Exceptional Room & Zone Loads Analysis for Building & HVAC Design

Accuracy, Depth, and Ease of Use

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IESVE Software for Loads Calculations, Sizing & HVAC Design

Move up to the best in loads analysis. From optimizing room and zone loads to detailed HVAC system and equipment sizing, IESVE HVAC software offers the most practical, efficient, and accurate tools available.

  • Efficiently input 3D geometry, envelope, internal gains, and location for accurate loads calculations. 
  • Include minimum ventilation requirements or choose local code minimum ventilation. 
  • Share reports, gain insights from in-depth results analysis, and iterate on building design. 
  • Transition seamlessly into detailed HVAC system sizing and optimization.

Design Conditions

Establish up-to-date external ASHRAE design conditions from thousands of pre-defined locations.

Construction Materials

Choose from hundreds of pre-configured assemblies or create custom designs from hundreds of material options.

Building Templates

Manage and assign thermal template datasets (setpoints, gains, etc.) to group of room or zones.

Generate Reports

Generate heating & cooling loads reports in spreadsheet and PDF formats.

APACHE: Loads Calculation Methods & Validation

Loads calculations with the world-renowned APACHE engine allows for easy-to-use access to the most robust industry methods, which require (sub)-hourly calculations that account for the storage and thermal mass of construction materials. 

Free On-Demand Webinar

This on-demand webinar covers Heating & Cooling Loads Calculations and HVAC Equipment Sizing and focuses on loads-specific use cases.

Watch the webinar

HVAC Equipment Sizing & Design Optimization

Airside Systems

  • 100+ Pre-configured HVAC Systems including a range of Baseline options
  • Single-zone systems (Split systems, DX, Packaged Heat Pumps, CRAC/CRAH, etc.)
  • Multi-zone Systems (CAV, VAV, DOAS, (In)direct Evaporative Cooling, UFAD, DV, etc.)
  • Zonal Systems (FCUs, Radiant Systems, Chilled Beams, Series/ Parallel FPBs, Heat Pump & VRF, etc.)
  • Ventilation calcs for ASHRAE 62.1, ASHRAE 170, CA Title-24, custom parameters, and numerous ventilation, exhaust, and make-up air configurations. 
  • Range of optional controls (Economizer, ERV, HRV, C02- and Occupancy-based DCV, Heat Recovery, Dual-Max VAV, SAT reset, etc.)
  • A HVAC System Design Wizard for easy configuration of HVAC systems and an automated sequencing of (1) load calculations, (2) equipment sizing, (3) Annual energy simulation, and (4) Generation of reports & schedules
  • All pre-configured systems can be modified and customized with drag & drop placement of equipment, controls, and airflow paths. Users can also create fully custom systems and edit a broad range of equipment and control parameters.

Plant & Waterside Systems

Pre-configured plant loop examples and customizable loops, including multiple pre-heating, pre-cooling, and heat-recovery options, secondary loops with independently controlled supply temperatures, and scheduled loads.

Heating Hot-Water (HW) with Boilers, Heat Pumps, Electric Resistance, and user-defined heating equipment.

Domestic Hot-Water (DHW) with storage tank losses, recirculation, and pre-heat options including drain-water heat recovery, solar heating, and condenser heat recovery.

Chilled Water (CHW) with air/water-source chillers, heat pumps, and user-defined cooling equipment.

Condenser Water (CW) with cooling towers, wet/dry fluid coolers, condenser heat recovery, and integrated waterside economizer.

Heat Pump (HP) loops with water- and ground-source heat acquisition and heat-recovery options for water-loop heat pumps and water-source VRF/VRV.

Heat Recovery Chiller (HRC) for moving heat from CHW to HW loop.

Thermal Energy Storage (TES) with ice and chilled-water storage tanks.

Controls including constant/staged/variable flow, primary-secondary loop options, supply temperature reset, heat-recovery, staging and sequencing of equipment, etc.

Plant-Only Simulation

Don’t have a 3-D model? … no problem!  ApacheHVAC plant loops can simulate without any 3D model building representation and only requires hourly time-series demand data (e.g. from external metered BAS/BMS sources).

IES Virtual Environment provides a free simple hourly import option from a CSV file which allows for Plant-only simulation in ApacheHVAC, enabling optimization of central plant and/or allowing coupling with energy generation from PV + Battery Storage, all within IESVE Software.

Reports and Results

The range of loads & HVAC sizing outputs from IESVE Software include spreadsheets, PDFs and customized visualizations:

  • Spreadsheet: Heating & Cooling Loads & Airflows
  • VistaPro Visualization for any room Loads metric
  • PDF: System, Zone & Room breakdown; boiler, chiller, VRF, DHW, coil & fan sizes
  • VistaPro Hourly Graph/Table for any HVAC equipment or at any schematic node


The ApacheHVAC application uses a flexible component-based approach that allows you to create or customize HVAC systems as you wish. Use either our library of HVAC systems, plant equipment & loops, or create your own systems from scratch.

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What our Customers Say


For us, IESVE is our all in one tool for doing loads, energy, daylighting, etc. Doing loads analysis is simple to run especially with the parametric tool in the VE. This tool allows us to test ideas and get results quickly efficiently, and the results are accurate. We now use the VE for all of our projects. On a recent office project, using the VE, we were able to improve glazing, reduce mechanical system size, and save the owner money all through the results of our analysis.

Miles Dake

Mechanical Engineer at ME Group

IES actively listens to and responds to the needs of its customers. Our mainstream design teams have given much deeper commitment to the use of the VE – the VE is not just for our one-of-a-kind high performance “jewel box” projects. We are taking advantage of the much more user-friendly load reports on our everyday work. The graphics and visualization tools built into the VE are making it much easier for our teams to understand and optimize system performance and sizing.

Kim E Shinn

Principal/Senior Sustainability Wizard at TLC Engineering Solutions

Got a Question?

Contact our team to find out more about load calculations and HVAC design sizing tools in the Virtual Environment.