fbpx
Home / How Does Low-E Reflective Insulation Work?

How Does Low-E Reflective Insulation Work?

We have put this blog together to help answer some of our most frequently asked questions about how reflective insulation and Low-E Insulation works. If you have any questions about using Low-E in a specific application, please get in touch.

Low-E Reflective Insulation is a very simple, very effective material that is it also easy to work with, made from recycled material, safe to handle, has no airborne fibres and is class 1 fire rated.

Low-E Insulation is not designed to replace all other insulation materials on the market. It is designed to reduce life cycle running costs, provide moisture protection, stops draughts, deaden sound but most importantly, to tackle issues which are usually left unaddressed by traditional bulkier insulation products.

If you would like to learn more about Low-E Insulation and see it compares to other reflective insulations and traditional insulation you can read our blog opposite

How does Low-E Insulation compare?

Some of the most common questions we get asked are; 

How does foil insulation work?

What is Emissivity?

Why is foil different from traditional insulation? 

Does foil insulation have an R-value? 

How do Airspaces work?

Are airspaces important?

Some of the most common questions we get asked are; 

How does foil insulation work?

What is Emissivity?

Why is foil different from traditional insulation? 

Does foil insulation have an R-value? 

How do Airspaces work?

Are airspaces important?

How does foil insulation work?

The first questions we need to ask is – Why Do We Insulate? 

Most people believe that we simply insulate to keep warm. In fact, we insulate for many reasons including comfort

– Airtightness
– Moisture control
– Thermal efficiency
– Reduce running costs

There is more to insulation than just retaining heat but before we talk about thermal efficiency, we first need to understand the basics of heat flow and we need to define three basic mechanisms of heat transfer

Heat is transferred by 3 different means.

Conduction is heat travels through a solid object, or between two objects that are in direct contact. You will feel conduction taking place if you leave a spoon in a hot cup of tea.

Convection is heat that is transferred by air currents. You can see convective heat rise from a hairdryer, or from the surface of a hot road.

Radiation – is transferred by electromagnetic waves which can pass through anything. Radiant Heat is produced by the Sun and heats the earth, but it is also produced by radiators in your home, and even your body radiates heat. When radiant heat meets a surface, it is either reflected away, or it is absorbed. Once absorbed it can be conducted or re-radiated on the other side. 

“Radiation is the primary mode of all heat transfer. The other two modes… come into play only as they interfere with the primary mode.”

  • Pelanne, Senior Research Specialist for Johns Manville (Energy Design Update, Feb. 93)

The most common ‘traditional’ insulation materials work by slowing down convection and conductive heat flow, but they do little to tackle radiant heat. To understand why that is, we need to understand how we measure an insulation materials ability to insulate. And we need to understand 3 thermal values; an R-value, and U-value and an E-value.

R-value – is a measure a material’s ability to resistance conduction heat flow. The higher the number, the better its ability to resist conductive heat flow. The thermal properties of insulation products are usually stated in R-values.

U-value – is a measure of a material’s ability to conduct heat. The lower the number the better its ability to resist conductive heat flow. The thermal performance of windows, doors and buildings is commonly stated in U-values. You can calculate a U-value from an R-value (U-value = 1/R-value)

E-value – is a measure of Emissivity. Emissivity is the ability to emit or transfer radiant heat through a surface.  The surface of every material has an Emissivity value.

What is Emissivity?

You may have heard of low E glass in windows. Well the ‘E’ stands for Emissivity and Low-E Insulation works the same way. Everything has an emissivity value. Here are the emissivity values for a list of building materials:

%

Wood

%

Glass

%

Concrete

%

Plaster

%

Asphalt

%

Fiberglass/cellulose

%

Brick

%

Aluminium

Most common building material have high emissivity values. Plaster and fibreglass have an emissivity value of approx. 0.90. That means that 90% of radiant heat that meets the surface of these materials will be absorbed and pass through the material.
Aluminium on the other hand has a very low natural emissivity value of 0.03. This means that only 3% of radiant heat to meets an aluminium surface will pass through it. Or another way to look at it, is that 97% of heat will be reflected back to the source.

As long as a product is made from aluminium and has a true low emissivity value it will reflect radiant heat. To understand why aluminium is important you can read aluminium -v- mylar here…

Why is foil insulation different from traditional insulation?

Traditional insulations work by slowing down conductive heat transfer, but they need to absorb heat in order to work. For years, to improve insulation standards we have just added more and more of the same traditional insulation materials. We thought that was all we could do.

That suited the manufacturers of those products who continually lobby the government to improve standard so they can sell more product. But regardless of how high an R-value is, if an insulation system doesn’t also have a low – E value it has no ability to reflect radiant energy. Very high R-values don’t stop heat transfer, they simply slow it down.

R-values   -v-   E-values

You cannot ignore the need for good R-values, but by addressing the R-values alone, you leave a large percentage of heat transfer being ignored.

It is wort noting that; although all three forms of heat transfer take place out of a building, 100% of the solar gain is radiant heat. When you consider how hard air conditioning units work during summer months to deal with solar gain, it might also be worth asked. Why Building Regulations don’t address solar gain in insulation standards?

Does foil insulation have an R-value?

Foil insulation achieves an R-value in two ways. The first is through the resistance of the core of the material and the second is through the air layer adjacent to the foil surface.

Reflective materials that do not have separating layer or Core, usually come under the title Radiant Barriers.

How do Airspaces work?

The easiest way of explaining how low emissivity airspaces work is to use a double-glazed window as an example. The two pieces of glass in a double-glazed window do nothing on their own, but when the layers of glass are separated by an airspace, it is the airspace that becomes efficient.

However, when there is a low emissivity surface (pure aluminium) on one side of the airspace, the airspace becomes nearly 5 times more efficient than the one in a double-glazed window.

Are Airspaces important?

Reflective insulation can work without an airspace but to declare an R-value the airspace must be present. Airspaces can be formed in numerous ways and can be as small as a 6mm, but they are most efficient between 6mm – 20mm.

Airspaces are extremely efficient because heat cannot conduct through an airspace. Once heat conducts through a wall and meets an airspace the only way for the heat to travel across that airspace is convection or conduction. Small airspaces (below 300mm) are too restrictive for convection to occur.

So the only viable way for the heat to escape is to radiate across the cavity. If the surface on the other side of the cavity has a low emissivity surface (aluminium) the heat gets reflected to the source.

*Radiant Barriers reflect radiant heat in the same way as all other foil insulations (As long as they are made from Aluminium)

Claiming an R-value

Some foil insulation companies simply claim a single R-value for their product. This is not correct!

The R-value of ANY reflective foil insulation will change depending on the size and orientation of the airspace beside the foil surface.

Summary – How Low-E Reflective Insulation works

Heat flows from warmer objects, airspaces, or surfaces to cooler ones, until there is no longer a temperature difference. In your home, this means that in winter, heat flows directly from all heated living spaces to adjacent unheated attics, garages, basements, and anywhere else that is cooler than your heated area.

Heat flow can also move indirectly through ceilings, walls, and floors. The opposite is true in the summer, where heat is transferred from outside into your cooler home.

The composition of Low-E Insulation with its recycled closed cell foam core means that it can successfully tackle all three forms of heat loss. The core provides a thermal break to reduce and stop conduction and convection. While the 99.4% pure aluminium low emissivity surface reflects 97% of radiant heat back to the source.

Low-E Insulation is not designed to replace all other insulation materials on the market. It is designed to reduce life cycle running costs, provide moisture protection, stops draughts, deaden sound but most importantly, to tackle issues which are usually left unaddressed by traditional bulkier insulation products.

You can read about the important of Air Tightness and Moisture Control here…

“I’ve used low e for the past 15 months. I’ve found it to work fantastic is all conditions. I’ve probably got 20 vans with it fitted and I’ve had no complaints from any of my customers about being cold. Some of the vans are used for skiing holidays in places that are -20C and more.”

J Cochran, Genesis, UK

“Our customers are delighted with the rooms. We are now offering Low-E Insulation as an update in ALL our sheds, summer rooms and log cabins.”

Alex E, Lancashire, UK

“I found Pet Pad online and thought it was a fantastic idea. I’ve put them in all the kennels and pens my doggie hotel. A few of my customers saw them and asked about them so now I’ve started selling them too. Everyone loves them, especially the pooches!”

Kate E, London, UK

“We used Low-E Insulation to insulate outdoor water tanks. We used to lose a lot of water through evaporation in the summer months. It is made a huge difference. We have now insulated of hot water tanks indoors, and we have noticed our energy bills have gone down too. I’d definitely recommend Low-E Insulation.”

Helen B, Ireland

“I bought the Low-E Insulation from eBay on a recommendation from a friend. It arrived very promptly and was very easy to cut and installing. I’m delighted! It’s certainly made a difference. I can feel that the kitchen gets warmer much quicker on the cold winter mornings.”

P Philip, Macclesfield, UK

“The insulation came in a very easy to handle strip. It was easy to install and I haven’t had any problems since it was installed.”

Andrea P, Dublin, Ireland

“The Spas heat up much quicker with the Low-E installed and we’ve also noticed a drop in energy consumption while they’re running. It’s a great product. We are now including it as part of the patented design of our tubs”

G Richards, VA, USA

“Installing the blind on a single glazed unit resulted in a reduction in heat loss of 54% across the window. That’s just as good as double glazing”

P Baker, Glasgow Caledonian University, Scotland

“We’ve installed Low-E Insulated strip curtains in a number of McDonalds and Burger King restaurants, as well as a number of off-licences and supermarkets chains. All our customers have been extremely happy with the product. There is no ‘bagging’ in the bottom of the curtains, and they last much longer than the previous product we […]

Brian W, Dublin, Ireland

“Ours is a very specialist application for storing some very expensive items. We have been looking for something just like Low-E Insulation for many years. We didn’t think it existed but I’m very glad we found it. It’s fantastic!”

D Davidson, Edinburgh, Scotland

“We need to keep the enclosures cool in the Dubai sun while our equipment it is not running. The enclosures that we install the Low-E into have been up and running for a while now and are all performing well. We’ve had no complaints. We are now installing more of them in Mozambique and Hong […]

Alan P, W Yorkshire, UK

“We make tents for a lot of different applications and we have to meet very strict standards. Micro-E Insulation is Fire Rated for use in tents, flexible, lightweight and easy to work with. We can run it straight through our sewing machines.”

Grant H, Yorkshire, UK

“The first time I used Low-E Insulation was on a project in Italy. We used it to simply line a closet on a yacht where there were issues with damp. I was amazed at how simple it was to install. I wish I found this material years ago. We’ve use it on a few projects […]

Bill S, Porto Turistico, Italy

“It was so quick and easy to install and I can’t believe the difference it has made. I wish we’d done it years ago. Thanks again.”

M Joyce, Dublin, Ireland

“I bought a kit online to make window mats from Low-E Insulation. The insulation was very easy to cut to the exact size I needed. The kit came with suckers and everything else I needed. The mats are great. They are completely blackout and keep my van nice and warm even on very cold nights.”

Stephen C, Cornwall, UK

“The car was built in 1958 and I wanted to make sure it survived another 50 years once we had finished refurbishing it. The Low-E was easy to install and more importantly, it was very thin. You’d never know it was there and it seems to have made a big difference. We’re very happy with […]

Dave C, Dublin, Ireland

“I’ve used low e for the past 15 months. I’ve found it to work fantastic is all conditions. I’ve probably got 20 vans with it fitted and I’ve had no complaints from any of my customers about being cold. Some of the vans are used for skiing holidays in places that are -20C and more.”

J Cochran, Genesis, UK

“We used Low-E to line the interior and the engine bay of our NASCAR, its working really well”

Dave P, NASCAR, USA

“We were unsure if Low-E Insulation would work for us so we ran a test. We insulated one van with Low-E and one with the traditional insulation we had been using. Then we brought both vans down to -4*C. The van insulated with Low-E held temperature 4 hours longer than the van without. The results […]

Cameron J, UK

“Are Pods are installed along the coast and up in the mountains. We tried using a few different insulation products, but Low-E has been by far the best. We’ve no issues with moisture, corrosion or nesting. There’s no draught in the Pods are they’re easy to heat.”

Thomas E, Ireland

Want to get hands on with our products?

Request a FREE sample today