Proper heat is paramount to your hedgehogs well-being. A temperature of 73-85* is comfortable for them.
In many instances, this cannot be practical to keep your whole house at the temperature — either place the hedgie in a smaller enclosed room with windows, or use one of the following supplemental heat sources:
Radiant heater – typically oil filled, and are very economical, and fire safe.
Reptile Heat Pad – this is not usable without adding ceramic floor tiles sandwiching the heat mat under the cage. A rheostat is needed for this.
Ceramic Heat Emitter – Again, a rheostat is needed. (see link) You also will need a stand to keep it above the cage, and not having it touch surfaces that could be damaged. You’ll need a porcelain topped reflective dome. Rheostat here. and stand is listed here.
All these products can be found elsewhere, though I find Amazon very convenient!