“We shape our buildings; thereafter they shape us.” - Winston Churchill
Built areas absorb around 40% of the primary energy produced on a global level. To remain comfortable, a building needs permanent heating and cooling. This means that it is subject to non-stop consumption.
The building itself and the construction project require a comprehensive approach if the goal is to significantly reduce the overall energy consumption level. For example, no heating and cooling system will be efficient if a building's walls are not thermally insulated. We need to consider several factors, each of them equally important for reducing energy consumption.
Romania, divided into four climate areas
From a climatic point of view, Romania is divided into four areas. The mountainous region is the coldest of these areas (considered the fourth zone), with temperatures that drop to -21 ̊C. The warmest areas are Dobrogea and Banat where the minimum temperatures are around -12°C.
Each region has its particular characteristics. For example, Bucharest is part of the second climate zone, with minimum temperatures of -15 °C, while Iasi and Cluj are part of the third area, with minimum temperatures of -18 ̊C. This means that a building in the north of the country would need to behave differently if it were located in the south region. Adjustments to the local conditions are necessary.
What are the basic principles for reducing a building’s energy consumption level?
Choosing the orientation of the building according to the cardinal points and the sun is an important first step when deciding on the placement of the new construction on the available land. The east-west orientation offers light throughout the day and the conditions for obtaining natural ventilation. The temperature difference between the facades results in the movement of the cold air towards the warmer one, which rises.
Additionally, the sun brings an important quantity of heat to the interior during the cold months through the windows. To prevent the excessive heating of the interior during the summer, it is necessary to provide shading systems such as retractable shutters, blinds, or pergolas with adjustable slats.
Another aspect to take into account when choosing the building’s orientation is the clear differentiation of the main spaces (where inhabitants spend most of their time), from the annexes or service spaces. Technical spaces, such as garages, stairs, elevators, bathrooms, warehouses, etc., do not need the same sunshine as those intended for living or working from home.
When discussing energy consumption reduction, whether for heating or cooling purposes, we are referring to the correct sizing of thermal insulation, the protective layer of a building against cold and/or heat. The envelope is the building’s interface between the interior and the exterior. It includes all the elements which are in contact with the exterior: the external walls, the roof, the slab above the ground, and the carpentry.
A very important principle of thermal insulation is continuity.
If during winter, our goal is to have a comfortable temperature of over 20° C indoors, while the external temperature is -10° C, we have a 32° C difference. If we want to keep a temperature of 24° C indoors during summer while the outside temperature is 40° C, then the temperature difference is at least 16° C, without considering the overheating effect of the finishes exposed to the sun during the day.
The external and the internal areas constantly exchange heat, with the cold air moving to meet the warm air. This analysis is performed for extreme summer and winter temperatures.
Common mistakes include those at the intersection with the concrete slabs in the cantilever (balcony type), canopies, and terraces where the thermal insulation is interrupted and pierced.
The thermal conductivity coefficient (λ) is used to determine a material’s thermal insulation abilities.
According to the regulations, reinforced concrete has λ = 17.9 W/m²K, and mineral wool has λ = 0.045 W/m²K.
The lower the thermal conductivity, the more the material will prevent heat from passing from one side to the other. We perceive the characteristics of some materials instinctively: some are cold (concrete) while others are warm (mineral wool). The λ coefficient measures and converts these hot/cold perceptions into numbers.
As an order of size, the building’s envelope encompasses a generous surface area. For a building with a built area of only 100 m² and a 5 m height, the envelope area is 2x100 m² (roof + floor) + 4 facades x (10 m x5 m) = 400 m²!
Thus, the quality of the thermal insulation and its correct sizing are important factors in reducing energy consumption.
Airtightness is the building’s ability to prevent the loss of optimal cold/hot air on the interior when closed. Once a building is heated or cooled, the goal is to maintain the chosen temperature inside. The most vulnerable areas are carpentry frames, doors, the areas where materials join, or areas that pierce the thermal insulation (grills, chimneys, vents, etc.).
The airtightness of a building is determined with the help of door-blower tests.
As a rule, this test is carried out after the assembly of the joinery. Pressurized air is inserted into the building through a door, then the resulting pressure losses are measured.
Colored smoke released by special devices placed inside the building allows us to observe exactly where the air leaks occur.
One principle of efficiency tells us that, rather than having 10 small windows of 1m x 1m (and a total of 10m²) which generate 40 corners of air tightness vulnerability, we should propose the use of one large, well-executed window with a size of 4x2.5m and only 4 corners.
The lack of a correct seal leads to a decrease in the house's ability to keep the heat inside even if the thermal insulation is sized correctly.
A building’s optimal air insulation is also accompanied by a correctly sized ventilation system which allows us to have fresh air inside.
The field of installations has become very complex. In addition to the usual electrical, sanitary, and thermal installations, it is important to understand that several systems that complement each other are required to reduce energy consumption. Depending on the sum of all consumers within a building, one or more installation systems are proposed.
Installations classification according to their role in reducing the overall energy network consumption:
• Renewable electricity production systems
• Systems that reduce energy waste
• Class A energy equipment/appliances – LED lighting, household appliances, etc.
Photovoltaic panels use the sun's energy and convert it into electricity. The main challenges are constancy (they depend on sunshine) and energy storage during nighttime. Storage solutions are available, however, they involve quite bulky and expensive batteries.
Solar panels use the sun's energy to heat water and turn it into domestic hot water or heating agent.
• Heat pumps – air-water | soil-water | water-to water
The heat pump can be considered a renewable energy system because it uses outside heat, in addition to electricity, to cool or heat the house's interior. The advantage of this system is that it can be used for both cooling and heating, and for preparing hot water.
The heat from the outside environment can come from air, water (water table), or soil (geothermal).
Ventilation systems with heat recovery
The ventilation system ensures the ventilation of a building by exhausting stale air and introducing fresh air. The integration of the heat recuperator in this circuit allows the exchange of temperature between the newly introduced fresh air and the discharged stale air. For example, in winter, before the hot 24 ̊ C air is exhausted from the room, it passes through a heat recuperator where the outside air enters with a temperature of -15 ̊ C. This means that the fresh air reaches the interior heated directly at 18 ̊C, having taken much of the heat from the exhaust air (when the heat recovery efficiency is 85%). Therefore, we are essentially recovering the heat from the area for which we have already used energy for heating purposes.
• Class A energy equipment/consumers – lighting, household appliances, pumps, etc.
Every piece of equipment that connects to an outlet has an energy consumption class. When we replace old appliances with ones that have a higher class, we are contributing to the reduction of the total energy balance of the building.
All the principles presented above are designed and decided upon starting with the project phase, then detailed. A project's success depends on three main factors: the quality of the design and details, the beneficiary's approval of the solutions, and proper execution.
All the elements, ideas, and requirements overlap during the execution phase. These include the architectural solutions, the structural requirements and the installation systems. The adequate accomplishment and implementation of all the details is essential to achieve the energy consumption reduction goal. Moreover, we also need to take into account requirements concerning the beneficiary's needs, aesthetics, structure, legislation, waterproofing, etc.
The architect's role is to look upon the inhabited space and to design it for the future, by taking into account its continuous and efficient use.
