--- title: "Roofing Felt - GWP and renovation use" canonical_url: https://fremtidenstegnestue.dk/en/knowledge/materials/tagpap markdown_url: https://fremtidenstegnestue.dk/en/knowledge/materials/tagpap.md author: "Fremtidens Tegnestue" page_type: material primary_intent: "Explain use, GWP and renovation relevance for Roofing Felt." primary_keyword: "Roofing Felt" audience: "Homeowners, studios and agents researching material choices." summary: "Roofing felt is bitumen-based roofing — one of the most widely used materials for flat roofs in Denmark. It is made from polyester felt impregnated with modified bitumen. It acts as vapour barrier, windproof, and waterproof. Lifespan of 20–30 years for conventional products, up to 40–50 years for the best qualities." 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/tagfolie relation: alternative-material - url: https://fremtidenstegnestue.dk/en/knowledge/materials/betontagsten relation: alternative-material - url: https://fremtidenstegnestue.dk/en/knowledge/materials/naturskifer relation: alternative-material - url: https://fremtidenstegnestue.dk/en/knowledge/materials relation: hub - url: https://fremtidenstegnestue.dk/en/knowledge/concepts/lca relation: concept status: published --- # Roofing Felt - GWP and renovation use Canonical URL: https://fremtidenstegnestue.dk/en/knowledge/materials/tagpap Markdown URL: https://fremtidenstegnestue.dk/en/knowledge/materials/tagpap.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 Roofing felt is bitumen-based roofing — one of the most widely used materials for flat roofs in Denmark. It is made from polyester felt impregnated with modified bitumen. It acts as vapour barrier, windproof, and waterproof. Lifespan of 20–30 years for conventional products, up to 40–50 years for the best qualities. ## 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 | 1.2 kg CO₂-eq/kg | | Density | 2–5 kg/m² | | Expected lifetime | 20–50 years (depending on quality) | ## Use - Flat and slightly pitched roofs - Vapour barrier under roof insulation - Foundation damp-proofing - Roof terraces ## Renovation relevance Replacing roofing felt is one of the most common renovation tasks on flat roofs. It is a good opportunity to add roof insulation and upgrade to more durable roofing. ## Comparison | Material | GWP | | --- | --- | | Natural slate | 0.058 | | Concrete roof tile | 0.25 | | Roofing felt | 1.2 | | Roofing membrane | 2.5 | ## FAQ ### What is the lifespan of roofing felt? Conventional roofing felt lasts 20–30 years. SBS-modified and glass fibre reinforced felt can last 40–50 years. Lifespan depends on UV exposure, temperature differential, and water stagnation. ### When should roofing felt be replaced? Signs of spent roofing felt: cracks and blisters in the surface, visible polyester felt, water pooling that doesn't evaporate, and leaks in the building. A professional roof inspection can clarify the condition. ### Can roofing felt be recycled? Old roofing felt can be partially recycled in road asphalt. It requires delivery to a specialist reception facility. Many roofing contractors offer disposal as part of a replacement job. ### Are there alternatives to roofing felt? Yes — roof membrane (TPO/EPDM) is an alternative with longer lifespan and lower CO₂ over long lifetime. Green roof (sedum/extensive vegetation) is another alternative that adds biodiversity. ## 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 - [Roof Membrane (TPO/EPDM)](https://fremtidenstegnestue.dk/en/knowledge/materials/tagfolie): alternative-material - [Concrete Roof Tiles](https://fremtidenstegnestue.dk/en/knowledge/materials/betontagsten): alternative-material - [Natural Slate](https://fremtidenstegnestue.dk/en/knowledge/materials/naturskifer): 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/tagpap) 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.