Passive House Retrofit
Modernised dwellings usually have a functional heat distribution system which there is no reason not to continue to use.
By upgrading the building envelope through insulation the heating consumption can be reduced, thereby allowing the system to run at a lower temperature. This in turn allows for more energy efficient systems to be used, such as condensing boilers and heat pumps.
The results of the research show that problems gained through thermal bridging actually decrease with increased exterior insulation, and there are generally less problems with moisture.
Contrary to popular prejudices, especially for modernization existing stock, it makes sense to aim for a high level of air-tightness. With uncontrolled leakage there is a risk of condensation through moisture in the air.
The planning principles for new buildings can be successfully transferred to upgrading properties. In upgrades that have already been completed, the air-tightness proved to be surprisingly good. In this context, Dr Feist, the founder of the Passivhaus Institute in Germany, also pointed out the importance of controlled ventilation: ”Those who call for air-tightness, also need to achieve adequate ventilation.”
After a thorough technical modernization of the thermal envelope, the windows are often the most significant remaining weakness. But it turns out that the rules known from Passive House developments are also adequate for the window installation, even under critical conditions. The use of Passive House windows has worked well for the upgrading of the demonstration projects.
Ensuring that the air in the building is changed regularly is an essential task, especially in old buildings. The recommended view of opening the windows fully twice a day for a short time is not sufficient for the removal of indoor air pollution. To maintain the air-tightness of the building envelope it is necessary to make domestic ventilation a component of a responsible modernization. This applies to the modernization of old buildings even more than with new buildings. Current experience shows that the following requirements are suitable for domestic ventilation:
• Air must be constantly renewed
• The most important task is the dehumidification of kitchen, bathrooms and toilets. All damp areas should therefore have air extraction
• The air exchange rates on the other hand should not be too high, otherwise it may lead to complaints of the air being “too dry”
Particularly noticeable in the heat balance of old buildings is the high heat loss through the exterior walls. It is therefore particular importance, not only from engineering but also an energy-efficient point of view, to make improvements to the thermal insulation. The often expressed view that one should exclude the exterior walls of the old buildings from the thermo-technical modernization is therefore not appropriate.
The heating requirement of the demonstration projects in Ludwigshafen and Nuremberg have been reduced to less than 30 kWh/(m²a). Thus, an improvement in existing buildings by a factor of around 8 has been achieved. Such far-reaching improvements were, until recently, even in professional circles often thought of as unrealistic. The documented measurements from the demonstration projects show that the actual results are even better than the calculated specific values.
According to the case studies, Passive House components are suitable for the modernization of existing buildings.
These measures:
• provide greater protection against moisture damage
• improve the thermal comfort due to higher surface temperatures
• raise the potential for energy-conservation drastically
The attractiveness of high-quality modernization increases with the use of highly efficient components, as the quality of life for residents increases significantly.
What also needs to be considered is the fact that modernization measures in buildings are a key driver for the economy. The measures outlined show that significant CO2 reductions are possible, with the CO2 reduction generated from the case studies being over 75%. Energy efficiency improvements are in a sector in which a reduced consumption also allows for increase in the appropriate use of renewable energy sources.
Source: PHI
