Modelling Natural Ventilation in IES-VE: Case studies & Research OutlookDaniel Coakley BE PhD CEM MIEI MEI Research Fellow, Integrated Environmental Solutions Ltd.Adjunct Lecturer, National University of Ireland Galway (NUIG)Secretary, ASHRAE Ireland

Technical Seminar: Ventilative Cooling & Overheating , April 20, CIT, Cork

Structure• Introduction to IES• Nat Vent Simulation in IES-VE• ASHRAE ‘Zero-Net Energy’ (ZNE) Challenge• Research outlook: Building Operations

IES Background• Founded 1994 with HQ in Glasgow;• Offices in UK, Ireland, USA, India;• Delivering sustainable solutions from building to city-scale;• Main software:

– IES-VE (Building simulation) – IES-SCAN (Building operations)

IES-VE SoftwareBuilding Performance Analysis Technology- Traditionally our focus was on creating

analysis tools for building design.- Our tools now encompass a bigger picture

of the built environment allowing for analysis on a bigger scale (e.g. city or community level) and at different building life stages.

- Understanding and analysing ‘real’ data at the Building Operation stage can drive actions which:

- Improve occupancy comfort.- Reduce energy use & CO2.- Reduce costs

IES SCAN / ERGON

ERGON - Import,manage and interrogatereal building data / schedules and use themin VE simulations.

IES-SCAN is a customisable web based portal and integrated data environment for operational data analysis complete with capability for energy forecasting, simulation

NAT-VENT SIMULATION IN IES-VE

Nat Vent Simulation Studies• Assess occupant comfort conditions (PMV) with respect

to air temperature, velocity, air quality etc.;• Demonstrate energy / cost savings by reducing need for

mechanical ventilation / cooling;• Minimise overheating risk;• Analysis of effectiveness of various ventilation

strategies, based on location / climate:– Natural, Mechanical or Mixed-mode strategies;

• Evaluate feasibility of designs such as: – Single-sided ventilation, DSF, cross-ventilation, whole-building

ventilation, Conventional systems, Displacement, Buoyancy, etc.;– Novel performance components – PCM, Solar collectors,

Windcatcher etc.

Relevant ModulesKey IES-VE Simulation modules:• MacroFlo – Simulate bulk air-flow driven

by wind pressure and buoyancy forces using a fast multi-zone thermo-fluid solver;

• MicroFlo – CFD analysis engine for internal / external air flow studies;

• ApacheHVAC – detailed HVAC design and analysis;

• ApacheSim – dynamic thermal simulation for building performance and load forecasting;

• VistaPro – results visualisation and analysis engine.

MacroFloIncorporates models of:• external wind pressure based on empirical

data;• stack effect (buoyancy);• flow characteristics of cracks / large

openings;• two-way flow;• resistance due to grilles and wall friction;• Rayleigh instability.

Inputs:• Building geometry & constructions;• Opening properties (e.g. wind exposure,

free opening area etc.)• Weather data (wind speed, direction etc.)• ApacheSim / HVAC information;• ERGON profiles (if required)

Outputs:• Air-flow mass / volume for openings;• Air-flow velocities;• Aggregated room / zone level air flows etc.

MicroFloFeatures• Air flow and heat transfer in and around buildings;• Simulate both internal and external air flow and

thermal problems;• Pre-set initial conditions for quicker convergence;• Discretisation options: Upwind (default), Hybrid

and Power Law;• A simulation monitor enables you to run, pause

and re-start calculations.

Inputs:• Boundary conditions (Air / surface

temperatures, mass-flows, gains etc.)• Surface object properties (e.g. grilles);• Shading surfaces (e.g. buildings,

topographical etc.)• CFD components (e.g. Radiators, air heat

source)

Outputs:• internal air flow temperature, direction and

velocity• external air flow direction and velocity• external static pressure

VistaPro result Visualisation• Visualisation and analysis (Post-processing);• Room and Node state display• HVAC process display

– Sensible cooling & heating, – Humidification and heating– De-humidification and cooling– Adiabatic mixing, cooling

• Time stepping• Comfort Zones• State frequency provides a very powerful

visual overview of a node’s air conditions for a given date

Performance Components• Pre-built manufacturer assemblies imported

to the Virtual Environment, providing a mix of geometry and thermal data as per manufacturer specification

• Components fall into three distinct categories: – Object – placed within rooms (e.g. CFD heat source,

Monodraught CoolPhase)– Space – part of the building model geometry (e.g.

Windcatcher)– Panel – placed on a surface (e.g. ActiMass activated

concrete thermal mass)

ASHRAE NET-ZERO ENERGY CASE STUDYCredit to Liam Buckley (IES) and the ASHRAE IES ZNE Team

5,000 m2 (53,600 ft2), 3- storey commercial office:• Minimum window-to-wall ratio: 30%• Minimum Energy Code: ASHRAE 90.1-2010 • Maximum Site Energy Use Intensity (EUI): 0 • Occupants: 268

• Minimum ventilation: ASHRAE 62.1-2007 • Plug loads: 8 W/m2 (0.75 W/ft2) • Occupied Heating Setpoint: 21°C (70°F) • Occupied Cooling Setpoint: 24°C (75°F) • Data Centre Load: 6 kW • Elevators: 2 Elevators in Core of Building • Service Hot Water: 1 gallon/day/person • Utility Rates: US-EIA Flat rates • The use of one design tool

ASHRAE ZNE Challenge

Zero-Net Energy Design ModelThe Design Team’s Meetings

• Realistic design in a challenging climate• Boulder, Colorado• TMY15 (2000-2014)• -4° to 93°F [-20 to 34oC] ext. dry bulb• 6% to 100% ext. RH• Large diurnal swings (30°F)

Zero-Net Energy Design ModelEarly Baseline EUI Target

• Baseline EUI: 33 kBtu/ft2/yr• Renewables: 20 kBtu/ft2/yr• Target EUI Reduction: 13 kBtu/ft2/yr

Zero-Net Energy Design ModelThe Final Architectural Design • New Baseline EUI: 53 kBtu/ft2/yr

• Renewables: 20 kBtu/ft2/yr• Target EUI Reduction: 33 kBtu/ft2/yr

Zero-Net Energy Design Model60 Second Virtual Tour of The Final Architectural Design

Zero-Net Energy Design ModelSolar Shading & PV-T Optimization

• Limit Solar Gains in Summer• Maximize Solar Gains in Winter• Maximize PV-T Potential

Incident Solar Radiation:

Zero-Net Energy Design ModelRenewable Wind Energy

• Net Zero Goal – More Renewables!• Building shape funnels wind (+3ft/sec)

• Wind = power• PV-T Panels

• PV-T and waste heat combo• Payback <5 years

Predominant Westerly Winds

Zero-Net Energy Design ModelECM: Natural Ventilation and Adaptive Thermal Comfort

• Run Natural Ventilation simulations with operable windows/vents; overheating.• Relocate printer stations & coffee stations to north office areas. Re-evaluate.• Utilize summertime diurnal swing and night-purge.• Expose thermal mass of internal floors.

• No offices above 25°C for 5% of occupied time (104 hours/year).

• No offices above 27°C for 1% of occupied time (21 hours/year).

Zero-Net Energy Design Model

• Diurnal Swing ~ 30 degrees. • Summertime heating setpoints were relaxed to

(65°F/58°F) in cooling season. • Analysis of operative temperature:

ECM: Natural Ventilation and Adaptive Thermal Comfort

Outside Dry-Bulb Temperature (°F)

Effective Night Purge Control (11pm-3am)

PPD (%) Snapshot:

Zero-Net Energy Design ModelECM: Natural Ventilation and Adaptive Thermal Comfort

• Internal Operable Windows to Atrium• Atrium is Negatively Pressurized.

Temp.OP (°F) Snapshot: 60-80°F PPD (%) Snapshot: 0-20%

Zero-Net Energy Design Model• Proof of Concept:

ECM: Atrium Design

Zero-Net Energy Design ModelAdaptive Thermal Comfort in the Offices

• Office Cross-Ventilation in Summer • Office Cross-Ventilation in Spring/Fall

• Warm air rising and mixing. • Cool air falling, but radiant floor eliminates cold draughts at ankles.

During winter, preheated OA is mechanically supplied to spaces.

Zero-Net Energy Design ModelFuture-Proofing the ZNE Status

• WeatherShift morphed the weather file 50 years. • (2000-2014) to (2046-2065).

• Projected EUI improved!?!• Warmer Winters• Warmer Summers

• 1,500 more hours between 60-75°F

• Internal Adaptive Comfort Ranges were uncomfortable. • Some cooling is required

Zero-Net Energy Design ModelFuture-Proofing ECM: Passive Down-Draught Evap. Cool Tower

Moisture Content Added

Air Temperature Decreased

Zero-Net Energy Design ModelThank You – Questions/Comments

Research Outlook

EINSTEIN Project• EINSTEIN: Simulation Enhanced Integrated

Systems for Model-based Intelligent Control(s)• Funding: EU-funded Marie Curie IAPP Project

(3 years)• Partners: IES and TCD• Topics

– Fault Detection– Prediction– Optimisation– Overall system integration

Fault Detection– Knowledge / Rule-based:

uses expert user experience

– Data-driven: uses historical building data, Statistical Methods, Empirical Data, Machine Learning

– Model-based; uses a calibrated detailed system model

Prediction / Optimisation• Multi-objective control optimisation;• Complies with user-specified

constraints (e.g. comfort);• Fault-tolerant control;• Integrates predicted weather

conditions, building thermal response, occupancy and economics (i.e. electricity / gas tariff);

Overall Integration

Building Data

IES-SCAN

Modelling / Prediction

Fault Detection / Optimisation

Intervention (DSS / Controls)

Useful LinksIES-VE Software• MacroFlo: https://www.iesve.com/software/ve-for-engineers/module/MacroFlo/462• MicroFlo: https://www.iesve.com/software/ve-for-engineers/module/MicroFlo/463• DiscoverIES Blog: https://www.iesve.com/discoveries/

ASHRAE Lowdown Showdown Case Study• CIBSE Article: http://www.cibsejournal.com/technical/down-to-zero-winner-of-ashrae-modelling-

competition/• IES Blog: http://blog.iesve.com/index.php/2015/10/14/the-ashrae-lowdown-showdown-we-won/• LowDown Showdown Video Overview: https://www.youtube.com/watch?v=xsbms0uB6w8

Thank you!

Daniel Coakley BE PhD CEM MIEI MEI Research Fellow, Integrated Environmental Solutions Ltd.Adjunct Lecturer, National University of Ireland GalwaySecretary, ASHRAE IrelandEmail: daniel.coakley@iesve.comWeb: www.iesve.com

Technical Seminar: Ventilative Cooling & Overheating , April 20, CIT, Cork