How Does Insulation Work in a House?

Thermal insulation is vital throughout building projects, both to reduce the amount of heat lost from a building and to reduce the overall heating costs. Heat is lost through several areas of a property, with different types of insulation tailored around each. In this section, we’ll examine how thermal insulation works throughout a building, showing why it’s so vital in construction projects.

How Does Heat Move?

Heat is, at a basic level, energy, that can move through a space in waves, changing all matter it comes across. Heat will move in three ways, convection, conduction, and radiation. Through all of these transfer methods, it will naturally move from hot to cold, seeking out colder spaces in a building.

• Convection: Convection is when heat energy moves through a free-flowing liquid or gas, such as water boiling in a kettle. As molecules are heated, they expand and move, bringing the heat energy with them.
• Conduction: Conduction is the transfer of heat between two molecules via direct contact. This occurs in solids, liquids and gases. An example would be how heating one side of a length of metal would lead to heat being conducted further along it.
• Radiation: Radiation is when heat is transferred through electromagnetic waves. This does not need any matter to move. The heat energy from the sun is a great example of radiation.

Within a home or other building, all three types of heat movement will occur. Heat energy will escape through solid walls via conduction, transferring from the interior of the building to the colder outside face. Air currents, such as through an open window, or a poorly sealed outer door, can cause convection-based heat loss. Radiation heat loss can also occur throughout a house, primarily through windows.

How Does Thermal Insulation Work?

Thermal insulation looks to reduce the ease of heat transfer. By creating a barrier, either within or on top of your surfaces, thermal insulation can either reflect radiation, or decrease the convection and conduction potential. Thermal insulation products are designed to limit or slow the transfer of heat, keeping it within a building, so materials with a low conduction rate will be used. They also have to take into account other factors, such as moisture risk, fire prevention, and acoustic insulation needs. This means that there are thermal insulation products designed around specific areas of a building, such as loose-fill insulation for cavity walls and insulation boards for attics. Insulating your home will increase its energy efficiency, minimising heat loss.

How Does Home Insulation Work?

Within a home, you will lose a significant amount of heat without thermal insulation. The most important areas to insulate are known as the thermal envelope, consisting of the outer walls, loft (or roof), and ground floor. Thoroughly insulating these areas will significantly reduce the heat loss in a home. Other techniques can also help, such as draught-proofing and installing double glazing. Home insulation will seek to reduce all types of heat movement from the interior to the exterior of a property. There are different insulation products intended for specific areas of a home, allowing you to tailor your insulation choices and maximise heat retention.

How Does Loft Insulation Work?

Heat loss through the roof of a building occurs through both convection and conduction. Installing insulation within the floor of your loft space will reduce the amount of heat that reaches your attic, keeping your house warmer for longer. Loft insulation substances have low conduction levels, and can be easily installed within a loft space.

How Does Cavity Wall Insulation Work?

Cavity walls, sometimes called double walls, have been built as standard on most houses constructed since the 1920s. Houses constructed from the 1980s onward should come with insulation installed, whereas older properties can have blown-in insulation fitted. Cavity wall insulation, or double-wall insulation, works to reduce heat transfer. Solid cavity wall insulation boards fitted within newer properties slow the conduction of heat, while blown-in loose-fill insulation retrofitted to older properties features pockets of trapped air that help to reduce conduction and convection.

How Does Solid Wall Insulation Work?

It is also possible to insulate solid walls, either by installing insulation to the internal facing of a wall or installing specialist rigid insulation boards to the exterior of your house. Installing external solid wall insulation is a more time-consuming process than internal, and may not be allowed on certain properties. Solid walls lose heat fast through conduction and thermal insulation products can work to limit that, with slow-conducting materials fixed to the walls of your home, keeping heat contained within it for longer. Externally or internally insulating your outer walls can limit heat loss in situations where cavity wall insulation cannot be installed.

How Does Carpet Insulation Work?

When looking to reduce heat loss through the ground floor of a building, installing products within the foundations can be an invasive and time-consuming process. An easier alternative is to install thermal insulation underneath the carpet of a home. An insulated underlay will help to reduce the heat being lost through the ground floor of your house, slowing the conduction of heat. Carpets also possess some insulating properties, though they shouldn’t be relied upon.

How Does Roof Insulation Work?

A drawback of loft insulation is that it will leave you with a cold attic, keeping heat within the house but leaving the upper areas without insulation. An alternative is to install insulation within the roof joists of your building, allowing you to have an insulated attic, that can be used as a living space if required. The solid boards commonly used for attic insulation reduce the passage of heat via conduction and convection, lowering the amount of energy needed to keep a building at a comfortable level of heat.

How Does Underfloor Insulation Work?

For more solid ground floor insulation, you’ll have options to install insulation either above your foundations in modern homes, or between the timber beams in older homes with suspended timber floors. This can help to reduce the heat loss, primarily through conduction, that occurs through a floor.

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