Passive Solar Architecture Pocket Reference

Second edition

David Thorpe

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781317616153
• Edition: 1
• Topic: Technik & Maschinenbau
• Subtopic: Regenerative Energieressourcen

This handy pocket reference contains a wealth of information on a range of topics including the principles of passive solar building and passive house, a ten-step design and build strategy, calculating solar irradiance, factors affecting the choice of building materials, passive heating and cooling principles and techniques in different climates, the Passivhaus Standard and natural and augmented lighting and notes on technology and building occupation. The book also includes conversion factors, standards, resources and is peppered throughout with helpful illustrations, equations, explanations, and links to further online resources.

Ideal for practitioners, architects, designers, consultants, planners, home builders, students and academics, and those working in development contexts, the book is intended to act as an aide memoir, a reference supplement, a resource and an overview of the field. Rich in background detail, the book also includes at-a-glance tables and diagrams, equations and key definitions.

1 Basic concepts

Passive solar and passive house architecture are separate but closely related and overlapping approaches to sustainable building. This is illustrated in Figure 1.1 and explained below. This book covers both passive solar and passive house design approaches, as they have much in common, and it combines the principles of each as far as possible.

1.1 Passive solar and passive house

The goal of passive solar architecture is to optimise the use of naturally available light and heat. This is achieved by designing the building with respect to the exterior conditions and location in such a way as to capture and keep thermal energy from the sun within the fabric of the building (if heating is required) or to prevent the heat gaining access in the first place (if cooling is required). A fundamental aspect of ‘passive’ solar design is sensitive orientation with respect to the sun for energy capture, lighting and shading.

Figure 1.1 Venn diagram showing how both passive solar and Passivhaus buildings are part of the class of low to negative carbon buildings, and how passive solar buildings can also be Passivhaus, but each can be independent of the other

The goal of passive house design is similar but slightly different. It is to manage thermal energy gain and loss, regardless of the source, so that a minimal amount of energy is needed to heat and cool the building. This entails controlling the number of air changes per hour and eliminating ‘thermal bridges’, which conduct heat or cold through the building’s exterior skin. Passivhaus (passive house in English) is a strict performance-related standard for this approach.

‘Passive’ solar is distinct from ‘active’ solar, which refers to solar thermal or electric technology. In principle, ‘passive’ means having no operable devices – for example, motors and pumps for heating or cooling, which are considered ‘active’. However, in practice most ‘passive buildings’ have some active components, such as blinds or heat exchangers.

Clearly, the two concepts – passive solar and passive house – overlap, but at their extremes, depending on the climate, can give rise to different building forms.

•The ideal form for a passive solar building in a temperate climate would be longer on the north–south-facing side than the east–west-facing sides, with double or triple-glazed windows on the sun-facing side and very small or no windows on the opposite side.

•The ideal form for a passive house design would be a cube. This is because it minimises the surface area to volume ratio, limiting heat loss.

Nowadays, passive solar design is approaching maturity. Since not every building can face south or be unshaded, passive house design is more widely applicable than traditional passive solar. In principle, a passive house building can be built anywhere. The same cannot be said of passive solar buildings. The signal design feature of traditional passive solar was long, sun-facing windows. These are not always needed or possible for passive house buildings.

In both cases, a comfortable interior climate is assured by using ventilation based on convection, controlled wind ingress, zoning and, where appropriate, heat exchangers or heat dumps, among other techniques.

Figure 1.2 Traditional passive solar architecture: the ‘Black Forest’ passive solar ‘earthship’ in Colorado Springs, Colorado. Made of rammed earth and reused tyres, its south-facing conservatory traps solar heat and stores it overnight in the thermally massive structure. It functions well in this location and climate, but would be inappropriate in, say, a hot dry climate or a city

Source: Michael Shealy, licensed under Creative Commons

Figure 1.3 This Passivhaus apartment block was built by construction company Rhomberg in the residential park Sandgrubenweg in Bregenz, Austria. Interestingly, two almost identical blocks were built: one to Passivhaus standard and the other to a ‘low carbon’ standard. They were subsequently monitored for energy use. The Passivhaus was supposed to have an annual heating requirement of 9.03 kWh per square metre and the low-energy house 33.23 kWh per square metre. In practice, the occupants in the passive house consumed 39.9 kWh per square metre and those in the low-energy house 36.3 kWh per square metre. The reason was that the occupants in the Passivhaus had the heating over two degrees higher than the designers had planned for: 22.1°C (71.78°F) instead of 20°C (68°F). This shows how occupancy behaviour can frustrate the best intentions of designers

Source: Andreas Praefcke, licensed under Creative Commons 3.0

Figure 1.4 A negative carbon house that is neither fully passive house or passive solar. The Solcer House, designed by Cardiff University’s Welsh School of Architecture, combines the Welsh Low Carbon Research Institute’s Solcer (smart operation for a low-energy region) programme with a research project about making buildings as power stations, conducted by Swansea University with industry pa...