Home Insulation Types Compared: Which Is Best for Your Project?

Why Insulation Type Matters

Choosing the wrong insulation type wastes money and underperforms. Each type has different thermal properties, moisture behaviour, installation requirements, and cost profiles. The right choice depends on where you are insulating, your budget, and whether you are doing the work yourself.

Use our insulation calculator to get precise material quantities once you have chosen your insulation type.

Insulation Comparison Table

Property	Mineral Wool	Rigid Foam (PIR/PUR)	Spray Foam	Reflective Foil
R-value per 100 mm	2.2–2.8	4.0–4.8	3.5–6.5	1.0–1.5
Cost per sqm (EUR)	4–10	12–25	20–40	3–8
DIY difficulty	Easy	Medium	Professional only	Easy
Moisture resistance	Low (needs vapour barrier)	High	High	Low
Fire rating	Non-combustible (A1)	Class B–C (foil-faced)	Class B–E (varies)	Class A–C
Best for	Lofts, stud walls, between joists	Flat roofs, solid walls, floors	Hard-to-reach cavities, irregular shapes	Loft top-up, radiant barriers
Lifespan	50+ years	50+ years	50+ years	30–50 years
Compression over time	Minimal	None	None	Can sag if unsupported

Mineral Wool (Glass Wool and Rock Wool)

Mineral wool is the most widely used insulation in Europe. It comes in rolls and batts that friction-fit between timber joists or studs. Installation requires no specialist tools — just a dust mask, gloves, and a long-bladed knife for cutting.

Pros: Cheapest per sqm, excellent sound insulation, non-combustible, widely available, easy DIY installation.

Cons: Lower R-value per thickness (you need thicker layers), absorbs moisture (must use a vapour barrier), itchy fibres during installation.

Best for: Loft insulation between and over joists, internal stud walls, suspended timber floors. The loft insulation calculator calculates exact roll quantities.

Rigid Foam Boards (PIR / PUR / XPS)

Rigid foam boards deliver the highest R-value per unit thickness, making them ideal where space is limited. PIR (polyisocyanurate) boards with foil facing are the most common choice for roofs, walls, and floors.

Pros: Highest R-value per thickness, moisture resistant, structural rigidity, clean installation.

Cons: More expensive, requires careful cutting and taping at joints, not flexible around irregular shapes.

Best for: Flat roof insulation, solid wall insulation (internal or external), insulating below concrete floors, and any application where thickness is constrained.

Spray Foam

Spray foam expands on application to fill cavities completely, creating an airtight seal with no gaps. Open-cell spray foam is cheaper and more breathable; closed-cell is denser with a higher R-value and moisture resistance.

Pros: Fills every gap and void, excellent air sealing, highest R-value (closed-cell), good for irregular shapes.

Cons: Most expensive option, professional installation only, difficult to remove or modify later, some mortgage lenders are cautious about spray-foamed roofs.

Best for: Difficult-to-access wall cavities, underside of pitched roofs, basement walls, and renovation projects where air sealing is critical.

Reflective Foil Insulation

Reflective foil works by reflecting radiant heat rather than resisting conducted heat. It is thin (typically 4–25 mm) and effective as a secondary layer but insufficient as the sole insulation in cold climates.

Pros: Very thin, lightweight, easy to install, acts as a vapour barrier, good for radiant heat reflection.

Cons: Low R-value on its own, requires an air gap to function, less effective in cold-dominated climates, can tear easily.

Best for: Loft top-ups, behind radiators, underfloor radiant barriers, and combining with other insulation types for a multi-layer system.

How to Choose

For most homeowners, the decision comes down to two questions:

1. How much space do you have? If thickness is limited (e.g., shallow rafter depth), use rigid foam for maximum R-value per mm.
2. Are you doing it yourself? If yes, mineral wool is the easiest and cheapest. If hiring, spray foam may be worth the premium for hard-to-access areas.

Calculate Your Insulation Needs

Use our free calculators to get exact quantities and costs:

• Insulation Calculator — rolls, boards, and vapour barrier
• Loft Insulation Calculator — loft-specific quantities
• Insulation Cost Calculator — compare material costs