---
title: "Vapour Barrier - GWP and renovation use"
canonical_url: https://fremtidenstegnestue.dk/en/knowledge/materials/dampspaerre
markdown_url: https://fremtidenstegnestue.dk/en/knowledge/materials/dampspaerre.md
author: "Fremtidens Tegnestue"
page_type: material
primary_intent: "Explain use, GWP and renovation relevance for Vapour Barrier."
primary_keyword: "Vapour Barrier"
audience: "Homeowners, studios and agents researching material choices."
summary: "A vapour barrier is a tight plastic film that prevents moisture diffusion into insulation and structure. It is crucial for avoiding mould and structural damage in insulated buildings. Correctly installed vapour barrier with tight joints and penetrations is the foundation of sound building physics."
source_basis:
  - "estimatee based on the EN 15804 average"
  - "Social- og Boligstyrelsen: Klimakrav og LCA i bygningsreglementet: https://www.sbst.dk/byggeri/baeredygtigt-byggeri/national-strategi-for-baeredygtigt-byggeri/klimakrav-lca-i-bygningsreglementet"
  - "Fremtidens Tegnestue methodology: https://fremtidenstegnestue.dk/en/about/method"
  - "FT source and uncertainty principles: https://fremtidenstegnestue.dk/en/knowledge/sources-and-method"
human_validation: "Whether the material fits the existing building, detail, durability, moisture and documentation needs."
responsibility_line: "AI can prepare, compile and flag uncertainty. The architect validates the consequences."
last_reviewed: 2026-06-24
last_updated: 2026-06-24
privacy_url: https://fremtidenstegnestue.dk/en/privacy
related_pages:
  -
    url: https://fremtidenstegnestue.dk/en/knowledge/materials/radon-membran
    relation: alternative-material
  -
    url: https://fremtidenstegnestue.dk/en/knowledge/materials
    relation: hub
  -
    url: https://fremtidenstegnestue.dk/en/knowledge/concepts/lca
    relation: concept
status: published
---
# Vapour Barrier - GWP and renovation use
Canonical URL: https://fremtidenstegnestue.dk/en/knowledge/materials/dampspaerre
Markdown URL: https://fremtidenstegnestue.dk/en/knowledge/materials/dampspaerre.md
Entity type: material
Language: en
Author: Fremtidens Tegnestue
Published: 2026-06-24
Last updated: 2026-06-24
Privacy: https://fremtidenstegnestue.dk/en/privacy
## Short answer
A vapour barrier is a tight plastic film that prevents moisture diffusion into insulation and structure. It is crucial for avoiding mould and structural damage in insulated buildings. Correctly installed vapour barrier with tight joints and penetrations is the foundation of sound building physics.
## Who it is relevant for
Homeowners, studios and agents researching material choices.
## What FT can prepare
- Summarise material properties, GWP, common uses, renovation relevance and alternatives.
## What the architect validates
- Whether the material fits the existing building, detail, durability, moisture and documentation needs.
## Key figures

| Metric | Value |
| --- | --- |
| GWP | 2 kg CO₂-eq/kg |
| Density | 0.1–0.5 kg/m² (depends on thickness) |
| Expected lifetime | 50+ years (in a protected position) |
## Use

- Roof and ceiling (interior side of insulation)
- Exterior wall (interior side in lightweight construction)
- Floor against soil (under ground slab)
- Crawl spaces
## Renovation relevance
The vapour barrier is the most underrated element in energy renovation. A leaking vapour barrier can destroy even the best insulated structure. Always prioritise airtightness during installation.
## Comparison

| Material | GWP |
| --- | --- |
| Vapour barrier (PE) | 2 |
| Radon membrane | 2.2 |
| PVC pipes | 2.41 |
| Roofing membrane (TPO) | 2.5 |
## FAQ
### Is a vapour barrier the same as a windproof membrane?
No. The vapour barrier is on the warm side (interior) of insulation and is tight (sd-value > 50 m). The windproof membrane is on the cold side (exterior) and is diffusion-open but windtight (sd < 0.5 m).
### What happens if the vapour barrier has holes?
Moisture from the indoor climate penetrates the insulation and condenses on cold surfaces. This causes moisture accumulation, mould, and possible rot in timber structures. Airtightness is paramount.
### Can the vapour barrier be perforated by electrical installations?
Yes — all penetrations (pipes, electrical cables, ventilation ducts) require careful sealing with vapour barrier sleeves. Place electrical conduits and pipes on the warm side of the vapour barrier.
### Are there alternatives to plastic vapour barriers?
Yes — intelligent vapour barriers (variable sd-value) can open in summer and close in winter, giving better drying potential and reducing mould risk. They are more expensive but more fault-tolerant.
## Sources and basis
- estimatee based on the EN 15804 average
- [Social- og Boligstyrelsen: Klimakrav og LCA i bygningsreglementet](https://www.sbst.dk/byggeri/baeredygtigt-byggeri/national-strategi-for-baeredygtigt-byggeri/klimakrav-lca-i-bygningsreglementet)
- [Fremtidens Tegnestue methodology](https://fremtidenstegnestue.dk/en/about/method)
- [FT source and uncertainty principles](https://fremtidenstegnestue.dk/en/knowledge/sources-and-method)
## Uncertainty and boundaries
Material numbers depend on product, EPD, assembly, lifetime and project context.
## Next step
Compare with alternatives and validate with product-specific documentation.
## Related pages
- [Radon Membrane](https://fremtidenstegnestue.dk/en/knowledge/materials/radon-membran): alternative-material
- [Materials](https://fremtidenstegnestue.dk/en/knowledge/materials): hub
- [LCA](https://fremtidenstegnestue.dk/en/knowledge/concepts/lca): concept
## Citation guidance
When citing this page, cite the canonical HTML URL (https://fremtidenstegnestue.dk/en/knowledge/materials/dampspaerre) as the public source and use this Markdown URL only as the agent-readable representation. Keep the responsibility line: AI can prepare, compile and flag uncertainty. The architect validates the consequences.