Energy Efficiency in Residential Buildings

This month we are launching a new series of publications focused on the construction, design, and renovation of multi-family buildings, maintaining as a basic condition the fulfillment of energy efficiency criteria in residential buildings.

A Slow home can also be part of a residential building.

Currently, and increasingly so, both governments and society in general are committed to a more sustainable and environmentally friendly future.

New interventions and constructions must meet minimum energy efficiency criteria, but despite this, it seems that developers, builders, and other industry stakeholders have not yet fully embraced this approach, and developments continue to be built without considering energy efficiency.

As for the existing housing stock, the problem lies in the fact that many buildings, homes, facilities, transportation systems, etc., are old and therefore do not comply with current regulations and would require significant investment to do so. Nevertheless, and we will address this topic later, there are renovation techniques that allow for significant changes in the energy efficiency of the buildings being renovated.

Regarding energy efficiency in new residential buildings, it is a different matter. Starting from scratch with the project, if it is developed with sustainability in mind and committed to minimal consumption from renewable sources, the result is usually successful.

Let us proceed step by step.

In today’s article, we will begin by explaining what energy efficiency in residential buildings is and how it is assessed.

Subsequently, we will address different design criteria from the perspective of energy efficiency in residential buildings, as well as certain strategies to minimize their consumption.

Finally, as conclusions, we will assess the viability and future of these constructions.

Although it is true that efficient products are increasingly promoted and made more accessible, not all products are efficient. To distinguish them, we must consult energy efficiency labels, whose function is to ensure the quality and efficiency of the product we choose.

Both in general and in the construction industry, if we opt for the efficient alternative, it is usually slightly more expensive, but the investment is quickly amortized as it will allow us to save significantly on energy consumption.

Adopting new sustainable consumption habits and learning to manage energy to reduce its consumption in homes are strategies that actively contribute to caring for our environment and saving in many ways.

Methodology for Energy Efficiency Rating in Residential Buildings

As we have stated, we consider a residential building to be more energy efficient than another if, to achieve the same comfort, it consumes less non-renewable energy.

To achieve this degree of energy efficiency in residential buildings, we must rely primarily on four factors:

The energy efficiency certificate for residential buildings is an official document prepared by a qualified technician that includes objective information about the energy characteristics of a property.

In this way, the dwelling is assessed based on its annual energy consumption under normal operating and occupancy conditions.

This certificate takes into account the production of hot water, heating, lighting, cooling, and ventilation. Therefore, it is very important to consider these aspects from the building’s design phases. By committing to passive strategies, renewable sources, and proper resource management, we can achieve a good energy rating.

The certificate concludes with the assignment of an energy label whose letter—A, B, C, D, E, F, G—will inform us of the energy efficiency level of our building, with A being the most efficient and G the least.

Design Criteria for an Efficient Residential Building

The energy efficiency criteria in residential buildings will be, broadly speaking, the same as when dealing with a single-family home.

The comfort of all users must be ensured, both in private spaces and, in this case, in communal areas.

Energy savings is a second basic criterion to follow when designing an efficient residential building. Therefore, to achieve the comfort we mentioned, we can rely on passive systems for capturing and storing energy, as well as the contribution of additional energy from renewable sources.

All of this to achieve a habitable, safe, comfortable building that is respectful of the planet.

Design of an Efficient Dwelling

For a residential building to be efficient, we must opt for bioclimatic architecture strategies to achieve maximum possible energy savings.

We must maximize the advantages provided by the location, surroundings, and the climatic characteristics of the area.

A second objective would be to design the building using passive climate control systems, achieving heating in winter and cooling in summer.

Location and Orientation of the Building

The position of the building must be adapted to the climate of the area where it is located.

Depending on the climate zone we are in, we will have a certain exposure to the sun and local winds. It is important to assess both solar radiation and temperatures, relative humidity, prevailing winds, and precipitation in the different seasons of the year.

Another aspect to consider is the morphology of the land where we locate the building. Having maximum knowledge of the topography and vegetation of the site is important to determine the best placement of the building on the land.

Volumetry, Compactness, and Openings for an Efficient Building

The best way to avoid energy losses is to have a building with a simple design and compact form to reduce the surface area of the envelope (which is where thermal losses occur).

Regarding interior layout, it is important to place rooms with less use (especially during daylight hours) on the north side. In our latitudes (northern hemisphere), the sun moves from east to west passing through the south, so that the north façade, as well as the rooms located there, do not receive direct solar radiation, tend to be cooler, and have indirect, diffuse but uniform light.

When addressing this topic, we can also introduce the subject of openings or façade apertures according to their orientation.

It is recommended, to achieve the best energy efficiency in residential buildings, that 40–60% of the building’s openings be located on the south façade, while the remainder is distributed among east, west, and north, with the latter being the least perforated.

The Façade: Thermal Inertia, Reduction of Energy Demand, Filters, and Color

The façade is the building’s outer skin and therefore its main protection. It receives direct solar radiation but also, if there are design flaws, can be the part through which we lose the most energy.

Providing it with a certain thickness or treating it with materials whose thermal inertia is high will help us smooth the temperature variation between interior and exterior environments, achieving an adequate level of comfort.

At the design level, the team of architects and builders must strive to reduce thermal bridges as much as possible.

It is also interesting to use construction systems and materials that allow for reducing the energy demand of the entire building. It is ideal to reinforce thermal insulation and its airtightness.

There are highly recommended systems or alternatives to consider in order to achieve good thermal efficiency in residential buildings. Opting for green roofs, green façades, ventilated façades, and even double-skin façades with treated glass are design options we can consider when thinking about the façade finish of a more sustainable multi-family building.

In addition, to control excessive heating of façades with greater solar radiation exposure, there are elements such as overhangs, balconies, canopies, structures with movable adjustable slat elements, shutters, awnings, etc.

Another important aspect to consider when designing the envelope or façade of an efficient residential building is its color. Color is vital as it directly intervenes or influences the energy exchange between the interior and exterior of the dwelling.

Generally, light colors facilitate the reflection of natural light and therefore help repel heat. In contrast, dark colors facilitate solar capture.

This is a strategy that, although it may seem of little importance, will in the long run help us improve the dwelling’s energy efficiency without requiring a large investment.

Ventilation and Climate Control

The ventilation of an energy-efficient building should use passive systems such as solar chimneys or Canadian wells, as they guarantee air circulation, its renewal, and in the second case also serve to keep the interior environment temperate throughout the year.

There are also other passive heating systems such as greenhouses, which allow us to harness the solar energy that accumulates inside due to the greenhouse effect, or Trombe walls, formed by an exterior glass enclosure plus an air chamber and an enclosure with high thermal inertia, such as stone, brick, or concrete, which also allows us to accumulate energy, heat the air, and introduce it into the interior of the rooms through perforations in the wall.

Water Utilization

Another important aspect to achieve good energy efficiency in residential buildings is the utilization and reuse of rainwater and greywater, as well as water-saving mechanisms.

First, by installing a storage tank and a pumping system, we can collect and use rainwater for irrigation and domestic uses that do not require potable water.

Greywater, that is, water from washing machines, sinks, and showers, can be reused for the toilet cistern by installing an independent system for collecting and channeling water to the toilet.

Finally, simply by installing water-saving mechanisms or diffusers in taps, showers, toilets, etc., we can save significantly on water consumption in dwellings.

Renewable Energy

Opting for renewable energy as the main energy source for a residential building is an option that significantly reduces energy consumption and contributes to decreasing CO₂ emissions into the atmosphere.

Generally, the most commonly used renewable energies in construction are: solar thermal energy, photovoltaic solar energy, and biomass boilers for heating and domestic hot water.

Viability in Multi-Family Buildings

Taking into account everything discussed in today’s article, we can conclude that energy efficiency in multi-family residential buildings can be perfectly achieved.

It all comes down to good initial design. It is necessary for the team of architects in charge of the project to have these premises of energy savings and sustainability clearly in mind.

By avoiding energy losses in the façade, windows, and other problematic points, as well as equipping dwellings with savings systems, utilization systems, and renewable energy sources, good results are achieved—all without requiring an excessively large financial investment.