Our flagship project is a so-called Plusenergiehaus or energy-plus building, which means that more energy is generated (ca. 7500 kWh/year) than consumed (ca. 4700 kWh/year). To reach this goal, the building envelope must be particularly airtight so that heat does not leak to the outside. The blower-door test is carried out twice (for an explanation, see the pictures below): the first time when the building envelope, including the windows, is complete to locate and close possible leaks and a second time when the entire building is complete.
Only recently, the first test was carried out, that is, the leakage test. Fortunately, no major leaks were found on the upper floor (wood frame construction). Only on the ground floor one leak was found in a wall section of the pre-existing building above an added brick wall, which could be easily closed by stuffing hemp into the gaps and finishing it with a plaster.
Despite the above-described leak and though the building had not yet been finished (no interior plaster finishes yet, doors with a sort of makeshift locks, lack of an external thermal insulation composite system on the ground floor, etc.), a fairly decent n50 value of 1.1 was recorded. This means that, at a pressure difference of 50 pascals between inside and outside, the air inside the building is replaced 1.1 times per hour due to leakage. For comparison reasons, we list here the n50 values as required by the German energy efficiency regulation EneV 2014 and the passive house standard:
- Buildings with natural ventilation (e.g. window ventilation): ≤ 3.0
- Buildings with HVAC systems (e.g. ventilation systems) ≤ 1.5
- Passive houses: ≤ 0.6
According to the engineering company Mikesch/Brannenburg, which carried out the blower-door testing, we have good chances to achieve the designed target value of ≤ 0.6 with this initial value.
To be able to provide good indoor air quality at this level of airtightness at all times, a CO 2– and humidity-controlled ventilation system with heat recovery will be installed. The latter will efficiently provide the rooms with the required fresh air. It will also turn off when windows are opened and the indoor air quality parameters are met (CO2 level < 800 ppm, relative humidity < 55%).