By David Olivier, B.Sc., M.lnst.E

Introduction

As well as Scandinavia, some countries on the mainland of Europe are making major efforts to improve the energy efficiency of their buildings, and utilise renewable energy sources. These countries include Switzerland, Germany and the Netherlands.

In these countries, there are hundreds of energy/buildings projects underway. To review and report on this work, the author recently made a visit to a number of projects in these countries, and a report on the subject has just been published**. This article describes one of the many interesting schemes underway.

Wädenswil

Ten semi-detached houses were built in this small town, near Zurich, in 1990-91. Four of them should use essentially zero energy for space heating. Even the other six should only use a few bottles of propane per winter.

The skill shown in the design of this project is one borne of years of experience. In most respects, it represents the state-of-the-art in energy-consciouS, solar building design.

The walls are concrete blocks, with external insulation of 180 mm extruded polystyrene, and the basement floor and footings rests on a raft of extruded polystyrene. There is a continuous layer of insulation around the houses, with minimal cold bridges. As a result, the houses achieve true U-values of about 0.15 W/m2K in the opaque fabric (by comparison, the measured heat loss through the walls of recent UK houses is six times faster).

Some windows use an advanced glazing system, with two selectively-coated thin plastic films suspended between the two layers of glass. Most windows are argon-filled triple glazing, with two selective coatings. The houses achieve a U-value of 0.85 W/m2K im the glazing (yet in new UK buildings, it is still legal to use single pane windows, which lose heat seven times faster).

Based on results from a previous house, the air leakage of these dwellings is expected to be less than 0.2 air changes per hour at a pressure difference of 50 pascals (5-15 times better than even the Swedish requirement, and 40-50 times better than new UK dwellings.) To ensure health and comfort, the houses have a mechanical ventilation system for winter use. This recovers 85% of the heat in the stale air, to pre- warm the fresh air.

The four "zero energy" houses also have a solar heating system with longterm heat storage, although because of the tiny heat loss, it is only 4 percent of the volume of the house. They should use no fossil fuel for space or water heating in average or mild winters. The other six have about 9 m² of solar collector area, for summer water heating. In winter, they are heated by a tiny pro pane-fired combined heat and power system.

The extra cost of building the four zero energy homes was 15%; the other six cost 10% extra (10% of Swiss building costs!). Compared to homes that just meet the Zurich building code, the annual fuel saving in these ten 180 m², three-and-a-half storey, semi-detached houses is about 850 GJ per year.

Conclusions

To prevent serious changes in world climate over the next 50-100 years, quite dramatic efforts will be needed to improve buildings' energy efficiency, and to use more renewable energy. The energy department of Zurich canton, which managed this project, should be applauded for its efforts.

It is clear from such projects on mainland Europe that new buildings can meet ambitious goals for reduced C02 emissions, with no further development. However, it is clear that present efforts in most countries, such as the UK, are totally inadequate. There is so much to learn.

* Principal, Energy Advisory Associates.

** Energy Efficiency and Renewables: Recent Experience on Mainland Europe. Available from Energy Advisory Associates, 8 Medow Drive, Credenhill, Herefordshire, England, HR4 7EF, tel. +44 432- 760787. Price £75 per copy incl. UK postage or surface mail.