Substack diary no.128: Sunday, 19th. April 2026

Clear blue skies, sunshine, a negligible breeze and 10 degrees celsius out there, so a fairly typical spring morning. In the sitting room the temperature has just this minute risen from 15 to 16 degrees and yet I do not ‘feel’ as cold as I did four weeks ago. I was reminded of studies in environmental psychology for my post-graduate degree course in 2004.

I was already aware of metabolic gain when modelling heat loads and demand for mechanical heating in buildings, especially houses. It is overlooked by most people, but not by energy professionals and, I would like to think, by architects and house builders. Metabolic gain is taken into account in the SAP model – the Standard Assessment Procedure – for housing energy surveys in the UK. I am now sitting in an armchair and writing this and in so doing I am emitting approximately 60 watts or so of energy in the form of heat. If there was another person in the room with me we would be generating at least 120W of heat; simply standing up would increase the heat gain and moving around would increase it further! That is why crowded rooms always feel warm.