Does Insulation Make Your Home Overheat?

Is your insulation secretly the reason your home keeps getting so hot this Summer? 

The simple answer is no.

The complicated answer is also no, but with the caveat that your insulation could probably be doing more to help keep your home from getting so hot in the first place.

There is, however, quite a bit of context that we’re missing with both of those answers. So, before we can really get into it, let’s pull back a bit and start by clarifying something that people are often unclear on: what insulation does.

So…

What Does Insulation Actually Do?

In simple terms, insulation is all about separating the temperature in your home from the temperature outside of it. At it’s core, insulation’s job is to keep your home comfortable, regardless of what’s going on outside of your home.

The thing is, heat naturally wants to spread itself out as evenly as possible. It’s a fundamental law of nature.

So, when you create an area with a significantly different temperature to the area around it — a warm house in winter, for example — then the heat in that area will want to start spreading out. And the bigger the temperature difference, the faster this process happens.

Of course, that’s a huge problem for anyone who wants a toasty warm home in the cold of winter, or a refreshingly cool home in the summer heat. You’d have to pour huge amounts of energy into your home to bring it to those comfortable temperatures.

Then you’d have to keep pouring energy into keeping things comfortable as those massive heat differences you’ve just created try to equalise themselves with the temperatures outside your home.

Fortunately, this is where insulation comes in. It’s job is to make it harder for heat to “move” through a space. In other words, good insulation resists the transfer of heat from one place to another.

Why?

Because, by making it harder for heat to move through a space, you make it much more energy efficient to make a space comfortable and, much more importantly, you make it much easier to keep a space comfortable too.

After all, when it’s harder for heat to move, it takes much longer for those temperature changes to equalise. Letting you keep those spaces warm in winter, or cool in summer, for much longer without needing to put more energy into it.

That’s why, when we’re talking about “good” insulation, we tend to think of it in terms of how well it resists the movement of heat. Because, fundamentally, the job of good insulation is to slow down the speed at which the temperature differences between the inside and outside of your house (or any insulated space, really) are able to equalise.

So, now that we’ve got a better understanding of what insulation is actually doing, we can turn our attention to answering our next question…

Why Is Your House Getting Hotter?

If insulation is designed to help keep the temperature outside of your home from being affected by the temperature outside of your home, then why does your home get so hot during the summer months?

Is insulation just better at keeping heat in than it is at keeping it out?

That’s actually not too far from the truth of what’s most likely making your home so hot in the summer. But let’s not get ahead of ourselves, and instead let’s take a clear-eyed look at the main difference in what you need from your insulation during winter and summer.

During the Winter, you want your home to be warmer than the temperature outside, and during the Summer, you want your home to be cooler than the temperature outside.

It might not seem like a big thing, but there’s actually a whole lot of difference between how people deal with being too hot vs how we deal with being too cold. However, even before we get into those differences, there’s a hidden aspect to how insulation works that does actually work against your insulation in the summer.

Solar Gain.

So, that brings us to a pretty important question: what the heck is solar gain?

Well, to answer that we need to take another look at how insulation blocks heat from moving.

How Heat “Moves”

Something most people know but don’t think about all that often is that there are three main ways that heat “moves” from one place to another: conduction, convection, and radiation.

For insulation to be able to do its job properly, it’s got to be able to handle all three forms of heat loss, and to understand why that’s difficult, we’ve got to take a quick look at how each of these forms of “movement” works.

To do that, you’re going to need to imagine a freshly brewed cup of tea (or coffee, if you’d prefer).

• Conduction is the process of heat moving through solid objects, and it’s how you feel the heat of the tea when you hold the cup.
• Convection is the process of heat moving through fluids and is the reason you feel the heat of your tea when you sip it. It works very similarly to conduction, but it’s also the reason why you can feel heatin the air around your tea (air is a fluid, trust us on this one).
• Radiation is the process of heat moving through radiation, and it’s part of the reason why your cup of tea will still go cold in a thermos. Heat moving in this way is often called “Radiant Heat”.

Now, as you’ve probably noticed already, two of those are pretty notable forms of heat transfer; that’s no accident. You see, conduction and convection are pretty direct forms of heat loss, and pretty much amount to “heat transferring by bumping into things”. 

Radiant heat, on the other hand, is pretty subtle. You’re unlikely to notice it directly, but that doesn’t mean you won’t notice the effect it has. Your tea will still go cold in a thermos, after all, even if it takes longer.

The Issue with Ignoring Radiant Heat

In most cases, conduction and convection are going to account for the vast majority of heat loss, since in most cases radiation is a comparatively minor way for heat to move away from most materials.

Because of that, most traditional forms of insulation elected to focus on preventing conduction and convection, without worrying too much about radiation because it was a much less significant portion of heat loss.

However, there is at least one kind of radiant heat that you can always expect to have to deal with in your home: sunlight. At it’s core, all light is just radiation, and sunlight is no exception. 

In fact, sunlight is made up of a bunch of different kinds of light. The kind we notice the most tends to be visible light, but you don’t need me to tell you that sunlight is warm.

That’s radiant heat. And since there’s so much of it in sunlight, we actually have a specific name for a space getting heated up by sunlight: solar gain.

So, what happens when you combine the fact that most forms of insulation aren’t designed to block radiant heat with the fact that, aside from sunlight, radiation is a relatively rare way for heat to move?

That’s right, you get a situation where your home gains a bunch of heat thanks to solar gain during these nice, long and sunny summer days, and then won’t let it back out because insulation is designed to stop heat from moving in or out of your home.

As you can see, it’s not the insulation that makes your home overheat in the summer, it’s incomplete insulation allowing solar radiation into your home, and not letting that same heat escape through conduction or convection, which is how most materials in your home will primarily work to let that heat out.

Okay, so with all of that being said, that still leaves us with an important question to answer…

What Can You Do To Keep Your Home Comfortable All Year Round?

Let’s start with the answer you’re no doubt expecting, and then we can get into some other things that you might want to to try out too.

Solution 1: Get Reflective Insulation

The single best thing you can do is to invest in a high-performance insulation product designed to protect against every single form of heat transfer. Something like our multifoil insulation products, which include high-quality radiant barriers, to ensure that your home isn’t simply getting baked by solar gain all summer long.

What’s more, these products are also ideally suited to help keep the heat you’re paying for from escaping your home in the winter, ensuring that the warmth you’re creating with your radiators is keeping you cosy, rather than escaping out into the winter chill.

Of course, a major insulation upgrade isn’t something to be done lightly, which is exactly why we offer free expert consultations with our world-class team. If that sounds like something you’d be interested in, all you need to do is book a discover session here.

Solution 2: Protect Your Home from Solar Gain

Since solar gain is likely one of the main culprits behind your overheating issues, a great way to solve the problem is to take steps to combat some of the worst sources of solar gain — especially if you aren’t going to invest in a reflective insulation solution like multifoil insulation.

So, where are the worst sources of solar gain?

It’s simple: any part of your home where there’s plenty of glass to allow sunlight in. For most homes, that’s going to primarily be windows and doors, although anyone with an conservatory will be more than familiar with how hot they can get too!

What can you do to protect against solar gain in these spaces?

The best thing you can do is to get a reflective covering, to both block the light out and reflect that radiant heat away from your home. Our Window Reflector Kits are designed to do the job perfectly, but pretty much anything that can block and reflect sunlight would do just fine.

Solution 3: Stop “Letting The Heat Out”

We mentioned earlier that people naturally try to deal with being overhot differently from how they try to deal with being too cold, and one of the biggest examples of that is the idea of “letting the heat out”.

People naturally want to open doors and windows in their home to let the heat out, or to let a breeze in. But that’s one of the worst things you can do when it’s hot outside. 

Why? Because heat wants to equalise!

Like we explained earlier, heat doesn’t move around at random. It always, always, always tries to equalise with the spaces around it. So, what happens when you open up your home to let the heat out? You get the exact opposite, and the heat from outside your house starts bleeding its way into your nice cool home.

The only time that opening your home up like that will work to cool things down is when the inside of your home is hotter than the outside. So before you open up your home, take a step outside and see if you’re going to be letting the heat in, rather than out.

Check Out Our Video On The Topic!