I've been reading a lot about composting & after 2 successful small batches (2 & 5 gallon buckets) I am hereby renouncing any statement which says that a minimum size 3'x3' is required for hot compost. The right nitrogen: carbon ratio is the only requirement in my experience.

I'm in Calgary, Alberta & though it has been hot lately, we're only talking 30 C (86 F) max & the bucket sits in the shade, so I'm sure that the outside temp doesn't have as much affect as the composting action itself, at least not compared to some hotter places in the south.

Rosie, Sugar Hill, GA

But as you suggest, the size of the pile is often mentioned without mention of the container/insulation/surrounding material.

Some piles, bins, composters are surrounded by bales of straw, plastic, metal, burlap, landscape fabric, etc. This is a consideration in how well the pile retain the heat that builds up in the compost core. But when folks say that it's hard to compost, there is a tendency to simplify things for them. A number of times I've read in this forum that the optimal size is 3feet by 3 feet by three feet. But I believe that the trueism is, from 3x3x3 to 5x5x5 in size for best results for the home gardener. And I don't agree entirely with that statement. I find a 4 foot diameter pile from 2 to 3 feet high is better than a 3x3x3 foot pile. Perhaps it was found to be easier for people to remember a figure like 3x3x3.