“The house is a kind of thermos where the temperature is evenly distributed across all rooms and stays constant at 21.5 or 22 degrees throughout the year. I’m neither hot nor cold, we sleep with a sheet and a thin bedspread, it’s 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 the economy. “For the energy bill of this house of 205 useful meters, I pay half the energy bill of the previous 160-meter chalet I lived in for rent and the feeling of warmth is not comparable,” says this Junta de Castilla y León official. And this despite the fact that the heating is electric and is located in Valladolid, a city in Castile and León where the winters are very cold.
Valentín Martín proudly tells that in 2022 he paid almost 300 euros a year for electricity (288 euros in 2021). Like Luis, he has fled fossil fuels and uses no system other than electricity to heat or cool his home. “Compared to a normal single-family house, I save between 2,500 and 3,000 euros in electricity every year,” says Rigger. And he continues: “You feel like you are in a new house every day, it is very cool in the summer and warm in the winter.” And above all: “I pay a lot less than I used to, 60% is a fixed term .”
The secret to having drastically reduced the energy needs of their houses, despite the crisis caused by the Russian invasion of Ukraine, is that they are passive houses, which have also received the international passive house certificate. Both are located in the El Peral urbanization in the southern part of Valladolid and were designed by the Alberto López Merino architectural studio. In this residential area there are already 74 certified and inhabited single-family houses, another 39 are under construction. In addition, work has just begun on a 69-storey building, the first of its kind with this certification in Valladolid.
Houses can be heated and cooled with very little energy consumption. The certificate, created by the Passive House Institute in Germany in 1996, guarantees that energy efficiency and comfort are maintained over the entire service life of the building. This title also certifies that they are able to save between 75% and 90% on heating and cooling needs. I eat? Because of their construction. “This allows us to anticipate what will be mandatory in construction in the future,” says architect López Merino, who began using the seal in 2010, in the middle of the real estate crisis, and was looking for a differentiating element.
The small additional energy requirement of the households can be covered with renewable energy. Luis and Valentin use an aerothermal system for air conditioning that produces heat in winter and cold in summer. In the case of Valentín, his 178-meter-high house, in which he has lived since 2018, goes one step further – its title is Passive House Plus – and has photovoltaic panels on the roof. So you only pay 300 euros for electricity per year. “From the end of March to the end of November I’m self-sufficient, I don’t pay for electricity, only the fixed term,” he says. His bill for November was 49.69 euros. Luis also just installed 12 solar panels.
Luis Méndez, in the kitchen of his home in the El Peral neighborhood (Valladolid). Emilio Monk
From the outside, these highly energy-efficient passive houses are like any other, hardly anyone would tell the difference. “It does not imply the use of a specific type of product, material or building style, but a way of building,” says Arturo Andrés Jiménez, President of the Passive House Building Platform (PEP). Once in the house, things change. “The difference is noticeable through the clean and comfortable breathing air. In summer, when it’s very hot outside, the temperature is pleasantly cooler. And of course that is reflected in the electricity bill at the end of the year,” they describe in the Passive House Institute. This German body has registered a certified area of more than 3.4 million square meters worldwide by the end of 2022, 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 key to the vault is in the house itself: in its windows, walls, thermal insulation, airtightness… “By making a very well insulated house, without air infiltrations, with high-performance carpenters, excellent thermal comfort is achieved, the whole house the same temperature in all rooms Likewise, the acoustic comfort is maximum and one of the things that owners appreciate the most,” says López Merino.
The basic principles of this construction are seven: bioclimatic design, thermal insulation, minimization of thermal bridges, airtightness, high-performance carpentry, controlled ventilation with heat recovery and sun protection. The lungs of the house are the heat recovery units, which allow the house to be ventilated 24 hours a day. “They recover between 80% and 90% of the energy that is inside the building and thanks to this the building is ventilated whether we open the windows or not,” says Jiménez. What’s more, “outside air arrives filtered, giving the feeling of clean air, free from odors and harmful particles,” adds López Merino.
The houses use thicker thermal insulation than traditional ones, reducing energy needs and the risk of disease in both 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 there are no thermal bridges, there are no weak points through which energy can be lost. “Conventional houses, on the other hand, usually have problems with poorly insulated walls, poorly executed construction joints and cold spots in the building envelope,” says Jiménez. The windows are high-performance: triple glazing with low-emission gases in their chambers (which increase insulation) and insulating frames and profiles. “A passive house can reduce the consumption of heating or air conditioning by up to 75%. And the window, the weakest part of the building envelope, must help make this saving effective by providing the necessary insulation and comfort. In addition, contributing to the saving of CO₂ emissions generated in buildings avoids further environmental damage to our environment,” explains José Miguel Cortes, Director for Spain and Portugal of Gealan, a German multinational manufacturer of PVC profiles for windows and doors. in Europe.
Also important are dynamic control systems such as a blind or an awning that, depending on the season in which we find ourselves, allow the entry and exit of light and energy at the discretion of the owner. “The adjustable roller blind is the best constructive option due to its mounting mechanism and the small footprint (with only 13 centimeters a large number of products can be integrated),” says Arkaitz Aguirre, Country Manager of Griesser in Spain. “They save a lot of energy to heat or cool passive houses. This means a 30% to 50% reduction in the energy required for air conditioning compared to a traditional system,” he adds.
The overinvestment in these certified passive houses – between 3% and 10% depending on the project type – is recouped in the first few years through energy savings.
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