Thermal Insulation

What is Thermal Insulation?

Thermal insulation works by interrupting heat’s natural path from warm to cold. That might be a layer of mineral wool in the roof or foam boards under a concrete slab - different forms, same purpose.

Most of us have experienced how insulation works in everyday life, even if we didn’t think of it that way. Wrap a scarf around your neck, use a picnic cooler to keep drinks cold, or put your hand inside an oven mitt. In every case, a simple layer stands between two temperatures, keeping heat from racing across. That principle underpins all building insulation.

How Does It Work?

Heat is always on the move. In buildings, it travels in three main ways: through solid surfaces, through air, and as invisible energy waves. Insulation is designed to push back against all three.

Conduction

Heat moves through a solid in much the same way it creeps along the handle of a cast-iron skillet. Put a layer of mineral wool or rigid foam in its path, and that chain reaction slows to a crawl. 

The tangled structure of these materials simply gives warmth nowhere quick to go, so it lingers inside the room instead of leaking through the fabric.

Convection

This involves heat carried by moving air. Insulation made from fibrous or cellular materials traps still air within its structure. 

Since air that isn’t moving transfers very little heat, those trapped pockets help block heat carried by air movement.

Radiation

Radiant heat moves as energy waves, like the warmth you feel from sunlight. Certain insulation products include shiny or foil-faced layers designed to reflect this type of heat, either bouncing it away in summer or back inside during colder months.

Why Thermal Insulation Matters

• Lower Energy Bills: When a building holds onto its heat in winter (and keeps it out in summer), you don’t need to rely as heavily on heating or air conditioning. That means systems run less often, energy use drops, and the savings start to show up in your monthly bills.
• Consistent Indoor Temperatures: Insulation eliminates those annoying cold patches near windows or walls. Rooms stay more stable throughout the day, without sudden swings or draughts, which makes for a more comfortable living or working environment.
• Reduced Environmental Impact: In buildings that rely on gas or oil, cutting heat loss means fewer emissions. Even electric systems benefit, especially when the power grid isn’t fully green. Insulation is a simple, lasting way to shrink your carbon footprint.
• Protects the Building Itself: Insulation helps keep moisture under control. When interior surfaces stay warmer, condensation is less likely to form. That means less chance of mould growth and damp. 

Types of Thermal Insulation

Blanket Insulation (Rolls and Batts)

This is one of the most widely used forms of insulation, especially in residential builds. It typically comes in long rolls or rectangular slabs and is made from materials like glass wool, rock wool, or in some cases, natural sheep’s wool. 

The sizes are designed to fit between standard roof joists, wall studs, or floor timbers, making it a straightforward choice for lofts and wall cavities. 

It’s flexible, easy to cut, and well-suited to both new builds and retrofits. It works by trapping still air between its fibres, which slows down heat loss. You’ll most often see it in lofts, timber-frame walls, and pitched roofs.

Rigid Insulation Boards

Foam boards (usually made from PIR, EPS, or XPS) are ideal when space is tight, as they offer strong thermal resistance relative to thickness. 

These are used under concrete slabs, in flat roofs, and in external wall systems. The closed-cell structure and gas-filled composition help block heat flow effectively. They’re lightweight, easy to cut, and work well where a uniform finish is needed.

Structural Insulated Panels (SIPs)

SIPs combine insulation and structure in one panel, typically a foam core sandwiched between OSB or plywood. 

They’re used in timber-frame construction to speed up the build process and cut down on thermal bridging. Because they're pre-fabricated, they slot together quickly and perform consistently.

Foil Insulation And Reflective Barriers

These work a bit differently. Instead of trapping heat, they reflect radiant energy away. 

You’ll find them in attic spaces, behind cladding, or combined with other materials. They’re most effective when installed facing an open air gap.