HUUM Rebuilt Its App From Scratch. The Biggest Change Is One You Cannot See.
By Arlene Scott
Correspondent, Research and Industry
- Published
- Reading time
- 4 min
SaunaNews is published by SaunaShare, Inc., which also runs SaunaShare.com and SaunaMarketplace.com, where we sell many of the products we write about. That experience may change what we write about and what we don't. Who owns SaunaNews
App 4.0 replaces the mobile client, the server infrastructure, and the communication pipeline between phone and wall panel. HUUM says control is 3x faster, and a new multi-sauna dashboard lets operators watch every connected sauna from one screen.
In this story4 sections
HUUM has released App 4.0, a complete rebuild by the Estonian heater manufacturer: a new mobile client, new server infrastructure and a new communication pipeline between phone and wall panel.
“This wasn’t a patch or a polish,” HUUM told SaunaNews directly. “This is a serious piece of engineering, built to serve you faster, more reliably, and at a scale ready for everything that comes next.”
The app, now called HUUM Sauna Control, went live on iOS and Android in mid-June 2026. Version 4.0.2 is the current release. It is a free download for anyone with a HUUM UKU WiFi or UKU 4G controller.
The biggest change is one you cannot see
HUUM says the most important part of the new app is invisible.
“Behind this new app is something you’ll never tap, swipe, or open, and that’s exactly the point,” the company wrote in its announcement. “HUUM has grown. A lot. So much, in fact, that we rebuilt our entire server infrastructure from the ground up. Every part of the engine that connects your phone to your sauna.”
“You won’t see it. You’ll feel it in every single tap.”
The specific claim is 3x faster communication between the app and the UKU control panel. HUUM says every command now responds instantly, with no delay between tap and heat.
That speed matters most for remote start. For an owner driving home who wants the sauna warm on arrival, the difference between a three-second lag and 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 Mid-June 2026, version 4.0.2 (current as of June 17)
- Scope Complete ground-up rebuild of app and server infrastructure
- Speed 3x faster app-to-controller communication
- Multi-sauna support All connected saunas visible from one screen
- Booking Schedule by day, time, and temperature, with recurring sessions
- Statistics Session history, cumulative sauna hours, per-session charts
- Dark theme Full dark mode throughout
- Safety Remote start only enabled when UKU panel confirms the sauna is empty and door is closed
- Compatibility UKU WiFi and UKU 4G controllers, iOS 15.1+, Android
- Price Free
- App Store iOS | Android
Multi-sauna control is aimed at operators
The headline consumer feature is smarter booking: set the day, time, temperature, and duration in seconds, save recurring sessions, and keep the next booking visible on the home screen. HUUM says the goal is that “your sauna is ready before you walk through the door.”
But the feature that matters most for operators is multi-sauna management. App 4.0 lets a single user view and control every HUUM-equipped sauna from one screen, with current temperature, target temperature, status, and alerts for each unit visible at a glance. “Online, offline, or heating,” HUUM writes, “you always know where things stand.”
At a hotel, gym, or spa running three or four HUUM units across a facility, 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 now gives operators a software layer that matches.
The full feature list
HUUM’s announcement to SaunaNews lists these App 4.0 features:
- 3x faster control: App and controller communicate three times faster, with instant response on every command
- All saunas in one view: Current and target temperature, status, and alerts for every connected sauna at a glance
- Smarter booking: Set day, time, temperature, and duration in seconds, with recurring sessions
- Advanced statistics: Total sauna hours, full session history, per-session heating charts
- Real-time alerts: Instant feedback on open doors, lost Wi-Fi connections, and remote-start safety checks
- Improved user management: Better handling of shared and commercial sauna environments
- Full dark theme: System-wide dark mode
- Accessibility improvements: Interface updates across the entire app
The UKU control system comes in three versions: UKU Local (wall panel only), UKU WiFi (app control via home network), and UKU 4G (app control via cellular for remote locations). 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.
Harvia now charges for remote start on Fenix
HUUM’s app has been on Apple’s App Store since August 2014.
Harvia is moving connected control to Fenix, where remote start requires a one-time MyHarvia Control upgrade. HUUM is betting that a ground-up rebuild makes its app a strong choice for operators.
The backend is the harder part to copy. A fresh UI can be designed in months; a rewritten backend that cuts latency by two-thirds means rethinking the data pipeline between phone, cloud, and wall panel. HUUM says: “We listened closely to your feedback, and then we went all in.”
