barcelona Green living health Reflections

How to achieve a sustainable and healthy home. Part 1: energy & water

By Paloma de NiuGreen, architect and co-founder of Niu Green; a Barcelona studio specialized in sustainable renovations.

If you are reading this, you have probably bought organic food, reused some furniture, saved on water, or even considered using a scooter or bicycle, either for your health or for sustainability. For years we have had options for greener food and transportation available to us, but have you thought about what happens to your home? We spend between 80 and 90% of our time indoors in more polluted spaces than outdoors, which greatly impacts our health. As if that were not enough, housing is usually our biggest energy, as well as economic expense.


This story, our story, began with a kind of restlessness. We lived in the city, but we loved nature. We wanted to live comfortably, but we were concerned about our impact on the environment. In short, we asked ourselves — “would it be possible to live sustainably in Barcelona?” Up until that time, there seemed to only be solutions for single-family houses and new buildings.

But what about all of us who lived in an apartment in the city?

Pablo is an engineer, and I am an architect. We wanted to improve our lifestyle, so we decided to look for an apartment and refurbish it. Being a pilot project, it had to have a limited surface, about 70m2, and be a penthouse. Although it has advantages, such as views or light, it was a big challenge because of how exposed it was climatically. We eventually found our guinea pig — a bright apartment in the Sagrada Familia neighborhood, in a beautiful building from the ’70s.

After two years of research, design, and renovation, of innovating and creating new solutions, but also recovering traditional solutions, we created the first sustainable housing project in Barcelona: Projecte À-tic. Today, we not only live in this apartment, but we’ve also opened its doors to the public to share and verify the results. Because it works!


So what is a sustainable home to us? It is one that provides a high level of comfort and health with a low environmental impact, which translates into ecological and economic savings. To achieve this, we studied the existing energy certifications, looking at water and energy, materials and health. Although these did not apply to apartments, only to buildings and houses, the development of some parameters could make our home a sustainable and healthy space.

Today we will tell you how we reduced our water and energy consumption through the integral renovation and what changes you can make even if you live in a rented apartment.

We will leave the two more qualitative aspects, materials and health, for the next article.

ENERGY: 65% savings

Thanks to an energy study, we found that 70% of consumption comes from air conditioning (heating and air conditioning) and domestic hot water (DHW), and therefore offer the greatest potential for improvement. The first step to reducing our energy demand requires working on the building skin. We started by insulating the façade and exterior walls with natural cork, avoidingg conventional materials such as rock wool and polyurethanes, whose particles we end up breathing.

In the openings, we installed wooden windows with high thermal capacities: wood is an insulating material by nature, unlike aluminum or PVC. They are all casement windows, as they are much more airtight than sliding windows.

We also incorporate passive elements, such as the pergola with vegetation and awnings that prevent overheating in summer, or the blinds, which prevent temperature losses in winter. They are automatically controlled by a domotic system focused on energy efficiency; it also manages the air conditioning, reducing consumption whenever possible, at night and by zones.

To reduce our consumption, we have water underfloor heating, which not only uniformly and pleasantly heats our home – and our feet! -but requires water at a low temperature compared to conventional radiators that reach 60ºC. Also, the hot water is generated with an aerothermal pump, a system that consumes 25% less than conventional pumps, reducing our consumption in showers and air conditioning. Of course, high-efficiency appliances were used, taking care of details such as not paneling the refrigerator, which would penalize its consumption. Thanks to the combination of the different systems applied, we have managed to reduce demand – and the bill – by 65%.

What if I live in a rented apartment?

You can always, always make small interventions. For example, evaluating the Isolation by detecting leaks in the windows. If you put a piece of paper near the frame on a windy day and it moves… you have a draft. If you can’t convince the owner to change them, you can at least seal them with weather stripping or insulating gaskets.

Even so, it is often our own use that increases our consumption. For example, in winter, it is advisable to ventilate for 10 minutes and, if possible, during the warmest hours of the day. Remember that an open window is like an open faucet!

Another problem we often see is the use of heaters. As soon as you get home, you turn it on full blast in the living room and bedroom. This can consume more than having all the radiators in the house on, which have more inertia than any air system and keep the temperature more constant (no ups and downs).

Finally, a great advantage we have today is that we can decide how and at what environmental cost all our electricity is generated, even living in the city. Companies like Som Energia provide electricity from renewable sources at more competitive prices and offering an annual analysis of your consumption with proposals to reduce it. If our schedule allows it, it is advisable to contract the service with hourly discrimination, which offers low-cost hours.

WATER: 40% savings

In a standard home in Barcelona, the average daily consumption is 105 liters per person. Of this, 60% of the water is consumed in the bathroom: 35% in the shower and 25% in the toilet – and that is if we have a dual flush.

As we did with energy, we looked for avoidable consumption points, such as daily losses while waiting for hot water to arrive to take a shower. To solve this, we installed a system that recirculates the water and prevents it from coming out until it is hot, avoiding both water and energy waste (from warm water).

Regarding the points of highest consumption, do we really need drinking water for the toilet? We decided to reuse the water from the shower for the toilet and designed a small system consisting of a pump and a 40-liter tank, which covers the daily demand of the toilet (3/6 liters per flush). The system is controlled by domotics, which automatically refills with tap water if the tank runs out. The only difference? The toilet smells like our soap.

Actually, 40% of the water in our home does not need to be potable, so we recover rainwater for the other toilet, irrigation, and cleaning of the terraces using a 300-liter tank that collects water from the communal roof and pumps it to the consumption points.

These measures have enabled us to save 40% of our daily consumption. This means about 16,000 liters per person per year.

What if I live in a rented apartment?

Good news: we can arrange the system that prevents water leaks until it is up to temperature in the shower. All we need is a space under the sink and an outlet nearby.

Another essential: change the chain to dual flush if you do not have it. If the toilet is not very old, we can buy the double flush button in any hardware store and change it from 15 liters to 3/6 liters per flush.

And finally, again we must insist on our use: “I wash the dishes by hand because of these couple of things”… Do you know that the new dishwashers nowadays only consume 10 liters per wash?

Our homes consume 40% of the planet’s energy, and we breathe them every day. Perhaps you can apply a single solution; perhaps you can transform your home: the options are already available. Projecte À-tic is one example, but what would happen if we all joined in?

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