PASSIVE HOUSE IN TRADITIONAL WAY.

The passive house concept is built around the minimisation of transmission losses of walls and roofs and maximising the use of adequate thermal insulation. The less the transmission heat losses, the more important are the ventilation losses which is possible by mechanical ventilation with heat recovery. With this system there are some technical aspects to be concerned, for example the energy consumption of fans, the prevention of freezing. Can be approached without mechanical ventilation? Can the passive house standard be approached in more traditional way?

Building Geometry

The surface to volume ratio

The surface to volume ratio is of fundamental importance from the point of view of the ratio of heat losses by transmission and ventilation. At the same insulation level the more compact the form is, the lower will be the heat losses by transmission.

The glazed ratio

The glazed ratio is the subject of a well balanced compromise since on one hand the U value of the window is higher than that of the opaque elements. The problem of solar access is the same for passive and other houses. The “standard” glazing of passive houses is triple, the nominal U value, including the frame is 0,8 Wm2/K and the g value is 0,5. The typical window area is 10 – 20 % of the floor area. 

Ventilation

The ventilation heat losses represent the crucial problem of passive houses. The standard solution of passive houses is a balanced mechanical ventilation system with heat recovery – this way 75- 90% of the ventilation losses are covered by the heat flow from the exhaust air. 

Solar preheating

The traditional solar measures include different techniques of preheating the fresh air. The simplest preheating measure is a wall collector below the window with air inlet under the window sill.  The key problem of the ventilation is the air flow control. Self intended, a passive house and a sample house without mechanical ventilation can be compared only, if the air change rate (and consequently the indoor air quality) are the same in both. Having a mechanical ventilation system the air flow control does not represent a new problem. In the case of natural ventilation demand controlled tricky vents should be applied.

 Conclusion

There is no argument against the passive houses with mechanical ventilation and heat recovery but the aversions of the owners should be taken into account. Many of them do not wish to take care of a “machine”, to check and change regularly the filters, they consider questionable the indoor air quality and the noise. The price of the system and the cost of operation and maintenance also need to be analysed.

Can the passive house standard heating energy demand be approached without mechanical ventilation and heat recovery? It is possible if the house complies with the majority of the following requirements:

·         Surface to volume ratio should be as low as possible

·         High quality windows - maximum U value of 0,8 W/m2K and the overall U value of the opaque elements should be between 0,12 – 0,20 W/m2K.

·          Solar gains - the glazed ratio has an optimum – if half of the window area is Equator facing, the optimum is about 15 % of the floor area (ratio depends on the orientation and solar access)

·         Air change rate - not exceed that of the mechanical ventilation – it is of key importance to use demand controlled air inlet and exhaust.

Blå Jungfrun, Sweden

Blå Jungfrun, Sweden

Blå Jungfrun is located in Stockholm Sweden and is an energy efficient apartment project that was built in accordance with passive house standards with proven conventional construction techniques.

Introduction

The building situated between Farsta and Hökarängen This is approximately 10 km south of central Stockholm. The project consists of numerous buildings which are all of passive design. There are four buildings in total which are 5 and 6-storeys high. The project was constructed by Skanska Sweden construction at a total cost of US$ 18 million. The projected was completed in late 2010. The apartment buildings were constructed with prefabricated frame structures and prefabricated concrete wall sections that were cast and covered with a plastic insulation façade on site.

Blå Jungfrun made history as it was the first high-rise public rental apartment development in Stockholm to be constructed according to Swedish passive house standards. After completion each rented apartment consumes less than half the energy of a conventional Swedish apartment building due to the reduced need for space heating.

Materials used

To comply with the strict passive standards the materials used during construction along with the construction methods are of great importance. The exterior walls of the project were insulated with expanded polystyrene. This insulation is a very lightweight, non-toxic material that consists of 98 percent air and is free from Chlorofluorocarbons (CFCs) and other harmful gases. Each and every construction material used had to comply with Skanska’s chemical database. This also included the indoor paint, which was certified according to the EU Flower ecolabel.

In all there were 15 000 tons of concrete used throughout the project. The project was sourced from Skanska´s own concrete plant, around 10 km from the site. Swedish wood and steel was also used on the project to ensure its sustainability.

Construction Methods

The minimisation of environmental impacts during construction is a major area during passive construction and it was no different in this project. The construction site was certified according to Skanska’s internal Green Workplace (GrönArbetsplats) environmental management system, April 2010 68CS : V4 which is aligned with Skanska Sweden’s ISO 14001 certification. In simple terms this meant strict working conditions;  higher emission standards for site machinery, energy efficient indoor and outdoor site lighting, and stricter standards for chemicals and waste management to name a few. Throughout this project the energy use itself was continuously noted.

Waste management was also a great concern in order to comply with passive regulations. Any waste developed on site was sorted on site and recycled at appropriate local recycling facilities and 95 percent of project waste had been recycled as of March 2010. Reduction of waste also played a large role in waste management. This was implemented by the use prefabricated structures that were manufactured off-site. Prefabrication is also an efficent way to speed up construction which is also environmentally positive.

The Blå Jungfrun project cost effectively met Swedish passive house standards through the inventive use of proven construction techniques. There is consequently potential for other projects to reach Swedish passive house standards by using conventional construction techniques in a similar manner.

' Out of the Blue' - County Wicklow, A Passive home

With many architects impressed with growing interest of the passive house concept Tomás O'Leary jumped in first to construct the first passive building in Ireland. From here O’Leary developed a company which now specialises in creating these energy efficient homes for others. Many Property owners across Ireland are, due to rising heating and running cost for dwellings, looking for alternative and more energy efficent methods within the home. With BER ratings effecting every building in Ireland from 2009 an energy efficient home is now far more appealing.

The Passive house is the most energy efficent building imaginable. O’Leary’s company, MosArt, began to introduce the method throught Ireland  after his first certified project in Co Wicklow called 'Out of the Blue'. The house has been Tomás's family home since 2005.O’Leary persisted with his vision of a clean, low-energy house and began researching Passive Houses to further his knolledge. The concept is based on minimising heat losses and maximising heat gains from the home. Certified Passive Houses must meet the Passivhaus Standard, a building standard developed by the Passivhaus Institut in Germany.

Even now sixteen years on the building is still a modern, bright, airy and energy efficient home that bears no comparison to the conventional terraced house they lived in previously. The house has attracted huge public interest. Passive housing techniques iclude  the reduction of  heat loss with insulation and by making the house airtight aswell as increase heat gains by taking advantage of free energy like solar power. It must be stated that an airtight Passive House is not a stuffy, the ventilation system within the building prevents this. The heat recovery ventilation system uses the heat from warm stale air leaving the house to heat the fresh cold air coming in.

The house itself is 4,000 sq. ft two storey split level design and was the first Certified Passive House in Ireland. O’Leary ensured a high level of comfort throughout the year using just 10% of the energy of a conventional house was maintained.This was achieved through high levels of insulation, southern orientation, air-tight construction and mechanical ventilation with heat recovery.

First Steps:

The Passive House:
A method Rather than a Building Style.
The details of a building, which is considering the passive method, should be developed and designed to suit the sites climate as well as the sites geographical conditions. Considerations should especially focus on the local building traditions and the specific climate conditions the site location has to offer. As climates vary immensely all over the world solutions must be adapted to each location. In the past poor results were achieved due to the rein action of passive methods used in California in mid-Europe where climates differ considerably. It must be remembered that the overall concept remains the same regardless of climate. It is a challenge to construct a nearly self-sufficient building. The physical equations remain the same only the construction conditions vary. In relation to heat in a passive build the heat demand is reduced by means of insulation, heat recovery, superwindows, passive solar gains and more. The definition of a passive house, in relation to heating, is therefore that the peak heating loads should be projected to a lower level than 10 W/m2. Heating load is just one example, cooling could be a of greater importance than heating in some climates. Some general rules of thumb are, comfort should be kept at a high level, solutions should be kept simple, insulation is highly recommended in all climates, shading is a necessity in all climates and heat recovery is need in all cold and hot climates. A traditional building design can be used as a starting point and then each element can be modified step by step.

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