Commercial Buildings Research Group

1. NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Whole Building Modeling
Using OpenStudio
Commercial Buildings Research Group
Andrew Parker
December 2016

2. 2
Agenda
• Baseline Automation
• Parametric Analysis Tool 2.0
• Roadmap

3. 3
OpenStudio Killer Feature: Measures
Measures: scripts that operate on model & results
• Transform model e.g., replace constructions, daylighting package, etc.
• Perform these actions repeatedly, consistently & quickly on any model
• An open way of extending functionality & transferring knowledge
Help!
Ich bin
expert!
Thanks!

4. 4
OpenStudio Killer Feature: Measures
Add Heat
Recovery
Measures: scripts that operate on model & results
• Transform model e.g., replace constructions, daylighting package, etc.
• Perform these actions repeatedly, consistently & quickly on any model
• An open way of extending functionality & transferring knowledge
• Can be arbitrarily surgical, e.g., daylighting measure sensitive to space-type
Daylighting
Package

5. 5
Baseline Automation – What Is It?
• Input: Proposed (as-designed) model
– Space types assigned
– Window construction types assigned
• Output: 90.1 Appendix G baseline model
– Internal loads
– Construction properties
– HVAC systems, controls, and efficiencies
Create
Baseline
Building

6. 6
Motivation
• Xcel Energy EDA Program pays for energy
modeling to inform design.
• Incentive based on energy savings.
• As code stringency increases:
– Savings shrink
– Therefore incentives shrink
– …but req’d modeling effort does not
• Automation helps more of the project budget
go toward meaningful analysis

7. 7
How it works
– Remove external shading devices
– Shrink the windows and skylights, if necessary
– Make sure all spaces are assigned stories
– Modify internal loads (just LPDs for 90.1)
– Add daylighting controls to each zone
– Apply prescribed construction types
– Set properties of those constructions
– Remove existing HVAC
– Add HVAC system w/ correct components
– Set properties used for air system sizing (SAT, delta-T)
– Add SAT reset, economizers, pressure reset, damper pos.

8. 8
How it works (cont’d)
– Set properties for water loop sizing
– Run a sizing run to autosize HVAC equipment
– Add controls that are determined based on cfm, gpm, %OA, etc.
– Apply baseline allowable fan power
– Multiple boilers/chillers/cooling towers per capacity
– Run a sizing run to size newly added boilers/chillers/cooling towers
– Apply baseline pumping power
– Apply minimum efficiency and performance curves for all HVAC
equipment based on type and capacity

9. 9
Challenges – Daylighting Controls
• Reality never as simple as examples
• Not everything is in model
– Cubicles
– Shelves

10. 10
Challenges – Ventilation Rates
“G3.1.2.6 Ventilation. Minimum ventilation system outdoor
air intake flow shall be the same for the proposed and baseline
building designs.”
I interpreted this as:
• Keep per-area and per-person OA rates from proposed
– (currently assumes proposed is ventilating at minimum required)
• If baseline system is MZ VAV, use VRP calculations
– If all zones set to 30% minimum damper position, VRP often reqs > 90% OA
– Instead, increase MDP on critical zones until system ventilation efficiency = 60%
• This can mean higher minimum intake rates than proposed
– Credits DOAS systems for ventilating more efficiently
This is an area that needs more work/thought. Plan on investigating
approach taken by T24/CEC.

11. 11
Limitations – 80/20 Approach
Currently Unsupported
• Lighting controls (occ/vac sensors) are assumed to already be present in proposed lighting
schedules, and will not be added or removed
• Exterior lighting in the baseline model is left as found in proposed
• Optimal start of HVAC systems is not supported
• Skylights are not added to model, but existing skylights are scaled per Appendix G skylight-to-roof
areas
• No fan power allowances for MERV filters or ducted supply/return present in proposed model
HVAC
• Laboratory-specific ventilation is not handled
• Kitchen ventilation is not handled; exhaust fans left as found in proposed
• Commercial refrigeration equipment is left as found in proposed
• Transformers are not added to the baseline model
• Zone humidity control present in the proposed model HVAC systems is not added to baseline HVAC
Known issues or limitations
• Some control and efficiency determinations do not scale capacities/flow rates down to reflect zone
multipliers
• Daylighting control illuminance setpoint does not vary based on space type
• Daylighting area calcs do not include windows in non-vertical walls
• Daylighting area calcs do not include skylights in non-horizontal roofs

12. 12
Testing & Validation
• ~20 real buildings
• From 3 engineering/modeling firms
– Group14 Engineering – Taylor Roberts
– Ambient Energy – Matt Steen, Eric Ringold
– NORESCO – Matt Leach
• Plus, community involvement
– Julien Marrec

13. 13
Supported Standards
• 90.1-2013
– Most heavily tested
• 90.1-2007 & 90.1-2010 BETA
– Not heavily tested, but working well
• NECB (Canada)
– In progress by NRCAN
• ECBC (India)
– In progress by LBNL & IIIT
• 90.1-2016 aka Addendum BM /fixed baseline
– Coming in FY17 by PNNL

14. 14
Parametric Analysis Tool (PAT) 2.0
• Why?
– New pattern for developers (web technologies)
– Less fragile file format
– New capabilities
• Optimization
• Sampling

15. 15
PAT 2.0 Demo

16. 16
OpenStudio Roadmap - 2017
• PAT 2.0
– Optimization, sampling
– Run on cloud
• New geometry editor
– Simpler than SketchUp
– Free
• Expanded support for advanced controls
• More Measures
• Portfolio-scale modeling applications