If you size the equipment as well as the ducts, there's now a link to HVAC Load Calc, our app that estimates a home's heating and cooling load. It's below the results on the Calculator and Check tabs and in the new Settings screen. Its App Store page opens inside this app, so when you close it you're back on the duct you were sizing. Settings opens from the gear on the Saved tab. The terms and privacy policy are there too.

Flex can now be sized the way it is usually installed. Choose Flex, then pick Stretched or 4%, 15% or 30% compressed. Sizing, Check, space options and saved reports all use the ASHRAE friction correction for compressed flexible duct. A 100 CFM branch that takes a 7 inch duct stretched needs 9 inches at 15% compression.

Find rectangular duct sizes that fit your available height and width. Compare options by velocity and friction, then check and save your choice. A worked example introduces the app on first launch. We also improved subscription loading and fixed missed taps after closing the keyboard.

Save a calculation with a project name and notes. Reopen its inputs later or share the original result as a text report. The app also restores your last calculation and keeps the last 20 completed results. Use the new friction-rate worksheet to calculate your design rate from available static pressure and total effective length, then apply it to the calculator. Recommended round and rectangular sizes now meet both the friction limit and the velocity guide. Send a recommended round size straight to Check, or use an undersized duct's inputs to find a suitable size.

Duct material now changes the answer. Galvanized, duct board and flexible duct each carry their own ASHRAE roughness, and flex needs a full standard size more than metal at the same airflow. Size a flex run as if it were metal and it always goes in over its design friction rate, by up to double. New Check tab for the duct that's already there: type in a round diameter or a width and height and read back its velocity, its friction rate, and the airflow it will actually carry, with a verdict against whichever limit binds first. Also: a friction rate you type in now survives switching between supply and return. Manual D designs a whole system to one rate, so the per-service defaults no longer overwrite a number you worked out yourself.

Fixes a crash when typing your own friction rate, keeps the Wheel and the Calculator on the same airflow, and stops the rating prompt from appearing before you've had a chance to use the app.