D e s i g n I s s u e s f o r N e t Z e r o – E n e r g y B u i l d i n g s
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systems (RES)) which are more likely to succeed in reaching the desired energy
performance.
Figure 2: NZEB design approach
In the following, an overview of the key components that affect NZEB energy
performance will be presented for each of the three research components, passive
approaches, energy efficient systems and renewable energy systems.
Passive Approaches Findings
As noted above, passive approaches play a fundamental role in NZEB design as they
directly affect the loads put on the buildings mechanical and electrical systems, and
indirectly, the strive for renewable energy generation. In this context it is understandable
why zero energy buildings design should start from passive sustainable design. With this
respect, and even though the buildings were designed to meet different energy
performance levels (according to national specific strategic needs), the first
characterization focuses on envelope thermo-physical characteristics and compactness
(Table 2). In general, passive solar energy concepts fall into three main
categories/challenges depending of the solar energy exploitation (heating, cooling,
lighting/appliances) and the relative strategies used (prevention, modulation,
rejection/collection, control). However, taking into account that all buildings are dealing
with heating challenges, it is natural that the passive strategies are oriented towards
solar heating maximization and prevention of heat loss strategies. In order to have a
clearer picture of the values shown in Table 2, and using Passive House standard as
reference, one can represent graphically the physical thermo-characteristics of buildings
envelope (Fig.3, Fig.4 and Fig.5). As it can be seen from figure 3, which shows the range
of thermal transmittances (U-values) found in the opaque envelope of selected case
studies, most projects under analysis present values as low as the one of Passive House
standard used here as reference for comparison. One interesting feature shown in figure
3 is that all buildings dealing with heating and cooling challenges are characterised by U-
values greater than the one indicated by the Passive House standard.
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PA
HEAT
AIR
LIGHT
HEATING
COOLING
LIGHTING
APPLIANCES
passive
ELECTRICITY
SPACE
HEATING
DHW
SPACE
COOLING
active res
