The Energy Rating of existing buildings, whose entry into force is expected in the near future not only It is an essential tool to stimulate the housing purchase, sale and rental sector, but It is a unique opportunity to save energy and therefore, cheap.
The existing housing stock in Spain presents, according to the results of the SPAHOUSEC study, carried out by the IDAE, an average Spanish household consumption of about 10,500 kWh per year. Previous studies carried out by the IDAE and the old MITyC gave a figure of about 0.85 toe. According to this report the block dwellings (floor type) in the area Mediterranean are those with the lowest energy consumption this being 0.53 annual toe. Instead and at the other end single-family homes in the continental sector present a average value of energy consumed of 1.69 toe/year. To level globally, single-family homes consume 2 times more energy than apartment-type homes.
The Energy Rating of single-family homes as a result of the Energy Certificate is a unique occasion to detect energy saving measures that will entail a improved labeling and a significant reduction in consumption energy and the associated cost.
The average consumption of single-family homes is 17,012 kWh/dwelling (0.061 TJ), which represents almost double the national average housing consumption. In this typology of dwelling, the use of the heating service predominates with a average value of 64% compared to 47%.
The single-family homes are lent, due to their construction characteristics and their air conditioning systems, to the use of unit-based low-temperature systems underfloor heating terminals . in the houses single-family homes are usually integrated renewable energy systems, primarily solar energy heat for ACS generation, with the prevalence of these systems much greater than in block houses. He energy labeling will lead to the detection of savings opportunities in single-family homes, which use natural gas or diesel as the main fuel.
Low temperature Geothermal Energy is based on operation in which for a depth greater than about 15 meters 20 m a stable temperature is maintained whatever the season of the year and weather conditions. This constant temperature makes the land an ideal focus for work with a water-water heat pump, using the ground as an evaporator (winter) or as a condenser (summer). Unlike an air-water type heat pump, the evaporator temperature (heating use) is not visible influenced by the outside air temperature, which makes that the COP is much higher. This advantage decreases to As we get closer to areas closer to the coast, where the temperature is much more uniform throughout the year, being in this case uncompetitive due to its high initial cost. After carrying out the energy rating of a home single-family home, a simple study can be carried out on the feasibility of installing a low energy geothermal energy system temperature by geothermal heat pump.
Considering an average energy consumption according to the study SPAHOUSEC, of 17,012 kWh/year, the consumption of energy for heating will be 10,888 kWh, Table I.
Table I. Power consumption annual
| Annual Energy………….. | KWh | % |
| Heating……………… | 10,888 | 64 |
| Total…………………………. | 17.012 | 100 |
For a typical 150 m2 house, 2 will require, on average, a vertical borehole with a total length of about 160 meters, corresponding to three soundings of about 53 meters. The types of single-family homes allow, easily, integrate this technology due to the little occupied floor space . The annual cost of the system heating is calculated for the general parameters indicated in Table II.
Table II. unit costs and yields
| Unit cost Diesel | 0.095 | €/kWh |
| Unit cost electricity | 0.145 | €/kWh |
| Unit cost electricity | 4,3 | |
| Medium performance boiler | 90€ |
Assuming an annual CPI value of 4% for the case of diesel and 3.20% in the case of electricity the costs of operation are shown in Table III.
Table III. costs of operation
| Cost Annual | Cost in 5 Years | Accumulated Savings 5 Years | Cost in 10 Years | Accumulated savings 10 Years | |
| Diesel | 1,149 € | 6,991 € | Total = €3,634 | 17,012 € | Total = €9,151 |
| BCG | €574 | 3,358 € | 7,861 € | ||
The cumulative cost and obtainable savings will be more than €28,000, therefore being a very profitable investment in the medium term with a return on investment of about 10 years. installation, without any subsidy, will have an approximate cost of about €10,800 including the geothermal heat pump.
Table IV. Savings in 20 years.
| Cost in 20 Years | Accumulated savings 20 Years |
| €50,363 | Total = 28,822 € |
| €21,542 |
Figure 1. Accumulated cost in 5 years
Figure 2. Accumulated cost in 10 years
Figure 3. Cumulative cost in 20 years
It is surprising, in these times of economic scarcity, see figures as impressive as that in 20 years of life in a home we will spend more than €50,000 on heating , This being an expense that will not generate any material good tangible. Having an efficient system will report a savings of more than €28,000, a not inconsiderable figure that can be destined to the purchase of a vehicle, food or education, among others. The energy rating obtained from the Energy Certificate is presented as an option to detect these savings opportunities and to give a added value to the properties that have these systems . It is important to note that the problem in these facilities is the initial investment, demonstrating that as always, everything that has to do with efficiency Energy is a financial problem, not an economic one. come back to flow credit becomes a necessity for our economy but also to improve our model energetic.
