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How Does Insulation in a House Work? Types, Factors, & Signs

man installing insulation

House insulation is one of the most important elements of a home, yet many people don’t know how it works. Insulation is simply a mechanism of trapping heat inside the house during winter and keeping cool air inside during summer. This helps to keep your home at a comfortable temperature year-round without having to use as much energy from heating and cooling systems.

If you want your home to be energy-efficient and comfortable, you need to make sure it’s well-insulated. In this article, we’ll explain everything you need to know about how insulation works and other related questions.

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How Does It Work?

First, you must understand how heat is lost or gained in a house to know how insulation works. Heat transfer takes place in three ways, including:


The most common form of heat transfer is conduction. It occurs when a warm object comes into contact with a colder object, and the heat transfers from one to the other. Conductive heat transfer is also known as thermal conductivity.

You can stop conduction by placing an insulator between two objects conducting heat to slow down or stop transferring heat. The heat can move through solid materials like walls and ceilings, as well as gaps around doors and windows. These are the main areas that you should consider insulating.


Convection is the heat transfer in liquids and air. Air is warmed when it rises and cools as it falls—the same as liquids. Warm air is less dense than cool air, so it rises, and cool air sinks to take its place.

Heat loss through convection occurs when warm air escapes through cracks in the house. You can reduce this by using insulation to balance temperature differences between inside and outside surfaces.

man installing insulation
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Radiation is the transfer of energy as waves or particles move from one place to another through a vacuum. It is simply the transfer of thermal energy by electromagnetic waves. Radiation accounts for most of the heat loss from houses during winter and gains during summer.

All these methods of heat transfer can be reduced by insulation. Different types of insulation are better at stopping different kinds of heat loss, so it’s important to choose the right type of insulation for your home.

The Insulation Process

Now that you understand the three modes of heat transfer in your house, you can start to understand how insulation works.

Heat always moves from warmer objects to cooler objects. So, in the winter, heat will move from the inside of your home to the outside. And in the summer, heat will move from the outside of your home to the inside.

Insulation works by slowing down the transfer of heat. The more insulation you have, the slower the transfer of heat will be. That’s why homes in colder climates tend to have more insulation than homes in warmer climates.

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The 6 Types of House Insulation

There are many types of insulation available for houses. Some are safer and more effective at keeping your home at a comfortable temperature. Here’s a rundown of the most common types of insulation:

1. Loose Fill (Cellulose)

man making cellulose insulation
Image Credit: Kurteev Gennadii, Shutterstock

Cellulose insulation is made from recycled paper products that are treated with fire retardants. It is often used in attics and walls. Cellulose insulation can be found in loose fill, batts, or rolls. It has a high R-value. R-value is the capacity for an insulating material to resist heat flow. The higher the value, the greater the insulating power. These values range from 1.5–7. Cellulose insulation is typically 3.5–4.0.

Cellulose insulation is also good at absorbing sound. Apart from ease of installation, it is also cost-effective. It even has a chemical that prevents bugs and pests from digging through and making it their habitat.

  • Widely available
  • Inexpensive
  • Average R-value
  • Needs professional installation
  • Dusty and messy during installation

2. Rigid Foam Panels or Foam Board

Foam board insulation is the most common type of house insulation. It comes in different densities and thicknesses, so you can choose the type that works best for your home.

Foam board panels are made with polyurethane, polystyrene, or polyisocyanurate. They come with different R-values. You can use foam board on ceilings, unfinished walls, and floors.

  • Has a high R-value
  • Water-resistant
  • Installation doesn’t need special equipment
  • The joints between the boards and sheets must be taped to stop airflow
  • The boards are too fragile to be installed underground

3. Spray Insulation

man applying spray foam insulation on the walls
Image Credit: Igor Meshkov, Shutterstock

Spray foam insulation is sprayed into the walls as they’re being constructed. It will expand to fill cracks, leaks, and gaps in existing walls to prevent air leaks. It is best for hard-to-reach and irregularly shaped spaces.

Spray foam insulation can be found in two forms: closed-cell and open-cell. Closed-cell spray foam insulation has a higher R-value than open-cell spray foam insulation. Its R-value is 6–7 per inch. Open-cell spray foam insulation typically has an R-value of 3–4 per inch.

Spray insulation has several advantages over other forms of insulation. It includes reduced air infiltration and improved energy efficiency. Besides, spray foam offers better soundproofing than other types of insulation.

  • Can be applied on any surface
  • Has a high R-value
  • Mitigates the transmission of sound
  • You don’t need vapor barriers with this insulation
  • The installation generates poisonous fumes
  • Needs professional installation
  • Costly compared to other insulation materials

Consult an insulation expert

Find an insulation specialist in your area, and get free, no-commitment estimates for your project.

4. Blanket Batts and Rolls/Fiberglass

Fiberglass insulation is made from recycled glass that is melted down and spun into fibers. It is among the most common types of insulation used in homes. It is typically found in rolls or batts. It is easy to install and is available in a variety of R-values of 2.5–4 per inch. You can use them for insulation on ceilings, unfinished walls, and floors.

  • Inexpensive and easy to install
  • Widely available
  • Can be installed on most surfaces around the house
  • Takes up a lot of space
  • Has a low R-value

5. Rockwool (Mineral Wool)

man installing rockwool insulation
Image Credit: brizmaker, Shutterstock

Rockwool is similar to fiberglass but with better fire resistance and sound absorption. However, it’s more expensive than fiberglass. You can install it in areas with plumbing pipes or wires present. It won’t break down like fiberglass does over time.

Also, you can use it in commercial buildings, such as warehouses, because it offers a higher R-value than other types of insulations. It is ideal for use on floors, ceilings, and walls.

  • Endures high temperatures
  • Doubles as both noise and thermal insulator
  • Durable
  • Costly
  • Not biodegradable

6. Blown-In Insulation

Blown-in insulation is made from glass fibers, rock wool, or reclaimed cellulose. It is perfect for hard-to-reach or irregularly-shaped spaces. The material is sprayed into wall cavities or attics through specialized equipment. It expands as it fills the space, then hardens to create an airtight seal.

  • Easily fills around ductwork and pipes
  • Inexpensive
  • Flame-resistant
  • Can cause eye, lung, and skin irritation
  • Holds moisture, which could harbor mold
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Factors to Consider when Choosing Insulation for your House

When you need to insulate your house, you need to look at the different types of insulation available and figure out what will work best for your home. Here are some crucial factors to consider:

  • Soundproofing: Soundproofing is crucial if you live in a noisy environment. House insulation with soundproofing capabilities will block out noise from outside sources and make your home quieter.
  • Presence of Allergens: If some people in your home suffer from allergies, look for allergen-free insulation, such as injection foam. Insulation like fiberglass batts or loose-fill cellulose contains particles that can irritate sensitive lungs and nasal passages if inhaled. Also, fiberglass does not block dust mites like other types of insulation.
  • A Suitable R-Value: The R-value is a measure of how well a material resists heat flow. The higher the R-value, the better the material is at resisting heat flow. So, you must choose insulation with an appropriate R-value, depending on the type of insulation you need and where you’re installing it. For example, if you want to install insulation in places that get wet often, choose one with a lower R-value because moisture will increase its R-value. But, if you’ll install it in dry areas, such as attics or walls, choose one with a higher R-value since moisture won’t affect its effectiveness.
  • Flammability: Choose an insulation material that does not catch fire easily. If possible, pick an insulation material that also doesn’t have fire-retardant additives. This makes it so you avoid toxic fumes when the insulation is exposed to heat sources, such as hot water pipes or electric fires.
  • Cost: Cost is a crucial consideration when looking for insulation for your home. While there are many types of insulation, they all come at different prices. Some are more expensive than others because they offer more benefits and features. You can choose an affordable type of house insulation so that you do not strain your budget, but check to see that it offers all the features you need in high-quality insulation material.
walls with spray foam insulation
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Parts of the House Should You Insulate More Than Others

Many parts of your house may need insulation, but some will need it more than others.

They include:
  • The Attic: The attic is on the top floor of the house. It has a lot of heat coming through it as it rises. In most cases, it causes the temperature difference between rooms on different levels of the home.
  • Crawl Space: You can easily forget about crawl spaces when insulating your house. They are usually not visible or accessible from inside the house, but they can be challenging to heat or cool as they don’t have any natural airflow like other areas of the home. The crawl space under your house affects the temperature inside. You should have an energy audit done to determine if it needs any work before insulating it. Crawl spaces are also damp and humid. It makes them perfect breeding grounds for mold spores and bacteria if they aren’t insulated well.
  • Walls: Walls are an excellent place to start when insulating. If they aren’t insulated, they may also be prone to condensation buildup, which can lead to mold problems.

The Pros & Cons of Insulating Your House

Advantages of Insulating a House
  • Reduces Energy Bills: In the winter, insulation prevents heat from escaping your home. This means your heating system doesn’t have to work as hard to maintain a comfortable temperature. In the summer, insulation prevents heat from entering your home. This helps keep your home cooler, which reduces the amount of energy you use for air conditioning
  • Improves Comfort: By keeping your home at a consistent temperature, insulation can make your home more comfortable year-round
  • Lasts a Long Time: Once installed, insulation can last for years. Some types of insulation like spray foam insulation even expand over time to fill in any gaps or cracks that may have formed.
  • Minimizes your carbon footprint
  • Safeguards your house from insects and fire
  • Increases your home’s resale value
Disadvantages of Insulating a House
  • Can Be Expensive: The initial cost of insulation can be high, but over time, the energy savings will offset the initial cost.
  • May Require Professional Installation-: Some types of insulation, like spray foam insulation, require professional installation. This can add to the initial cost.
  • Can Cause Moisture Problems: If not installed properly, insulation can cause moisture problems. Most insulations are not waterproof. They’re also susceptible to moisture unless you use a barrier with the house insulation.
  • Health Risks: Fire retardants and chemicals used in the installation can be a health risk.

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Barriers That Can Boost Your Insulation’s Effectiveness

Some types of insulation must be used with a barrier to mitigate the moisture content getting in through the walls and reduce heat transfer into the house. You can use a barrier without house insulation, but you cannot use it in place of house insulation. Here are some you can use:

Vapor Barriers

Vapor barriers are used with insulation to keep moisture out of the walls and prevent mold growth. They work by preventing water vapor in the air from reaching the wall surface, where it can condense into a liquid.

These vapor barriers are installed between the home’s exterior and interior walls. You can also install them between your flooring and subfloor.

You’ll often find vapor barriers in new construction projects. They prevent moisture damage caused by leaks in plumbing pipes or roofing materials.

Radiant or Reflective Barriers

Radiant barriers are an excellent addition to your insulation system. They reflect radiant heat into the room, thus reducing heat transfer through the walls, floors, and ceilings. They also allow air to pass through.

Usually, radiant barriers are made of thin aluminum sheets, foil, or plastic films. They are effective in houses with high ceilings and large windows, which allow more radiant heat to enter the house.

Asbestos Insulation Roof
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Signs Your House Needs Insulation

Your home is probably the biggest investment you will ever make. It can also be your source of comfort and enjoyment, but only if it is well-insulated. Here are several tell-tale signs that your house needs insulation:

  • Varying Temperatures in Different Rooms: If you have a cooler room than the others in your home, it may be time to consider adding more insulation. The temperature difference between rooms can be caused by poor airflow or insulation.
  • High Energy Bills: The amount you pay in energy bills depends on how well insulated your house is. The more the air leaks in the walls and ceiling, the more the heat escapes from your house into the outside air. It’ll result in higher energy bills since more money is spent on heating and cooling systems to keep up with the temperature changes inside the house.
  • Temperature Fluctuations: Regardless of the time of the year, if you can’t keep your home at a relatively stable temperature, it could be a sign that you need some more insulation.
  • Drafts: Drafts are caused when warm air leaves your home through gaps between the door frames, windows, and other openings in your house. The best way to prevent this is by adding more insulation above windows or under doors. This way, less warm air escapes from these areas when they’re closed.

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What Insulation Is the Best for the Exterior Walls of Your House?

The best insulation for the exterior walls is fiberglass batt insulation. It’s made from glass fibers compressed together into batts or rolls.

Fiberglass batt has a high R-value. It lasts longer than other types of insulation because it doesn’t absorb water or lose its effectiveness over time. This insulation is usually installed between the studs on an exterior wall. There’s no vapor barrier needed.

Is Installing House Insulation a Do-It-Yourself Project?

Installing insulation can be a DIY project but check with your local building department before starting. Some municipalities have specific guidelines about house insulation.

Usually, insulation is installed with other home improvement projects. In this case, it’s best to hire a professional contractor with experience working with these materials.

How Long Does Insulation Last?

The lifespan of an insulation product depends on the quality of the installation and the materials used. Usually, insulation can last for 15–20 years.

portable airconditioner
Image Credit: Piqsels

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While you may not think much about house insulation, it’s crucial to understand what it does, how it works, and why you need it. House insulation is a great way to reduce energy bills and improve comfort. But it’s important to choose the right type of insulation for your climate and budget. Regardless, be sure to hire a professional installer, especially if you choose spray foam insulation.

Featured Image Credit: Bilanol, Shutterstock


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