Wind directions, November, 2001

 

Questions for text:

1. Why do we consider roofs as a part of our cultural heritage?

2. Speak on the functions of solar collectors and PV panels.

3. What will an influence on the roof design be?

4. What ca you say about solar roofs in different countries?

Passive Solar and Daylight

By Poul E. Kristensen – DTI Energy Vision

The roofs and facades of buildings have multiple functions – providing shelter for rain and wind, and a barrier for high or low external temperatures. However the growing concern to Reduce energy consumption and pollution has led to additional functional Requirements of the roofs and facades of buildings.

The environmental impact of building can be minimised effectively by utilizing heat and light from the sun. The roofs and facades can be used as active filters of solar power. The integrated energy facades is the key building element in achieving this. Two research projects of the European JOULE Research Programme illustrate this transition of the building envelope from a passive climate protection to an active energy filter for the building.

Design Center in Linz

The 31.000 m² design center in Linz Austria has a fully glazed envelope, consisting of double glazing with integrated microlouvres. These microlouvres are designed so that all direct sunshine is redirected out of the building. Only diffuse light is allowed to enter this exhibition building, providing ample daylight at an even distribution.

The filtering of direct sunlight from diffuse light is made possible through the design of the fixed louvres so that the correspond to the specific orientation and slope of the roof, and the latitude of the site. Radiation from those parts of the sky where direct solar radiation can occur is cut off, whereas diffuse radiation from the rest of the sky is allowed to enter the building. This innovative glazing system was developed by Lichtplannung Bartenbach in Innsbruch Austria, and it is produced by Siemens in Germany. The architect of the Design Center is professor Thomas Herzog from Munich Germany.

The Brundtland Center in Toftlund

The Brundtland Centre in Denmark is a 2000 m² office and exhibition building. The architect of the building is KHR Architects in Virum DK. The energy design and engineering is by Esbensen, Consulting Engineers in Sonderborg, Denmark.

The two storey building is designed around a central glazed atrium. This atrium serves as a thermal buffer zone for the adjacent building, and provides passive solar heating. The root of the atrium is a shed roof, with clear glazing to the north. The south sheds are utilised for production of solar electricity. The photovoltaic PV elements are integrated in the glazing, allowing only a small part of radiation from the south to enter the room. The glazing has a u-value of approximately 15 W/m2K.

The PV elements of the roof can thus serve multiple purposes providing shelter for wind and rain, thermal insulation and shading, and solar electricity and natural daylight for the building. As the advances in glazing and PV technologies accelerate, we come closer to building homes and offices that will make a positive impact on the environment - by producing more energy than they consume throughout their lifecycle.

Wind directions, November, 2001

Questions for text:

Tell about functions of buildings, roofs and facades.

What are they used for?

3. Speak on the design center in Linz (Austria).

What can you say about the Brundtland Center in Toftlund?

Describe functions of PV elements of the roof.

 

Zero energy housing

By Emil ter Horst - Novem

 

Dutch thinking about sustainability ascribes considerable importance to zero energy housing. And it's more than just thinking. A number of pilot projects have already demonstrated the practical feasi­bility of the concept.

The zero energy concept is that the annual energy consumption of a house or building should be equal to the amount of energy produced by it. It assumes that all energy will be generated by sustainable methods and that energy consump­tion will be kept as low as possible. Energy production may be achieved, for example, by using passive solar energy for space heating, solar collectors for water heating and photovoltaic (pv) modules for electricity. Energy demand is reduced by extensive thermal insulation and ener­gy-efficient systems and appliances. Since no concessions are made as regards comfort, zero energy housing is not a Spartan option reserved for idealists but a realistic basis for 21st century architec­ture.

 

The zero energy house in the Dutch town of Woubrugge is a demonstration project set up under IEA task 16. The photo shows the roof-mounted solar collectors (left) and pv-modules which produce excess summertime energy matching the amount of energy purchased in the winter.

 

Modern zero energy concepts usually involve a connection to public energy supplies. In that case, the term “zero energy” refers to a zero (equal) balance: excess solar power generated during the day is delivered to the network “in exchange” for, electricity drawn from the same network during the evening and night. Or, alternatively, excess power generated during the summer - when the pv-modules will regularly produce more than is needed - can be exchanged for extra energy to meet the wintertime demand.

The zero energy concept creates a new role for the roof. It no longer simply pro­vides necessary protection from the ele­ments, but becomes a fifth facade with a whole range of functions: to supply elec­tricity and thermal energy, to help with cooling and daylighting and even, for example, to collect rainwater to flush lavatories.

All-electric zero energy house in Zandvoort, The Netherlands. Every conceivable measure has been taken to minimise energy consumption hi this house while retain­ing all the usual comfort of a modern home. In the first year, 1995, the pv-modules alone supplied 2976 kWh, compared with total energy consumption of only 2592 kWh: so this is actually a sub-zero energy house.

 

Clearly, this kind of concept is likely to attract interest. Not only is it a visible manifestation of sustainability, but it will very soon be a cost-effective approach to building. The additional investment required can be partially offset by sav­ings on traditional roofing materials and the systems produce year-on-year sav­ings - something which cannot be said for traditional tiles.

All things considered, the zero energy concept is a logical basis for develop­ment projects, and one that is already feasible using current technology. Even so, we cannot expect an instant switch to universal zero energy building: the con­cept is too different from traditional approaches for that to happen. The “fifth façade” idea demands a cultural revolu­tion in the construction industry and amongst the other parties involved. Utilities, government authorities, plan­ners, architects, contractors roofing spe­cialists and building service companies will all have to learn to think in sustain­able terms in order to be capable of con­structing sustainable buildings. And, equally importantly, the new building materials (like solar collectors and pv-modules) must be carefully designed to avoid any possible problems of sizing, diversity, connectivity etc. on the draw­ing-board, not to mention the actual building site. To guarantee this, great efforts are currently being made in the Netherlands and elsewhere to achieve coordination between the various parties involved in the sustainable building field.

In the Netherlands, photovoltaic solar energy in the built environment is seen as the most promising sustainable ener­gy option for the 21st century. In order to be in a position to exploit that option, great attention is already being paid to optimizing the layout of future develop­ment projects in terms of solar orienta­tion - this being an essential precondi­tion for sustainable building. The zero energy concept has a major role to play, for example as the driving force behind the large-scale use of solar energy in the coming decades.