BR18 A4-A5: The Complete Guide to Climate Requirements for the Construction Process

A4 and A5 are two modules in the life cycle assessment (LCA) framework under BR18 — the Danish Building Regulations 2018. They cover the climate impact that occurs during the construction process itself, i.e. before the building is occupied.

Module A4 covers the transport of building materials and heavy equipment from the manufacturer or supplier to the construction site. This includes intermediate terminal handling (storage, reloading) and transport of waste materials.

Module A5 covers everything that happens on the construction site: energy consumption (electricity, heating, fuel for machinery), handling of construction waste across 15 defined fractions, and removal of excavated soil if classified as waste.

Since July 1, 2025, A4 and A5 combined have a separate limit of 1.5 kg CO₂e/m²/year. This is independent of the materials' climate impact (A1-A3) — you cannot borrow from one budget to cover the other. Learn more about the two separate CO₂ budgets.

The A4-A5 requirements didn't emerge overnight. Here is the regulatory timeline:

Date	Event
May 30, 2024	Political agreement adopted: "Supplementary agreement on national strategy for sustainable construction". A4-A5 established as a separate requirement.
July 1, 2025	A4-A5 requirements take effect. Limit: 1.5 kg CO₂e/m²/year.
2027	Limit tightens to 1.3 kg CO₂e/m²/year.
2029	Limit tightens further to 1.1 kg CO₂e/m²/year.

Additionally, an analysis is planned for mid-2026 to assess whether outdoor areas should be included from mid-2027. The direction is clear: the requirements will only get stricter.

Not all construction projects are affected equally. Here are the rules:

New construction

• All new buildings over 50 m² must document A4-A5 and comply with the limit.
• Unheated buildings under 50 m² are exempt.

Extensions

• Apartments, offices, institutions: A4-A5 documentation required regardless of extension size.
• Single-family homes, row houses, holiday homes: Only if the extension exceeds 250 m².

Exemptions

Certain building types are exempt from the limit, but must still document:

• Hospitals
• Prisons
• Waterworks
• Defense buildings

These must complete the calculation but are not subject to sanctions if they exceed the limit.

A central principle in BR18 is that the climate calculation is split into two completely separate budgets:

Budget	Modules	Limit
Materials and operation	A1-A3, B4, B6, C3-C4	Varies by building type (e.g. 7.5 kg for offices, 6.7 kg for single-family homes)
Construction process	A4 + A5	1.5 kg CO₂e/m²/year (same for all building types)

The critical point: you cannot borrow between the two budgets. Surplus on materials cannot compensate for exceeding the construction process limit — and vice versa. The two accounts are completely isolated. We explain this in detail in our article on the two separate CO₂ budgets.

This is one of the most common misunderstandings, and it can prove costly if only discovered at project completion.

Module A4 covers all transport-related emissions from materials and heavy equipment to the construction site. Specifically, you must document:

• Transport of building materials from factory/supplier to site. Emissions can be calculated in several ways: via standard values based on material weight and distance (Table 10), via actual fuel consumption (Table 8.2), or via EPD data from the manufacturer.
• Transport of heavy equipment (cranes, scaffolding, large machines) to and from the site. Equipment under 1 ton is exempt (the 1-ton rule).
• Terminal handling — storage and reloading between transport links, e.g. when materials transfer from ship to truck.
• Transport of waste materials — materials that are not incorporated into the finished building.

Relevant tables in BR18 Annex 2

• Table 10: Standard values for transport emissions (kg CO₂e per ton-km for different transport modes).
• Table 8.2: Fuel-based emission factors — used when you know the actual fuel consumption.

Rule of thumb: the more precise your data (actual km, actual fuel), the lower your A4 result compared to standard values. See our in-depth comparison of standard values vs. measured data.

Module A5 is typically the most data-intensive. It covers all emissions from activities on the construction site itself:

Energy consumption

• Electricity: Lighting, power tools, site cabins, construction drying.
• Heating: District heating, drying of structures, heating of site cabins.
• Fuel for machinery: Diesel/petrol for construction equipment. Machines under 1 ton are exempt.

Construction waste

BR18 Table 11 defines 15 waste fractions, each with its own emission factor. You must sort and weigh waste per fraction. Important: if you mix waste in one container, it is penalized at the emission factor of the worst fraction.

Soil and removal

• Construction waste: Transport of waste from the site to receiving facilities.
• Excavated soil: Only included if the soil is classified as waste.

What is NOT included in A5?

• Water consumption — not part of the A5 calculation.
• Machines and equipment under 1 ton.

Relevant tables

• Table 11: Emission factors for 15 waste fractions.
• Table 10: Transport factors for waste and soil (alternatively, you can use the flat rate of 0.06 kg CO₂e/m²/year).
• Table 8.1/8.2: Energy and fuel factors.

The method choices differ for A4 and A5. A4 (transport) gives you a free choice between four methods, while A5 (construction site) primarily requires measured data.

A4 — Transport (four methods)

Method	Data source	Advantages	Disadvantages
Kilo-based standard method (Table 10)	Material weight × generic distance × emission factor per ton-km	Easiest to use. No data from carrier needed.	Conservative values — up to 70× higher than measured data. Requires mandatory addition of +0.04 kg CO₂e/m²/year.
Distance-based method (Table 10)	Material weight × actual distance × emission factor per ton-km for the chosen transport mode	More precise than the standard method — uses actual distance and transport mode.	Requires knowledge of actual distance and transport mode per delivery.
Fuel-based method (Table 8.2)	Actual fuel consumption from the carrier	Typically gives the lowest result. Full traceability.	Requires fuel data from each carrier.
EPD data (EN 15804)	Manufacturer's environmental product declaration with A4 module	Product-specific. Can be lower than standard values.	Not all products have EPDs. Distance assumptions may differ from reality.

A5 — Construction site (primarily measured data)

Item	Method	Data source
Electricity, heating, fuel for machines > 1 ton	Mandatory measured data	Electricity meter, heat meter, fuel receipts (Table 8.1/8.2)
Construction waste (15 fractions)	Optional	Weighing slips + Table 11 emission factors, or EPD data
Transport of waste and soil	Optional	Measured data or fixed rates (0.06 kg CO₂e/m²/year)

Recommendation: Use measured data for the largest items (transport of concrete/steel, diesel for machinery, electricity consumption) — this typically gives the lowest result. Supplement with standard values for smaller items. You can freely mix methods within the same project. Read our detailed guide to standard values vs. measured data.

A45 lets you compare all three methods per emission, so you can automatically choose the method that yields the lowest — and still correct — result.

Responsibility for A4-A5 documentation is distributed across several parties, but there is one fundamental rule:

Party	Responsibility
Building owner	Bears the public-law responsibility. The municipality contacts the building owner if documentation is missing or the limit is exceeded. The building owner cannot delegate this responsibility away.
Advisor	Typically performs the LCA calculation and compiles data from all parties. Coordinates between contractors.
Contractor	Must supply the actual data: fuel consumption, invoices with transport details, weighing slips for waste, electricity readings. Without the contractor's data, the calculation is impossible.
Municipality	Issues the occupancy permit. Spot-checks approximately 10% of cases.

The typical mistake: the contractor assumes it's the advisor's problem, and the advisor assumes the contractor will supply data unprompted. Define responsibilities in contracts from the start. Read our in-depth article on A4-A5 responsibility.

A practical workflow from project start to occupancy permit:

1. Planning (before construction starts)

• Conduct an early LCA screening to identify the largest CO₂ contributors.
• Define data responsibilities in all contracts: who delivers what, when, and in what format.
• Choose calculation methods for the major items (measured data vs. standard values).
• Set up a project in a calculation tool — avoid starting with blank spreadsheets mid-construction.

2. During construction (ongoing)

• Collect data continuously: invoices, delivery notes, fuel receipts, electricity meter readings, waste weighing slips.
• Upload documentation at least once a month — avoid accumulation.
• Monitor the running CO₂ status against the limit.
• React early if approaching the limit: switch to low-emission transport, optimize waste sorting, consider HVO diesel.

3. Completion (at project handover)

• Perform the final "as-built" LCA calculation with actual data.
• Generate a BR18-compliant report with full traceability from invoice to calculation.
• Submit documentation to the municipality together with the completion notification.
• Retain all supporting material — the municipality can conduct spot-checks.

These mistakes appear repeatedly. They can delay the occupancy permit or push your CO₂ budget over the limit unnecessarily:

1. Believing you can borrow from the materials budget

The two CO₂ budgets are completely separate. Surplus on A1-A3 cannot compensate for exceeding A4-A5. Discover this too late, and there is no workaround.

2. Delaying data collection until the end of the project

Missing data at project completion forces you to use conservative standard values — which are often 2-3 times higher than actual figures. This can mean the difference between compliance and exceeding the limit. See our practical guide to data collection.

3. Mixing waste in a single container

Unsorted waste is penalized at the emission factor of the worst fraction. Proper sorting into BR18's 15 fractions can significantly reduce the waste CO₂ contribution. Learn more about hidden CO₂ traps on the construction site.

4. Underestimating drying energy and site cabin heating

Energy consumption for drying and site cabin heating is often a surprisingly large item. Especially during winter, it can account for 30-40% of the entire A5 budget.

5. Coordinating via spreadsheets between multiple parties

When main contractor, subcontractors, and advisor exchange data in separate Excel files, version conflicts, missing traceability, and double entries arise. A shared digital tool eliminates this risk.

Several approaches exist for handling A4-A5 calculations:

Tool	Type	Strengths	Limitations
LCAbyg	Free, government-backed	Covers full LCA (A1-D). Recognized by authorities.	Not specifically designed for A4-A5. Requires supplementary Excel. No AI or automation.
A45	SaaS platform	Purpose-built for A4-A5. AI-powered invoice scanning. Automatic calculation per BR18 Table 8, 10, 11. Team collaboration. Real-time compliance tracking.	Focuses exclusively on A4-A5 — use LCAbyg or other LCA software for A1-A3.
Excel	Manual	Flexible. No license required.	No traceability. Error-prone. No automation. Difficult to share between parties.

Regardless of which tool you choose, the critical factor is starting data collection early and maintaining it continuously. The most expensive choice is to wait. Read our detailed comparison of A45, LCAbyg, and Excel.