Start with attic use and the existing roof layers. Insulating the roof slopes and insulating the floor of an unheated, closable attic are different choices. Exterior work requires coordinated consideration of height, junctions and tile retention.
How does attic use influence insulation planning?
A heated bedroom beneath the roof presents a different question from an attic used only as closable storage. Mention future intentions as well, because a storage space may later become living accommodation. The location of insulation needs to match that use.
Milieu Centraal distinguishes insulation of roof slopes from insulation of the attic floor. This does not make the apparently cheaper option automatically suitable for every home. Describe access, internal finishes and known moisture concerns so an adviser can establish which components need examining before a particular arrangement is selected or a product is ordered.
Which existing layers and later changes matter?
An older tiled roof may subsequently have received insulation, a membrane or a new internal lining. The visible tiles do not reveal that history. Gather records of earlier work and identify what can be seen from the attic. Unknown membranes or materials should not be identified solely by colour.
Further investigation may be needed to understand the build-up. The selected combination must account for moisture behaviour and connections around windows and penetrations. Adding insulation without establishing the existing layers is not a supported renovation strategy, even if the proposed product has an attractive thermal value or is commonly used elsewhere.
How should exterior height differences be resolved?
Exterior insulation can raise the roof build-up. This affects connections to gutters, walls and neighbouring roofs that are not being renovated. Ask how these transitions are addressed in the proposal. Ridges and roof windows may also form part of the same arrangement.
Comparing quotations only by insulation thickness therefore misses important work. Discuss whether existing tiles can remain and which components need temporary removal. Check address-specific requirements where height or appearance changes are proposed. Resolve those questions during preparation, rather than discovering on the final working day that a junction or permission issue was outside everybody’s assumed scope.
How can performance and execution be recorded together?
Ask which materials will be installed and how junctions and interruptions will be handled. Product performance is useful information, but it cannot be separated from insulation continuity and the surrounding construction. Record which existing layers are retained.
For an owners’ association, that may matter when an adjacent section is renovated later. Discuss internal and external finishing separately, including which rooms need to remain usable and who undertakes any making-good. The website’s roof planner gathers preferences and dimensions; designing the insulation assembly requires a separate assessment using the actual roof, its moisture behaviour and the agreed future use of the attic.
Frequently asked questions
Does an unheated storage attic always need slope insulation?
Not automatically. Insulating a closable attic floor may be another option. Current and future use determine which arrangement should be investigated.
Can existing tiles return after exterior insulation?
That can be investigated. Condition, dimensions and altered junctions must suit the new build-up and the availability of compatible replacement components.
Why does an existing under-tile membrane matter?
Its properties influence moisture behaviour across the complete assembly. Establish what is present before designing additional insulation or selecting a new internal lining.
Consulted 19 September 2026. Check requirements for your own address and selected system.