Radiant barriers may be one of the most versatile energy-saving products in the marketplace today. Yet some consumers may not fully understand what radiant barriers are or how they work. But the reality is, the science behind radiant barriers is pretty straightforward: radiant barriers reflect heat back to its source. By mixing this fundamental concept with others like conduction, moisture, and the passage (or blockage) of air gaps, you can start to unlock many possibilities in a variety of applications.
Before we explain concepts like air gaps, reflectivity, and emissivity, let's define exactly what we mean by the term "radiant barrier."
What is a Radiant Barrier?
A radiant barrier is a type of metallic insulation material that blocks and redirects the passage of radiant heat, assisting in the energy performance of a building. Some varieties resemble heavy duty aluminum foil and consist of a single layer of double-sided reflective material. Other varieties feature bubble layers which help prevent the buildup of moisture and condensation.
Radiant barriers have two properties that make it effective against radiant heat transfer: reflectivity and emissivity.
Reflectivity: the redirection of heat back to its source. Usually measured in a % value. The higher the number, the better.
Emissivity: the amount of heat absorbed by the material. Usually measured in a % value. The lower the number, the better.
Double-sided radiant barrier works both ways—making your home cooler in the summer and warmer in the winter
Both sides of our radiant barrier products have metalized aluminum that creates a high resistance to heat transfer, reflecting up to 96% of radiant heat back to its source. In the summer, it can block the heat from entering your home when you place a radiant barrier in your attic. In the winter, it can keep heat from escaping your home. Because of its high-resistant nature, this also means radiant barriers have a very low emittance of heat energy, meaning little to no heat is absorbed by these products.
Our radiant barrier products are generally used in the walls, floors, and attic spaces of your home or structure to keep radiant heat out. But, they can be found all around you in places you may not realize, such as:
- Sunshades in vehicles which help keep the interior of the vehicle cooler.
- Pizza delivery bags which help keep deliverable pizza hot and fresh.
- The inside lining of winter/skiing jackets which help keep you warm and dry.
- Insulated drinking cups that keep your drinks hot or cold.
What type of radiant barrier do I need?
The type of radiant barrier you need will depend on a variety of factors like geographic location, local building codes, the type of application, and more. EcoFoil offers a variety of radiant barrier products that can reduce energy bills in a variety of applications. All EcoFoil radiant barrier varieties are lightweight and easy to handle/install.
Bubble Insulation. Two layers of radiant barrier with polyethylene bubbles in the middle. Comes in single bubble and double bubble varieties. Used in basement walls and ceilings, in metal buildings, and even under concrete.
Solid Radiant Barrier. Straightforward, simple, and effective in many applications. When used with tape, this product doubles as a vapor barrier which can save you from having to buy vapor barrier separately in applications where a vapor barrier is required per local building codes. This variety is not to be used in attics.
Perforated Radiant Barrier. The only choice for attic applications. Tiny perforations allow the passage of air, promoting air movement through the material and preventing buildup of moisture which can lead to mold and mildew.
How Does Radiant Heat Work?
As you may know, heat travels from warmer air to colder air in three different ways:
- Conduction: When you touch something warm, that form of heat transfer is known as conduction. This form of heat transfer occurs when physical contact is made between two solid surfaces.
- Convection: Heat energy which is transferred between a surface and air/fluid at different temperatures is known as convection.
- Radiation (radiant heat): the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles transmitted as heat, light and electricity. A common example is sunlight or the heat you feel when you hover your hand over your stove.
The best and most applicable example of radiant heat is the heat that comes from the sun. Between the sun and the earth’s atmosphere there is no air to conduct or convect energy. Energy from the sun radiates through space and is not converted into heat until it hits matter (like air) in our atmosphere, your car seats, or a home’s roof.
The graphic of boiling water shown below is a great example of all heat transfer methods at play: conduction occurs when the pot transfers its heat to the handle through direct contact; convection occurs when the heat transfers from warm water to the cold water; and radiation occurs when the heat waves project outside of the burner.
The Air Gap Is Key
In order for radiant barriers to be truly effective, you need to have air space on at least one side of your radiant barrier.
This is one of the most important concepts when installing a radiant barrier, regardless of the application. The worst thing you could do is sandwich the barrier between two products such as roof sheeting and shingles, or drywall and foam insulation. Doing so would convert the radiant heat into conductive heat, essentially transferring the heat directly through the material. By maintaining the air gap, radiant heat is reflected away instead of getting absorbed by the materials in your home.
By maintaining the air space on one side or your radiant barrier, you will keep keep that air contained at a consistent temperature (i.e. the way your beverage stays hot or cold in an insulated cup).
No matter the installation, air is crucial for radiant barriers:
Walls: You can either recess the barrier into the stud cavity or roll it across the studs and attach furring strips or strapping prior to hanging drywall.
Floors: All you need to do is install the radiant barrier a few inches below the tubing and you will have an air gap above and below the foil.
Attics: You will already have two airspaces: one between the barrier and the sheeting and the other is the air inside the attic. Our perforated radiant barrier product is designed to allow the passage of moisture, which prevents buildup of mold and mildew in your attic.
The next time you are planning your DIY radiant barrier project, just remember to include an air gap on at least one side of the barrier. It is as simple as that! The information in this article is simply an overview of the materials, applications, and considerations one must make when installing a radiant barrier in their home, business, metal building, or any type of structure where temperature and energy costs matter. If you have any questions about your specific application, one of our friendly product experts can help point you in the right direction.
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