What is a greenhouse gas account?

A complete guide to greenhouse gas accounting

The terms come thick and fast in construction right now: LCA, EPD, TEK17, greenhouse gas calculations. But what do they mean in practice? And more importantly, how do you produce an account that actually gets approved?

A few years ago a greenhouse gas account was something enthusiasts did on pilot projects. Today it is routine. With the requirement in TEK17 and expectations from banks and clients, anyone who builds needs to understand the basics of a life cycle assessment.

This article explains what a greenhouse gas account is, how a life cycle assessment is structured, and what it takes to get one right.

What is a greenhouse gas account?

A greenhouse gas account for a building is a calculation of the total greenhouse gas emissions, measured in CO2 equivalents, associated with that building across its whole life.

The method is called life cycle assessment, or LCA. Instead of looking only at emissions from the construction site, an LCA takes in the whole picture: from raw materials being extracted, through manufacture and transport, to the building being demolished and its materials recovered sixty years from now.

Which modules a life cycle assessment includes

To make greenhouse gas calculations comparable, Norway follows NS 3720:2018. It divides a building's life into four main phases:

• Phase A, production and construction. Emissions from manufacturing materials (A1 to A3), transport to site (A4) and the construction process itself (A5). This is usually where the largest emissions sit, often called embodied carbon.
• Phase B, in use. Emissions from maintenance, replacement of materials (B4) and operational energy use (B6).
• Phase C, end of life. What happens when the building comes down: demolition, waste transport and waste treatment.
• Phase D, beyond the life cycle. The potential for reuse and recycling in the next life cycle.

Why you need a carbon calculator

The theory behind LCA is logical. The practice is complex. A modern building has thousands of components, each with its own emission factor, transport distance and service life.

Doing those calculations by hand in a spreadsheet is theoretically possible and practically risky. It is slow, easy to get wrong, and painful to update every time the project changes.

That is why most teams now use a dedicated carbon calculator. A good one does three things:

1. Brings quantities in easily, straight from a BIM model or a spreadsheet import.
2. Maintains the EPDs for you, matching your materials against a library of environmental product declarations or generic values.
3. Structures the report, so the result follows NS 3720, TEK17 and whichever certification scheme you are working to.

Three ways to get greenhouse gas calculations right

Whether you are meeting the minimum in TEK17 or chasing a BREEAM Outstanding rating, the route to lower emissions is much the same. These three make the biggest difference to the bottom line of the account.

1. Start at the sketch stage, before it is too late

Early phase is where you have the most influence. It is where building form, structural system and material concept are decided. Once the ground is broken, a large share of the emissions is already locked in by choices that have been made. Certification schemes such as BREEAM therefore award points for carrying out calculations at sketch stage. Use a simple calculator early to test scenarios: what happens to emissions if we choose mass timber instead of steel?

2. Ask for EPDs, and drop the generic figures

Environmental product declarations are the currency of a greenhouse gas account. An EPD is a verified document stating exactly how much CO2 a specific product emits. Without one you fall back on generic averages, which are usually conservative and carry a safety margin that counts against your result. Schemes such as the Nordic Swan Ecolabel often require product-specific EPDs as evidence of compliance. Choose software that suggests EPDs from EPD-Norge automatically.

3. Go after the heavyweights first

Do not spend time calculating door handles and light switches before the big items are under control. In practice concrete, steel and aluminium are by far the largest emission sources in a building.

• Concrete. Moving from standard concrete to low-carbon class A or B can cut emissions sharply without changing the design.
• Steel. Choosing steel with a high recycled content, or reused steel, makes a large difference.
• Aluminium. Aluminium facades take a lot of energy to produce. Check whether the supplier uses renewable energy in production, for example Norwegian hydropower.

Getting started with your greenhouse gas account

Producing a greenhouse gas account does not have to be complicated. Reduzer guides you through the whole process, from early phase to finished building.

It brings EPDs in automatically, calculates to NS 3720, and generates reports ready for TEK17, BREEAM, FutureBuilt and the Nordic Swan Ecolabel.

Book a demo with our experts here to see how it works.