What HVAC Duct Designer processes, what stays on the device, and what RevenueCat sees when you subscribe.
Last updated: 3 May 2026 · Effective: 3 May 2026
Summary
HVAC Duct Designer is a professional engineering tool. Sylvanity does not operate any user-account system, advertising, analytics, telemetry, or crash-reporting service for this app. All of your projects, calculations, and settings are saved on the device and never transmitted to Sylvanity.
The only data that leaves the device is what is required to operate auto-renewing in-app subscriptions: the app communicates with Apple's App Store (on iOS) or Google Play Billing (on Android), and with our subscription-management provider RevenueCat, so that we can verify your subscription status and restore your purchases on a new device. The categories of data this involves are described below.
Who we are
HVAC Duct Designer is published by Sylvanity B.V., a private limited company based in the Netherlands. Sylvanity is the data controller for the limited subscription-related processing described in this policy, for the purposes of the EU General Data Protection Regulation (GDPR). You can reach us at info@sylvanity.eu.
Where the app is available
HVAC Duct Designer is distributed through the Apple App Store (iPhone and iPad) and Google Play (Android phones and tablets). The same privacy practices apply on both platforms, with the platform-specific differences noted below (Apple App Privacy Nutrition Label vs. Google Play Data Safety; Apple StoreKit vs. Google Play Billing).
Information we do not collect
The app contains:
No user accounts, no login, and no registration system operated by Sylvanity.
No analytics, telemetry, or crash-reporting SDKs operated by Sylvanity or any third party.
No advertising and no advertising identifier (IDFA / Android Advertising ID) access. The app does not request App Tracking Transparency permission and does not perform tracking as defined by Apple's App Tracking Transparency framework.
No access to your contacts, photos, camera, microphone, location, calendar, reminders, motion, health data, or files outside the app's own sandbox.
Information stored on the device
To make the app useful between sessions, HVAC Duct Designer saves the following on your device using each platform's standard local-storage mechanisms — Apple UserDefaults for small flags and SwiftData (the platform's local persistence framework, backed by SQLite inside the app's sandboxed container) for projects and calculations on iOS; SharedPreferences for small flags and a Room SQLite database inside the app's sandboxed files directory on Android:
Your saved projects and calculations (duct geometry, airflow, materials, fittings, results).
The start date of your free trial, used to compute how many trial days remain when the device is offline.
Whether onboarding has been completed.
This information stays on the device. It is not transmitted to Sylvanity and is not used by RevenueCat, Apple, or Google. Uninstalling the app removes all of it.
Subscriptions and purchase data
HVAC Duct Designer offers an optional auto-renewing subscription (HVAC Pro) that unlocks the full feature set. Subscription processing involves three parties besides you:
Apple (for App Store purchases) or Google (for Google Play purchases) acts as the merchant of record. Your payment details, billing address, and tax information are handled by Apple or Google under their own privacy policies. Sylvanity never sees your payment card or your full billing address.
RevenueCat, Inc. (a US-based service) is our subscription infrastructure provider. RevenueCat receives, on our behalf:
An anonymous "App User ID" that RevenueCat generates for your installation. We do not link this ID to any name, email address, or other personal identifier.
The Apple or Google receipt for any purchase you make in the app, which contains the product identifier, the original purchase date, the latest renewal date, and the transaction ID.
Standard technical metadata sent automatically with every API request: app version, device model, operating-system version, country code, and IP address (used by RevenueCat for fraud prevention and immediately discarded after the request).
RevenueCat uses this information solely to determine whether your subscription is active, to allow you to restore purchases on a new device, and to provide Sylvanity with aggregate (non-identifying) statistics about subscription performance. RevenueCat's own privacy practices are described at revenuecat.com/privacy.
Sylvanity sees only the aggregate dashboards provided by RevenueCat (for example, total subscribers, churn rate). We do not see your name, email address, payment details, or any identifier that could be used to contact you.
This processing is what is reflected in the app's Apple "App Privacy Nutrition Label" as Purchases — Purchase History (linked to you, used for app functionality) and Identifiers — User ID (linked to you, used for app functionality), and in the Google Play "Data Safety" section as Purchases — Purchase history (collected, processed ephemerally) and App activity — Other actions (collected, processed ephemerally). The "linked to you" classification is required by Apple because the App User ID is associated with your Apple ID at the StoreKit layer, even though Sylvanity itself never receives any directly identifying information.
Permissions the app uses
HVAC Duct Designer does not request any sensitive runtime permission on either platform. It does not access the camera, microphone, location, contacts, photos, calendar, reminders, motion, Bluetooth, or any other sensitive device permission, and the app's Info.plist (iOS) contains no permission usage descriptions because none are required.
On Android, the app declares only:
android.permission.INTERNET — required to communicate with Google Play Billing and RevenueCat for subscription verification.
android.permission.ACCESS_NETWORK_STATE — required so the app can detect whether a network is available before attempting subscription-related calls.
com.android.vending.BILLING — required to use Google Play Billing for in-app subscriptions.
None of these are runtime-prompt permissions; they are install-time declarations and the user is not asked at runtime to grant them.
Required-reason API use (iOS)
Apple requires apps to declare specific reasons for using certain "required-reason" APIs. HVAC Duct Designer's PrivacyInfo.xcprivacy manifest declares two such uses, both with the lowest-impact reason code in their respective categories:
NSPrivacyAccessedAPICategoryUserDefaults, reason CA92.1 — access user defaults to read or write information that is only accessible to the app itself (the on-device project, calculation, and settings storage described above).
NSPrivacyAccessedAPICategoryFileTimestamp, reason 3B52.1 — display file timestamps to the user (used when listing saved projects with their last-modified dates).
No other required-reason APIs are used. The manifest also declares NSPrivacyTracking as false and an empty NSPrivacyTrackingDomains list, reflecting that no tracking takes place.
Third-party software
HVAC Duct Designer uses the following third-party components:
Apple StoreKit (iOS) and Google Play Billing Library (Android), the platform-provided in-app purchase APIs. These are governed by Apple's and Google's own privacy policies.
The app does not include any other third-party SDK that collects, transmits, or processes user data.
Data retention
On-device data is retained for as long as the app is installed and is removed when you uninstall. Subscription receipts held by RevenueCat are retained for the duration of the subscription and for a reasonable period after cancellation for restore-purchases support and for tax and accounting record-keeping (typically up to seven years, as required by Dutch and EU tax law). Apple and Google retain transaction records under their own retention policies.
International data transfers
RevenueCat is established in the United States. The transfer of subscription receipts and the anonymous App User ID from your device to RevenueCat is therefore an international transfer of personal data within the meaning of the GDPR. RevenueCat acts as our data processor under a Data Processing Addendum that incorporates the European Commission's Standard Contractual Clauses (Decision (EU) 2021/914) as the transfer mechanism. Apple and Google handle their own international transfers under their respective frameworks.
Lawful basis for processing (GDPR)
For users in the EU, EEA, and UK, we rely on the following lawful bases under Article 6(1) of the GDPR for the limited subscription-related processing described above:
Performance of a contract (Article 6(1)(b)). Sending your purchase receipt and anonymous App User ID to RevenueCat is necessary to deliver the HVAC Pro subscription you have purchased: to verify that the subscription is active, to restore previous purchases on a new device, and to apply the subscription entitlement inside the app. Without this processing we cannot honour the subscription you bought.
Compliance with a legal obligation (Article 6(1)(c)). The retention of subscription and invoice records for up to seven years is required by Dutch and EU tax-and-accounting law — in particular the Dutch fiscale bewaarplicht (Article 52 of the Algemene wet inzake rijksbelastingen) and the EU VAT record-keeping rules. This applies to the aggregate subscription data Sylvanity receives from RevenueCat.
Legitimate interests (Article 6(1)(f)). RevenueCat uses the IP address attached to each API request for fraud prevention and discards it immediately afterwards, and provides Sylvanity with aggregate, non-identifying dashboard statistics (for example total subscribers and churn rate) so we can operate and improve the subscription. Our legitimate interest is running a sustainable subscription business and protecting it from fraudulent purchases; this interest is balanced against your privacy by limiting the data to an anonymous App User ID, by not profiling you, by not using the data for any purpose outside the subscription, and by giving you the right to object — see the next section.
Is providing this data optional? The 7-day free trial works without any subscription, and only an anonymous App User ID is exchanged with RevenueCat to confirm that the trial is still active. If you choose to subscribe, providing the receipt is a contractual necessity — without it, Apple or Google cannot bill you and we cannot grant the HVAC Pro entitlement. You can stop providing further data at any time by cancelling the subscription and uninstalling the app; records already created are retained as described in the “Data retention” section above.
No automated decision-making or profiling. Sylvanity does not engage in automated decision-making or profiling that produces legal or similarly significant effects on you, within the meaning of Article 22 of the GDPR.
Your rights under GDPR and equivalent laws
Under the EU GDPR (and equivalent laws in the United Kingdom, California, Brazil, and other jurisdictions), you have rights of access, rectification, erasure, restriction, portability, and objection regarding personal data held about you.
Because the only personal data Sylvanity processes in connection with this app is an anonymous App User ID tied to your subscription receipt, the practical way to exercise these rights is:
Access / portability: email info@sylvanity.eu with the App User ID shown in the app's About / Settings screen and we will request the corresponding record from RevenueCat and supply it to you.
Erasure: email the same address with your App User ID and we will request its deletion from RevenueCat. Note that subscription transaction records held by Apple or Google for tax and audit purposes are not within Sylvanity's control and must be handled through Apple's or Google's own channels.
Restriction / objection: uninstalling the app stops all further data transmission. Cancelling the subscription stops all further subscription-related processing.
You also have the right to lodge a complaint with your national data protection authority. In the Netherlands this is the Autoriteit Persoonsgegevens (autoriteitpersoonsgegevens.nl).
Children, security, and changes
Children
HVAC Duct Designer is a professional engineering tool intended for adult HVAC technicians, designers, contractors, and engineering students. It is not directed at children, is not listed in the App Store Kids Category, and we do not knowingly collect personal information from anyone under 16 years of age.
Security
On-device data is protected by your device's standard sandboxing and disk encryption. Subscription-related communication with RevenueCat, Apple, and Google takes place over TLS. Sylvanity operates no servers that store personal data about you and therefore presents no server-side breach surface for your personal information.
Changes to this policy
If this policy ever changes (for example, if we add an optional cloud-sync feature, change subscription provider, or add a new platform), we will update this page and the "Last updated" date at the top. Material changes will also be noted in the App Store and Google Play release notes for the relevant version.
Contact
Questions about this policy or about the app's privacy practices? Contact us:
Sylvanity B.V.
Treubstraat 21 U314
2288 EH Rijswijk
The Netherlands