How can I keep my fermenting veggies, kefir and komucha warm in winter?

We use an old esky or a styrofoam box and place a heater mat inside along with anything that needs to ferment at room temperature. 

The heater mats are adjustable so can be turned up during the coldest months of winter and keep everything in the box or esky fermenting very well.

This is kombucha in our heater box and veggie fermentation works great too.