Energy from theSun 301Solar energy in building design
All buildings benefit from unplanned gains of so-
lar energy through windows and, to a lesser extent,
through the warming of walls and roofs. This is
called ‘passive solar gain’; for a typical house in
the UK it will contribute about fifteen per cent of
the annual space heating requirements. With ‘pas-
sive solar design’ this can relatively easily and in-
expensively be increased to around thirty per cent,
while increasing the overall degree of comfort and
amenity.The main features of such designare to
place, so far as is possible, the principal living
rooms with their large windows on the south side of
the house, with the cooler areas such as corridors,
stairs, cupboards and garages with the minimum of
window area arranged to provide a buffer on the
north side. Conservatories can also be strategically
placed to trap some solar heat in the winter.
The wall of a building can be designed specif-
ically to act as a passive solar collector, in which
case it is known as ‘solar wall’ (Figure 11.12).^49 Its
construction enables sunlight, after passing through
an insulating layer, to heat the surface of a wall of
heavy building blocks that retain the heat and slowly
conduct it into the building. The insulating layer, al-
though allowing sunlight to pass through, prevents
thermal radiation from passing out. A retractable
reflective blind can be placed in front of the insula-
tion at night or during the summer when heating of
the building is not required. A set of student resi-
dences for 376 students at Strathclyde University in
Glasgow in southwest Scotland has been built with
a ‘solar wall’ on its south-facing side. Even under
the comparatively unfavourable conditions during
winter in Glasgow (the average duration of bright
sunshine in January is only just over one hour per
day) there is a significant net gain of heat through
the wallto the building.Figure 11.12Construction of a ’solar wall’. The insulation material is about 100 mm thick and consists of
open honeycomb channels of transparent polycarbonate material.