Renovating a 100- year-old barn with Passive House technology

Transcription

1 Renovating a 100- year-old barn with Passive House technology I3 Stefan Oehler oehler faigle archkom, Germany 1 INTRODUCTION What means Passive House? First it is a real good idea. And like all good ideas it is simple, ingenious and brilliant: a house that doesn t need to be heated actively but that is being heated passively by the sun. In wintertime: passively heated A cold car can be heated in wintertime without expenditure of energy - passively. The windows have to be closed and the car has to be parked in the sun. The Passive House works just the same. The heat is collected by the windows and is kept inside by good insulation. This reduces the heating demand up to 80 %. In summertime: passively cooled If the windows of a car are opened at night the car will cool down fast because of natural ventilation. To keep the car as cool as possible during daytime the car is parked in the shadow. The Passive House reacts similar. Night ventilation, sun shelter and insulation keep it cool - completely passive, without technical support. 1

2 Year by year: less energy demand The remaining heating and cooling demand can be covered much easier with modern High Tec than that of a conventional building. Only about 20 % of the typical amount of energy is needed. Individual technical solutions provide a maximum of efficiency to cover the lasting energy demand. The inhabitant feels more comfortable as the flow of energy is reduced by 80 %. Experience is the key Everybody can learn to build energy-efficient. It needs theoretical and practical experience we built the first freestanding Passive House in Europe, the Passive House Oehler. There had been a lot of question marks starting with the insecurity, whether the calculation program of the Passive House Institut, the PHPP, is working properly in our case. Nobody knew at that time because nobody tried it out before. It took us a lot of time to find out and every detail of the construction hat to be invented to meet the very high demand of thermal quality. All the following houses needed less time and had fewer question marks, adding one piece of experience with every building we realised the biggest Passive House, the office building Energon Ulm with 420 working spaces. In the meantime we have learned a lot like how to produce prefabricated timber elements for the facades, providing good insulation, air tightness and avoiding serious thermal bridges. And with increasing experience the freedom of design and construction is growing. Even the economical efficiency increased. The Energon Ulm is providing a much better indoor climate and was build 10 % cheaper than an ordinary German office building. Building renovation A lot of building renovations do the wrong things to reduce their high loss of energy. They start with very expensive techniques like photovoltaic, hot water collectors or other new technical equipment. If the same amount of money is taken to improve insulation and air tightness this will save much more energy and running costs. Insulation and air tightness is usually the first and most efficient way of building renovation. There should always be an economical hit list for all the possible renovation steps. If the Passive House standard is taken as state of the art, it will turn out that 99 % of all existing buildings could be renovated, providing a huge potential of energy saving. Even if all new buildings would reach Passive 2

3 House standard this would not influence the energy consumption of all European houses too much because of the very small portion of new buildings. Sustainability has to deal with the very bad condition of all the existing buildings. They often have a consumption of kwh/(m² a) that means litres of oil per m² and year. The biggest lacks are weak insulation, bad windows, thermal bridges, no insulation in the roof or in the cellar and a very high air untightness. At the same time the very poor comfort in these buildings with cold and draughty rooms, hot radiators, low humidity and cold surfaces does not meet our present ideas of living comfort. Building renovation always starts with insulation, air tightness and a ventilation system. 2 THE BARN The barn: what we found We were offered a typical south German barn, built around 1880 and rebuilt with several changes and additions for pigs, horses, different functions etc. The barn is situated right in the middle of a little, narrow village and there is almost no direct sunlight reaching the facades of the Figure 1: The barn, before the renovation. 3

4 barn. The two-story high wooden roof construction was assembled without any engineering calculation and would not fulfil any of our recent requirements. The whole roof was in a bad shape. The ground was clay and the most interesting part were the outer walls, made out of 60 cm thick rubble masonry. The walls had been in an acceptable shape. The barn: what the house-builder wanted The house builder wanted to live in that barn and he wanted to use this huge space as a sort of loft with entrance, living room, eating, cooking and playground for the children. The barn is situated next to an old living house and a new connection between these two buildings had to be realised. He wanted to see the rubble masonry from the inside of his new living room. The whole space should be open up to the roof top and illuminated with roof lights in addition to the new windows and doors, which should be oriented to the garden with old apple trees. It should be comfortable in summer and in winter and there should be enough daylight inside. The barn: what we did With our experience in all kind of Passive House construction and details we used the typical Passive-House-elements and constructions. And all the Figure 2: The barn, after the renovation. 4

5 time we had to think about the economy. That is why the result is not a passive house, because all the circumstances had not been very good, but we achieved a house with only twice as much heating demand as a Passive House, a so called 3-liter-house, needing only 33 kwh/(m² a) for heating and staying cool in summer. We achieved a very comfortable indoor climate and a generous loft-architecture. The house-builder likes it. 3 TECHNIQUES Rubble masonry and insulation We could keep the old 60 cm thick rubble masonry and made them visible from inside. On the outside and on the roof we fixed prefabricated timber elements, insulting the whole building with these Passive-House-Elements. The wall elements stand on gab to the masonry to be sure that these old walls will be ventilated from all sides. The roof elements could be posed easily on the 60 cm thick walls. All elements are filled with 30 cm mineral wool for insulation. The old walls and the timber structure of the roof stay visible and don t have to stand temperature differences, rain, snow and sun. One wall was standing exactly on the borderline to the neighbour and we could not insulate on the outside. 30 cm thick mineral wool was packed on the inside of the wall and we had to be very careful to cover the whole insulation with a vapour-tight folio to avoid penetration of moisture from inside. To restore of the rubble masonry we asked a team of specialists, who are working in the neighbourhood for the world famous monastery Kloster Maulbronn. But I tell you restoring rubble masonry is a very expensive hobby, every single gap has to be treated personally. The floor slab was made out of concrete, swimming on a 20 cm thick insulation. Mechanical services The huge space of 113 m² and a height of 5,4 m up to the roof top has a heating demand of 33 kwh/(m² a), calculated with the PHPP (Passive House Program). We call it a 3-liter-house, because the demand would be 3 litres of oil per m² and year, which is less than half of the heating demand required by law. There is a Passive-House-like ventilation system with heat exchanger but without any external preheating in the ground. The 5

6 ventilation system has the only task to provide fresh air; there is no heating through the medium air. Two ordinary hot-water radiators next to the great windows are heating the room. They run with a calorific value gas heating system. There are very little additional internal and solar gains. 4 LOFT ARCHITECTURE WITH PASSIVE-HOUSE- STANDARD Because of economical reasons we did not reach the Passive-House- Standard. It would have been too expensive to reach this goal, as we had to deal with some fixed facts. There was no way to put insulation beneath the old walls. They had to remain as a 60 cm thick thermal bridge down to the ground, loosing too much heat for a Passive House. One wall on the borderline had to be insulated on the inside, all the other walls from the outside. That caused a constructive change from an inside insulation to an outside insulation, producing another thermal bridge. Another important fact was the missing of any direct sun light. The barn is surrounded on all sides by buildings and there are almost no solar gains. These are the most important points for not becoming a Passive House. But that was not most important for us, as we wanted to build economical. We wanted to provide a comfortable indoor climate without any danger of long-term damage of the construction. To heat such a huge space with a height of over 5 m is only possible with an Passive-House-like envelope because there must not be any cold air in winter time dropping down the walls and no heating up in summer time because of a hot roof. Equal temperatures all over means a maximum of comfort. The Passive House Standard is the most comfortable and most economical way to deal with huge comfortable open spaces. The indoor climate of a high and wide space like this 113 m2 wide loft architecture can only be managed with a high efficient combination of extremely good insulation, air tightness and heat recovery - the principles of a Passive House. Passive Houses allow more architectural freedom in creating big comfortable spaces. 6

7 REFERENCES Architect/writer: stefan oehler oehler faigle archkom solar architektur melanchthonstr bretten Germany Tel: