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It is interesting that all comfort criteria are automatically fulfilled in an optimum way with the requirements of the Passive House Standard - Improved thermal insulation simultaneously improves thermal comfort. This can be explained as follows:
The practical consequences are that with very well-insulated external building components, the temperature of the interior surfaces varies only slightly from the surrounding temperature in the room; this applies both in summer and winter. This means that the inner surfaces of the external components are pleasantly warm even in winter (external walls, roofs etc. not more than 1 °C below the indoor air temperature, window surfaces a maximum of 3 to 3.5 °C below this [Pfluger 2003] ). “Passive House quality”, particularly for windows, can even be defined as follows: the insulating effect of a window suitable for Passive Houses must be so efficient that even under the coldest design conditions,
θ area - θ surf ≤ 3.5 °C
still holds true. These small temperature differences have the following effects on all comfort criteria:
|Fig. 1: Air movement near a Passive House window: Due to the small tempe-
rature difference between window surface and room air, the speed of air
descent at the window is very low. At the floor level, the air is diverted: the
maximum air speed is still 0.11 m/s at a distance of approximately 10 cm
from the Passive House window (Uw = 0.8 W/(m²K)). This is a barely percep-
tible value. If the insulating effect of the window is not so good, the air
speeds rise to critical levels, therefore it is advisable to place heaters under
“ordinary windows”. (CFD simulation: J. Schnieders, PHI).
|Fig. 2: Infrared image of a Passive House window|
from the inside. All surfaces (window frame,
casements, and glazing) are pleasantly warm
(above 17 °C). The temperature doesn't fall below
15 °C even at the glass edge.
(Image: PHI; object: Passive House in Darmstadt-
|Fig. 3: A double-glazed window of an old buil-|
ding is shown here.The average surface tempera-
tures are already below 14 °C. But there are also
noticeable thermal bridges due to installation,
particularly where the window meets the con-
crete wall. The results are radiant temperature
asymmetry, draughts, and cold air pockets in
(Infrared image: PHI: offices of the Institute).
|Fig. 4: Double-paned low-e glazing (in a
newly fitted window), which has higher
surface temperatures (16 °C on average).
The poorly insulated conventional
window frame is particularly noticeable
here. Passive House frames enable a
significant improvement of the quality.
All the comfort criteria have been ideally fulfilled, without the need for a compensating heating surface. That is why the Passive House room “automatically” has a radiant heat climate, regardless of how the heat is provided. Furthermore, as large temperature differences do not arise, there is also less air movement. The results presented here are documented in the publication [Pfluger 2003] .
Findings from three independent research projects have confirmed that these characteristics of well-insulated building envelopes can be observed in practice:
[Pfluger 2003] Pfluger, R.; Schnieders, J.; Kaufmann, B.; Feist, W.: Hochwärmedämmende Fenstersysteme: Untersuchung und Optimierung im eingebauten Zustand (Anhang zu Teilbericht A), 2003, Internet Publication (in German)
(Highly insulating window systems: inspection and optimisation in the installed state, Appendix to Sub-report A)
[Schnieders 2002] Schnieders, J.; Betschart, W.; Feist, W.: Raumluftströmungen im Passivhaus: Messung und Simulation HLH 03-2002, Seite 61
(Indoor air flows in the Passive House: measurement and simulation HLH 03-2002, page 61; Abbreviated online version in German: Residents' experience)
[Lipp 2004] Lipp, B. und Moser, M.: Heizsysteme und Behaglichkeit: Ist Behaglichkeit physiologisch messbar? in: AkkP Protokollband Nr. 25, Darmstadt, 2004
(Heating systems and comfort: is comfort physiologically measureable?, in Protocol Volume No. 25, Darmstadt 2004; Abbreviated online version in German: Thermal comfort)
[Hermelink 2004] Hermelink, Andreas: Werden Wünsche wahr? Temperaturen in Passivhäusern für Mieter; in: AkkP Protokollband Nr. 25, Darmstadt, 2004
(Can dreams come true?: Temperatures in Passive Houses for tenants, in Protocol Volume No. 25, Darmstadt, 2004; Abbreviated online version in German: Residents' interview)