Terms of Service

These terms govern your use of HVAC Duct Designer, the mobile application published by Sylvanity B.V., a private limited company based in the Netherlands ("Sylvanity", "we", "us"). By installing or using the app you agree to these terms. If you do not agree to these terms, do not install or use the app.

HVAC Duct Designer is an educational app for HVAC learners. It supports duct sizing, velocity, and pressure-loss calculations using standard engineering correlations (Darcy–Weisbach, Colebrook–White, ASHRAE fitting-loss tables, etc.). Do not use it to produce construction documents, building permits, code-compliance submissions, or any installed mechanical system. Access to the calculation features is gated by an auto-renewing subscription, "HVAC Pro", which includes a 7-day free trial when you first subscribe. The app is distributed through the Apple App Store (iPhone, iPad) and Google Play (Android). The same terms apply on both platforms, supplemented by the relevant platform's standard end-user terms (see Section 15).

HVAC Duct Designer is intended for HVAC learners: engineering students, apprentices, trade-school learners, and self-learners. It is not directed at children and is not listed in the App Store Kids Category or Google Play's Families program.

Subject to these terms, Sylvanity grants you a personal, non-exclusive, non-transferable, revocable licence to install and use HVAC Duct Designer on any compatible device that you own or control, for personal, educational, and study use only. The licence does not cover professional engineering use, design-for-construction work, or any use whose output is relied on for an installed system.

This licence is also subject to the standard end-user terms of the application store from which you obtained the app. For Apple App Store downloads, this means Apple's Licensed Application End User License Agreement. For Google Play downloads, the Google Play Terms of Service apply.

You may not:

• Copy, modify, decompile, or reverse-engineer the app, except to the extent expressly permitted by applicable law (including, where applicable, EU Directive 2009/24/EC).
• Redistribute, sell, sublicense, rent, or lease the app or any part of it, including any subscription entitlement.
• Use the app or any output from it to construct a competing product, dataset, or library.
• Remove or alter any copyright, trademark, or other proprietary notices in the app.
• Use the app in a way that violates applicable law or that harms the device, network, or other users.

HVAC Pro is offered with a 7-day free trial delivered as part of the auto-renewing subscription. When you subscribe, the free trial begins immediately and you have full access to the HVAC Pro feature set. Apple or Google captures your payment method up front but does not charge you during the trial; the subscription continues automatically at the regular price unless you cancel before the trial ends. If you cancel before the trial ends, no charge is made and access continues until the end of the 7-day window; afterwards the app's calculation features become unavailable until you re-subscribe. Your saved projects and calculations remain on the device throughout and are not deleted.

HVAC Pro is sold as an auto-renewing subscription with a monthly or annual term, billed through the Apple App Store or Google Play depending on where you obtained the app. Specifically:

• Price and term for the available subscription periods are shown to you on the in-app subscription screen and on the App Store / Google Play product page before you commit to purchase. Local taxes and currency conversion are applied by Apple or Google.
• Auto-renewal: the subscription renews automatically at the end of each billing period at the then-current price, unless you cancel at least 24 hours before the end of the current period. Renewal is processed by Apple or Google.
• How to cancel: you can cancel at any time from your device's subscription-management screen. On iOS: Settings → [your name] → Subscriptions. On Android: Google Play Store app → Profile → Payments & subscriptions → Subscriptions. Uninstalling the app does not cancel an active subscription.
• What happens after cancellation: your HVAC Pro access continues until the end of the current paid period; afterwards the app's calculation features become unavailable until you re-subscribe. Your saved projects and calculations remain on the device and are not deleted, and access is restored when you re-subscribe.
• Refunds are handled by Apple or Google under their respective refund policies, not by Sylvanity. Sylvanity has no ability to issue refunds for App Store or Google Play purchases.
• Price changes: if we change the subscription price, Apple or Google will notify you in accordance with their platform rules and you will need to confirm the new price before the next renewal can occur. If you do not confirm, the subscription will not renew.
• EU consumer right of withdrawal: EU consumers normally have a 14-day right of withdrawal for digital purchases. Where the app asks you, at the time of subscribing, to consent to immediate performance of the digital service and to acknowledge that the right of withdrawal is lost once performance begins, that consent is given under Article 16(1)(m) of Directive 2011/83/EU as amended. Where no such consent is captured, the standard 14-day right applies, and refunds for that period are processed by Apple or Google under their refund policies.

The trial is offered only once per Apple ID or Google account, as enforced by the platform: it is delivered as a StoreKit / Google Play introductory offer attached to the HVAC Pro subscription, and Apple or Google will not allow a second free trial on the same account.

The HVAC Duct Designer app, including its source code, calculation engine, artwork, sounds, branding, copy, and content, is owned by Sylvanity and protected by copyright, trademark, and other intellectual-property laws. The app uses the RevenueCat SDK and platform-provided in-app purchase libraries under their respective licences. Nothing in these terms transfers ownership of any part of the app to you.

HVAC Duct Designer is an educational tool. The values it produces are estimates, computed by applying published engineering correlations and material data to the inputs you provide. They are intended for learning, not as engineering deliverables, and have not been validated for any specific project, jurisdiction, or installation. Do not use them for design, procurement, permitting, installation, commissioning, or any safety-critical decision. The app must not be used for emergency, life-safety, fire-safety, smoke-control, medical, industrial, hazardous-environment, or other safety-critical HVAC decisions.

You are solely responsible for how you use any output, including:

• Treating any output as a study aid, never as a basis for procurement, construction, or operation of a real system.
• Verifying any value against applicable national and local building, mechanical, fire, and energy codes.
• Verifying any value against applicable industry standards (ASHRAE, SMACNA, EN, ISO, NEN, and any others that may apply).
• Verifying any value against the manufacturer's data sheets for the relevant equipment.
• Considering project-specific safety, acoustic, and indoor-air-quality requirements that the app does not model.

The app is not a substitute for the judgement of a qualified mechanical engineer or licensed HVAC professional. Sylvanity accepts no liability for any consequence of using the app or its output, including any design, installation, repair, code violation, system failure, injury, property damage, cost, or delay. Use of the app is at your own risk.

HVAC Duct Designer is provided "as is" and "as available". To the fullest extent permitted by applicable law, Sylvanity makes no warranties, express or implied, regarding the app, including any implied warranty of merchantability, fitness for a particular purpose, accuracy, or non-infringement. We do not warrant that the app will be uninterrupted or error-free, that defects will be corrected, or that the app will be compatible with any future operating-system version. We may provide updates, bug fixes, or support at our discretion, but we do not guarantee any specific support response time, feature availability, or continued compatibility with future devices or operating systems.

We give no warranty, representation, or fitness for any professional, commercial, regulatory, or safety-critical purpose. The subscription price reflects this limited scope.

To the fullest extent permitted by Dutch law and applicable EU consumer-protection law, Sylvanity is not liable for any indirect, incidental, special, consequential, or punitive damages, or for any loss of profit, revenue, data, or goodwill, arising from your use of (or inability to use) the app or from any reliance on its output, even if we have been advised of the possibility of such damages. Sylvanity's total cumulative liability arising from or related to the app, on any theory of liability, is limited to the lesser of (a) the total amount you have paid to Apple or Google for HVAC Pro in the three months preceding the event giving rise to the claim, or (b) ten euros (€10).

Nothing in these terms limits or excludes any liability that cannot be limited or excluded under applicable law, including liability for gross negligence, intentional misconduct, death or personal injury caused by negligence, or your statutory rights as a consumer.

The app processes only the limited data needed to operate subscriptions; everything else stays on your device. See the Privacy Policy for full details.

Sylvanity may update the app from time to time and may update these terms when the app's behaviour, the subscription model, or applicable law changes. Updated terms will be posted on this page with a new "Last updated" date. Material changes will also be noted in the App Store and Google Play release notes for the relevant version. Continued use of the app after a change takes effect means you accept the updated terms. If you do not accept the updated terms, you should cancel any active subscription and uninstall the app.

You may stop using the app at any time by uninstalling it; if you have an active subscription you should also cancel it from your device's subscription-management screen as described in Section 6. Sylvanity may discontinue the app, or any version of it, at any time. If the app is removed from the App Store or Google Play, an existing installed copy will continue to work for as long as your subscription remains active and verifiable on the relevant store. An active subscription will continue to be billed by Apple or Google until you cancel it.

These terms are governed by the laws of the Netherlands. Any dispute arising from these terms or your use of the app will be brought before the competent courts of the Netherlands. This is without prejudice to any mandatory rights you have as a consumer under the laws of your country of residence, including the right to bring proceedings in the courts of that country.

The end-user terms of the application store from which you obtained the app apply in addition to these terms. If there is a conflict between these terms and the application-store terms, the application-store terms prevail to the extent of the conflict and only with respect to the matters they cover (for example, the refund policy and the in-app purchase mechanics).

For users who downloaded the app from the Apple App Store, you acknowledge that these terms are between you and Sylvanity, not Apple. Apple is not responsible for the app, its content, or any failure to conform to any warranty. Apple is, however, a third-party beneficiary of these terms and may enforce them against you.

For users who downloaded the app from Google Play, the Google Play Terms of Service and Google Play's subscription rules apply to your purchase, and Google is responsible for the billing and refund elements of the transaction.

If any provision of these terms is held to be invalid or unenforceable, the remaining provisions remain in full effect. These terms, together with the Privacy Policy and the applicable application-store terms, are the entire agreement between you and Sylvanity regarding the app, and replace any prior agreements on the same subject.

Questions about these Terms of Service? Contact us:

Sylvanity B.V.
Treubstraat 21 U314
2288 EH Rijswijk
The Netherlands

KvK: 96488646
BTW: NL867632860B01

Email: info@sylvanity.eu