Tools You Need for Building Science

RED Calc Pro is Ready for You.
Are You Ready?

Do Your Work Like a Pro!
The FUTURE Depends on You.

RED Calc Free

Free building science calculation tools used by building professionals around the world. RED Cal tools are the gold standard of building science calculation aids!

RED Calc Pro

Save time, reduce mistakes, use your smartphone, auto-save to RED Cloud, save and print reports, include work orders, organize your work with folders, work offline. Work smarter.

Who Uses RED Tools?

Wx Assistance (WAP)

  • Energy auditors
  • Inspectors
  • QC inspectors
  • Monitors
  • Crew leaders
  • Subcontractors
  • Trainers

Home Performance

  • Contractors
  • Energy auditors
  • Ventilation designers
  • Inspectors
  • QC inspectors
  • Program designers


  • Energy auditors
  • Inspectors
  • QC inspectors
  • Subcontractors
  • Trainers

Code Enforcement, etc.

  • CEOs
  • Home builders
  • Research analysts
  • Engineers
  • Building science instructors
  • Homeowners

RED Calc Free Tools

RED Calc Pro


  • Mobile friendly
  • Works on major browsers
  • Tools based on consensus codes and standards
  • Autosave to RED Cloud
  • Fully functional offline mode
  • Advanced error reporting
  • Auto-repair characteristics
  • Customizable reports (PDF)
  • Locking for data protection
  • Custom tool and folder templates
  • Math-on-the-fly calculator for inputs
  • Collapsing/expanding tool sections
  • Popup help (click any label)
  • Step-control for input values
  • Notes feature for folders and tools
  • Choice of U.S and metric units
  • Markdown-enabled report forms
  • Detailed results info
  • Multi-tab/window syncing
  • Available by monthly or annual subscription, individuals or teams
RED Calc Pro is the #1 set of Building Diagnostics tools for energy and building analysts. Give it a try today!
RED Calc Pro home screen
Home screen and main menu
Folder, tools, and menu
Folder, tools, and tool menu
Tool-selection menu
Section of ASHRAE 62.2-2016 tool
Math on-the-fly highlighted
ASHRAE 62.2-2016 tool with menu
ASHRAE 62.2-2016 tool on smartphone
Popup Help, a feature of all tools
Customized tool report
Notes tool report

Air Leakage Metrics, A Rising Star

As new and existing buildings become tighter as a result of our attempts to save energy and slow global climate change, the ability to measure building tightness and convert the tightness to a useful metric becomes more important.

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Effective Zone Pressure Diagnostics

Zone Pressure Diagnostics (ZPD) can be a useful and effective tool for determining the effectiveness of a designated pressure barrier. What can you do to increase the accuracy – or reduce uncertainty – of your results? Following these simple rules will help you hit your target.

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Double-Duty Exhaust Fans: Good or Bad?

The installation of double-duty exhaust fans in existing dwellings is common. This practice can save money and time on the job and provides a simpler ventilation solution for the occupants. But is it a good idea?

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