Our All-Electric Future (collected short essays from 1990s)

National power is sourced from coal, gas and nuclear power stations and from wind farms.
UK gas and nuclear electrical production are dependent (in part) upon imports.
The international supply of electricity recognises the interconnectedness of the European distribution of electricity. The UK buys electrical power from Europe, notably France, to supplement its own production. Electrical supply independence rather than interdependence is unrealistic in the short term, and even though we can envisage a more benign future, security is uppermost in the politicians’ minds of those countries dependent upon imports to generate it.

Logically we should aim for zero energy exchange between inside and outside of the building. Insulating a new building is very easy, and very economical. 150mm of high performing insulation will achieve this, or high performance 30mm multi-foil properly installed.

Thus, the imperative is also to reduce the demand for heat and electricity within buildings by occupants.

The heat generated within buildings is degraded chemical energy, light energy, and electricity. Chemical energy comes from the food we eat and generates about 100 w of sensible heat / person. Light is about 100 lumens per watt, whether it is from efficient fluorescent electric light but does require 3w to produce from a carbon fuel. Natural light is also about 100 lumens per watt.

The light energy in a building depends on the light level.
500 lux is 5w/sqm – which is not a large heat gain. If the lighting is inefficient with a common Coefficient of Utilisation of say 0.3, then to get 500 lux the light input is 1500 lumens /sqm or 15 w/sqm. This is now a different level of heat production from light within the building.
The light energy degrades to heat and appears as a nuisance in the summer but helps to heat the building in winter.
The other electricity to be degraded is principally computing in a modern office and in a domestic dwelling refrigeration, TV, cooking, hot water leakage, fans and so on (about 8 w/sqm).

The servers of a modern office are an important source of heat that must be harnessed.

For a domestic dwelling, the heating target is to design the building so that the degraded energy as heat can keep the building warm for 24 hours per day on a typical cold, overcast day.
Heat gains from windows as light is of course included. At 20 w/sqm of glass for 8 hrs per day it is useful for its contribution offsetting electricity for electric light.
Ventilation for people is a major issue. 10l/s per person represents by far a major part of the heat load. It is a slightly over-sized figure. However, ventilation must be heated by exchanging heat in outgoing air with incoming fresh air. The ventilation should be controlled by reference to the number of people Carbon dioxide is the modern reference. Then fan energy is minimised automatically.
The infiltration ventilation by untreated outside air has to be a minimum, say 0.05 A/C per hour. No letter box. No overflow pipes. No cracks in construction. Specified leakage rates for openable windows.

Light is a problem. Natural light is carbon free and available for 8 hours per day in winter. Glazed areas must be the minimum to meet the natural light target, and to minimise heat loss in the coldest weather. Solar gain is not particularly useful because when it appears it is a surplus of heat that has to be rejected.

For a home, say 50lux (daylight or artificial light) is adequate for most activities except focused practical activities, and the energy even for electric light is quite low. However, an office with 500+lux light represents over half the carbon footprint. Current office design light levels are too high. Lower light levels, say 75 lux, supplemented by individual 15w task lights would be a good modern design standard to aim for.