Fencalc XA2021
Assembly definition
The roof assembly includes roof covering, structure, ceiling and insulation layers that contribute to thermal performance.
How to use the diagram
Read the visual first, then connect each label to the lesson text and your calculator inputs. The aim is to make every assumption visible before you calculate.
Learning Objective
Identify all roof elements that form part of the envelope.
Different roof zones
Flat roofs, pitched roofs and mixed construction may need separate treatment.
Practice Task
- Sketch a roof build-up.
- Label each thermal layer.
Calculator Tip
Separate roof types instead of forcing one value across unlike assemblies.
Worked Example: Roof Assembly Evidence
Scenario
A pitched roof uses ceiling-level bulk insulation and a reflective membrane under the roof covering.
Calculator Entry
Create separate entries if different roof zones use different assemblies or insulation locations.
Step-by-step method
- 1List each roof layer from outside to inside.
- 2Check whether required air gaps exist for reflective layers.
- 3Confirm bulk insulation thickness and continuity.
- 4Flag penetrations, compressed areas and thermal bridges for inspection.
Expected conclusion
A declared product value is useful only when the installed assembly matches the product assumptions.
Common Mistakes
- Using insulation product values without checking air gaps and installation conditions.
- Ignoring gaps, compression, service penetrations or thermal bridges.
- Combining unlike roof assemblies into one unexplained value.
Quick Knowledge Check
1. What should you confirm before applying this lesson to a project?
Roof types are identified.
2. Which piece of evidence should support the main input in this lesson?
Sketch a roof build-up.
3. What is the safest action if the information is incomplete?
Flag the missing evidence, use a conservative assumption where appropriate, and avoid claiming compliance until the information is confirmed.