2.1 Solar and Non-solar tower blocks, Gorbals

The 23-storey ‘solar’ tower block has been retrofitted as such, with unheated glazed spaces buffering generously glazed, east or west facing living rooms, since 2003. Originally completed in 1958, the blocks underwent an earlier phase of upgrade in the mid-1990s, with insulation, for example, lowering U-values of the solid parts of window facades from 0.99 to 0.51 W/m2K. The 21st C improvements included further insulation taking these external walls to a U-value of 0.23 W/m2K, in addition to window replacement. The ratio of glass (i. e. excluding window frames) to floor area in living rooms is 41.6%; while that for the sunspaces is 130%. However, the additional outer layer of double-glazing, together with the 1.2 m projection of the floor slab and low ceiling height of 2.3 m, does have a significant impact on sunlight penetrating the window aperture. Heating was also upgraded in 2003 with a traditional ‘wet’ system of delivery by radiators, supplied by communal gas boilers. Total energy costs for gas and electricity were estimated to average typically circa £10 per week for two and three-roomed flats, noting that all such estimates will have risen since the time of surveying, mainly during 2006.

The ‘non-solar’ tower, again 23-storeys, constructed in a similar heavy concrete system to the solar one in 1970-73, belongs to an era of greater financial stringency and has a mix of one, three and four-roomed flats on each floor. There were no open balconies for conversion to sunspaces, and living room window areas are some three times more modest, the ratio of glass to floor area reduced to 13.7% (one third of the solar %). Again windows face due east or west, and although, in compensation, there are no projecting slabs to shade these apertures, living room depth has increased from circa 4.2 m in the ‘solar’ case to 5.5 m ‘non-solar’. The U-value of walls, a dense pre-cast concrete ‘sandwich’ with 25 mm of expanded polystyrene insulation, is estimated to be 0.78 W/m2K; while original single-glazed windows were replaced with double-glazed uPVC ones in the late 1990s and heating is by electric storage units on a ‘heat with rent’ tariff. In this case costs for heat are estimated to be about £9 per week, plus £12.50 for electricity (total £21.50).

The urban context for both tower blocks is virtually identical, hence eliminating key differences such as local retail facilities, transport availability, views and so forth.

2.2 Solar and Non-solar medium-rise blocks — Glasgow Green and Partick

The two medium-rise case studies also have certain contextual similarities, but physical differences are more marked. The ‘solar’ block is six storeys high, with 3-room flats, and faces south on to Glasgow Green, the oldest public park in the city — a superb outlook — in an area of the city undergoing regeneration. The ‘non-solar’ block is nine storeys high (4 layers of 3-room maisonettes over ground floor flats and communal accommodation), and its main rooms face due west, looking diagonally to a sports field. — a valuable amenity. This is

in an area classed as high-amenity ‘West End’, which has a track record of sustainability over more than a century.

The solar block was a flagship housing association project for Glasgow 99, City of Architecture and Design; and is constructed to a reasonably high specification in terms of insulation, windows etc. — e. g. U-value of walls 0.23 and roof 0.16 W/m2K. The construction in this case is a steel frame, with copper-clad timber-framed walls and concrete separating floors. Like the solar tower, the ratio of glass to floor area of living room is generous without including the north-facing window — 25% (the living room is relatively narrow at 3.25 m, but unusually long at 11.0 m). In this case a direct solar gain strategy has been adopted, with a sizable ‘outdoor room’ to one side off the kitchen. Ceilings are also significantly higher than the towers or the other medium-rise block at 2.75 m. Although it has twelve flats in total, and only two of these opted into the study, it is the only example of ‘invisible’ gas heating by warm under-floor coils, as well as the only example of heat recovery, with a relatively sophisticated MVHR system serving all main spaces. Occupants estimate respective weekly heating and electricity costs to average £7.50 and £3.20.

The non-solar block was constructed in the 1960s with reinforced concrete floors and spine walls. Outer walls vary in construction — outer leaf facing brick, cavity and inner leaf brick or concrete; solid block-work and timber-framed panels; U-values varying from circa 1.0 to

1.6 W/m2K. Original windows have been replaced with double-glazed uPVC (living glass:floor 13.7%), and heating is by a mix of electric storage and non-storage appliances. On average, occupants (generally elderly) were paying £18.50 per week in winter and £ 13.00 in summer for electricity.

2.3 Quasi-solar low-rise reference blocks

A fifth quasi-solar (well oriented, with glass 28% of living room floor area) scheme has been included in this study as a further reference. It is a late-1970s (completion 1981), 3-storey version of tenement housing with flats accessed from common stairs, and all flats having either an open balcony or small private garden. The location is again within Glasgow’s ‘West End’ and the degree of permeability, enclosure and verdant landscaping secures a pleasant ‘oasis’ within its confines. Original cavity brickwork has been cavity-insulated (U-value 0.42 W/m2K), windows are now double-glazed with uPVC frames and heating is by individual ‘combi’ gas boilers, with radiators in all main spaces. The weekly gas and electricity cost for a typical two-room flat for the elderly is approximately £7.50 (reflecting energy-efficiency, size and, perhaps, frugality).