Direct gain

Direct gain is the design technique in which one attempts to concentrate the majority of the building's glazing on the sun-facing facade. Solar radiation is admitted directly into the space concerned. Two examples 30 years apart are the author's house in Sheffield, designed in 1967 (Figure 5.2) and the Hockerton Project of 1998 by Robert and Brenda Vale (Figure 5.3). The main design characteristics are:

• Apertures through which sunlight is admitted should be on the solar side of the building, within about ±30° of south for the northern hemisphere.

• Windows facing west may pose a summer overheating risk.

• Windows should be at least double glazed with low emissivity glass (Low E) as now required by the UK Building Regulations.

• The main occupied living spaces should be located on the solar side of the building.

• The floor should be of a high thermal mass to absorb the heat and provide thermal inertia, which reduces temperature fluctuations inside the building.

• As regards the benefits of thermal mass, for the normal daily cycle of heat absorption and emission, it is only about the first 100 mm of thickness which is involved in the storage process. Thickness greater than this provides marginal improvements in performance but can be useful in some longer-term storage options.

• In the case of solid floors, insulation should be beneath the slab.

• A vapour barrier should always be on the warm side of any insulation.

• Thick carpets should be avoided over the main sunlit and heat-absorbing portion of the floor if it serves as a thermal store. However, with suspended timber floors a carpet is an advantage in excluding draughts from a ventilated underfloor zone.

During the day and into the evening the warmed floor should slowly release its heat, and the time period over which it happens makes it a very suitable match to domestic circumstances when the main demand for heat is in the early evening.

As far as the glazing is concerned, the following features are recommended:

• Use of external shutters and/or internal insulating panels might be considered to reduce night-time heat loss.

• To reduce the potential of overheating in the summer, shading may be provided by designing deep eaves or external louvres. Internal blinds are the most common technique but have the disadvantage of absorbing radiant heat thus adding to the internal temperature.

• Heat reflecting or absorbing glass may be used to limit overheating. The downside is that it also reduces heat gain at times of the year when it is beneficial.

• Light shelves can help reduce summer overheating whilst improving daylight distribution (see Chapter 14).

Clestory Sunspace Design

Figure 5.2

Passive solar house, Sheffield 1960s

Figure 5.2

Passive solar house, Sheffield 1960s

Indirect Solar GainAttached Sunspace Indirect

Direct gain is also possible through the glazing located between the building interior and attached sunspace or conservatory; it also takes place through upper level windows of clerestory designs. In each of these cases some consideration is required concerning the nature and position of the absorbing surfaces.

In the UK climate and latitude as a general rule of thumb room depth should not be more than two and a half times the window head height and the glazing area should be between about 25 and 35 per cent of the floor area.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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