You may have heard the term thermal insulation and found yourself wondering what it means. Thermal insulation refers to insulating something — from building materials and clothing items to your water heater, coffee thermos, electrical appliance cables, or wiring — from heat transmission.
Most often, however, the discussion of thermal insulation is about construction and home insulation. The building industry uses thermal insulation to reduce the heat loss or heat gain through the house envelope (external walls, windows, roofs, foundations, and more). Adequate insulation (and proper, routine maintenance) also helps keep your HVAC system from working overtime as it prevents air leaks. In essence, insulation is what keeps the air you’re paying to heat and cool inside your home where it’s needed and Mother Nature’s temperatures outdoors.
Choosing the proper home insulation can be a daunting task. When doing your research, you’ll consider the cost of the material, how effective a particular type of insulation material will be, and whether or not it will end up saving you money in the long run.
This guide will explain how thermal insulation works not only for your home but also for other important areas of your everyday life.
What Is Thermal Insulation?
Thermal insulation inhibits heat transfer (thermal energy) between objects in thermal contact by conduction or convection, or in a range of radiative influences, such as the sun or a fire. Let’s explain these components a bit more.
Because a thermal insulator is not a good heat conductor and has low thermal conductivity, thermal insulation is used in buildings and manufacturing processes to prevent heat flow: both heat loss from low temperatures and heat gain from high temperatures.
We often associate the term thermal insulation with home or building insulation. However, the term “thermal insulation” is just another way of saying insulation, and it applies to more than just home insulation. In fact, it shows up in everyday areas of our lives.
Thermal insulation can apply to the insulated bottle where you keep cold water or hot coffee. Insulation is also used for clothing. For example, the protective gear that firefighters wear is insulated as is the warm winter jacket that keeps the cold away and the warmth of your body next to your skin.
Refrigeration parts, mechanical systems, and automotive internal combustion engines also use various types of thermal insulation.
Heat flow is transferred from one material to another by conduction, convection, or radiation. As a quick review, conduction is when heat transfers within or between solid objects. Convection is when heat is transferred through the movement of fluid. Radiation is when heat radiates outward from light or gas as with the sun or a campfire.
Insulators are used to minimize or prevent the transfer of heat energy by any of those means.
Thermal insulation is measured by thermal conductivity, and materials that are low in thermal conductivity are used for insulation. Besides thermal conductivity, density and heat capacity are also important properties of insulating materials depending on what they are being used for.
What Is the Purpose of Thermal Insulation?
The primary purpose of insulation is to limit energy transfer between the inside and outside of a system. Energy can refer to heat energy, radiant energy, or electrical energy.
Thermal insulation is intended to increase energy efficiency, protect against radiant heat, and either contain or block out heat energy. Proper insulation is one of the best ways to create a more energy-efficient home.
How Does Thermal Insulation Work?
Thermal insulation creates a barrier between a hot and a cold object. It reduces heat transfer by either reflecting thermal radiation or decreasing thermal conduction and convection from one thing to the other.
Reflective insulation and radiant barriers function by lowering radiant heat gain.
The R-value of thermal insulation measures how well a material insulates. Increased insulation thickness will proportionally increase the R-value.
R-value measures your insulation’s ability to prevent heat from seeping into and out of your home. Higher R-value signifies better insulation performance. R-values can range from R-1.5 to R-7 and the thickness of insulation you need will depend on where you live.
For example, if you live in a very cold area, you probably need insulation with an R-value of at least R-49. To reach that, you’d need to install at least seven inches of insulation with a value of R-7.
What Are Examples of Thermal Insulation?
You can find thermal insulation in just about everything in your home, from your clothing to your coffee mug and the wiring or cables on any of your electronics, walls, ceiling, and windows.
Here are some good examples:
- It may surprise you to learn that air is an excellent thermal insulator. For example, when you wear a thick jacket, it traps air between the fabric and your body — the air holds your body heat in rather than allowing it to pass through your jacket to the outside world.
- Dry cotton is a terrific thermal insulator. However, if it should become wet, it becomes a conductor. For example, you might wear cotton long johns and jeans to go out and build a snowman, and you feel pretty comfortable. But if you were to fall in the snow and your jeans soak through with wet snow, you’ll find yourself shivering in no time. That’s because damp cotton becomes a conductor, so the heated air between your skin and jeans will quickly be lost into the surrounding cold air.
- Your favorite tea mug may be made of ceramic. Ceramic is a good thermal insulator, keeping your drink hot for longer than a regular glass would.
- If you’ve ever poked your head up into the attic of your house, you probably noticed there is a thick layer of fluffy pink fiberglass insulation. Fiberglass is highly effective as a thermal insulator and can hold the heat inside of your entire home.
- Thick glass windows can help insulate your home on a hot day, keeping the cool air indoors and the heat out. That’s because well-manufactured glass can be a good thermal insulator.
- Rubber is another great thermal insulator. Rubber guards against the danger of being shocked by electrical energy, which is why most electrical cables are encased in rubber.
What Are Some Types of Thermal Insulation?
Since there are various forms of heat energy, there is a need for different types of conductors and insulators. Materials that transmit heat are thermal conductors. Materials that inhibit heat are thermal insulators.
Common thermal insulators are wool, fiberglass, rock wool, polystyrene, polyurethane, goose feather, perlite. These thermal insulation materials are very poor conductors of heat and are therefore good thermal insulators.
For the purpose of this discussion, we’ll talk about the best thermal insulation for your home or building.
Before selecting an insulation material that is suitable for your home, you ought to consider a few things — for example, the R-value, price, insulation properties, and environmental impact. Some insulation materials are more commonly used than others. Here’s a list of the top five you’ll likely come across.
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Fiberglass
Fiberglass is among the more commonly used insulation materials thanks to its affordability and effectiveness. Fiberglass is less expensive to install than any other insulation material on the market, and its R-value is equivalent to many others. Fiberglass works by weaving fine strands of glass into the insulation material.
Because of the fine glass strands woven throughout, you must use safety equipment (gloves, mask, glasses, and overalls) to avoid glass powder or minuscule shards of glass getting into your eyes or lungs or irritating your skin.
Non-flammable and with R-values ranging from R-2.9 to R-3.8 per inch, fiberglass is an excellent option for home insulation.
Mineral Wool
Mineral wool refers to a few different types of insulation, such as fiberglass created from glass that has been recycled, or rock wool made of basalt. You can buy mineral wool in batts (rolls) or loose material.
Most mineral wools don’t have additives to make them fire-resistant. As such, that means they are not suitable for conditions that include extreme heat.
The R-value of mineral wool ranges from R-2.8 to R-3.5.
Polystyrene
Polystyrene foam is a waterproof thermoplastic foam used in residential and commercial buildings. Boasting superb sound and temperature insulation properties, it’s ideal for wall insulation. Polystyrene is rigid and has a smooth surface.
There are two types of polystyrene: expanded (EPS) and extruded (XEPS), which most know as “Styrofoam, although this is actually not correct as Styrofoam® is a trademarked product.
Higher-end XEPS has an R-value of R-5.5, and EPS has a value of R-4.
Polyurethane Foam
Spray polyurethane foam (SPF) is created by a mixture of chemicals and materials that respond upon contact, expanding to create a surface barrier that seals air, insulates, and seals out moisture. Lightweight, SPFs have an R-value of about R-6.3
Cellulose
Cellulose is eco-friendly because it’s made of about 75-85% recycled paper — typically old newspapers — and discarded denim. The rest of the material that makes up cellulose insulation systems is usually a fire retardant like ammonium sulfate or boric acid.
Compact and fire retardant, this insulation material can help reduce fire damage.
Cellulose has an R-value between R-3.1 and R-3.7.
Which Type of Insulation Is Most Effective?
It depends on the situation. If you’re building a new home, the most effective type of insulation will probably be very different from that which you’d use if you’re remodeling your older home.
That said, closed-cell foam has the highest R-value of any insulation, around R-6.2 per inch, but can be expensive.
How Do I Install Thermal Insulation In My Home?
Your best bet is to hire a contractor to do thermal insulation installation for you. However, if you’re the DIY type or at least pretty handy with building materials and home repairs, you may want to have a go at it yourself.
When installing home insulation, always follow the manufacturer’s instructions. Here are some things you need to do before you begin:
- Find out about your local building codes. There may be vapor barrier requirements where you live, and your municipality may have a ruling about the required R-value.
- Check for gaps around plumbing, ductwork, wiring, crawlspaces, windows, and basements. Those areas will need to be sealed using caulking or foam insulation material.
- If you’re insulating your attic, be sure to measure out the area between the joists. If you’re working on your unfinished walls, you’ll need to take measurements between the studs. Once you’ve got all your measurements in place, you’ll be able to measure and cut the correct width of insulation material.
- Likewise, if you’re insulating framed walls, you’ll need to measure thickness so that your insulation material is sufficiently thick to fill the space.
- Some good calculators online can help you with the estimates you need to purchase the right amount of insulation for your space.
Thermal Insulation: It Keeps Us Cozy and Safe
Thermal insulation has many uses and, whether seen or unseen, it serves to protect us in a myriad of ways.
It helps you save energy and be more eco-friendly. It helps you save money on your electric bill and keeps you comfortable indoors. Insulation also keeps your soup hot for your lunch break and helps keep your local firefighters safe. Each time you send your kids out to play in the snow, you know they’ll be protected by the thermal insulation of their snowsuit or jacket.
Ranging from organic materials to manmade, thermal insulation comes in many forms and substances — and we use it for almost everything, whether we realize it or not. Most of the time when we think of thermal insulation, we think of home insulation, but as you’ve learned, it’s so much more than that. It’s a part of your everyday life.
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