My Taco is in a glass tank with a wide-mesh lid on top. The room temperature in winter stays at about 19 - 20 °C with rarely approaching 18 °C during nights (as typical for houses in our location, there is no heating; summers get hot, but we also have no cooling, so use a fan and open the windows during summer if we think it's a bit too hot (for us)). That works well for both us and the dragon; we can get the tank to appropriate temperatures all year long. Otherwise - house with heating in a region that makes it necessary - I might have put the enclosure in a room we heat during day (in cold regions, we heated rooms such as living room or office to about 19 - 20 °C) and would use a ceramic heat emitter during the night for the dragon's enclosure.
Running AC (cooling) is something we would avoid even if existing; we just don't like the noise such a thing makes and how it feels (I really hate it when somewhere, e.g. at a workplace, AC cannot be switched off! I'm okay with cooler room temperatures but just not with cooling). In that case of overly hot, we likely would reduce heat sources in the enclosure, e.g. trying it with switching out the basking lamps with appropriate LED or using a LED and weaker basking lamps. But really too hot for a dragon should not happen too frequent?
Taco did brumate more than 3 months during this (his first) winter; he generally reacts very much to tiny variations in temperature and light, and generally what he sees (weather) through the windows. A cloudy day, or a day a bit cooler than the one before, he won't come out much of his burrow despite technically the temperatures are fine. During brumation, on especially sunny days he came out from his burrow for a bit. (Similar to their behavior in the wild, as I've read.) He ended brumation exactly on winter solstice - I guess that tells something.
Regarding insulation: Foam or cork plates would indeed be an idea. Another idea that extends this: building a climbing background that doubles as insulation. The back and one side of Taco's tank has a climbing background made from MDF, styrofoam, construction foam, tile glue and sand. This is then glued to the glass with safe silicone for fish tanks to prevent it from tipping over. I don't know how much insulation it adds as I made it immediately after buying the tank and the main purpose was not insulation but enable extra space for climbing. But I would suggest a solution similar to this especially in case the tank doesn't have something for climbing on at least one side. There are plenty of tutorials online if you look for some of the above materials and "reptile" or "tank". Taco uses this area a lot and I'm happy that he has more to climb than just a branch and a stone.
For a quick look: You can see it here in the photo attached to the first posting
Also make sure there is enough "stuff" in there. Like wood, stones or sand (or other substrates), as they safe heat way better than if there would be more air in the tank.
Agree very much on that. I personally think (my opinion) that most tanks I see look to me very "empty". Of course the dragon should have enough space to move around, but I would for sure add more. Also: Added "furniture" can provide extra space the dragon can use, instead of a mostly inaccessible volume. I see it similar to a room: Extra height in a room used by humans just makes it harder to heat and we can't use the extra volume - but we can use some of the extra volume in our room if we add another level, e.g. we would add a bunk bed, a bouldering wall or another raised area. Same goes for a reptile enclosure.
