Parameters of an Ecological Air The costs of some resources, which were supposed to be inexhaustible, have increased and the low availability of some others has led to a redirection of the approach and parameters for the design of buildings and air conditioning systems, seeking to make them more efficient and environmentally friendly.
This reconceptualization seeks the definition of a new air, an ecological air that is innovative, by adding new methods and procedures to those already known, that the quality of the indoor air is optimized, that its maintenance and operation are minimal, of low environmental impact, and that it can be automated to be monitored, measured and controlled centrally, in search of its supervision and continuous improvement.
The conceptualization, design and execution of an ecological air, whether for a building or housing, involves and integrates important parameters that the designer must consider to carry out his work, among which are:
Analysis of the architectural context Requirements of thermal and visual comfort of the occupants Acoustic quality and permissible and adequate noise level Health of the users and indoor air quality (IAQ) Selection of equipment, its benefits and limitations Typology of materials and insulation Natural and artificial lighting Environmental impact Feasibility and efficient use of energy Low or no waste generation
The review, assessment and application of these parameters, as well as some more that are part of those already mentioned, in practice correspond to a chronological sequence in a proposed study area; for example, in a house (see figure 1)," located in a city in the southern part of the country, with an altitude of 380 meters above mean sea level, where the average dry bulb (Bs) and wet bulb (Bh) temperatures range between 37° and 24° Celsius and with recorded maximum and minimum temperatures of 40° and 6° Celsius, respectively.
After locating and identifying the characteristics of the environment of the house room, the following result was achieved: it is located to the southwest with dominant winds from the south, with affectation in the natural ventilation, not being adequate for the dilution of the concentration of carbon dioxide, emitted by the users of the house.
It is also observed that, due to the orientation and latitude of the house room, as well as the study area (see figure 2) the radiant loads in the conforming structural elements are predominant in the early hours of the day, throughout the year; information that can be verified in the heat gain tables.
Through an analysis of the thermal load of the study area (Figure 2) and considering the structural materials of the architectural project, it was obtained that the thermal load to be lowered is 43,170.00 BTU/h. With this result it is necessary to review and rethink the selection of the construction materials used, in order to reduce the thermal load to be reduced.
An alternative solution that gives good results is the installation of an insulating material in walls and slabs (whenever the architecture allows it is highly recommended); use semi-rigid sheets of extruded polystyrene, which, having a closed cell structure, has low thermal conductivity (k = 0.20BTU in / °Ft 2h), almost does not absorb water or develop mold or rot.
To make an adequate evaluation and selection of the insulating material used, we must check that it complies with the ASTM D1621, ASTM C272, ASTM D696 and ASTM E96 standards, established by the American Society for Testing Materials.
Another rethinking that needs to be done and that is very beneficial to reduce the load is the use of tinted glass or smart glass (thermochromic glasses, which depending on the incidence of light change their tonality). Undoubtedly, with the seconds better results are obtained and are more recommended than the tinted ones, since, regardless of the reduction of thermal load, the use of interior lighting in hours of less natural lighting is not affected, since they allow the passage of more light. The voltage with which they operate is 6 volts; therefore, the power consumption is about 0.1 watts for each square meter and for each time you change tonality; that is, it only consumes every time it is required and not during its operation, consumption that, if compared with the savings in electricity consumption, both of the air conditioning equipment and of the interior lighting, is very low.
The analysis of thermal loads is carried out for the second time, with the aforementioned modifications, and a reduction of 35% is obtained on average throughout the house, a result that decreases the equipment, electricity consumption and increases the useful life of the air equipment.
From the results obtained, the Variable Refrigerant Volume VRV system is selected, which operates with ecological refrigerant R410A. The benefits to obtain with this system are:
Reduce power consumption by using scroll compressors that include variable frequency drives to ensure smooth starts without current peaks, which improve motor rotation and make it more efficient. Anti-corrosion coating on the coil of the condensing unit. Use of environmentally friendly coolant with low environmental impact. Independent operation of each unit by air conditioning zone. Automated and centralized operation, if required, since the system has the capacity to handle uniform humidity and temperature parameters for the entire house, through a central control that allows the option of remote monitoring. The variety of indoor evaporator units that can be installed (high wall minisplits, ceiling floor minisplits, floor units, cassette type, fan & coils) allows the adaptation to varied civil works. Modular condenser is located inside a machine room, within the limits of the house room; isolates the noise produced, both from the occupants of the house and from the adjoining properties, also solving the problem of visual impact that would be generated, by leaving the condensing unit in sight.
The acoustic quality, as well as the noise levels, is of special care. Some aspects that must be taken care of are external noises due to traffic or open windows, interior noises generated by activities carried out in the house room; although in this case greater importance will be given to those produced by the components and accessories of the equipment to be installed such as:
Discharge grids Air return Fastening elements Turbines Ducts Evaporator units Handling units Condensing units, among others.
The acoustic quality will also be affected by the amount of air that circulates inside the room that is subject to study, which is why the PCMs (cubic feet per minute) must be calculated, which are directly proportional to the dimensions of the place to be conditioned (length, width and height) and inversely proportional to the changes per minute obtained from a ventilation table.
From this table it is obtained that the changes of fresh air per minute for a house are in the range of 2 to 6, in order to avoid acoustic quality problems and the increase in the concentration of gases, such as carbon dioxide and some others that affect the quality of indoor air. It is of special care not to make an air delivery below these ranges nor to feed air at high discharge speeds, as the acoustic quality would be affected.
It is well known that indoor air quality affects not only the comfort of users, but also affects their health, since dust, toxic materials, spores and bacteria can cause irreversible damage, also causing the syndrome of sick buildings. Due to these factors, it is necessary to correctly select a filtration system and the appropriate filters for the size of particles, since placing filters that are capable of filtering a particle size smaller than required, will have an impact on both the sizing of the equipment and its consumption.
For the case of houses room the use of the NAFA guide for the ANSI/ASHRAE 52.2 – 1999 standard suggests that, for residential applications, we can use filters with an average efficiency of 20 to 35%, with MERV of 4, giving options such as: washable, fiberglass and disposable metal filters.
The use of UVC lamps (type C ultraviolet light lamps), in air handling systems for the elimination of bacteria, fungi and mold that are generated during operating and downtime, brings as a benefit the prevention of diseases and the formation of organic films in the evaporator coil. While it is true that these accessories increase electricity consumption, when the cooling capacity is measured to compare the efficiency before and after the use of the lamps, increases in the cooling capacity of up to 45% can be verified, which, without a doubt, returns the equipment to its original conditions, reducing the demand in the consumption of the equipment or system.
For the equipment of the area under study in Figure 2, 400 CFM, equivalent to 1 TR, with a UVC emitter of 16" long, with a consumption of 75 watts, was taken as a parameter.
As can be seen, the design and construction of an ecological air is the integration of several criteria and parameters that allow us to achieve low energy consumption, efficient use of energy, indoor air quality and low environmental impact.
