Homes prepared for the climate emergency

*Update: Please contact our team for current pricing.

Currently, we can affirm that climate change is the greatest threat we face as human beings. We know that we have caused an unprecedented crisis and that, even if all greenhouse gas emissions were to end today, the effects on the climate and the stability of ecosystems resulting from human impact will extend for hundreds of years.

Our responsibility is to act now to avoid the catastrophic effects of a climate escalation that threatens our survival as a species, but also to ensure our generation adapts to the challenges of an uncertain world in which the stability we have enjoyed over the last century will cease to exist.

In recent years, and especially following the signing of the Paris Agreement in 2016, it seems that climate awareness has begun to take root at all levels. Both governments and institutions are starting to wake up and take more or less effective or urgent actions to mitigate the climate crisis and adapt to it.

But what can we do as individuals?

Just as individuals take measures to reduce our ecological impact, we can also take steps to prepare our adaptation to climate change. Without a doubt, these measures involve adapting our homes to a climate emergency scenario.

The international body IPCC, the Intergovernmental Panel on Climate Change, assesses the impacts, adaptation, and vulnerability to climate change, addressing decision-makers regarding policies to tackle this situation. [2]

In Spain, an increase in temperatures is expected, with much more severe heatwaves and periods of high temperatures with water supply shortages. How will our homes respond to this new reality?

And how will the hydrographic system adapt to the increasingly common periods of drought or storms that force us to restrict or ration municipal water supplies?

What would happen in the case of pandemics or border closures that threaten the constant supply of food?

An increasing number of families are aware of the threats of the reality we face and seek to build or adapt their homes to the climate emergency; this is what has recently become known as resilient housing or, on a larger scale, resilient communities.

Homes prepared for the climate emergency

Throughout this section, we will delve into the various resources we can utilize: water, wind, solar radiation, the earth, and heat from the air or the ground, as well as different ways to incorporate them into the design of homes prepared for the climate emergency. Furthermore, such resources are not only utilized throughout the home’s lifespan but can also be used directly for its construction, such as building systems that use resources from the land itself, like earth or wood. Additionally, we will consider which supplies are susceptible to problems in the event of a climate emergency.

Water

Water is essential for human life, both for hydration processes and hygiene. In the last decade, running water has come to be considered an unquestionable basic supply in developed countries and a primary necessity in developing countries.

In the case of Europe, despite not being an arid continent, data on the pressure exerted on freshwater is concerning. Various studies conducted by the European Commission indicate that a water exploitation index higher than 20% implies that the water resource is under stress due to clearly unsustainable use that does not account for long-term resources. Spain is in this situation, alongside other countries such as Belgium, Bulgaria, Cyprus, Italy, and Malta. [3]

Water collection

There are two main water collection systems: rainwater harvesting or underground wells.

Rainwater harvesting

Rainwater collection is closely related to the rainfall patterns of each area, and its use is typically associated with garden irrigation.

In the case of Spain, rainfall is highly variable, combining periods of heavy rain in spring with significant shortages in summer. Therefore, the efficiency of water collection systems for irrigation is often questioned, as periods of low rainfall coincide with periods of high irrigation demand. This leads us to oversize rainwater tanks that must store large amounts of water during rainy periods for use in the summer.

This sizing is carried out based on the collection surface area, rainfall, and the surface factor—that is, whether it is a flat, pitched, or green roof. From there, one must consider the annual demand and the drought period to be accounted for, making it a calculation that is somewhat difficult to pinpoint.

Anticipating that climate change will involve an increase in these drought periods, having a rainwater tank becomes a resilience alternative, no longer just for garden irrigation but for the household supply.

It is important to know that rainwater collection is not direct, as at the start of each collection, one must allow time for cleaning dirt from the catchment area, which will be greater the longer it has been since the last rain. Since the goal is to store perfectly clean water in the tank, there is also the possibility of installing a series of filters directly in the downspouts and roof gutters, as well as directly at the tank inlet.

The technology and the large volume of these tanks impact their high cost, as well as their significant visual impact. To prevent the latter, there is the possibility of installing underground tanks, which further increases the budget due to excavation costs, as well as the need in some cases for a pump to lift the water to a higher level. However, it is a resource that solves the need to protect the tank from ultraviolet rays and heat. [4]

Municipal building regulations are increasingly inclined toward requiring these types of tanks on the plot, especially in the case of single-family homes with gardens.

Underground wells

Water collection through underground wells depends on the presence of groundwater; therefore, in many cases, their installation will not be possible, nor will it be economical depending on the depth of the water table.

For their installation, it is necessary to excavate a well and install an extraction pump to push the water up to ground level.

Water reuse

Regarding water reuse, we usually classify it into different stages of water types based on its future use: water for human consumption, water for personal hygiene, irrigation water… A paradigmatic example is the Venlo City Council project in the Netherlands, which we describe in the article on Circular economy in architecture.

In this building, five different water recirculation networks are distinguished: municipal drinking water, rainwater, greywater, yellow water, and blackwater, understanding the use of reclaimed water as the key proposal for resolving integrated water cycle management in the short term.

Greywater utilization

The strategy stems from the awareness that certain daily applications do not require water of potable quality, such as toilet cisterns, domestic outdoor cleaning, or the irrigation system, which we will cover in the next section. For such uses, greywater from showers and washbasins, appropriately treated, is an effective and suitable alternative.

Greywater is differentiated between raw greywater (RGW) and recycled greywater (RGW). Raw greywater consists of domestic wastewater from showers, bathtubs, and washbasins. The intention is to exclude water from kitchens, bidets, washing machines, and dishwashers due to the possible presence of contaminating chemicals and pathogens, always depending on the type of filtering and purification system to which the water is subjected. Converting this water into the recycled greywater category involves its appropriate treatment and preparation to be delivered to its new supply point.

By applying the appropriate technology, the consumption of water suitable for human consumption in our buildings can be reduced by up to 40%, reserving it for strictly necessary uses. In this way, we manage to reduce the average of 127 liters per person that constitutes daily water consumption in Europe. In relation to this figure, bathroom cisterns have a lot to do with it, with flushes ranging between 3 and 6 liters, the refilling of which represents an estimated demand that can reach 45 liters per day per person, a very high percentage of total expenditure.

Similarly to the case of rainwater, it will be necessary to calculate the demand for treated water compared to greywater production, and the larger volume will determine the size of the tank, which is very small as it is refilled every day.

All components of this network must be in a circuit independent of the system for water suitable for human consumption, avoiding the risk of cross-connections. In turn, the system must guarantee the supply of mains water even in cases of a possible power outage, so we must duplicate the installation.

In conclusion, it is a system that works but involves a high investment that takes a long time to amortize due to the still relatively low cost of water in our country.

Water for garden irrigation

For garden irrigation, the approximate calculation considers 2 to 6 liters/m²/day, a highly variable figure depending on the type of vegetation and the season of the year, again representing a high water expenditure despite being recycled, whether from rain or greywater.

With the idea of reducing this consumption, there has recently been much work with so-called xeriscaped gardens, which aim to work with native species, consequently adapted to the climate and rainfall. Thus, unlike the gardens we are used to, which are always green and full of grass with imported species that consume a lot of water, xeriscaped gardens use local shrubs and dryland plants, such as sedums, succulents, or aromatics.

Water purification

The water purification system is part of the treatment process, which generally includes the following stages: greywater collection and storage, the treatment itself, and the storage and pumping of the treated water.

Generally, treatments can be classified into the following systems: physical, physical-chemical, and biological systems. [5]

Physical systems, as the name suggests, only employ filtration systems based on geometry, such as meshes or rings. Additionally, they may contain a system for separating oils and fats by decantation. While these treatments are the most economical and have the lowest maintenance, today it is difficult to consider them as anything more than mere pre-treatments due to their low efficiency.

Physical-chemical systems combine the previous filter with disinfection systems, thus managing to separate oils and fats, emulsions, colloids, suspended particles, organic matter, and turbidity. The filters can be more technical, such as sand or multi-layer filters, and the use of chemicals basically consists of dosing coagulants and disinfectants, the most common being sodium hypochlorite. Conversely, it is a treatment system with a high maintenance cost.

The technologies being most developed recently revolve around biological filters, which achieve the degradation of organic matter present in greywater through microorganisms, whose growth is encouraged by supplying oxygen to the system.

For this, it will be necessary to use ecological soaps, without chemicals, to avoid killing the bacteria or plants that perform this work. In some cases, it may be advisable to install a direct drain to the sanitation network where highly toxic products or those with a strong chemical load, such as bleach or solvents, can be disposed of.

Among the most commonly used biological systems are sequential batch reactors, which use activated sludge; membrane bioreactors, which use microfiltration membranes in addition to the biological process; or naturalized biological systems, which use a specific type of vegetation for the natural supply of oxygen to the water—such as phyto-purification systems. This oxygen, as we have indicated, promotes the proliferation of microorganisms, which are found in the form of a layer on a substrate in contact with the water to be treated.

At the urban level, there is a major problem in the lack of separation between rainwater and wastewater networks, which end up mixing in the general sanitation network. These are two types of water that should not be mixed, as one is clean while the other contains fecal and chemical remains.

Countries like England have already included a regulatory requirement for public roofs to have drainage that does not discharge into the sanitation network. In the Spanish case, regulations are beginning to pursue this objective with initial attempts at municipal-level regulatory mandates.

Energy

Today, it seems inconceivable to live in a house with the energy limitations that the previous generation experienced. Society is accustomed to standards of comfort that seem difficult to reverse.

However, it is no coincidence that, linked to the awareness of the environmental crisis, many users are becoming aware of the need to reduce consumption. In fact, logic tells us that the lower the consumption of energy and renewable resources, the lower the need for energy production.

Passive strategies involve a direct reduction in consumption, making the design more ecological and increasingly less dependent on any energy source.

So-called nearly zero-energy buildings have been included in the Spanish Technical Building Code (CTE) since June 2020 through the update of the Basic Document HE requirements on the limitation of energy consumption. [6] These are homes that practically invest no energy in heating or cooling and limit their primary energy consumption to lighting and electronic devices.

Next, we will divide this section into two subgroups, corresponding to the two types of energy mentioned: thermal energy and electricity. Thermal energy is used in the production of hot water for heating and DHW (domestic hot water), while electricity is used both for powering electronic devices and lighting, as well as for electric heating and cooling.

Electricity

As previously mentioned, climate-resilient homes must be capable of generating their own electricity to power artificial lighting and appliances, as well as electrical systems for climate control. To achieve this, various generation mechanisms are available.

Turbines or wind generators

A wind generator is an electrical device with a turbine that converts the kinetic energy of the wind—the energy of motion—into electrical energy. It consists of one or several small-scale windmills that can be installed in a home and are automatically oriented by an incorporated weather vane. Additionally, they have a safety system to prevent damage.

These are devices subject to recent technological advances, which facilitate smaller dimensions and consequently greater functionality. For example, a conventional wind generator from the Bornay brand starts operating at a wind speed of 2 meters per second, which is only 7.2 km/h. With strong winds exceeding 30 m/s, the blades change position and the wind generator brakes to avoid excessive stress.

The latest innovations design turbines that can be installed on the roof of the house like a chimney, connecting to the installation in a similar way to a solar panel. An example of these types of systems is the Graeme Attey Wind Turbine [7], a wind generator that aims to be a revolution for achieving domestic electrical self-sufficiency.

However, like any device that generates electricity, its handicap lies in the technical limitations of the batteries where the energy is stored, which end up being very expensive and offer very little autonomy.

Photovoltaic panels

The way photovoltaic panels capture energy is indirect; they capture solar radiation and convert it into electrical current through the movement of photons. One must avoid confusing photovoltaic panels with thermodynamic solar panels (for heating water), which we will discuss later in the section on hot water generation.

The more intense the light, the greater the amount of electricity generated. Therefore, the number of panels, their position, and their orientation will be of great importance in their capture. Thus, their optimal orientation will be facing south, corresponding to an azimuth of 0º, while their ideal inclination will depend on the latitude of their location, around 35º.

The panels are made up of a set of photovoltaic cells, which in turn are composed of one or more sheets of a semiconductor material covered with glass to reduce heat loss.

Most cells are made of silicon and have efficiencies between 14% and 17%. So-called ‘second-generation cells’ are also manufactured, which are cheaper but have lower efficiencies, from 10% to 12%. Lately, work has been done with systems with efficiencies between 25% and 30%, but this involves significantly higher prices.

All of this implies really low yields, with a truly high energy cost derived from the extraction and transformation of silicon at high temperatures. Furthermore, as there is only radiation during the day, the discontinuity of energy is high, and it will be more necessary than ever to be able to store it to use it during the night.

Therefore, it is important to ensure a lifespan of no less than 30 years, as provided by higher quality panels, and to evaluate options for optimizing the use of this energy. This can be through storage in batteries, an option still in its infancy, or through storage in the form of hot water, for example, via an aerothermal machine that uses electricity to heat and store water in an inertia tank.

Storing energy

As we have been indicating across the various electrical energy generation systems, the importance always lies in where to store it. This is especially true for photovoltaic panels due to their discontinuity of capture between day and night, intrinsic to solar radiation.

A relatively recent option is Tesla batteries, the product currently offering the greatest autonomy on the market, although other companies manufacture domestic batteries, such as Nissan and Solar Rocket.

Tesla is a pioneering company in the manufacture of electric cars that is positioning itself in the domestic battery sector, aiming to revolutionize the way we produce and consume energy. This is very good news at the Spanish level, where the implementation of the so-called Sun Law meant a total penalization of self-consumption, by not allowing the surplus energy generated to be fed back into the grid for possible use by other users.

Although these batteries can be applied to different systems, including non-renewable energy sources, they are designed to work alongside a photovoltaic panel installation. The number of batteries needed for a house depends on the size and energy demand of the home, which results in the installation of approximately one or two batteries for the supply of a home, as well as for homes prepared for the climate emergency.

In the case of Tesla models, the PowerWall 2 model reduces its dimensions so much that it aims to become practically a household appliance, specifically reaching 80 cm x 115 cm x 15 cm. It weighs 120 kg, which allows it to be hung directly on the wall. Furthermore, its installation is possible both indoors and outdoors, safe for human contact, and requires no maintenance. In a pioneering way, it can be controlled via electronic devices to constantly monitor its performance and analyze its possible optimization.

It has an energy capacity of 13.5 kWh, with an efficiency of 90%. The price fluctuates around €7,500, which makes it possible to consider a potential amortization of the investment in a few years, as it is an installation that will allow us to completely disconnect from the electrical grid. For its part, Nissan offers its xStorage domestic battery, weighing 60 kg, with a power of 4.2 kWh and a value of €4,000.

However, we are talking about devices with a very high ecological manufacturing cost that we must not fail to take into account in the analysis of their life cycle.

Production of hot water for heating and DHW

What options do we have for heating water?

Biofuel

Biofuel is an option based directly on tradition, which considers the land as a resource and also values its local character. If we commit to the sustainable growth of forests that provide us with organic waste that we can burn to obtain DHW and heating, we can have this need met in a self-sufficient way.

However, it is true that if we consider an average plot of about 500 – 1,000 m², we cannot ensure wood self-sufficiency. That is where community collaboration becomes relevant, as well as the presence of a local forest park managed for such a purpose.

The most widespread criticism of energy generated through the burning of biofuel is precisely the fact that it is generated through combustion, as that produces greenhouse gases (GHG). However, we are talking about the combustion of a material that has been absorbing CO₂ throughout its life, so the ecological footprint ends up being balanced, and can even become negative.

Two positive aspects when evaluating the feasibility of building a house with biomass are the possibility of amortizing the initial investment in about 2-3 years, thanks to its high power and low cost. Thus, being combustion, we can obtain a large amount of energy in a short time with an investment much lower than that of aerothermal and geothermal systems.

The demand for DHW and heating in a home can be resolved with a 16-25 kW boiler, with a budget of €2,000 to €3,000. Similarly, individual stoves of 7-10 kW are sold in Spain for about €800. However, it is true that it is a system in which a monthly fuel price must be taken into account. Fortunately, unlike diesel, the trend for pellets is downward as it is a renewable material.

Geothermal energy

Geothermal energy is based on the stability of the temperature inside the earth, which remains the same all year round at a depth of 20 m. Through this difference between indoor and outdoor temperature and thanks to the use of a heat pump, we manage to extract thermal energy continuously.

Thus, the value of geothermal energy lies in its stability; 24 hours a day, every day of the year, it produces energy regularly without being affected by the weather, making it very suitable for homes prepared for the climate emergency. Consequently, it will be more efficient in continental climates than in temperate ones. Other benefits include the possibility of installation in already built homes and its zero aesthetic impact as it is buried.

However, the need to excavate wells increases its installation cost, making it up to 20% more expensive than the installation of its alternative, aerothermal energy. An approximate budget for a single-family home of 200 m² involves a total of €25,000 – €30,000, taking into account the cost of the geothermal heat pump and its accumulator (€12,500), two geothermal collection probes (€5,000), and an alternative photovoltaic installation with its distribution system, such as underfloor heating (€5,000).

Among all renewable energies, the installation of geothermal energy is the one that requires the greatest initial investment, so it is very important to evaluate the profitability in the medium and long term, with an amortization time calculated at about 7 years thanks to its high performance.

Aerothermal energy

Aerothermal energy is based on utilizing the air temperature, requiring only an outdoor unit to capture the air temperature. The biggest handicap is the lack of continuity of this energy, which reaches a capture peak in summer, a time when demand is minimal.

A negative point of building a house with aerothermal energy is primarily the price, as it requires a series of quite expensive installations. An example is the inertia tanks, necessary because aerothermal energy does not allow for immediate hot water like a gas boiler, which works at high temperatures, and that represents an additional cost. The heat emitters associated with this energy generation system are also expensive, both underfloor heating and low-emissivity radiators.

With all this, the installation costs of an aerothermal system for a single-family house in the same 200 m² home we analyzed for geothermal energy include an aerothermal heat pump with an accumulator (€12,500), with a data management system and an outdoor temperature probe, as well as the alternative photovoltaic installation and a distribution system (€5,000). The final budget ranges between €20,000 – €25,000, with an amortization time of about 10 years due to its lower performance compared to geothermal energy and its lack of continuity.

On the blog, we developed a comparative article between these two energies under the title Differences between geothermal and aerothermal energy.

Solar or thermodynamic panels

There is an alternative consisting of panels that allow energy to be stored via hot water, i.e., thermal energy. Their technology consists of heating a heat-carrying liquid found in the tubes that compose them. They are primarily intended for the production of hot water for bathrooms or heating and do not depend directly on the sun to capture energy. In fact, they are capable of generating thermal energy on rainy or cloudy days.

Solar panels represent an efficient option in relation to their competitive prices when compared to photovoltaic panels, due to their much simpler system. They can cost less than €100 compared to the minimum €8,000 that a photovoltaic panel is worth. Furthermore, they are a good investment as they can be amortized in 5 years.

Food supply

As we indicated at the beginning of the article, in the event of a climate emergency or any other type of crisis, food supply becomes indispensable. If we manage to also turn our home into a solution for our food supply, or at least ensure fresh products, we will have much less to worry about when facing an adverse situation.

To all this is added all the benefits that having a vegetable garden brings us for growing our own food, utilizing the land as a base for vegetation growth. By carrying out this practice, we are achieving economic as well as ecological savings, becoming aware of the investment of time and care that such a practice requires.

The benefits of self-grown products are many, from their naturalness, the fact that they are organic and local, to the ecological savings on transport and their absence of chemicals and transparency of information.

At the same time, we are becoming aware of our excessive meat consumption, simply caused by the ease with which its purchase is offered to us and the disconnection from the ecological implications of its production.

Furthermore, the space and attention requirements for a vegetable garden can be turned into an excuse to generate collaborations between neighbors and social fabric. Perhaps it is not worth having a plantation for a single family, but we find a way to share a garden and generate a sense of community around it.

To all this, we bring up the subject of the dry toilet, which instead of consuming water and generating wastewater, provides us with so-called compost, which we can reuse to fertilize our garden. This will allow us to do without fertilizers and ensure the naturalness of our food.

Waste

Awareness of waste reduction alongside consumption reduction is the next step. In fact, the concept of the Zero Waste Home that we developed in a blog article is increasingly relevant, with its 5R philosophy (refuse, reduce, reuse, recycle, and compost). It is not so much an economic cost, but a constantly critical and revisionist attitude.

In the case of a total disconnection from the grid by homes prepared for the climate emergency, we have to add the variable of what we do with waste production, as well as the water we are going to discard.

Waste

Ideally, our waste production can become solely organic, as we have previously applied the first 3Rs (refuse, reduce, and reuse).

At this point, we have the option to recycle, which in most cases we entrust to public management without realizing that only half of the waste actually gets recycled. Therefore, the best option is to generate only organic waste, which we can use to turn into compost, achieving a home that neither consumes grid energy nor generates waste that it cannot self-manage.

Sanitation

Regarding the management of waste resulting from sanitation, we return to the logic of prevention being better than cure. Blackwater is very difficult to manage, and in the best-case scenario, it accumulates in a septic tank that must be emptied annually. However, we can avoid the generation of this waste through a dry toilet, leaving only greywater to be managed.

Greywater comes from personal hygiene, washing machines, or household cleaning. If we take the precaution of not using products containing chemicals, this water can be filtered naturally in a wetland with plants or serve directly for irrigation at the end of its ‘useful life’, thus generating zero sanitation waste.