BS Tools is a toolkit of calculators designed for HVAC and other Building Science (BS) applications, as an alternative to more tedious, manual methods.

Note: We are in the process of transitioning to a "freemium" model. Purchasing the app now grants full access. In the future, the app will be free to install, for access to some utilities, with a single in-app purchase to grant remaining utilities. Currently, the marketplace indicates that there are "In-app purchases", though this is only shown as one will eventually be available to users once we make this transition. Current users will not have to pay any additional fee.

Utilities

Single Point Psychrometrics:
This calculator provides psychrometric properties of air at a glance. It's great for changing humidity units.

Mixed Air Psychrometrics:
This calculator provides instant psychrometric properties of the resulting air of two mixed air streams, e.g. ventilation air mixed with return air.

Duct Calculator:
In a word, it's a classic 'ductulator'. This tool accepts any two choice inputs among CFM (Air Flow Volume), Duct Diameter, Friction Rate (Head Loss), and Air Velocity. This utility will then provide the other two parameters for you. You can enter either a round diameter, or two rectangular dimensions. This tool will optionally display both round and rectangular dimensions, if given a first rectangular dimension, or by inputting a rectangular duct size.

Smallest Zone Calculator:
This calculator can be used to gauge how much excess air is acceptable in a heating or cooling system.

Bypass Calculator:
Paired with the Smallest Zone Calculator, this can tell you how much air you can bypass, which uses different parameters dependent on whether you are cooling or heating. This includes a couple notable features: The Cooling Bypass CFM Limit section gives both conservative and aggressive values, based on the expected settled air temperature. Also, the Heating Bypass CFM Limit section features a mini calculator to help you adjust your rated BTUH for elevation.

IR Wall Insulation:
This calculator can help you estimate the R-Value of a wall, with Infrared (IR) exterior and interior surface, and interior ambient temperatures. The key feature of this tool is providing a common wall material that best matches your readings with a general degree of confidence in that match. We also include tips on measuring for best results.

Parallel R-Value:
This calculator provides an overall R-Value (and U-Value) for a wood frame building assembly* (typically a wall), given the R-Values of different materials and their areas or proportions present in the assembly. *Not for use with metal framing.

Note:
The above calculators use IP (inch / pound) units.

Unit Converter:
Converts units.