Did you ever just try and place mother on top of hot water tank. The tank stays warm and you get some heat from the vent off the top. I did this in Calgary with 2quart jars and had PLENTY.
at work i used the top of the fridge which was very warm.
I put mine in a cupboard above the fridge and it seems to work great. Even in winter. Althought I did a lot more kefir before the KT, but it seems to be working the same.
If your temp is lower like you've stated, it will just take a little longer to brew. I wrap my brewing container in a towel and keep it under my sink. Works well
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