using bim to close the performance gapb) feeding back bem results to bim 2. updating bem with bms...
TRANSCRIPT
USING BIM TO CLOSE THE PERFORMANCE GAP
Introduction
There is a gap in performance!
There is a mismatch between the expectations around the performance of new buildings and the reality of utility bills. This difference between expected and realised energy performance has come to be known as the « performance gap »
There is a gap in performance!
There are many reasons for this: 1. Building energy modelling difficulties during design
2. Changes to the specification during construction
3. Squeezed commissioning period leading to incomplete work
4. Unanticipated occupant behaviour or changes in building use
Strategies
Make more realistic expectations Build closer to design
Actual Building
BEM Actual Building
BEM
Agenda
1. BIM and design (BEM) a) Using BIM to populate BEM b) Feeding back BEM results to BIM
2. Updating BEM with BMS (model calibration)
3. Improving actual building with BEM conclusions
4. Using newly acquired knowledge for design
Building Energy Model
Building Management System
BIM and Design
VIRTUAL ENVIRONMENT
BIM 4 Analysis
Actual Building
BEM BIM
BIM 4 Analysis
gbXML,
Excel
BIM 4 Analysis
Model calibration
Model calibration
Model calibration
Goes up to 65% in offices
30% Reduction in Lighting Load
Goes up to 65% in offices
62% Reduction in Equipment Load
Model calibration
The combined impact of the actual equipment on the annual boiler energy compared with the Compliance profiles is shown below
Compliance model predicted 34% less heating energy when compared to the calibrated model
Bridging the Discrepancy
Dynamic Simulation Model + Operational Data
Actual Building
Gap between predicted and actual performance can be closed
to 5-10%
• Measured consumption data compared to results from initial Enhanced Model
• Electricity Usage from Motor Control Centres (MCCs) and per floor panels & Half Hourly gas data
• Simulation parameters in the Enhanced Model were tweaked to provide a close match to measured consumption
Simulated Electrical Consumption against measured electrical consumption – Nov 2015.
Case study: NHS Trust in London
Case study: NHS Trust in London
End Use CVRMSE NMBE
Electricity (Monthly) 2.1 -0.4
Electricity (Hourly) 14.3 -0.8
Gas (Monthly) 8.6 0.4
HVAC (Monthly) 6.1 -3.4
Small Power (Monthly) 2.5 2.2
Model calibrated to a Monthly level, but IES was also able to calibrate the Electricity to an Hourly level
Benchmark Model Results
ASHRAE Guideline 14: Model is “calibrated” when the Coefficient of Variance Root Mean Square Error (CVRMSE) is below 15% and Net Mean Bias Error (NMBE) is ± 5% for monthly calibration. If hourly calibration data is used, these requirements shall be 30% and 10% respectively.
Improving actual building
• Identify underperforming parameters
• Detect faults
• Test possible improvements (retrofit)
Using Calibrated BEM
Build deeper knowledge
• To make better BEM at design stage
• Occupancy
• Equipment
• Imperfect controls
• To investigate so far neglicted improvement areas
Using acquired knowledge
SUMMARY
Using BIM to close the performance gap • BIM is used to populated initial BEM
• BEM updates BIM on critical points
• BMS used to calibrate BEM
• Calibrated BEM used to control building operation, investigate options for
improvements
• More reliable information used for initial BEM at design stage
