Last updated: October 1, 2026
This policy explains what Thermist LLC ("Thermist", "we", "us"), based in Boston, Massachusetts, collects when you use thermist.com, the Psych Chart and other free calculators, Equipment Builder, your Thermist account and the Thermist add-in for Autodesk Revit, and what we do with it. It forms part of our Terms of Use.
Your account. When you sign in with Google or with an email and password, we keep your email address, and from Google your name and profile picture. Sign-in itself is handled by Google Firebase Authentication; we never see your Google password, and Firebase stores email passwords for us in hashed form.
Subscriptions. Payments are processed by Stripe. We keep your Stripe customer and subscription ids, your plan, seat count and billing status. Your card details go to Stripe and never reach our servers.
Revit add-in licensing. For each add-in seat we keep the Autodesk user name (stored as a one-way hash as the record's key), the license type and expiration dates, the email used to start a trial or verify a seat, and whether that email is verified. If you assign a seat to a colleague by email, we keep that address to link the seat once they verify it.
What you make. If you are signed in, your Psych Chart charts and Equipment Builder sketches are saved to your account as you work, and families you build are stored so you can download them again. When you share a chart, the chart is stored under its short link.
Uploaded cut sheets. A PDF you open in Equipment Builder is uploaded to our server so it can be traced. Text on the cut sheet is read in your browser.
Calculations. Calculator inputs (duct, pipe and steam sizing, psychrometric states, chart PDFs) are processed to give you the answer and are not kept, unless you save or share the chart as above.
Technical data. Our servers see your IP address, which we use briefly to limit abuse (for example, daily caps on share links and on the trace engine) and which is kept with an Equipment Builder build job while it runs. Our hosting provider keeps standard request logs.
Contact form. Messages sent through the contact page are collected with Google Forms.
The site uses Google's tag (Google Ads) to measure whether our ads lead to visits and sign-ups; Google may set cookies and collect information about your visit for this. You can manage how Google uses this data at adssettings.google.com or block these cookies in your browser.
The Psych Chart and Equipment Builder also keep your current work and a few preferences in your browser's local storage, so the page remembers them on your next visit. That data stays on your device; clearing your browser's site data removes it.
We do not sell your personal information, and we do not share it with others for their own marketing.
We share data only with the service providers that run parts of the Services for us, and only what each needs:
Anyone who has a chart's share link can open that chart. We may also disclose information if the law requires it, to protect our rights or users' safety, or to a buyer as part of a sale of the business.
You can see and delete your saved charts, sketches and families on your account page. To get a copy of your data, correct it, delete your account, or remove a shared link, contact us through the contact page. Deleting add-in license data deactivates that license. You can opt out of trial and marketing emails at any time; we will still send messages you need about your account.
Data travels over HTTPS, account data is reachable only with your sign-in, and card details are held by Stripe. No system is perfectly secure, so we cannot guarantee that data will never be exposed, but we will tell affected users as the law requires if it is.
The Services are for professionals and are not directed to children under 13. We do not knowingly collect their information.
We are in the United States, and our providers process data in the United States and other countries.
We may update this policy. We will post the new version here with a new date, and tell account holders about material changes.
Questions or requests about your data: use the contact page.
