The cleanest wood-burning sauna stove: HUUM's Hive Heat explained

The Hive Hive by HUUM requires less wood, emits less carbon, and has shorter safety distances. It was origonally designed for German sauna enthusiasts but has become popular in the UK.

What is the environmental impact of a wood-burning sauna stove? And, actually, do they have a future at all amid increasing concern in the UK and elsewhere about the impact of wood-burning sauna stoves on the environment?


We sell wood-burning sauna stoves so you probably won't be too surprised to hear us say that the answer to that second question is 'yes'.


However, we're not going to greenwash over any concerns. We're actually really excited about how we can preserve the tradition of wood-burning saunas while also massively improving their environmental impact. As it happens, Anni in our team is one of Estonia's leading experts on carbon counting, including for sauna manufacturers here, and is currently helping create our own country's legislation for environmental export declarations.


But what's happening in the UK?


Despite the impression you might have got from headlines, the UK isn't moving towards a ban on wood-burning stoves but is taking a lot of good steps as part of the government's Clean Air Strategy to radically lower their impact. This is being acheived through better regulations to encourage innovation and higher standards among manufacturers and improved awareness among consumers, including best usage practises.


As a result, new wood-burning stoves are far more efficient at converting fuel into heat with far less unwanted byproducts like carbon and ash, and the wood you can buy to fuel it must have a low moisture content to further improve that efficiency. This isn't just good for the environment, but also your health and bank balance.


HUUM has been at the forefront of innovation, including for its Hive Wood stoves, since before these new rules came into force. You can download the Hive Wood manual here below, which includes technical and performance details:

Manual for HUUM wood-fired Hive Wood sauna stove 2022
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Download PDF • 1.32MB

These Hive Wood wood-burning stoves are available in 13 kW and 17 kW sizes in its standard design (with the stove door inside the sauna hot room so you can load it up and see the flames while enjoying the sauna) and also 17 kW "LS" version, which has an elongated stove door designed to go through a wall so that it can be heated from the next room or outside.



However, there is also a newer, specially adapted version version of HUUM's Hive wood-burning stove, which is even more efficient and environmentally-friendly.


It's called the Hive Heat and it's available as a 12 kW standard version and a 12 kW LS version with through-the-wall heating.

To understand HUUM's Hive Heat, let's talk about Bundesimmissionsschutzverordnung.


I know. It doesn't exactly roll off the tongue. But Bundesimmissionsschutzverordnung is the legislation that Germany introduced in order to lower the environmental impact of their own wood-burning stoves. Yet,oddly enough, it's also improving environmental standards for saunas in the UK due to demand for stoves here compliant with that legislation (which are sold with this mark below).

The legislation is called BImSchV for short. Still not very catchy, but bear with me. As in the UK, it also sets limits and targets for all wood-burning stoves but at a stricter level. It focuses on reducing carbon emissions and dust output as well as improving efficiency.


The regulations were phased in so that they became even stricter in 2015, which is why we now talk about it as BImschV II. And the legislation now also applies in Austria and Switzerland. Stoves that comply with these rules can be used in all three countries, including in urban areas. The exact requirements are a bit technical and vary by type of stove but the limits are set between 0,02 – 0,04 mg/m³ for dust and between 0,25 – 1,50 g/m³ for CO.


As a result, wood-burning stove makers such as HUUM had to adapt their stoves and get them independently verified and tested for compliance in order to continue delivering to Germany, Austria, and Switzerland with their stricter rules.


The Hive Heat is the end result and you can download its performance certificate that demostrates its compliance here:

Declaration-of-Performance-HEAT12 (1)
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Download PDF • 195KB

You can also take a look at the manual for the Hive Heat here:

Manual for HUUM wood-fired HIVE Heat sauna stove 2022
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Download PDF • 869KB

The Hive Heat uses slightly different materials, such as a cast iron stove door, and a more innovative air flow system aimed at burning the wood as cleanly and efficiently as possible. For example, as you can see in the manuals, the Hive Heat has a far lower flue gas temperature, which is 292 C rather than 430/443 C. This is a good indicator of how much more heat is going into the stone and then into the room rather than up out of the chimney. That lower chimney temperature, by the way, also reduces the risk of fire.


So what's going on inside? Take a look below. You can see there are two fresh air feeds into the stove to feed the flame from above and below, which leads through carefully thought out air channels.



But what's all this got to do with British sauna builders?


We'll be honest. When these stoves were first designed, we didn't realise there would be demand from the UK. They are slightly more expensive to reflect the higher production costs so we didn't initially introduce them to the UK where they are not legally required.


Yet our own sauna building partners - who know the fundamentals of good sauna design better than anyone - soon started asking for them. One aspect that particularly stood out for them is the shorter safety distances required as part of the BImschV II legislation. This gives sauna builders more flexible design choices, particularly where space is tight. For example, horse boxes have been particularly popular for pop-up beach saunas in Britain so the Hive Heat with its smaller safety distances is perfect for those spaces.


Popular saunas like Beach Box Spa in Brighton and Fire, Salt, & Sea in Worthing both use Hive Heats, for example. And if you haven't yet watched our Great British Sauna Tour then you can check out our episode about Beach Box Spa here.



We think the BImschV II legislation provides a good model for how the UK could improve its own wood-burning stove regulations in the future. In the meantime, we are recommending the BImschV II compliant Hive Heat as the wood-burning stove of choice to all sauna builders in the UK. It's not just better for the environment, but it's safer, healthier, more flexible for sauna designs, and costs less to heat, which can more than offset the slightly higher cost


Email us at tere@estoniansaunas.com if you have any additional questions.


Thanks for reading. You can take a look at all our wood-burning Hive Heat and Hive Wood sauna stoves here and we also now stock chimney sets for them here.