Calculating the performance of your building project

Measuring Carbon - Illustration

If the built environment is to achieve its net zero carbon goals, it is essential we calculate performance in the same rigorous way across all building projects.

We want the industry to be able to make meaningful comparisons and be able to learn from each other. To make this happen, we need equivalent performance data.

For this purpose, we aim to have all Timber Development UK case studies include the below performance measurements – which are quickly becoming industry standard.

These performance measurements are:


Upfront Embodied Carbon (A1-A5)

This encompasses all emissions associated with the materials and construction processes of a building or structure, from cradle to practical completion.

Measurement: kgCO2e/m2 | Kilograms of carbon dioxide equivalent per. square metre

Calculation: Embodied carbon = total embodied carbon / GIFA

More information: IStructE. How to calculate embodied carbon, Whole Life Carbon Assessment for the Built Environment (rics.org), Assessing the Carbon-Related Impacts and Benefits of Timber in Construction : Timber Development UK


Stored Biogenic Carbon

Timber sourced from a sustainably managed forest will have sequestered biogenic carbon. This is the carbon dioxide absorbed and stored in the product.

Measurement: kgCO2e/m2 | Kilograms of carbon dioxide equivalent per. square metre.

Calculation: Stored biogenic carbon = product density × timber content x moisture content

More information. TDUK. Stored biogenic carbon calculator. Assessing the Carbon-Related Impacts and Benefits of Timber in Construction : Timber Development UK


Operational Energy (B6) in kWh/m2.yr

The average annual energy consumption of a building, otherwise known as Energy Use Intensity (EUI). It is a good indicator for building performance.

Measurement: kWh/m2.yr | Kilowatt hour per square metre of floor area of the dwelling per year.

Calculation: Operational energy = annual energy consumption / gross internal floor area


Airtightness at 50pa in m3/hr/m2

Air permeability testing is a mandatory requirement under Building Regulations Part L. It is essential for understanding the thermal efficiency of a building.

Measurement: m3/hr/m2 | Metres of lost air per hour and per metre square of the building envelope

Calculation: To be tested, a dwelling will need to be temporarily sealed while the test is taking place, while a suitable external opening is selected where a fan will be attached.


Overall area-weighted U-Value

A U-value is a measure of the rate of heat transfer, in this case taken as the average overall transfer of heat from the inside to the outside of a building.

Measurement: W/m2K| Watts per metre squared Kelvin

Calculation: U-Value = 1/(Sum of all R-Value)


Design Life

This is the period of use as intended by the designer, after which a building may need to be replaced. Before this period has elapsed, it should remain fit for its intended purpose.

Measurement: Years

Calculation: As per the design requirements and decisions taken.


Whole Life Carbon

Life cycle stages and modules, overlaid by definitions of upfront, embodied, operational, and whole life carbon.