Tools You Need for Building Science

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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
Cover of ASHRAE 62.2-2016

ASHRAE 62.2 Morsels

As a fifteen-year member of the ASHRAE 62.2 committee, I am often asked about the more difficult or contentious details of the 62.2 standard. These questions range from how to measure dwelling height, should the basement be included in the floor area, or how to determine the airflow rate of balanced ventilation. This is the first of two articles including a collection of these questions from users of the 62.2 Standard and the RED Calc 62.2 tools, along with my best answers.

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Best Practices for Residential Ventilation

Ventilation installation practices are usually based on ASHRAE 62.2 in the U.S., the only question being which version of this standard is used by the relevant program. ASHRAE 62.2 is a minimum standard, not a best-practice standard. As a fifteen-year member of the ASHRAE 62.2 committee, I am often asked about the best ways of exceeding the 62.2 standard for good indoor air quality.

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Major Study Shows ASHRAE 62.2 Ventilation Works!

A significant research report published in April of this year by the National Center for Healthy Housing (NCHH) found that subsidized multifamily housing with ASHRAE 62.2-compliant ventilation had better indoor air quality than housing without 62.2-compliant ventilation. This important research states: “Levels of four of the five indoor contaminants improved substantially with [continuous] mechanical ventilation.”

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