Along the last decades, the energy consumption in buildings has increased considerably due to the increase of the comfort demands. However, a more environmental awareness of the energy saving together with regulatory changes is helping to reduce this consumption.

In order to reduce the energy consumption effectively, is essential to know which are the installations that a building must have. The evaluation of the performance of systems is important, but there are other factors such as the real degree of comfort they can offer or the flexibility users will have that should also be taken into account.

The design of the facilities and the other elements of the building must be done simultaneously. Active systems are gaining importance and, therefore, can be combined with passive systems to gain in comfort without wasting energy. This dependency between the two systems will be more important once the demand for less consuming energy buildings increases, since the active systems of a building with almost no energy consumption have nothing to do with those of a conventional building.

Air conditioning

Most of the energy consumption in buildings is due to the necessity for heating and cooling them. Therefore, the decisions made when designing the air conditioning system will have a great impact on the final energy consumption.

A good air conditioning system not only considers the best performing available equipments, but also the guarantee of a high comfort level and flexibility for users when managing the system. If this systems cause discomfort, for example, due to a high air velocity propulsion or temperature differences between spaces, users will start managing the system wrongly. The most common practices are the opening of windows with the air conditioning system on, the cover of valves, the assignation of extreme set-point temperatures,…

The air systems present several advantages regarding the energy saving. For instance, they allow making free cooling, installing heat recovery systems and controlling air humidity levels. However, they are not the most adequate system for all the cases because they require a lot of space to install the ducts and a maintenance service is needed to clean these ducts regularly.

The air-water systems can be of several types. For example, there are the aerotherms and the radiant systems. One of the main advantages of these systems is that they require less space than air systems. Concerning the aerothermal system, it allows a great control of the air conditioning because the temperature of each place can be controlled and it can heat and cool at the same time. The radiant floor and ceiling systems allow giving a better sensation of comfort and, since they have a temperature of impulsion of the moderate water, they increase the performance of the water production.

The water systems are characterized by not having treated air: there are no air handlers or central air handling units. Nowadays, all new buildings must have a forced ventilation system. Therefore, a separate ventilation system must be installed. The terminal units will be aerothermal if there is production of cold and heat. In case of only having heat production, the terminal units can be conventional radiators or radiant surfaces. These systems allow doing a zoned control using thermostatic valves. However, it is necessary to have an installation of two tubes, so that when turning off a device, the entire system will not be interrupted.

Direct expansion systems are much simpler than the other systems mentioned so far. There are two types: the compacts and splits ones. In the case of the splits, they have one internal and one external unit, joined by the refrigerant ducts. The compact devices have all the elements of the refrigerator circuit in the internal unit. Its installation is simple but they are noisy. This problem is not found for the split systems, because the compressor, which is the element that makes more noise, is outside.

There are many possibilities when designing the air conditioning system of a building. Here we have seen some examples, but many combinations of elements can be done to create systems that adapt to each buildings needs. The main conclusion is that the performance when generating heat or cold will influence the final consumption, but there are other factors to take into account that will also affect a lot in this consumption. For example, it is very important that the system can be adapted correctly to the real needs of the users, so it is easier to manage the air conditioning and can save energy without giving up comfort.

Boilers

There are two basic factors to consider when choosing a boiler: its performance and the fuel that will use. These factors will determine the energy consumption and the environmental impact of the hot water production.

Conventional boiler

This type of boiler drives the water at a temperature between 70 and 90ºC and must have a minimum return temperature of 55ºC. Due to the high temperatures required, this boiler has a considerable energy consumption.

If the temperature is reduced, it is possible to save energy, but conventional boilers can not work at lower temperature in order to avoid acid condensation. If the water vapour produced during combustion is condensed and it is combined with sulphur in the combustion of diesel fuel, sulphuric anhydride and sulphuric acid is produced. Due to their corrosiveness, they damage the boiler. If it is a natural gas boiler, the problem persists because of the carbonic acid production.

Low temperature boilers

These boilers are designed to produce few condensations, although they work with a temperature of water supply between 35 and 40ºC. The key is the use of a double wall with an air chamber between the combustion gases and the water. Hence, the contribution of heat to the water is dosed and it avoids reaching the dew point.

These boilers are constructed in such a way that, in case of water vapour condensation, they do not damage the internal ducts. This allows adapting the temperature of operation according to the calorific demand, and, therefore, they can adapt to the characteristic heating curve of a building.

Condensation boilers

These boilers are characterized for taking advantage of the latent heat of the water vapour contained in the combustion gases phase change. This heat is transferred to the water before it is heated by combustion.

The exchange surfaces of these boilers must be especially resistant, and they must use pressurized burners to reduce the excess air and thus, the dew point.

Biomass boilers

These boilers are not characterized by their efficiency, but by the type of fuel they use: wood chips, wood shavings, pellets, etc.

At present, biomass as a fuel plays a strategic role, due to its contribution to the good management of forests, the valorisation of wood waste, the saving of fossil fuels and for containing CO₂ emissions.

The disadvantage of solid biomass as a fuel is the need for a considerable size space to store the fuel.

Direct expansion systems

The most common direct expansion systems are the split refrigeration systems or heat pumps. These systems are characterised by having a high performance in comparison to boilers. The reason of its high performance, above 100%, is that the heat pump instead of producing heat, transfers it from one point to another one. It takes advantage of one of the gases property: when a gas is compressed, it increases its temperature and when it expands, the temperature is reduced. To understand correctly the process, it is simplified explained: first the refrigerant enters to the compressor, where it increases its temperature. Then, it comes out at a very high temperature. The outside air temperature, even if it is more than 30ºC, will have a cooler temperature. Therefore, when exchanging heat with the outside air, the refrigerant cools “for free”, without any effort. This coolant continues to the expansion valve, and when expanded, it cools even more. In this way, when it goes through the inner unit, the refrigerant is so cold that absorbs heat from the interior environment. Then goes back to the compressor, closing the cycle. Thus, it has been proved that heat pumps cool very economically, because only a movement of heat from the inside to the outside is needed. When it is winter, the cycle is reversed but the process is exactly the same.

The performance of a heat pump is usually expressed in so much per one, not in percentage as in boilers. The COP refers to the heating performance and the EER, to the cooling performance.

A traditional heat pump has a COP ranging from 2.5 and 3, which are higher values of performance than boilers. Even so, the inverter heat pumps present even higher values due to the use of a variable refrigeration flow that allow adapting to the thermal needs of each moment.

Ventilation

Nowadays, new constructed buildings must have a mechanical ventilation system. The main reasons for using them are:

To guarantee a correct indoor air quality for the concentration of CO2. Ventilating the building through the imperfections of the thermal envelope is a huge mistake, specially taking into account that more watertight buildings are made every day. In buildings located in polluted areas, such as cities or industrial areas, the mechanical ventilation allows filtering the air. It has been widely proved that prolonged exposure to environmental pollution can cause different diseases; therefore this measure can improve people’s health as well as the comfort and energy efficiency of the building. This can also be an advantage for people suffering from allergies, since pollen and other allergenic agents can be filtered too. It also offers the removal of odours from the outside and the possibility of pre-treatment of the air entering to ensure that it has ideal conditions.

Mechanical ventilation can be an energy saving tool if designed properly. On the one hand, they can be used to ventilate when it is strictly necessary. On the other hand, it is possible to use a Canadian well or geothermal system to preheat or pre-cool the air. A heat recovery system installation can also be done, so that the conditioned air that has to be expelled for healthiness reasons, serves to condition the air temperature coming from the outside.

Lighting

A good lighting should provide adequate light, during the adequate period of time and in the right place. Therefore, offering users a correct comfort without suffering visual fatigue.

The type of lamp is usually the first thing to check when evaluating the efficiency of a lighting installation, but there are other factors that also have a great impact on the final energy consumption and users’ comfort.

In the domestic sector, the most common is to find filament, fluorescence or LED lamps. LED technology is intended to replace the others because of its efficiency, durability and other advantages in comparison with the other technologies. For instance, fluorescent lamps have components that can be harmful for health.

In office buildings or other kind of buildings, is usual to find T8 or T5 fluorescent lamps, metal-halide lamps and sodium vapour lamps. In the case of fluorescents, there are different types regarding the kind of ballast chosen, which influences the installation characteristics. The ballast is the component that limits the lamp current consumption to its optimal parameters. From the point of view of the energy efficiency, three types of ballasts can be distinguished: magnetic standard, magnetic of low losses and electronic ballast. The electronic ballast is the one that allows saving more energy, up to 25% compared to a standard magnetic device. It also extends the lifespan of the lamps up to 50%, makes the ignition of the lamp instantaneous and avoids the blinking of light. Therefore, a fluorescent with electronic ballast will be more efficient and will provide more comfort to users.

The design of the lights has an influence on the visual comfort. If the illumination is poorly designed, it will force users to employ more powerful lamps to prevent visual fatigue or it will create blinding to users.