Do I need it?
The sparks putting it in says that the heating pad can just be laid on the bathroom floor (which is new green 22mm chipboard). The builder says we'd waste heat if we didn't have an insulation pad under the heating pad.
Since these two don't get on, I'm left deciding what to do. I'm inclined against because the sparks is the pricklier of the two, and I'm a coward. More particularly, it would build the floor up too much compared to the landing outside the bathroom.
Any opinions?