HVAC APPLICATIONS
HVAC APPLICATIONS
Climatic comfort is a complex concept, since it depends on a large number of variables,
both objective and subjective; moreover, the conditions within confined spaces are
subject to transients and the occupants themselves, aware or not, can implement
adaptive behaviours.
In terms of thermo-hygrometric comfort, the two main parameters to be controlled are
the temperature and relative humidity of the air; during the design of the HVAC system,
desired values are defined, which are then taken as a setpoint values by the control
and regulation devices.
Actually, there are several combinations of temperature and relative humidity resulting
in a comfortable climate defining a “comfort zone” that may be represented in a
diagram. Some home automation devices allow this zone to be defined by means of
five parameters (minimum and maximum temperature, minimum and maximum relative
humidity and absolute humidity), informing system supervision when the combination
of measured values is outside the comfort zone.
The EN ISO 7730 standard offers the design tools to assess not only the overall
comfort experienced by occupants of moderate thermal environments using the PMV
(Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied) indexes, but also
any local discomfort using four indexes that consider respectively the air currents, the
vertical air temperature gradient, the temperature, the floor temperature and the radiant
asymmetry.
References
EN ISO 7730:2005 Ergonomics of the thermal environment - Analytical determination
and interpretation of thermal comfort using calculation of the PMV and PPD indices and
local thermal comfort criteria
Thermo-hygrometric comfort
When we talk about air quality, we generally think of the outdoor air, due to polluting
and climate-altering emissions caused by production activities, vehicle traffic or winter
heating of buildings. But today we are aware that problems of poor air quality can arise
even indoors, due to pollutants from both inside and outside the building and by the
increase in the concentration of CO2 produced by human presence.
This is not to be underestimated, since in Europe, on average, more than 90% of one’s
time is spent indoors: in Italy, for example, 55% in the home, 33% in the workplace,
4% in other environments, while only a residual percentage of time is spent outdoors.
In addition, 10 to 20 m³ of air are inhaled every day, depending on age and activity:
this corresponds to an air mass that varies between 12 and 24 kg, much greater than
that of food and drinking water consumed every day.
In this case we are talking about air quality in confined spaces (IAQ, or Indoor Air
Quality), a topic that has come back in recent years when we began to build and
renovate buildings in accordance with the provisions of the law following the directive
on energy performance in buildings (2002/91/EC). With the aim of minimising heat
loss to the outside, buildings are now strongly insulated and fitted with sealed doors
and windows; this increases energy efficiency, but still makes them airtight. In these
conditions, air renewal by manual opening of windows alone is inadequate and people
are exposed to the risks of increased concentration of slowly but constantly emitted
pollutants from the synthetic products used in the construction sector and from the
consumer products present in all buildings.
If exposure to pollutants becomes very prolonged over time, the problem is no longer
just the well-being in confined spaces, but can also seriously affect people’s health. It
is therefore clear why it is important to take all the necessary precautions to ensure
high air quality.
Several studies show that adequate ventilation in the workplace leads to higher
productivity and fewer absences for health reasons. In school environments, high air
quality helps students to concentrate, while in commercial buildings it makes shopping
time more enjoyable. On the other hand, the room ventilation means an energy cost that
can become relevant. The control of air renewal by the home automation system makes
it possible to reach the best compromise between high air quality and high energy
efficiency. Using home automation for this purpose also means reducing the number of
sensors to be installed and making multifunctional use of the devices and signal wiring
already provided in the building for other functions, such as air conditioning, lighting
or shading control.
Air quality
Air temperature [°C]
Relative humidity [%]
comfortable
too humid
too dry
medium
comfortable
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14
16
18
20
22
24
26
28
0
10
20
30
40
50
60
70
80
90
100
Buildings constructed or renovated in accordance with
the latest legal requirements offer considerable potential
for increasing energy effi ciency, but to fully exploit this
potential it is necessary to optimise the operation of the
various technical systems. Building automation systems
provide for this; the control functions of the heating
system are a fundamental part of it. According to the EN
15232 standard, during the design phase it is possible
to evaluate the energy savings obtained by adopting increasing levels of automation and to
place the building in one of the four energy effi ciency classes defi ned: from A (more effi cient)
to D (less effi cient). The functions of HVAC systems contribute signifi cantly to energy
effi ciency: heating, cooling, ventilation, humidifi cation, dehumidifi cation and production of
hot water for sanitary use.
This European Standard specifies also:
• a structured list of control, building automation and technical building management
functions which contribute to the energy performance of buildings; functions have
been categorized and structured according to building disciplines and so called
Building automation and control (BAC);
• a method to define minimum requirements or any specification regarding the
control, building automation and technical building management functions contributing
to energy efficiency of a building to be implemented in building of different
complexities;
• a factor based method to get a first estimation of the effect of these functions on
typical buildings types and use profiles;
• detailed methods to assess the effect of these functions on a given building.
Class A: includes buildings with high energy performance, equipped with control and
automation systems (BACS) and technical plant management (TBM) characterized by
high levels of accuracy and completeness of automatic control.
Class B: this includes energy advanced buildings, with control and automation systems
(BACS) and technical plant management systems (TBM) that allow centralised control.
Class C: includes standard buildings from the energy point of view, equipped with control
and automation systems (BACS) with basic functionality. It is also the class used as a
reference for calculating effi ciency factors.
Class D: includes buildings that are not energy effi cient and have only traditional technical
systems, without any automation.
The Italian Interministerial Decree of 26 June 2015 (“Minimum Requirements” decree)
prescribes for non-residential buildings a minimum level of automation corresponding
to Class B for the control, regulation and management of building and heating system
technologies (BACS).
References
EN 15232-1:2017 Energy Performance of Buildings - Energy performance of
buildings - Part 1: Impact of Building Automation, Controls and Building Management
Energy classifi cation of buildings (EN 15232)
In recent years, the interest in building control and automation systems has considerably
increased: now they are considered by directives and standards as a fundamental
element to achieve the ambitious energy efficiency objectives of the European Union,
while maintaining a high level of comfort in all situations.
The energy efficiency and performance of buildings has been a focus of attention for
designers, builders and end-users since 2002, when Directive 2002/91/EC on the
energy performance of buildings was published. The second revision of this Directive
(2018/844/EU) aims at spreading intelligent technologies as much as possible inside
buildings. This latest version is therefore particularly important for the sector of home
automation and building automation, as it actively promotes the widespread use of
these systems. The directive requires that non-residential buildings with heating (or
heating and ventilation combined) systems with an effective rated output of more
than 290 kW must be equipped with automation and control systems by 2025, while
for residential buildings there is a requirement for continuous electronic monitoring
to measure the efficiency of the systems and inform owners (or administrators) if
significant efficiency drops or need for maintenance occur. To these must be added
effective control capabilities to optimize power generation, distribution, storage and
consumption.
The Directive also introduces the Smart Readiness Indicator (SRI), which provides
summary information on the intelligence of the building to all interested parties: end-
users, designers, builders, investors, operators and service providers. The indicator
summarises the ability of the building to maintain energy efficiency and its functioning
by adapting its energy consumption using, for example, available renewable sources. In
addition, the building must adapt its operation to the needs of end-users, ensuring ease
of use, the thermo-hygrothermal comfort of the interior and the ability to communicate
data on energy consumption.
The Directive also recognises that building automation and monitoring is a cost-effective
alternative to technical inspections, particularly in large non-residential buildings and
condominiums.
The way in which certain articles of Directive 2018/844/EU are implemented has
been described in more detail in the recommendations subsequently drawn up by the
European Commission, which serve to support Member States in preparing national
transposition measures. The recommendations definitively recognise that the use
of intelligent systems in buildings is essential to achieve the targets set for energy
efficiency by 2030 and decarbonisation of the building stock by 2050.
References
Directive 2018/844 amending Directive 2010/31/EU on the energy performance of
buildings and Directive 2012/27/EU on energy efficiency
Recommendation 2019/786 on the renovation of buildings
Recommendation 2019/1019 on the modernisation of buildings
Building automation and European directives
A
B
C
D
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