Insulation and retrofit installers A–Z dictionary
UK trade reference · plain English
Safety: if a material might contain asbestos, leave it undisturbed and do not drill, sand or break it. Have it surveyed, and use a licensed asbestos contractor for removal: HSE requires a licence for most asbestos removal work.
Insulation is part of a building system, not just a product thickness. Moisture behaviour, ventilation, airtightness, thermal bridges, fire precautions and the condition of existing fabric must be considered together. Existing buildings can need a different approach from new construction. A proposal should explain its assumptions, interfaces and inspection points, not promise a universal saving from one material. Use these definitions to question the complete design and handover.
This A–Z combines useful technical vocabulary with links to full references where the article meets our depth and sourcing checks. An unlinked definition is intentionally kept here rather than turned into a shallow standalone page. Read a quotation against its actual scope: a familiar word is not a complete specification.
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A
- Airtightness
- Control of unintended air leakage through the building envelope. It must be coordinated with planned ventilation.
F
- Fabric first
- Prioritising appropriate improvements to the building envelope before assuming equipment alone will resolve demand or comfort issues.
G
- Getting into insulation work
- Insulation work includes several occupations, from domestic building-fabric improvement to commercial and industrial thermal insulation. These need different materials, access and assessment. A career route should identify the intended sector and teach the complete assembly rather than assume that adding the thickest available product is always a suitable improvement.
I
- Interstitial condensation
- Moisture condensing within a construction build-up under relevant conditions. Surface appearance alone cannot establish its absence.
L
- Loft insulation
- Loft insulation reduces heat flow through the upper part of a building, commonly by insulating at ceiling level in an unheated loft. Other roof constructions use insulation in different positions.
R
- Retrofit assessment
- Evaluation of an existing building to inform a suitable improvement plan, rather than a product-only sales survey.
T
- Thermal bridge
- An area of increased heat transfer associated with geometry or material changes. Details matter as well as the main insulation layer.
U
- U-value
- Heat transfer through a specified element under defined conditions. It is not the same as the conductivity of one material.
V
- Vapour control layer
- A layer with a specified resistance to water-vapour movement. Position, continuity and interfaces depend on the build-up.
- Ventilation strategy
- The planned way of supplying and removing air for the building and its use, coordinated with envelope changes.
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Sources and further reading
Linked article sources support the technical background; informal usage is editorial and varies by region. Full specification and legal requirements must be checked in the original.
Sources checked: 8 November 2026. General reference, not instructions for safety-critical DIY. National regulations and current standards must be checked for the project.
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