Prevention of thermal bridges is one of the most efficient savings measures, as experience with Passive House construction has shown. Building envelopes consist not only of standard construction elements like walls, roof and ceilings, but also include edges, corners, connections and penetrations. The heat loss at these points is generally higher (thermal bridges). Observing some simple rules helps to reduce losses caused by such thermal bridges.
For example: A balcony slab which is part of the concrete ceiling inevitably leads to additional heat losses, because it penetrates the insulation and conducts heats towards the outside. The use of a thermal break element must be planned to minimize these losses. A good solution, for example, is to position the balcony in front of the facade and provide separate supports.
The Passive House concept aims at a “thermal-bridge-free“ con-struction, reducing thermal bridges so much that they do not have to be taken into account in calculations. Specific information concerning this issue and many specially developed products are now available to designers and manufacturers. Ensuring that the building envelope is airtight reduces the risk of structural damage. Achieving an airtight construction requires careful planning and execution. An airtight building can be effectively achieved, for example, by full plastering on the inside, sheeting, reinforced building paper, or wood composite boards. Quality workmanship and the proper installation of all airtight building materials and products (e.g. windows and doors) are also important. The Passive House Institute provides planning tools for durable, exceptionally airtight constructions.
The air should not flow randomly through the walls (building envelope), driven by the wind and temperature differences. These types of air flows are not sufficient to provide consistently good air quality. They are uncomfortable (at times too much air, often too little air) and can cause structural damage as leaks in the building envelope allow warm moist air to flow from the inside towards the outside. The air cools down, condensing the moisture and causing mould and rot. Poor sound protection and significant heat losses are further disadvantages of leaking houses. Therefore, every building should be airtight! In the Passive House, a ventilation system provides for sufficient and lasting fresh air. With careful planning, it is possible to construct buildings in an airtight way. Property developers and architects with Passive House experience know exactly how to do it. For each Passive House, a building airtightness test (the so-called “Blower Door“pressure test) is carried out at a suitable point in time to make sure the stringent quality requirements are met. The test is performed by creating positive-pressure followed by negative-pressure, and measuring the total leakage. Any leaks detected can then be sealed.
An airtight house has many advantages: it is free from draughts, prevents structural damage, improves sound protection, saves energy and is comfortable.