Heat map, depicting large amounts of data

Playing with open data from Junta de Castilla y León, I decided to create a Map of building's emissions and consumption in Castilla y León.

It is a heat map that uses the 'energy performance certificates' of the buildings. The result needs some interpretation as areas with no information available can wrongly lead to think that they are areas with low consumption or emmisions.

So, strictly speaking, the intensity of the heat map points to areas with low efficiency and/or high concentration of buildings with available information on their CEE.

The first challenge at development level, so far, has been to reduce the 46.3 MB (and rising) of information downloaded from the Junta's website to two 3.7 MB files. One for efficiency and one for consumption.

The next step is request Junta's data 'in pieces and grouped' according to the area of the map that is being viewed. I made a first attempt but I didn't implement it because either the downloads generated were too large or the visualisation obtained was not reliable. It's not that it can't be done, it's just that I haven't thought it through yet. Or so I think.

The CEE heatmap is made with Leaflet and the plugin simpleheat.