“The house is a kind of thermos where the temperature is distributed evenly throughout all the rooms and remains constant at 21.5 or 22 degrees throughout the year. I am not hot or cold, we sleep with a sheet and a thin bedspread, it is a very pleasant feeling of comfort”. Luis Méndez talks about his house as if it were his greatest treasure. And not only for personal well-being, but also for economic ones. “For the energy bill of this house of 205 useful meters, I pay half that of the previous 160-meter chalet in which I lived for rent and the feeling of warmth is not comparable,” says this official from the Junta de Castilla y León. And this despite the fact that the heating is electric and that it is located in Valladolid, a Castilian and Leonese city where winters are very cold.
Valentín Martín proudly recounts that in 2022 he barely paid about 300 euros a year for electricity (288 euros in 2021). Like Luis, he has fled from fossil fuels, he does not use any system other than electricity to heat or cool his house. “I am saving between 2,500 and 3,000 euros a year in electricity compared to a normal single-family home,” says this rigger. And he continues: “You have the feeling of being in a new house every day, it is very cool in summer and warm in winter.” And, above all, “I pay much less than before, 60% is a fixed term.”
The secret to having so drastically reduced the energy demand of their homes, despite the energy crisis caused by the Russian invasion of Ukraine, is that they are passive houses that have also obtained the international Passivhaus certificate. Both are located in the El Peral urbanization, in the southern area of Valladolid, and have been designed by the architecture studio of Alberto López Merino. In that residential there are already 74 certified and inhabited single-family homes and another 39 are under construction. In addition, work has just begun on a 69-story building, the first of its type with this certification in Valladolid.
Houses are capable of heating and cooling with very little energy consumption. The certificate they hold —created in 1996 in Germany by the Passivhaus Institut— guarantees that their energy efficiency and comfort will last throughout the useful life of the building. This title also certifies that they are capable of saving between 75% and 90% of heating and cooling needs. I eat? Because of the way they are built. “It allows us to anticipate what will be mandatory in construction in the future,” says the architect López Merino, who began using the seal in 2010, at the worst of the real estate crisis, looking for a differentiating element.
The little supplementary energy that homes require can be covered with renewable energy. Luis and Valentín use an aerothermal system for air conditioning, which generates heat in winter and cold in summer. In the case of Valentín, his 178-meter-built house, in which he has lived since 2018, goes one step further — his title is Passivhaus Plus — by having photovoltaic panels on the roof. Hence, he only pays 300 euros a year in electricity. “From the end of March to the end of November I am self-sufficient, I do not pay electricity, only the fixed term”, he says. His bill for November was 49.69 euros. Also Luis just put 12 solar panels.
From the outside, these highly energy efficient passive houses are just like any other, hardly anyone would be able to tell the difference. “It does not imply the use of a specific type of product, material or architectural style, but rather a way of building”, says Arturo Andrés Jiménez, president of the Passivhaus Building Platform (PEP). Once inside the house, things change. “The difference is noticeable due to the clean and comfortable air that is breathed. In summer, when it is very hot outside, the temperature is pleasantly cooler. And, of course, at the end of the year it shows on the electricity bill”, they describe in the Passivhaus Institut. This German body has registered until the end of 2022 a certified area of more than 3.4 million square meters in the world, more than 5,250 buildings. In Spain, they exceed 238,000 square meters divided into 237 projects and in the next two years they will reach 352, according to the PEP.
The keystone is in the house itself: in its windows, walls, thermal insulation, air tightness… “By making a very well insulated house, without air infiltrations, with high-performance carpentry, it is possible to achieve a Excellent thermal comfort, having the entire house at the same temperature in all its spaces. Likewise, the acoustic comfort is maximum and is one of the things that the owners recognize the most”, says López Merino.
The fundamental principles of this way of building are seven: bioclimatic design, thermal insulation, minimization of thermal bridges, hermeticity, high-performance carpentry, controlled ventilation with heat recovery and sun protection. The heat recuperators, which allow the house to be ventilated 24 hours a day, are the lungs of the house. “They recover between 80% and 90% of the energy that is inside the building and, thanks to this, the building is ventilated regardless of whether we open the windows or not,” says Jiménez. And, in addition, “the air from outside arrives filtered, so that the sensation is of clean air, without odors, without harmful particles,” adds López Merino.
The houses use greater thicknesses of thermal insulation than traditional ones, thus reducing the demand for energy and the risk of pathologies appearing, both in summer and winter. Luis Méndez goes on to talk about the special foundation so as not to transmit the cold from the ground and about the more robust walls, with which, yes, “useful meters are lost”.
The design guarantees the continuity of the insulation at all points of the house envelope, so that there are no thermal bridges, there are no weak points through which to lose energy. “On the contrary, conventional houses usually have problems as a result of poorly insulated walls, poorly executed construction joints and cold spots in the envelope,” says Jiménez. The windows are high-performance: triple glazing, with low-emissive gases in their chambers (which increase insulation) and insulating frames and profiles. “A Passivhaus home can reduce the use of heating or air conditioning by up to 75%, and the window, which is the weakest part of the building envelope, must contribute to making this saving effective, providing insulation and comfort. Furthermore, contributing to the savings in CO₂ emissions produced in buildings also avoids causing more environmental damage to our environment”, indicates José Miguel Cortes, director for Spain and Portugal of Gealan, a German multinational manufacturer of PVC profiles for windows. and doors in Europe.
Dynamic control systems are also important, such as a blind or an awning, which allow the entry and exit of light and energy at the will of the owner depending on the season of the year in which we find ourselves. “The adjustable blind is the best constructive option due to its installation mechanism and the little space it takes up (with just 13 centimeters a wide variety of products can be incorporated),” says Arkaitz Aguirre, country manager of Griesser in Spain. “They save a large amount of energy to heat or cool passive buildings. This translates into a 30% to 50% reduction in the energy demand needed for air conditioning compared to a traditional system”, he adds.
The overinvestment in these certified passive houses —between 3% and 10% depending on the type of project— is recovered in the first years through energy savings.
THE COUNTRY of the morning
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