Flexwatt (without control) doesn't get as hot as some other kinds of UTH, & if your house is too cold, there's only so much it can do. Hard for me to tell, but
is there any way to further insulate the enclosure? Also, UTH may not be "enough" to heat the air in a larger cage or in a set-up with thicker substrate (like for
holding humidity). You may just need to supplement the UTH in this situation. Every set-up (& household) is different, & ya gotta do what ya gotta do.