Where does the data come from?
CarbonBuzz relies on users entering design energy use data from M&E reports and Post-occupancy evaluation data from energy bills and meter readings.
Post occupancy evaluation is an important method for designers and consultants to gain insight into the relationship between design and actual performance. The industry experience is that forecast design energy usage is usually less than the actual
Actual emissions are obtained through meter readings or utility bills after the building has been occupied for a period of time such that its use is considered stable. This would normally be at least one full year to enable an account to be made of the impact of variation in occupancy patterns and the change of the seasons. CarbonBuzz will provide a standard template for architects and engineers to discuss the energy use of their buildings and share design information online.
How does CarbonBuzz address the differences between design and actual energy use data and how does CarbonBuzz relate to Part L and EPCs and DECs?
CarbonBuzz will help designers to better understand this discrepancy and bridge it. Its use will focus their attention on the assessment of energy uses that are not reported as part of the Part L or EPC assessment such as appliance loads, occupancy level, operating hours and possible special uses. Energy use of lifts, display lighting, refrigeration and similar occupier defined activity are similarly omitted from the regulatory assessments. All of these will have a major impact on a buildings' actual energy use.
It also helps designers to align forecast and actual energy use data irrespective of whether the project has been assessed through the Part L, EPC or DEC systems allowing 'like-for-like' comparisons from design to completion.
CarbonBuzz will also help the construction industry deliver buildings that perform to design expectation by collecting data on how buildings perform in use. It will identify the causes of possible discrepancies between designed energy use and actual performance, and draw attention to the importance of submetering for easier building pathology.
What benchmarks does CarbonBuzz use?
At the heart of CarbonBuzz is the ability to benchmark project emissions benchmarked during both design forecast and post occupancy.
Design forecast emissions are calculated during the design phases and can be updated throughout the project. The database currently holds only one set of data. These emissions are calculated through the use of thermal modeling techniques or steady state calculations by the M&E engineers. They are normally outlined in the M&E report from stage C onwards and as part of the Part L assessment. Case studies demonstrate the data source and entry.
It is important to remember that CarbonBuzz is a voluntary benchmarking platform and not a certification process.
How does CarbonBuzz calculate the CO2 emissions from the energy use data entered?
For design forecast figures CarbonBuzz uses the Part L emissions factors to convert energy use data to a carbon emissions profile for the project except for electricity where the DEC rating of 0.55 kgCO2/kWh is used to allow like-for-like comparisons between design forecast and actual emissions.
Each emission factor is defined according to the amount of carbon emitted, in kg, for each kWh of energy produced or consumed. The factors work as multipliers and permit an equivalent comparison of emissions from different types and sources of energy.
Different electricity grids will have different carbon factors associated with them.
The UK national electricity grid is currently rated at 0.55 kgCO2/kWh as indicated in DEC methodology. Other local grids will have a different factor that can be input as required.
Fuel types will also vary in their emissions.
Gas heating has an emission factor of 0.194 kgCO2/kWh and Biomass heating a factor of 0.025 kgCO2/kWh. Some fuel types have emission factors which are dependent on their source, such as biodiesel. These specific figures can also be input by the user as required.