SBEM - Colville Building

Why Colville building?

This building was chosen based on the following criteria:
• Building shape simplicity: the simplicity of the shape of each floor in this building makes the measuring of the different floor areas easier. This makes inputs into the SBEM model simpler.
• Building drawings: to scale floor plans were provided by the University Estates Department so an accurate measuring of the floor areas corresponding to different system types was possible.
• Building data: EPC data and meter readings were provided by the University Estates Department so that the model outputs could be compared with existing data.
• Poor performer: the Colville Building has a very poor thermal performance so there is scope for upgrades.

Colville Schematics.jpg

Figure a: Colville Building (left) and floor drawings provided by the University of Strathclyde Estates Department

Model geometry

The methodology to build the model was to divide the building in 15 different areas according to the type of Systems (radiators, convectors, air handling units, etc.) described in the Colville Building drawings provided. There are some rooms with different systems so the task to assign only one system to one room is inaccurate, which is why a system area approach was used.

A spreadsheet was used for the measuring task. The following elements of the building were measured:
• Windows, number and surface
• Doors, number and surface
• External Curtain Wall, area and perimeter
• External Brick Wall, area and perimeter
• Internal Wall, area and perimeter
• Ground floor, area
• Ceiling, area
• Roof, area
Following this, each system zone matches a HVAC systems.


Simulation results

Energy

Table a indicates that a total energy saving of 11% can be achieved by upgrading the fabric in the Colville building. These savings are achieved through a reduced heating demand (Figure a).

Table a: SBEM energy use and savings from fabric upgrades for the Colville building

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SBEM Annual Energy Consumption.jpg

Figure a: Breakdown of annual energy consumption before and after fabric upgrades.

CO2 emissions

Table b: SBEM CO2 emissions from Colville Building before and after fabric upgrades.

SBEM CO2 Emissions.jpg


Summary

SBEM is a useful tool for calculating energy and carbon savings. However, it offers no transparency for the results. The drivers for the savings are not clear. The purpose of the software is simply to check building compliance and upgrade potential with current regulations using the National Calculation Method (NCM). Any flaws in the calculation of the savings (such as inaccurate assumptions regarding occupancy patterns or plug loads) are due to flaws in the NCM.

The predicted savings are realistic in their magnitude and consistent with existing examples in literature.