Envelope and protection

Insulation Materials

Insulation only works as part of a build-up. The same board in two different walls can behave very differently depending on what sits either side of it, how continuously it is installed, whether air can bypass it and how moisture moves through the assembly.

These entries describe what each insulation material is and the topics that surround it — moisture behaviour, air movement, fitting tolerance, compatibility with adjacent layers. They contain no thermal calculations, no performance figures and no claim that any material will deliver a given energy outcome. Those are matters for a qualified professional working on the actual build-up.

22 reference entries · educational materials reference · suitability always depends on the complete assembly and qualified professional review

Scope

What this category covers

Where the boundary of this part of the library sits, including what it deliberately leaves to qualified professionals.

Mineral, glass, natural-fibre, foam and reflective insulation materials
Insulation formats: batts, rolls, boards, blown, sprayed and panel systems
Composite systems where insulation is combined with a finish
Not covered: U-value or thermal calculations, condensation risk analysis, energy modelling

Start here

Frequently referenced entries

A starting point, not a ranking — these are simply the entries most people arrive looking for.

Mineral wool insulation →Fibrous insulation spun from melted rock and mineral feedstock, supplied as rolls, semi-rigid batts, rigid slabs and loose fill for walls, roofs, floors and partitions.Polyisocyanurate board →Rigid faced foam board formed by reacting isocyanate with polyol, produced continuously between bonded facings and used in roofs, walls, floors and insulated linings.Wood fibre insulation →Insulation made from defibred wood, supplied as flexible batts and as rigid boards, including profiled grades intended to be built into sheathing and sarking positions.

All entries

Every insulation entry

The complete set for this category, in reference order.

Entry describes

Role in an assembly

Part of a building

Mineral wool insulation →Fibrous insulation spun from melted rock and mineral feedstock, supplied as rolls, semi-rigid batts, rigid slabs and loose fill for walls, roofs, floors and partitions.

Glass wool insulation →Fibrous insulation spun from melted sand and recycled glass, supplied mainly as light compressible rolls and batts for lofts, timber frames, floors and partitions.

Expanded polystyrene →Rigid insulation moulded from steam expanded polystyrene beads and cut into boards, used in external wall systems, floors, cavities, formwork and below ground work.

Extruded polystyrene →Rigid closed cell polystyrene board formed by extrusion, with a smooth skin and profiled edges, used in loaded and moisture exposed positions after professional review.

Polyisocyanurate board →Rigid faced foam board formed by reacting isocyanate with polyol, produced continuously between bonded facings and used in roofs, walls, floors and insulated linings.

Phenolic foam board →Rigid closed cell board made from a foamed phenolic resin with bonded facings, raised where a slim rigid insulation layer is wanted in walls, roofs and internal linings.

Cellulose insulation →Loose fibre insulation made from recycled paper with mineral additives, installed by machine as a blown loft layer, a dense packed cavity fill or a damp sprayed application.

Sheep wool insulation →Resilient batt and roll insulation made from scoured sheep wool, usually blended with a binder fibre, fitted between studs, joists and rafters in timber construction.

Wood fibre insulation →Insulation made from defibred wood, supplied as flexible batts and as rigid boards, including profiled grades intended to be built into sheathing and sarking positions.

Spray foam insulation →Two part polyurethane foam mixed at a spray gun and applied in place, where it expands and cures bonded to the surfaces it lands on, in open cell and closed cell forms.

Multifoil insulation →Thin flexible roll built from reflective metallised films interleaved with wadding or foam layers, raised where the depth available for insulation is tightly constrained.

Aerogel insulation →Insulation built around silica aerogel, most often a thin flexible blanket of aerogel held in a fibre carrier, used selectively at details where almost no depth is available.

Hemp fibre insulation →Flexible batt and roll insulation made from the bast fibre of the hemp plant, usually blended with a binder fibre and mineral additives, for stud, rafter and joist positions.

External wall insulation →A layered system fixed to the outside of a wall, combining an insulation layer, a reinforced base coat and a finish, together with the beads, trims and reworked opening details it needs.

Cellular glass →A rigid inorganic board made by foaming molten glass into sealed cells, normally cut and bedded in adhesive or hot bitumen rather than friction-fitted into a stud bay.

Expanded clay fill →Fired clay granules expanded into light ceramic pellets and poured dry as a loose insulating fill that is raked to a level, drains freely and carries load by interlock.

Expanded cork board →A rigid insulation board made by steam-expanding cork granules until the cork's own resin binds them, giving a dark, vapour-open board with no added binder in its body.

Foamed glass aggregate →A lightweight angular gravel made by foaming recycled glass into closed cells, placed and compacted in layers so that one material forms both a fill and an insulating layer.

Hemp-lime infill →The woody core of the hemp plant bound in a lime binder, mixed wet and cast or sprayed around a frame as a jointless, non-load-bearing insulating wall body that dries slowly.

Sandwich panel →A factory-made element of two metal faces bonded to an insulating core, spanning between supports as one piece, with an interlocking side lap that carries its gasket and hidden fixing.

Polyester insulation →A soft synthetic insulation quilt of polyester fibres bonded to each other by heat, with no binder resin and no mineral fibre, fitted between studs, joists and rafters.

Vacuum insulation panel →A made-to-size panel whose micro-porous core is evacuated and sealed inside a gas-tight envelope, and which cannot be cut, drilled or pierced without ceasing to be what it is.

Browse by role

By the role the material plays

The same entries, clustered by what they typically do in an assembly. A material can appear in more than one cluster because it genuinely plays more than one role.

Substrate and base

Backgrounds and bases that other materials are fixed or applied to.

Thermal layer

Materials whose role in the build-up is thermal.

Weather barrier

Layers that shed or resist rain, wind and weather.

Sandwich panel →

Moisture and air control

Thin layers that control where moisture and air are allowed to move.

External surface

The visible outer face of a wall or roof.

Where they appear

Parts of a building this category touches

An orientation aid only — it does not imply that any entry is suitable for that part of a particular building.

Foundations and groundworks · 5
External walls · 20
Roofs · 17
Internal walls and ceilings · 15
Floors · 19
External works and landscape · 2

Elsewhere on Build Design Hub

Planning guidance for this subject

This library explains what materials are. These sections help with choosing between them and preparing for the conversation.

Exterior materials guides →Planning guidance for the external envelope.Building envelope checklists →Preparation before envelope conversations.Renovation guides →How upgrade and retrofit work is planned.

Building Systems Encyclopedia

The assemblies these materials sit in

A material page explains what a substance is. These pages explain how the assembly around it is organised, what roles its components perform and which interfaces matter.

Building envelopeEnvelope Control Layers and Continuity →The continuous planes running around an enclosure — air, vapour, water and heat — and the interruptions that decide whether that continuity actually exists.Building envelopeExternal Wall Build-Up Systems →Complete external walls read as a layer order: where in the thickness of the wall water is stopped, and in which direction the wall is allowed to dry afterwards.Building envelopeRoof Assembly Systems →Roofs answering two questions at once: where the insulation sits relative to the deck, and how the water-shedding layer achieves continuity across the whole surface.

Materials & Systems Encyclopedia

Reference entries for building materials, product formats and system components — what they are, what their behaviour depends on and what to ask about them.

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