Glass or wooden sauna door: which is better?

The door is the part that causes the most trouble and loses the most heat. The material matters less than four things that quotes usually say nothing about.

Glass door

It lets in light and visually opens up the space. In a small 2 m barrel sauna that makes a big difference: the sauna stops feeling like a dark box.

Toughened safety glass is robust and the easiest to keep clean. It does not warp with moisture, so it closes years later just as it did on day one.

The downside: glass conducts heat more readily than 44 mm timber, so losses are slightly higher. With a good seal, that is negligible compared with the heat lost by simply opening the door during a session.

Wooden door

It holds the heat a little better and matches the rest of the build. On a solid-timber barrel it looks natural.

The drawback is real: wood moves with moisture and temperature, glass does not. After a few seasons the hinges may need adjusting, and if ventilation is neglected a door can warp until it no longer sits flush.

The seal matters more than the material

It decides the heat loss, and it is the first thing to wear out. A simple test: with the sauna heated, run your hand around the closed door. If you feel a warm draught, the seal is not making contact.

A new seal is cheap, and it is the least expensive thing you can do to burn less wood. Replace it every few seasons.

Three safety rules

The door opens outwards, always. If someone feels dizzy and slumps against it, it must open from the outside.

No lock on the inside. A sauna is never locked, under any circumstances.

A door handle made of wood or another material that conducts heat poorly. A metal handle gets hot at 90 °C, and people grab it by reflex.

Door closer or spring

A small thing that genuinely saves wood: the door closes by itself instead of staying ajar for half a session because someone stepped out.

With guests or children it is not a luxury but what keeps the temperature up without anyone having to watch it.

What to check when buying

Does the door have a seal, and what type: silicone or brush?

Does it open outwards?

What is the handle on the inside made of?

Is there a door closer, and if not, can one be added?

Adjustment and care

Lubricate the hinges once a year before the season. A sticking door is not just annoying: forcing it shut wears the seal faster.

Wooden doors may need adjusting after the first and second season, once the timber has settled. That is normal maintenance, not a defect.

Clean glass with clear water and a little vinegar. Glass cleaner leaves a smell that comes back in the heat.