Terms of Use

Last updated 13 October 2026. By using Wallcalc you agree to these terms. If you do not agree to them, please do not use it.

1. What Wallcalc is

Wallcalc is a free calculator that models heat flow and moisture movement through a wall assembly and compares a design against published energy code requirements. It runs in your browser. It is offered as an engineering aid and as a teaching tool.

2. It is not professional advice

Wallcalc does not provide engineering, architectural, construction or legal advice, and using it does not create a professional relationship of any kind. Its output is a model, not a design, and not a certification of compliance with any code, permit, standard or contract.

Any wall you intend to build should be reviewed by a licensed design professional who is responsible for it, and checked against the code actually adopted by your jurisdiction, which may differ from the published model code and may have been amended locally. Where this tool and an authority having jurisdiction disagree, the authority governs.

3. No warranty

Wallcalc is provided "as is" and "as available", without warranty of any kind, express or implied, including without limitation any implied warranty of merchantability, fitness for a particular purpose, accuracy, or non-infringement.

Real walls are built by people, from materials that vary, in weather that varies, with workmanship this tool knows nothing about. Material properties are drawn from published data and some are marked provisional. Climate figures are long-run normals, not a forecast and not your site. No representation is made that the calculations are free of error or suitable for any particular assembly.

4. Limitation of liability

To the fullest extent permitted by law, JHL, LLC and its members, managers, employees and agents will not be liable for any damages of any kind arising from your use of or inability to use Wallcalc, including without limitation direct, indirect, incidental, consequential, special or exemplary damages, loss of profits, loss of data, construction defects, moisture damage, mold growth, remediation cost, or the cost of substitute goods or services, whether in contract, tort including negligence, strict liability, or otherwise, and whether or not advised of the possibility of such damages.

Where liability cannot be excluded as a matter of law, it is limited to one hundred United States dollars in total.

5. You are responsible for how you use it

You are responsible for the inputs you provide, for judging whether the model suits your situation, and for anything you build or decide not to build. You agree to indemnify and hold harmless JHL, LLC and its members, managers, employees and agents against any claim arising from your use of Wallcalc or from work carried out in reliance on it.

6. Ownership and permitted use

You may:

use it, free of charge, for personal or commercial work;
share links to it, including share links that carry a design;
print or export its report and use that in your own documents, with the attribution the report carries.

Without written permission you may not:

copy, host, redistribute or sell the tool or any substantial part of it;
extract or reuse its data tables as a dataset;
build a derivative or competing tool from its code or data;
scrape it by automated means, or remove its attribution.

To ask about licensing it, get in touch through jaylyonvt.com.

7. Your data

Designs you create stay in your own browser. They are not uploaded, and there is no account. A share link carries the whole design inside the link itself, so a design is only shared if you share the link. Ordinary web server logs record requests to the site.

8. Sources

Climate normals come from NOAA NCEI United States Climate Normals 1991–2020 and Environment and Climate Change Canada Canadian Climate Normals 1981–2010, with solar data from NASA POWER. Material properties come from published standards, manufacturer technical data sheets and evaluation reports, and are cited in the tool. Code requirements are taken from the IRC and IECC published by the International Code Council and the National Building Code of Canada published by the National Research Council. Those organizations are the authority on their own documents; this tool is not affiliated with any of them, and nothing here is endorsed by them.

9. Availability and changes

Wallcalc may change, move or stop being available at any time, without notice. These terms may be updated; the date at the top shows when. Using the tool after a change means accepting it.

10. Governing law

These terms are governed by the laws of the State of Vermont, United States, without regard to conflict of law rules. Any dispute will be brought in the state or federal courts located in Vermont.

Wallcalc terms of use

Terms of use