HUUM Rebuilt Its App From Scratch. The Biggest Change Is One You Cannot See.

HUUM’s sauna platform now runs on a completely rebuilt app and server infrastructure. Photo: HUUM.

HUUM has released App 4.0, a completely new version of its sauna control application built from scratch. The Estonian heater manufacturer did not patch the old app or layer a fresh interface over existing code. It replaced everything: the mobile client, the server infrastructure, and the communication protocol between phone and UKU control panel.

The app, called HUUM Sauna Control, went live on the Google Play Store and Apple App Store on June 12, 2026. It is a free download for anyone with a HUUM UKU WiFi or UKU 4G controller.

The Biggest Upgrade Is Invisible

HUUM says the most important change in App 4.0 is one users will never see. The company rebuilt its entire server infrastructure to deliver a faster, more reliable connection between the app and the UKU control panel mounted on the sauna wall.

The result, according to HUUM: 3x faster communication. Every tap in the app, from adjusting target temperature to checking live heating progress, should respond noticeably quicker than the previous version.

That matters most for remote start, the feature HUUM owners use the most. When you are driving home from work and want the sauna warm by the time you walk through the door, a three-second lag versus a one-second lag is the difference between trusting the app and walking over to the wall panel.

Key Facts: HUUM App 4.0

Release date: June 12, 2026

Version: 4.0 (complete ground-up rebuild)

Speed improvement: 3x faster app-to-controller communication

Multi-sauna support: Manage all connected saunas from one screen

Booking: Schedule sessions by day, time, and temperature, with recurring bookings

Statistics: Session history and cumulative sauna hours tracking

Accessibility: Improved interface plus full dark theme

Safety: Remote start requires UKU panel confirmation that the sauna is empty and the door is closed

Compatibility: Works with UKU WiFi and UKU 4G controllers

Price: Free (iOS and Android)

Multi-Sauna Support Is the Commercial Play

The headline consumer feature is convenience: booking from the home screen, recurring session schedules, dark theme. But the feature that matters most for SaunaNews readers is multi-sauna management.

App 4.0 lets a single user view and control multiple HUUM-equipped saunas from one screen. For a homeowner with one sauna, that is a nice-to-have. For a hotel, gym, or spa operator running three or four HUUM units across a facility, it changes the management model. One staff member can monitor heating status, check door sensors, and schedule sessions across every sauna without switching accounts or toggling between views.

HUUM has offered commercial-grade hardware since its UKU system first shipped. The multi-sauna dashboard in App 4.0 now gives operators a software layer that matches.

What Changed Under the Hood

The full feature list in App 4.0:

Start, stop, and adjust sauna temperature remotely

Set exact target temperature and session duration

Schedule sessions by day, time, and temperature, including recurring bookings

Watch live status: current temperature, target temperature, and heating progress

Manage multiple saunas from a single dashboard

Track cumulative sauna hours and browse full session history

Receive real-time alerts for door status, connectivity, and safety events

Improved user management for shared and commercial environments

Full dark theme

Accessibility improvements throughout the interface

The UKU control system comes in three versions: UKU Local (wall panel only, no app), UKU WiFi (app control via home network), and UKU 4G (app control via cellular, for remote cabins without broadband). App 4.0 works with both WiFi and 4G variants. The UKU system supports heaters up to 18 kW and is compatible with electric heaters from multiple manufacturers, not just HUUM.

Where HUUM Fits in the Smart Sauna Market

HUUM was the first sauna manufacturer to ship a smartphone-connected control system, back in 2014. That head start gave it a decade of installed base, but the original app accumulated years of technical debt.

The competitive context has shifted. Harvia phased out Xenio WiFi and moved remote start behind a paid upgrade in its Fenix line. Saunum has been iterating on its own app with the Leil software updates. Operators who need reliable app control for commercial environments now have fewer options than they did two years ago, and HUUM is betting that a ground-up rebuild positions it as the most capable remaining choice.

The rebuilt server infrastructure is the part competitors cannot easily replicate. A fresh UI can be designed in months. A rewritten backend that cuts latency by two-thirds requires rethinking the entire data pipeline between phone, cloud, and wall panel.

Early Feedback

The app currently holds a 2.5-star rating on Google Play across 126 reviews, though that score reflects years of legacy ratings from the previous version. At least one early review of App 4.0 reports an issue with the safe-start feature resetting after roughly a day, which would prevent remote starts until manually re-enabled at the panel. HUUM has not publicly addressed the report.

For operators considering the upgrade, the safe-start reliability question is worth monitoring. The feature is the linchpin of HUUM’s remote-control safety model: the UKU panel must confirm the sauna is empty and the door is closed before the app can fire the heater. If that confirmation does not persist reliably, the app’s most-used feature becomes intermittent.

Why It Matters

Smart sauna control is becoming table stakes for commercial installations, and the manufacturers who get the software right will lock in operator loyalty for years. HUUM’s decision to scrap its existing app and rebuild from scratch, server infrastructure included, is the kind of investment that only makes sense if you believe the control layer is as important as the heater itself. For an Estonian manufacturer competing against Harvia’s global distribution, the app may be HUUM’s strongest differentiation play.

The Bottom Line

HUUM App 4.0 is a complete rebuild, not a refresh. The 3x speed improvement, multi-sauna dashboard, and rebuilt server infrastructure signal that HUUM sees software as a competitive weapon, not an afterthought. The early safe-start report deserves watching, but the architecture underneath is the real story. Download is free on Google Play and the Apple App Store.