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2 Stratification: The temperature stratification of air is
also imperceptible with the passive house window. Therefore the heating
element can be placed also at an inner wall while still reaching optimal
comfort in accordance with ASHRAE Comfortclass "A". (computation: J.
Schnieders, PHI). A comparison with a "normal window" in a short film
you can watch
Fig. 3 Passive
House Practice: Infrared image of the interior side of a passive
house window. All surfaces (wall structure, window frame, and the glazing)
are pleasantly warm (over 17 °C). Even at the glass edge, the temperature
doesn't fall below 15 °C (light-green portion)
Fig. 4 Typical
Practice: For comparison, here is a typical old building's
window. The center of glass surface temperature is already below 14 °C.
In addition, there are large installation thermal bridges, particularly
where the window meets the concrete wall. The consequences: significant
eadiant temperature asymmetry, drafts, and pooling of cold air in the
Fig. 5 low-e glazing (2 panes) already have higher surface temperatures (16 °C in the average). Additionally, the poor insulation of the conventional window frame is remarkable. Passive house frames allow a dramatic improvement in insulating quality. (IR fotography: PHI, in the corridor of the institute)
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Comfort is determined by many very subjective feelings, even the color of the environment plays a certain role - with each person being influenced uniquely. However, it is well documented that a substantial part of comfort depends on "thermal comfort". The results are contained in International standards (ISO 7730) with a major portion due to the work of the Danish scientist P. O. Fanger
Fanger's comfort equation is derived from the concept that for optimal thermal comfort the heat loss of the human body is in an equilibrium with its heat production. This forms a relationship between the activity (e.g. sleeping, running...) and clothes as well as the properties of the thermal environment, which are:
There is a range of combinations of the four comfort parameters mentioned in which the comfort is very good: This is the so-called comfort field. It can be determined by the Fanger equation, documented in ISO 7730. It continues to be important according to this standard that
Regarding the last point, P.O. Fanger writes: "the greater the variation of the thermal field of an area, the greater the expected number of dissatisfied people."
What does this have to do with the Passive House?
It is exciting that by the requirements of the passive house standard all comfort criteria are automatically optimally fulfilled - substantially improving the thermal insulation simultaneously improves thermal comfort. This can be understood as follows:
The practical consequence: With highly insulating external construction components, the temperature of the interior surface is only slightly different from the other temperatures in the area; this applies both in summer and winter. In the winter, the interior surfaces of the external construction components are comfortably warm (external walls, roofs etc. at the most 1 °C under the ambient temperature, window surfaces maximally 3 to 3.5 °C under it [ 1 ]). The definition of "Passive House quality" windows is straightforward: The insulating efficiency of a window suitable for Passive Houses must be so good that under the coldest design conditions, the equation:
θ area - θ Oberfl ≤ 3.5 °C
still holds true. These small temperature differences have the following affects on the comfort criteria:
Because all of the comfort criteria are fulfilled, without the need for a compensatory radiation heating surface, everythere in the Passive House there is "automatically" a radiant heat climate, independently of how the heat is supplied. More still: since there are no large temperature differences, air movement remains small. The results represented here are documented in the publication [ 1 ] (internet source, German).
The comfort characteristics of well insulated buildings can be observed in practice and is confirmed by three independent research results:
Also at the current Passive House conference there will be a discussion of the comfort topic.
[ 1 ] Pfluger, R.; Schnieders, J.; Buyer, B.; , W. Feist: Highly insulating window systems: Investigation and optimization in the installation (appendix to interim report A), Internet publication (German)
[ 2 ] Schnieders, J.; Betschart,
W.; , W. protects: Room air currents in
the passive house: Measurement and simulation HLH 03-2002, page 61
[ 3 ] Lipp, B.
and Moser, M.: Heating systems and comfort: Is comfort physiologically
measurable? in: AkkP proceedings NR. 25, Darmstadt, 2004
[ 4 ] Hermelink,
Andreas: Do desires become true? Temperatures in passive houses
for tenants; in: AkkP proceedings NR. 25, Darmstadt, 2004
To in this connection the question of the importance of the heat capacity is often discussed. Further information on this topic: Daemmen_oder Speichern.HTML.(German)
Dr. Wolfgang Feist © Passive House Institute;