About this demo

The business is invented

Fettle is a theme demonstration. The business, the phone number, the registrations and the address are made up. Nobody is taking bookings.

The arithmetic is not

Every price on this site is computed from one rate card and the labour and materials recorded against each job. There is no price field anywhere in the theme. Change the hourly rate in the Customizer and every figure on every page moves together, including the ones in the admin.

The radiator calculator is the standard steady-state heat loss method — fabric plus ventilation — with published U-values by construction period. The radiator correction uses the manufacturers’ index of 1.3, which was checked against published correction tables at five points between 20 and 60 K before anything was built on it, along with a set of invariants: no temperature difference must mean no loss, doubling the difference must double the loss, better construction must never lose more, and a fully glazed wall must contribute no opaque wall area at all.

The background

It is a real solve of the heat equation on a 256 by 256 grid, stepped on the GPU, with the jobs on the page as its heat sources. It is not a model of anybody’s house and does not pretend to be. If your browser cannot give it a floating point render target it is simply not drawn, and the page sits on plain paper instead.