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planning:thermal_protection:thermal_protection_works:insulation_works_-_evidence_no.2_heating_energy_use_in_a_well_insulated_new_building

Energy use for heating in a well insulated new building

Here is further evidence that insulating buildings allows for significant energy savings. This example is independent of the [planning:thermal_protection:thermal_protection_works:insulation_works_-_evidence_no.1_measurements_at_a_highly_insulated_wall| measurements at a highly insulated wall]]and it is based on the energy consumption data recorded in highly insulated newly built constructions.

Measurements

The following image shows the heat consumption data recorded in a highly insulated building, the first Passive House in Darmstadt-Kranichstein in Germany.

 This diagram shows the recorded data for heating energy. Left: Average consumption in existing buildings in Germany; approx. 160 kWh/(m²yr). All other values: energy use for heating measured in the terraced house in Darmstadt Kranichstein (four apartments, 156 m² each, occupied since 1991): Average consumption: 9.2 kWh/(m²yr).

The diagram says it all:

• Existing buildings in Germany use an average of 160 kWh of fuel (oil or gas) for heating alone – see statistics from the companies in charge of heating bills. For calculation purposes: 1 litre of fuel oil or 1 cubic metre of natural gas each have a calorific value of approximately 10 kWh.
• The data recorded in the Passive House in Darmstadt Kranichstein, on the other hand, shows a stable consumption of as little as 9.2 kWh per square metre of living space.

This means: Passive Houses require less than 10% of the energy used by typical central European buildings. In fact, the amount of heat required is negligibly small – so small that such a house could be heated by a few candles.

Why do Passive Houses require so little energy for heating?

First of all Passive Houses are extremely well insulated including extra thick layers of insulation on all exterior walls and the roof as well as super-insulated windows. The ventilation system is equipped with a heat recovery unit. If even a single element of this concept did not work as planned, the heat loss would be considerably higher and the expected energy use would increase accordingly. During the first year, for example, the window frames hadn’t been insulated yet and the insulation of the basement ceiling hadn’t been completed. As a result, more energy (although still very little) was used during that first year.

The energy savings in this highly insulated house show quite clearly that the concept works and that good insulation works.

Agreement with calculations

There are currently more than 20,000 Passive House dwelling units in use (as of 2010). The energy use for heating has been measured in many of these buildings and has always proven to be extremely low. You will find a systematic comparison with statistical methods under Energy efficiency of the Passive House Standard: Expectations confirmed by measurements in practice. Other documented Passive House projects can be found in the Passive House database.
The values recorded in these Passive Houses agree very well with the generally accepted calculation methods used in building physics. The following diagram shows a comparison with the European EN 832 standard.

 This energy balance has been drawn for the Kranichstein Passive House (end-of-terrace house) according to the European EN 832 standard. The calculated value for heating is 10.5 kWh/(m²yr). The actual energy use recorded between 1991 and 2006 was 9.2 kWh/(m²yr) i.e. slightly lower. (This variation remains within the accuracy limits typical for such measurements and calculations.)

Please note that heat gains from heat sources inside the building (people and appliances) are rather small. All heat gains have been recorded and accounted for in detail. This proves that the house is not heated by hidden “power consumers“. Yet, all four apartments are always comfortably warm. Even in winter, the temperatures in the house may exceed the setpoint due to intensive solar heat gains. As a result of these “unusable” solar heat gains, the actual heat losses may exceed those which have initially been calculated based on the setpoint temperature. The degree to which solar heat gains can be used can be determined using a formula included in the EN 832 standard, a method which has proven to be highly effective. It is mostly based on the U-values of the exterior building components which are used to calculate the heat losses shown on the left side of the graph – except for the ventilation heat loss which is based on the exchanged air volumes and the heat recovery system (see Energy balances).

Conclusion

Careful measurements have been carried out over and over and have proven the excellent agreement between theory and real-life data The measurements carried out in this example prove very clearly that improved insulation works and that the generally accepted calculation methods provide reliable results, in particular with the U-value being an appropriate indicator for the energy lost through exterior building components.