BR18's climate requirements: CO2 limits for new construction
How the Building Regulations put numbers on construction's climate footprint
Introduction
Construction accounts for a large part of Denmark's total carbon footprint — both from the materials used and from the construction process itself. The Building Regulations (BR18) for the first time in 2023 set a specific figure for how much CO2 a newly built house may emit over its lifetime and the requirements have since been tightened.
2023: the first limit values
From 1 January 2023 it became a requirement for building owners to prepare a life cycle assessment (LCA) for all new buildings. From then until 30 June 2025, new buildings over 1,000 m² had to meet an upper limit of 12 kg CO2 equivalents per m² per year for the total climate footprint, calculated over a period of 50 years.
Summer 2025: requirements tighten significantly
From 1 July 2025, a climate calculation (LCA) must be made when constructing buildings and extensions — not only for buildings over 1,000 m² as before. Exempt are, among others, unheated buildings under 50 m² and extensions under 250 m² to detached houses, terraced houses and holiday homes (BR18 § 297, subsections 2-3). At the same time, the limit value has been lowered from 12 kg to between 4.0 and 8.0 kg CO2 equivalents per m² per year, depending on the building type (§ 298, subsection 1).
| Building type | Limit value |
|---|---|
| New buildings over 1,000 m² (1 January 2023 – 30 June 2025) | 12 kg CO2e pr. m² pr. år |
| Holiday homes under 150 m² (from 1 July 2025) | 4.0 kg CO2e per m² per year |
| Holiday homes of 150 m² or more (from 1 July 2025) | 6.7 kg CO2e per m² per year |
| Farmhouses, detached houses, terraced, linked and semi-detached houses (from 1 July 2025) | 6.7 kg CO2e per m² per year |
| Apartment buildings and offices, retail and warehouses (from 1 July 2025) | 7.5 kg CO2e per m² per year |
| Other buildings (from 1 July 2025) | 8.0 kg CO2e per m² per year |
| The construction process, modules A4-A5 (from 1 July 2025) | 1,5 kg CO2e pr. m² pr. år |
Coming: 2027 and 2029 (not adopted yet)
A broad political majority agreed on 30 May 2024 to tighten the requirements in two steps: in mid-2027 and in mid-2029. The figures are to be set «based on the latest knowledge and data». As of 6 October 2026 they are not in BR18. The latest amendment to BR18 is BEK nr. 1485 of 1 December 2025.
Expected limit values in the agreement (kg CO2e per m² per year)
| Building type | 2025 (in force) | 2027 (expected) | 2029 (expected) |
|---|---|---|---|
| Holiday homes under 150 m² | 4,0 | 3,6 | 3,2 |
| Detached houses, terraced houses, tiny houses and holiday homes of at least 150 m² | 6,7 | 6,0 | 5,4 |
| Apartment buildings | 7,5 | 6,8 | 6,1 |
| Office buildings | 7,5 | 6,8 | 6,1 |
| Institutions | 8,0 | 7,2 | 6,4 |
| Other new buildings | 8,0 | 7,2 | 6,4 |
| The construction process | 1,5 | 1,3 | 1,1 |
| Average | 7,1 | 6,4 | 5,8 |
The limits are differentiated by building type
For the first time, BR18 operates with different CO2 limits depending on the type of building being constructed. A detached or terraced house may emit at most 6.7 kg, an apartment building or an office 7.5 kg and other buildings 8.0 kg CO2e per m² per year, while small holiday homes under 150 m² have the lowest limit of 4.0 kg. The difference is because the building types have different typical material quantities and operating patterns. The differentiation is meant to make the requirements fairer across the construction sector's very different types of project.
A new boundary for the building process itself
Beyond the building's overall lifetime carbon footprint, an independent threshold is introduced for climate impact from the construction process itself — that is, transport of materials and equipment to the site, energy consumption on the building site and waste management along the way. This part of the footprint must be kept below 1.5 kg CO2 equivalents per m² per year and is included as a separate part of the overall life cycle assessment.
- 01Transport of materials and machines to and from site counts
- 02Energy consumption for machines heat and lighting on site counts
- 03Handling and disposal of construction waste counts
- 04The requirement should push construction sites towards less waste and greener operation, not just greener materials
Responsibility lies with the client, but decisions start early
It is the project owner who is formally responsible for ensuring that a project meets climate requirements, but the crucial decisions are often made already in the design phase — in the choice of construction principle, materials, and building size. The earlier in a project the carbon footprint is considered, the cheaper and easier it is typically to comply with the limit, because you can choose other solutions from the start instead of having to correct them later.
What does it mean for construction workers?
For craftspeople and contractors the requirements mean the climate account is no longer something architects and engineers calculate at the desk — it is something that must be documentable for the specific construction site. Material choice waste transport and energy consumption on site become all figures that count towards the overall calculation and which each individual employee's working methods help influence.
It places new demands on documentation out on site: quantities of material must be accounted for waste must be recorded and transport of materials must be documented. The craftspeople and foremen used to keeping track of these figures will experience that their daily record keeping gets a clear place in a larger statutory account.
- 01From 1 July 2025, an LCA must be made when constructing buildings and extensions — with few exceptions
- 02The limit value depends on the building type: 4.0-8.0 kg CO2e per m² per year
- 03The building process has its own independent limit value of 1.5 kg CO2e per m² per year
- 04Early choices in design have a significant impact on whether requirements can be met