Glad to hear you now have a UTH - next question everyone is going to ask - is it being controlled by a thermostat or dimmer? These regular heat mats bought from pet stores can exceed temps of 105+ so it is very crucial to regulate the heat in some way.
UTH is used for belly heat not ambient temps,either keep that room warmer to achieve a good temp or try to put the tank somewhere that you can put a CHE over top to achieve proper ambient temps. Plus an hour is a very short amount of time to judge a heat source...wait a day and see where it's at but do not leave that thing on unless you have a thermostat.
How is your humidity been holding up? We used to use damp towels/clothes when we had the grated lid, it worked wonders but was just annoying having to soak the clothes every other day.