Terms & Conditions

HVAC Toolkit (the Service) is provided by MJTOOLS ( “MJTools”, “we”, “us”), trading as MJTools, operating the website toolhvac.com. By creating an account or using the Service you enter into a binding agreement with MJTOOLS.

By registering, signing in, or continuing to use the Service you agree to these terms and to our Privacy Notice and Refund Policy. If you do not agree, stop using the Service. We may update these terms; material changes will be announced in the app or by email, and continued use after the change means you accept the updated terms.

If you use the Service on behalf of a company, you confirm you have authority to bind that company. If you use it as an individual, you confirm you are of legal age in your country.

HVAC Toolkit is engineering software for mechanical designers and service technicians: heat load and duct sizing calculators, static pressure and VRF pipe sizing, radiator sizing, air terminal selection, sheet-metal take-offs, refrigerant PT charts, a 2D drawing board with CAD underlay, cost quotations, and an AI-assisted diagnosis assistant. Features available to you depend on your plan (free tier, trial, Pro, or Team).

Engineering results are aids, not certified designs. Outputs are based on published industry methods (ASHRAE, SMACNA, Manual J-style and EN 442 correlations) and on the data you enter. You remain the responsible engineer: verify every result against the applicable codes, manufacturer data, and local regulations before construction, procurement, or commissioning.

You must give accurate registration information and keep it current. You are responsible for keeping your credentials confidential and for all activity under your account. Tell us at support@toolhvac.com if you suspect unauthorised access. Accounts are personal; on a Team plan each seat is for one named person and seats must not be shared.

We grant you a limited, non-exclusive, non-transferable, revocable right to use the Service for your own professional or internal business purposes within the plan you selected. You must not:

• reverse engineer, decompile, or attempt to extract the source code or calculation engines;
• resell, sublicense, rent, or redistribute the Service or its outputs as a competing tool;
• circumvent plan limits, paywalls, trial periods, usage quotas, or authentication;
• copy or scrape the interface, content, or data sets in bulk.

You must not misuse the Service. In particular, you must not:

• use it for any unlawful purpose or in breach of any applicable law or export control;
• commit fraud, send spam, or impersonate another person or organisation;
• infringe anyone’s intellectual property, confidentiality, or privacy rights;
• interfere with the security or integrity of the Service — no malware, probing, penetration testing without written consent, vulnerability exploitation, credential stuffing, denial of service, automated scraping, or unreasonable load;
• upload drawings, CAD files, or other content you do not have the right to use.

You keep ownership of the projects, drawings, CAD files, calculations, and other content you upload or create (Your Content). You grant us a limited licence to host, store, process, and display Your Content solely to operate and support the Service for you. We do not sell Your Content and we do not use it to train third-party AI models.

The diagnosis assistant sends the fault description and system data you enter to a third-party AI model provider to generate suggestions. You are responsible for the prompts you submit, for not entering personal data or confidential third-party information you are not allowed to share, and for how you use the output. AI output may be inaccurate or incomplete; it is decision support only and is not a substitute for on-site inspection by a qualified technician, nor for regulated professional, safety, legal, or financial advice. We may restrict, filter, or refuse requests, and may limit AI usage per plan.

MJTOOLS (and its licensors) retain all right, title, and interest in the Service, including the software, calculation engines, databases, documentation, design, and the MJTools and HVAC Toolkit names and logos. Nothing in these terms transfers any of our intellectual property to you.

Paid plans (Pro and Team, billed monthly or annually) renew automatically for the same period until cancelled. Prices are shown on the pricing page in USD; taxes are calculated at checkout.

Payment, billing, currency, taxes, invoicing, subscription renewals, cancellations, and refund mechanics are handled by our reseller and are governed by Paddle’s Checkout Buyer Terms together with our Refund Policy. You can cancel at any time from the Plan & team section of your dashboard or via Paddle; access continues until the end of the period you have already paid for.

Our order process is conducted by our online reseller Paddle.com. Paddle.com is the Merchant of Record for all our orders. Paddle provides all customer service inquiries and handles returns.

We work to keep the Service available and accurate, but we do not guarantee uninterrupted, timely, secure, or error-free operation. Maintenance, updates, third-party outages, and factors outside our control may cause downtime, and features may change or be discontinued. To the fullest extent permitted by law we disclaim all implied warranties, including merchantability, fitness for a particular purpose, and non-infringement.

We may suspend or terminate your access, with notice where reasonably practicable, if you materially breach these terms, fail to pay amounts due, create a security or fraud risk, or repeatedly or seriously violate our acceptable use rules. You may stop using the Service and delete your account at any time. On termination your licence ends; you can export your saved worksheets and drawings before closing your account, and we then delete or anonymise your data as described in the Privacy Notice.

To the fullest extent permitted by law, we are not liable for indirect, incidental, special, or consequential loss, or for loss of profits, revenue, data, goodwill, or for design, rework, equipment, or construction costs arising from reliance on calculation or AI outputs. Our total aggregate liability arising out of or relating to the Service is limited to the fees you paid in the twelve months before the event giving rise to the claim.

Nothing in these terms excludes or limits liability for fraud or fraudulent misrepresentation, for death or personal injury caused by negligence, or for any other liability that cannot be excluded by law.

You will indemnify MJTOOLS against claims, damages, and reasonable costs arising from Your Content, your unlawful or unauthorised use of the Service, or your breach of these terms.

These terms are governed by the laws of Lebanon, and the competent courts of Beirut, Lebanon have exclusive jurisdiction, without prejudice to any mandatory consumer rights you have in your country of residence. Order-related disputes are handled first by Paddle as Merchant of Record.

You may not assign these terms without our consent; we may assign them as part of a merger, acquisition, or sale of assets. Neither party is liable for failure to perform due to events beyond its reasonable control. If a provision is unenforceable, the rest remains in force. These terms, together with the Privacy Notice and Refund Policy, are the entire agreement between us.

Contact: support@toolhvac.com.