THE PERFORMANCE GAP Introduction There is a gap in performance! - - PowerPoint PPT Presentation

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

Johan Haeberle

Johan.haeberle@iesve.com +33 610 533 265 www.iesve.com www.iesve.com/DiscoverIES