Energy
Off-grid self-sufficient home
Who would like to live in a home where you do not pay electricity or water bills? Today I will explain how to live in an off-grid self-sufficient home.
Nowadays, more and more adjectives are entering our vocabulary that refer to the eco world: self-sufficient, ecological, sustainable… words we see associated with cars, restaurants, supermarkets, or even travel. They all refer to a more balanced lifestyle that respects the planet’s natural resources—something we all aspire to for the future.
When we talk about an off-grid self-sufficient home, we mean a type of dwelling that supplies itself and is able to produce the energy it consumes.
In other words, an off-grid self-sufficient home is a zero (or near-zero) consumption dwelling, as it does not need any external energy source or resource input to meet its occupants’ comfort needs.
How can a house like this work? Is it possible nowadays?
These homes have their own networks that harness and obtain resources from natural sources such as the ground, the sun, the wind, rainwater, etc., and they have energy conversion systems for their own use.
That said, you will always need to adapt to the characteristics of the land and also shape your lifestyle and budget, bearing in mind that you are building a home now for an off-grid future, free from energy company bills.
Zero-consumption home. From traditional architecture to the latest techniques
Building an off-grid self-sufficient home today means going back to basics. One hundred years ago, homes did not have running water or electricity, and their inhabitants had fewer needs.
That is precisely the key: an off-grid self-sufficient home must meet two basic requirements: on the one hand, reduce to a minimum the energy consumption needed for daily life, and on the other, rely on renewable sources to cover any demand that may arise.
If we look back in history, we will realise that even before the Industrial Revolution and the exploitation of coal, oil, and other unsustainable energy sources, traditional homes were an excellent example of zero-consumption homes.
They had no energy sources other than those provided by natural resources. They adapted to the climate, making the most of it to minimise the home’s energy consumption.
Making use of solar orientation, wind power, and water was very important. Household waste was also managed so that nothing was wasted, as it was used to produce compost, and dirty water was reused for irrigation.
Thick walls improved airtightness and indoor comfort. Due to their thickness, they balanced thermal changes through an architectural process or strategy known as thermal mass, which regulates temperature exchange between indoors and outdoors.
Thermal mass and insulation. What can we learn from traditional construction?
Rural houses are a type of construction that originated between the 10th and 13th centuries.
Their construction is closely linked to their use, whether for farming or livestock. They are usually isolated and oriented according to the sun’s path to make the most of both light and heat, improving indoor comfort conditions.
They were usually built with local materials and techniques. Thus, zero consumption was not limited to operational terms; it also began by minimising costs from the very first steps of the construction process.
Walls between 50 and 70 cm thick were intended to maintain a stable, pleasant indoor temperature. This, technically known as thermal mass, is explained as a material’s ability to store heat.
A sufficiently thick wall stores heat and releases it slowly indoors. This means that in winter, at night, we receive the heat accumulated throughout the day. In summer, the house stays cool during the day, and when heat is released indoors (at night), that is when we ventilate with the cool night breeze.
And you may wonder: how was this achieved? In summer, the heat the wall receives and stores from the sun takes several hours to reach the interior, so you notice it at night, when it is cooler outside. With the help of windows, we can dissipate excess indoor heat in summer and store it, if convenient, in winter.
Another important point to consider is that the layout and organisation of the house and its rooms also encouraged maximum energy efficiency.
Typically arranged over three floors, masías placed on the lower levels all the rooms that could produce heat (kitchen, living room, stables, etc.). The middle floor was used for the most everyday rooms, such as the living area or bedrooms. Finally, the attic was usually used as a pantry or storage space.
Unlike traditional rural houses, today’s residential construction systems aim to save on materials and time. That is why thick thermal-mass walls are no longer used, and insulation is chosen instead.
What we will aim to achieve when building a self-sufficient home is to combine both properties: thermal mass to store heat inside the home, and insulation to prevent heat from entering.
Key principles for making your home an off-grid self-sufficient home
To make your home an off-grid self-sufficient home, you can use different techniques and systems to reduce energy consumption as much as possible. Let us see what they are.
To reduce energy consumption:
Solar radiation harvesting
Solar capture is essential for any type of home, whether it is a zero-consumption home or not.
You should make the most of the sun as an inexhaustible and beneficial energy source, not only for lighting but also for its ability to warm surfaces and for its positive effects on our health.
For a zero-consumption home, it is very important to orient rooms and design windows according to their position in relation to the sun’s path.
In our climate, a south-facing orientation is best for harnessing solar radiation, especially in winter. In summer, however, if the sun is very intense, you will need window shading to limit solar gain.
Using deciduous vegetation is recommended because, in addition to allowing solar gain in winter and filtering it in summer, it promotes ventilation, renews and cools the air, and provides very pleasant visual comfort.
Thermal Insulation
Thermal insulation in walls is vital to prevent energy losses from inside the home once it has been captured.
The thickness of this insulation layer must be suited to local conditions. Typically, conventional construction uses around 5 to 10 cm, but for a zero-consumption home the recommended thickness is 15 to 25 cm, or even 30 cm, depending on the energy demand of each wall type.
You should choose breathable insulation materials to avoid condensation caused by possible indoor humidity.
At this point, windows and wall openings play an important role. The chosen frames must ensure there are no thermal bridges (i.e., uninsulated points), and you should also try to match the insulation performance of the wall and the window to avoid temperature differences that would cause condensation at the joints.
It is important to look at the U-value when choosing glazing (its ability to transfer heat from inside to outside, or vice versa). It should be low and aligned with the U-value of the walls.
Thermal Mass
As mentioned earlier when discussing the wall, the heat you capture can be retained with walls made of materials with high thermal mass. Concrete or brick are examples of materials with this capacity, allowing heat to be stored and released after a few hours.
It is advisable to place these materials where they will receive sunlight for as many hours as possible.
Natural Ventilation
We must not forget that a home must also ensure adequate volumes of natural ventilation.
In summer, for example, installing covered outdoor porches, patios, and operable windows will help ventilate the home. Using airflow by placing openings at opposite ends of rooms will facilitate air movement.
Air renewal must be ensured all year round, either naturally or with the help of mechanical extraction systems.
On the other hand, using renewable energy, despite requiring a considerable initial investment, pays for itself in around 5–10 years and can fully cover a family’s energy consumption, provided the household adapts its lifestyle and reduces excessive consumption.
Energy supply through renewable sources
Solar panels
Installing solar panels can be used both to generate electricity and to heat domestic hot water.
Today there are three types of panels on the market:
a. Photovoltaic solar panels: when radiation reaches the panels, electrons gain energy and move, creating an electric current. These types of panels are currently being replaced by more efficient and cost-effective ones.
b. Photovoltaic-thermal panels: instead of generating electricity directly, these panels work by heating the tubes they are made of. Inside these elements there is a heat-transfer fluid that is heated and then circulates through the home.
These panels work by surface area, so they take up more space and are intended for producing hot water for bathrooms or heating.
c. Thermodynamic solar panels: these are the most commonly used panels today, both for their efficiency and their smaller size. They are somewhat more expensive, but the initial investment is offset by their efficiency. They do not depend directly on the sun to generate energy, so they can produce it on rainy or cloudy days.
Geothermal energy
Geothermal energy comes from the ground. Geothermal systems harness the higher temperature of the subsoil to heat a fluid or air that is introduced into the home at a constant temperature of around 20°C.
It is a sustainable choice, but for private projects at Slow Studio we usually recommend installing other, more efficient and cost-effective energy systems. You can contact us for guidance, as each case is very different and various factors must be assessed before choosing one system or another.
Water harvesting and filtration
To obtain water, you can use two different systems. If you are fortunate enough to have water on your land, you can dig an underground well; if not, you can collect rainwater.
As for greywater, which is inevitably produced at home—whether from the shower, washbasin, or dishwasher—it can be filtered through plants in the garden itself, returning the water to the natural ground. Of course, in this case you should use eco-friendly soaps that do not harm the environment.
The water, now free of contaminant particles, flows into a pond or a tank. Depending on its subsequent use, it will go through another filtration system to finish purifying it. It is estimated that the wetland surface area should be around 5 m² per person.
Waste management. Reduce, reuse, recycle
Responsible waste management involves global social awareness, primarily encouraging the minimisation of waste generation. It does not usually increase the cost of the home, either during construction or in use. It is an attitude.
We must become aware of reducing both consumption and waste. Reuse elements that can have a second or third life, and finally learn to recycle organic matter by composting for plants.
There are many options you can choose, but in this respect the most important thing is to be original and creative, and to be willing to contribute personally to reducing your own consumption and your home’s consumption to zero.