’re talking about, we can come back to the crux of the matter.

Is Foil Insulation any good?

It’s a pretty subjective question, but that doesn’t mean we can’t take a stab at answering it. So, let’s start by clarifying what makes insulation “good” in the first place…

• Performance: How well does it prevent heat transfer?
• Space: How much space does it require, and how efficiently does it use that space?
• Versatility: How easily does it adapt to the needs of varied projects?
• Ease of Installation: How straightforward and simple is the install process?
• Value for Money: Do the benefits justify the cost?

Now that we have a quick and cheerful criteria for what makes “good insulation”, let’s take a look at how our different types of Foil Insulation stack up against that criteria…

A Quick Note About Our Assessment of Foil-Backed Insulation:

A LOT of the performance of Foil-Backed Insulation will depend on the product the foil is attached to. For the purposes of this post, however, we’re going to be taking a look at the impact of just the integrated Foil Backing itself.

If you’d like to see a comparison that takes the performance of “traditional insulation” products into account instead, then we’d recommend taking a look at this post…

Radiant Barriers:

Radiant Barriers are an excellent addition to the performance of any insulation project, as they provide reliable protection against a form of heat loss that is often left unchecked by the majority of traditional insulation solutions.

As a result, Radiant Barriers can provide a significant boost to thermal performance. However, they do have a key limitation in that Radiant Barriers only provide significant protection from thermal radiation.

This means that they must rely on other products to provide protection from conductive and convective heat loss, making Radiant Barriers incapable of “comprehensive” thermal performance.

While Radiant Barriers absolutely provide a big boost to performance, we felt that their inability to protect against two out of the three forms of heat loss meant that we couldn’t give them more than half points; which is why we ultimately decided on a score of 2.5 stars for performance.

Foil-Backed Insulation:

Overall, the benefits provided by the foil in Foil-Backed Insulation will be extremely similar to those provided by a Radiant Barrier, which may leave you wondering why we’ve knocked a full star off of the score for these products.

Well, the unfortunate reality is that Foil-Backed Insulation will absolutely provide a worse performance than a traditional Radiant Barrier, even when installed flawlessly. This difference in performance comes down to one simple factor: air gaps.

You see, to provide the best possible performance, reflective insulation must be installed with appropriate Air Gaps on either side of the product. We cover the reasons for this in more detail in this blog post, but the relationship between the performance of a Radiant Barrier and the inclusion of appropriate air gaps is the core of the issue with the performance of Foil-Backed Insulation.

After all, because the foil in this insulation is directly attached to the insulation product, regardless of what that product might be, it cannot perform as well as it would if it was installed with an appropriate air gap. In short, the thermal performance of the foil is inherently undermined in Foil-Backed Insulation. And that is why we’ve given it just one and a half stars. It’s better than having no protection against radiant heat transfer, but ultimately worse than pretty much any other form of reflective insulation.

Multifoil Insulation:

Multifoils is, in many ways, the ideal combination of “traditional” insulation and modern reflective insulation.

Its layered structure, including both foil and wadding layers, allows it provide comprehensive thermal protection to keep all forms of heat transfer in check.

It can (and should) be installed with appropriate air gaps to maximise its protection against radiant heat transfer, while still providing a high-level of insulation against direct heat transfer via conduction and convection.

What’s more, these insulators will often also provide the same additional benefits that Radiant Barriers can provide, allowing them to provide even more performance beyond the realms of just thermal insulation. All together, there really isn’t an element of performance where multifoil is lacking, which is exactly why we gave it five stars out of five.

Multifoil Insulation:

Compared to the vast majority of traditional insulation solutions, multifoil is an incredibly slim product; especially given the sheer amount of benefits it manages to provide in the limited space that it uses.

However, to deliver the performance and range of benefits that multifoil products do, they end up having to use far more space than the other kinds of foil products require. So, while they deliver impressive space-efficiency in terms of insulation as a whole, in terms of foil insulation it’s clear that there are products that take up far less space. And that’s why we went with four out of five stars.

Radiant Barriers:

Lightweight and highly flexible, Radiant Barriers are able to adapt to meet the needs of pretty much any insulation project, which makes them an incredibly versatile insulation product.

What’s more, many Radiant Barrier products are designed to provide additional benefits, which you would normally need to rely on additional materials for. For example, many Radiant Barrier products act as Vapour Barrier products, as well as reflective insulation, extending the versatility of these products beyond a question of just flexibility and into the benefits that they provide as well!

The only real “issue” with their versatility is the fact that they require air gaps to provide their maximum performance. This is true of any reflective insulation product, of course, but it does put a slight limit on how you can use a Radiant Barrier. That slight restriction is why we decided to knock half a star off of this score.

Foil-Backed Insulation:

Zero stars might seems a little harsh, but there really is no other option when you consider the fact that the foil in these products is integrated directly into the insulation it comes with.

Not only does that keep you from installing the foil in any way that wouldn’t suit the insulation it’s attached to, but it also actively undermines the performance of the Radiant Barrier (as we’ve already mentioned). Given all those issues, we thought that zero stars was the only way to go.

Multifoil Insulation:

The flexibility and light weight of multifoil makes it incredibly versatile as an insulation option, in much the same ways as Radiant Barriers. As does the capacity of multifoils to provide the benefits of vapour barriers and other additional products, just like a Radiant Barrier can.

However, despite their many similarities in terms of versatility, there are a couple of key differences…

1. Multifoil products are, of course, substantially thicker than most Radiant Barriers, many of which are less than a millimetre thick.
2. On the other hand, multifoil insulation is able to provide comprehensive protection against all forms of heat loss, while radiant barriers are only equipped to handle one of three.

Considering all of these factors together, we felt it was fair to say that multifoil insulation is every bit as versatile as a Radiant Barrier product, which is why we’ve given this a score of four and a half stars as well.

Radiant Barriers:

Radiant Barriers are incredibly light and highly flexible. They can be securely installed with zero professional equipment. What’s more, the process of installing a Radiant Barrier is both incredibly straightforward, and well-documented should you require clear guidance.

In fact, the only real negative point when it comes to installing Radiant Barriers is that their need for air gaps does add an additional layer of complication to an otherwise very simple process.

All together, we thought that four and a half stars is a solid reflection of the straightforward, simple installation process you can expect from a Radiant Barrier.

Foil-Backed Insulation:

This is the flip side of the versatility issue. These foil layers are integrated directly into the product, which means there is no installation required. We were on the fence about it, but ultimately decided that installing a product can’t get any easier than doing nothing at all, which is why we gave this the full five out of five stars.

Multifoil Insulation:

Just like Radiant Barriers, the flexibility and light weight of multifoil insulation make it an extremely easy material to install, particularly since you don’t need professional tools to install multifoil. And, just like Radiant Barriers, it is true that the need to include air gaps does add a slight layer of complication to the install process.

However, the reason why we’ve gone with four stars for multifoil’s “Ease of Installation”, rather than the four and a half that we gave to Radiant Barriers, is because there is simply more to handle with multifoil insulation.

Multifoil insulation is obviously incredibly slim in comparison to almost any other form of insulation. However, it is hard to compare to the incredibly thin nature of a single Radiant Barrier. That difference in thickness, along with the need to consider the internal wadding layers of multifoil when cutting and sealing the product, makes it just a bit more complicated to install than your average Radiant Barrier.

Of course, this kind of insulation is still incredibly simple and straightforward to install — even if it’s technically easier to install a Radiant Barrier — which is why it’s still at 4 stars out of five.

Radiant Barriers:

Radiant Barriers do provide a fair bit of high-quality (and highly needed) performance to the projects that they are used in. Not just in terms of protection against radiative heat loss, but also thanks to their additional benefits, such as vapour control.

However, they are fundamentally limited in terms of their thermal performance. They will never be able to provide total, comprehensive protection and that does limit their value somewhat.

In short, we felt that 3 and a half stars was a good way to present the impressive value of Radiant Barriers, while also reflecting the fact that they do leave room for improvement in several areas.

Foil-Backed Insulation:

While these products certainly have their issues when it comes to performance and versatility, you can’t deny that they do provide the value of a Radiant Barrier to a product that would otherwise do nothing to prevent heat loss through radiation.

That being said, the performance and versatility issues with this kind of foil insulation means that the value being provided is unfortunately (and dramatically) limited, which is why we decided to give Foil-Backed Insulation one and a half stars out of five.

Multifoil Insulation:

When it comes to sheer value, it’s hard to find an insulation product that provides more than multifoil insulation. They provide comprehensive thermal performance, outstanding space efficiency, practically unparalleled flexibility, and plenty of additional benefits (including several that normally require the use of additional products, such as a vapour barrier).

However, the modern nature of multifoil insulation does come with a handful of drawbacks. The complexity of these products along with their relatively niche usage does make it harder for many insulation professionals to simply pick up and use. What’s more, their composite nature does also make it somewhat harder (and therefore more costly) to manufacture than some “traditional” insulation products.

That being said, the sheer amount of value being provided by multifoil — across pretty much every area that matters — more than makes up for the slight increase in price and complexity. Particularly given that multifoil manufacturers make an effort to provide clear, understandable guides on their usage. With all of this in mind, we determined that 5 stars made the most sense for this score.

The Verdict

So, now that you’ve seen how we’ve scored each kind of foil insulation and why we’ve given them the scores we have, let’s close everything off with an answer to our big question.

Is Foil Insulation Good? Yes. When used appropriately, each type of foil insulation has the potential to provide a solid benefit to your insulation projects.

Ultimately, however, the answer is always going to depend on the needs of your project. So, why not grab one of our FREE Sample Packs and you can tell us if foil insulation is a good fit for your project…

Finally, if you enjoyed this post and you’d like to see more like them, then the best way to make sure you know when we post new content like this is to Join Our Mailing List which you can do by filling out this quick form…