Category Archives: EuroSun2008-5

Use Solar Heat to reduce non-renewable energy use

Подпись: Fig. 5: Collector may not be installed on farm house, must be on the rear shed, requiring the nut tree to be cut down. (Photo: AEU Ltd.) 3.1. Goal, benefits and problems

If the goal is to reduce dependency on non­renewable energy, at a certain point energy delivered from a solar thermal system becomes less expensive than energy saved from conservation measures, i. e. the marginal cost of the last increment of insulation or triple verses double glazing. Installing solar collectors or a pv system as part of a renovation is not always easy, however. Panels may be forbidden because they disturb the character of an historic village. Figure 5 shows the outline of the proposed and refused location for roof solar panels. The building commission allowed that the panels could be mounted on the shed to the rear, which, however is shaded by an old, noble nut tree.

Well done renovations drastically shorten the

heating season. A solar active system can then cover the minimal space heating demand of the spring and fall as well as the hot water demand, allowing other systems to be shut down for much of the year. This saves wear and extends component life spans. Two system types are reviewed here, a water system and an air system. Each has its special advantages for a given application.

Strategy: Solar water systems

Three years after a young Swiss couple purchased a single-family house built in 1942 the oil furnace had to be replaced. This was the motivation to completely renovate the house, including a 13 m2 drain-back solar system (fig. 6) with an 800 L storage tank.

The renovation also included adding roof, wall and basement ceiling insulation (220,

200 and 80 mm). The windows were replaced with units glazed with a Ug of 0.55. The oil burner was replaced with a wood pellet stove and a ventilation system with 80% heat recovery was added. As a result, the solar system is able to cover much of the space heating in spring and fall and all the domestic water heating demand in summer. The annual primary energy demand for space and water heating was drastically cut from 230 to 47 kWh/m2, or an 80% reduction. This means instead of burning 3,500 litres of heating oil per year and they burn only 1 tons of wood pellets [6].

Strategy: Solar air systems

Solar heat from a collector can be transported by air, instead of water. No anti-freeze is needed and a possible leak causes no damage.

Over the years this technology has been used in the renovation of many houses, schools and industrial buildings [7]. An example of a very practical application, solar heating second homes, is given here.

Often after a stone rustico or wooden chalet in the Alps, log cabin in Scandinavia or masonry cottage in the Mediterranean has been purchased, it must be renovated. While vacant it becomes cold, damp and mouldy. When the owners arrive, the air and bedding smell musty and it likely takes forever to bring the mean radiant room temperature up to a comfort level. Too often the solution is an electric resistance heater set at a low temperature during the owner’s absence. Because occupancy is only for short intervals, investment in insulation or better windows is difficult to justify. Thus, the auxiliary heating, even at a low temperature setting, consumes much energy. Solar air collectors can deliver sun-warmed air by free convection thereby maintaining a minimum room temperature and dryness. Optionally, a small pv-powered fan can increase the air flow and hence collector efficiency. Figure 7 shows an application in Koroni, GR. The two 6m2 collectors each include a 50Wp pv section to power the circulation fans which can circulate up to 200m3/h. [8].

Use PV to offset non-renewable energy use

Some of the housing renovation projects studied included a PV roof. Decisive is the price at which the local utility is required to buy back the solar electricity. For example in Switzerland as of Jan. 1, 2009 electricity providers must buy back solar power for 25 years for all approved pv installations built since Jan. 1, 2006. For systems <10 kW the buy-back rate for attached PV systems is €0.46 and for systems integrated into the roof or facade €0.56. [9].

An exemplary project where PV was part of a comprehensive renovation is the apartment building in Staufen. The 110 m2 PV installation on the south-facing roof (fig. 1) has a nominal output of 14.7 kWp. In 2006 it fed 14’300 kWh into the grid. The motivation of the owner, Guido Erni, was to provide retirement income. Also part of the renovation were insulation of the attic floor (140 mm), facade (200 mm) and basement ceiling (100 mm); a new ventilation system with 85% heat recovery and replacement of the oil furnace by a heat pump. The results: primary energy use for space and water heating was reduced 65% from 154 to 54 kWh/m2 [10].

Use passive solar design to reduce energy use and improve life quality

Replacing windows with highly insulated units can reduce heat losses to such an extent that solar gains cut heating costs (fig. 8). To minimize unnecessary window opening time and drafts, frame vents can be installed. [11]. Enlarging window openings in walls, when possible, amplifies these savings and admits more daylight. Daylight can also be led into interior spaces by a light pipe [12 + 13].

An example is the renovation of the row houses Kroeven in Roosendaal, the first large — scale passive house renovation project in Holland. Single pane windows were replaced by triple pane glazing in passive house frames.

In addition the walls were insulated with 200 mm XPS and the roof with 360 mm of

cellulose. A new ventilation system was added. A 90% savings in energy consumption resulted, with the annual primary energy for space and water heating being cut from 219 to 21 kWh/m2 [14].


Renovating existing housing can provide living space with superior comfort, very low energy consumption and a special charm. The examples presented here from Austria, Germany, Greece, Italy, the Netherlands and Switzerland demonstrate that it is possible to achieve energy savings up 90 percent, while preserving the special character of the projects. Solar energy is a viable, economic alternative to the costly, last increment of conservation measures in order to achieve the goal of drastically reducing dependency on non-renewable energy and production of CO2. In some of the projects photovoltaic panels were included in the renovation package. When the primary energy value of the solar electricity is deducted from the greatly reduced energy demand for space and water heating, these projects achieve a nearly zero-energy balance.


[1] IEA SHC: Renovation Examples, http://www. iea-shc. org/publications/task. aspx? Task=37

[2] Feist, W.: Passivhaus Kriterien, http://www. passivhausprojekte. de/kriterien. php

[3] GAG Ludwigshafen am Rhein Passivhaus im Mietwohnungsbestand: Hoheloogstrafie 1 und 3, WittelsbachstraBe 32, DE-67061 Ludwigshafen, www. gag-lu. de

[4] Calderaro, Valerio: Historic Building in Modena, IT, www. iea-shc. org

[5] Domenig-Meisinger, Ingrid: Passiv House Renovation, Makartstrasse, GIWOG Gemeinnutzige Industrie-Wohnungs-AG Linz http://www. hausderzukunft. at/results. html/id3951

[6] Fehr-Bigger, Hubert, Architekt, Dorfhaldenstrasse 30, CH-8880 Walenstadt Enz, D & Hastings, R.: One-Family House in Walenstadt CH, www. iea-shc. org

[7] Hastings, R. & Morck, O.: Solar Air Systems, Vol. 1 Built Examples, Vol 2 A Design Handbook, Earthscan, London, ISBN 1 873936 85 0 and 1 873936 86 9, www. earthscan. co. uk

[8] Grammer Solar GmbH: Twinsolar, Oskar-von-Miller-Str. 8, DE 92224 Amberg, www. grammer-solar-bau. de

[9] Stickelberger, David: Fakten zur Kostendeckenden Einspeisevergutung KEV fur Solarstrom, Swissolar Infoblat 16.Apr. 2008, www. swissoolar. ch

[10] Enz, D. & Hastings, R.: Apartment Building in Staufen, CH, http://www. iea-shc. org/publications/task. aspx? Task=37

[11] Passivent: Background Ventilation, 2 Brooklands Road, UK-Cheshire M33 3SS, www. passivent. com

[12] Velux: Sun Tunnel Natural Light, VELUX Company Ltd., Woodside Way, UK-Glenrothes Fife KY7 4ND, http://www. velux. co. uk/Products/SUN+TUNNELS/

[13] Glidevale Ltd.: Sunscoop Tublar Roof Lights, 2 Brooklands Road, Cheshire UK-M33 3SS www. glidevale. com

[14] Frank, E. and Bekx, M: Rowhouses, Kroeven in Roosendaal, Holland, Franke Architekten,

Postbus 151, 3360 AD Sliedrecht, Holland, info@frankearchitekten. nl