GENERAL INFORMATION

Single Family House TR80

Construction year: 2023

Climate zone: Csa - Hot-summer Mediterranean climate

Barcelona, Spain

Architect

Batlleiroig, Authors: Joan Batllei i Clàudia Amías
Owner

Private owner
Consultant

-

Architect

Batlleiroig, Authors: Joan Batllei i Clàudia Amías
Owner

Private owner
Consultant

-

The renovation project for the TR80 single-family house in Barcelona is developed around three fundamental principles: the life cycle of materials, energy efficiency, and efficient water management. The combination of these three starting points has resulted in a refurbishment that respects the built heritage while responding to contemporary needs for sustainability and comfort, achieving a Passive House Plus certification. The project is located in a Barcelona neighborhood built between 1946 and 1953 in a post-war context, driven by the need for affordable housing construction. Today, it has become a neighborhood classified as a Heritage Site with Elements of Interest. Originally, the house consisted of a ground floor and a first floor, but its rear terrace was at the same level as the building's ground floor, creating an independent basement. Our proposal consisted of removing the floor slab between the basement and the terrace, modifying the elevation, and connecting this outdoor space with the basement level, thereby creating a garden at the rear. Given the project's construction pre-existences, it was decided to conceive the new project like a Matryoshka doll: a historical, heavy, and rigid outer box containing a modern, lightweight, and flexible inner box. The interior structure not only supports the existing facade but also allows for a home free of structural constraints, improving its thermal and acoustic insulation as well as indoor humidity levels. This strategy allowed us to preserve the external appearance of the house without compromising on a comprehensive upgrade. The design principles applied to the project regarding Energy are divided into two main strategies. The first is based on solving the building's performance at a passive level through its construction systems. Since it was a renovation of a building oriented mainly East-West, the proposal incorporates improvements to the thermal performance of the existing envelope, the elimination of thermal bridges, high-performance windows, guaranteeing high airtightness, and the incorporation of solar shading. The second strategy focuses on active systems; thus, it is designed under the requirements of the Passive House Plus certification through a controlled ventilation system with heat recovery, powered by high-performance aerothermal energy. Additionally, a photovoltaic production system is integrated onto the roof to guarantee self-consumption.

Building gross area & Net area

180 m²

Number of floors above ground and below ground

1 floor above ground and 1 below the ground

Average net area per dwelling

180 m²

Types of outdoor and common areas

The garden includes two strategically placed deciduous trees to provide shade and color depending on the season.

Charging station (yes/no)

Yes

Other relevant aspects

The house is developed according to the passive house principles achieving a Passive House PLUS certificate.

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S(ch)austall renovation, naumann. architektur

Technology solution sets

Heating, cooling and ventilation

The official definition of the Passivhaus standard states: "A passive building is one that can guarantee climate comfort by supplying energy for heating and/or cooling solely through ventilation air. This ventilation flow rate is the minimum required to guarantee hygiene in interior spaces (30m2 per person in residential use)." This is why the project's active systems are resolved through a dual-flow ventilation system equipped with a heat recovery unit. The cooling and heating coil is powered by a specific aerothermal system. In contrast, the DHW (Domestic Hot Water) relies on its own small, low-capacity, low-consumption aerothermal unit. Separating the aerothermal systems allows the former to be turned off for six months of the year; furthermore, during the summer, it prevents the system from having to reverse its cycle every few minutes to generate DHW, thereby reducing energy consumption and improving the durability of the equipment. The Water Cycle: The house features three distinct water circuits for different functions. Potable water is used exclusively for cooking and personal hygiene. The greywater collected from the showers and bathroom sinks is routed to a treatment system for filtration and storage. It is subsequently used to flush the toilets, and any surplus drains into a large rainwater storage tank. Rainwater from both the house roof and the side porch is collected in this tank. All of this accumulated water is then used for irrigation and cleaning. Under a high-occupancy lifestyle, the home uses an average of 80 liters/day of potable water per person, whereas the average in the Barcelona metropolitan area stands at 106 liters/day per person.

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Building Technology	Type of System	Technology	Distribution System	Product Manufacturer or Company	Consultant
Primary Heating System	Centralized	Air source heat pump	Air	Mitsubishi	-
Cooling System	Centralized	Air source heat pump	Air	Mitsubishi	-
Ventilation	Centralized	Balanced mechanical ventilation with heat recovery at building/apartment/room level Not integrated with the heating system (Electric boiler)	Air ducts	Zehnder	-
Domestic Hot Water	Decentralized	Not integrated with the heating system (Electric boiler)

Renewable energy production

The Passive House Plus standard requires the building to produce at least as much energy as it consumes. Due to the bioclimatic strategies applied in the design, the heating and cooling demands are limited to 5 kWh/m² and 17 kWh/m² respectively, remaining well below the certification thresholds. Including lighting and domestic hot water (DHW), the total annual energy demand is estimated between 5,500 and 5,600 kWh/year. These figures may vary depending on user behavior and the specific operation of lighting and DHW systems. To offset this consumption, the project incorporates a photovoltaic system with 11 panels (divided into groups of 5 and 6 units) facing East-West, covering a total solar collection area of 21 m² (approximately 1.86 m² per panel). Each module has a peak power output of 425 Wp, resulting in an installed power density of 235 Wp/m² and a total system capacity of 4.73 kWp. The annual electricity production is estimated at 5,700–5,800 kWh. Consequently, the building achieves a net-positive energy balance. However, it should be noted that this energy balance calculation excludes electric vehicle charging and other auxiliary uses.

Electrical storage battery:

No
Photovoltaic rooftop system:

422 kWp each panel

Energy Renewable Technology	System Type	Main PV Panel orientation	Total Installed Capacity (KWP)
PV Systems (KW peak installed, surface area, total or per m²)	Roof integrated PV system	East West	4,75

Envelope technology

Building envelope

Ecological Construction: The Matryoshka Strategy Since the building was heritage-listed due to its external appearance but was in a severe state of decay and completely outdated regarding contemporary environmental standards, the decision was made to preserve the facades and construct a new shell within. This new inner skin had to provide high insulation and a net-zero carbon footprint; therefore, timber was chosen as the primary material. Designing to the millimeter—as if it were a Matryoshka doll—posed a significant challenge. Maintaining a continuous 4 cm perimeter gap between the two boxes was highly complex, as the existing historical structure had been built with traditional, less precise methods and was out of plumb in all three dimensions. Despite this, the assembly was executed with millimeter precision, piece by piece, until the puzzle was completed. To optimize the thermal envelope and prevent condensation, this 4 cm cavity was subsequently filled with blown-in EPS beads, creating a continuous insulation layer. Timber Structure and Rapid Assembly To minimize the carbon footprint and ensure a highly efficient envelope, the new structure was built using local timber from the Catalan Pyrenees and assembled using highly industrialized processes by a specialized local company. In just 15 days, all three levels and the roof were erected, significantly accelerating the construction process and minimizing waste. Airtightness, Waterproofing, and Windows: The sealing of the house is divided into two distinct functional layers: 1. The Outer Layer (Waterproofing): A waterproof yet breathable membrane placed on the exterior of the lightweight timber frame, which continues seamlessly across the roof. 2. The Inner Layer (Airtightness): A vapor barrier and airtight membrane placed on the interior side of the timber frame. Following a hydrometric study of the facade, this membrane was specified with variable vapor permeability depending on whether it was in contact with the ground (basement) or the outdoor air. All window joints were detailed using three levels of sealing: expansive tape on the exterior, elastic foam around the perimeter, and sealing tape on the interior, supplemented with liquid sealant for the corners. Finally, the main entrance door was designed with the exact same performance specifications as a window to avoid creating a thermal weak point. All windows feature triple glazing filled with argon gas and warm-edge thermal break spacers. Nature as a passive strategy The incorporation of the garden into the proposal allows biodiversity to be used as a passive strategy to improve the building's energy performance. The garden includes two strategically placed deciduous trees to provide shade and color depending on the season. Additionally, the garden features a vegetable patch and a composting unit to close the nutrient loop and minimize waste. The climbing plants are designed to act as seasonal shading elements, reducing radiation during the summer.

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The construction features a hybrid timber system: the external walls consist of a lightweight timber frame with insulation inside, while the interior walls and floor slabs are made of Cross-Laminated Timber (CLT). The Facades: Insulated with 12 cm of wood fibre plus 4.5 cm of rock wool within the interior service cavities. The air gap between the existing wall and the new structure was filled with 4cm EPS insulation

Wall	Material Used	U Value
Wall type 1	Exterior to interior: Existing brick wall + 4cm EPS Insulation + Timber frame with 12 cm of fibre insulation + 4,5 internal linning with mineral wool.	0,17

The Roof consist on a ventilated Mediterranean tile roof insulated with 16 cm of rock wool above the CLT.

Roof	Material Used	U Value
Roof type 1	Ventilated Mediterranean tile roof insulated with 16 cm of rock wool above the CLT.	0,18

The floor slabs consist of 15 cm cross-laminated timber (CLT) panels, complemented by a batten system housing rockwool insulation, an impact-sound insulation membrane, and finished with a hardwood parquet floor. The Ground Slab is Insulated with 12 cm of XPS due to its direct contact with the ground.

Basement: Yes

Heated basement: Yes

Partially heated floors: No

Due to the project's pre-existing conditions and the fact that it is a listed building, the window-to-wall ratio was dictated by the existing structure. Consequently, the selection of windows was crucial to guarantee sufficient solar heat gains. For this reason, the choice of the solar factor was highly relevant in this case, with a value of 0.62

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Window	U Value	G Value	Shading Type
Window type 1	1,1	0,62	Shutters /Venetian blinds

Performance and energy savings

Use stage

Energy use in relation to consumption is determined by its annual performance. Regarding the self-production comparison, the value stands at 104%, since the annual balance shows a higher production than consumption.As for self-consumption, it remains subject to monthly behavior. As shown in the image, energy demand exceeds production during the winter months, while the trend reverses in summer, generating significantly more energy than required. Consequently, the self-consumption balance stands at 75%."

Primary energy demand

5.500 kWh

Self-generation

n/a

Self- consumption

n/a

Yearly PV energy production

5.700 kWh

Culture and climate

Actions that impact energy performance

The Climate of Barcelona Living in a city where temperatures remain close to user comfort zones practically all year round encourages the active use of both indoor and outdoor spaces. Admittedly, summer periods are characterized by high humidity and a muggy sensation, which makes outdoor spaces uncomfortable during peak hours. Despite this, the climate zone allows the local culture to remain deeply tied to outdoor social and sporting activities throughout the year. But How Do You Live Without Opening Windows? Waking up every morning breathing fresh air, with humidity levels maintained between 40% and 50%, and a temperature that does not vary by a single degree all night—regardless of the weather outside—is priceless. The home has no dedicated heating or conventional air conditioning system, yet it remains at the user's desired temperature. The ventilation system is equipped with an inline heating and cooling coil that conditions the ventilation air itself. This minor energy input alone is capable of maintaining the house at the ideal temperature. Additionally, a dehumidifier is integrated to handle the muggiest periods of the summer. Biophilic Spaces Having a garden at the rear of the property allows residents to enjoy the home's outdoor space all year round, while reinforcing the connection between the users and natural environments. These biophilic spaces have been designed to include a vegetable garden for self-consumption.

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©ELKE

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Culture Climate Survey

Discover more about cultural aspects

Peb tips for designers by designers

How to achieve successful Plus Energy Buildings

Advice on building technologies

Decoupling HVAC and DHW Production: Separating the production systems for climate control and Domestic Hot Water (DHW) significantly enhances overall system efficiency. Separating the aerothermal systems allows the climate unit to be turned off for six months of the year. Furthermore, during the summer, it prevents the system from constantly reversing its cycle every few minutes to generate DHW, thereby reducing energy consumption and extending the equipment's lifespan.

Climate and cultural adaptation

Proactive Comfort Management: In projects engineered for high energy performance—such as those achieving Passivhaus Plus certification—it is crucial to design the property so that users do not feel the need to open windows as a reactive measure to discomfort. Implementing mobile solar shading solutions is an excellent way to proactively mitigate overheating. Outdoor Integration: From a cultural standpoint, particularly within the Mediterranean climate, providing functional outdoor living areas—such as gardens or similar spaces—is essential to support the local lifestyle.

Building certification process

Early Integration: Certification protocols should be initiated at the earliest stages of the project. Understanding all compliance criteria from day one and being proactive in gathering data prevents unforeseen bottlenecks during the final review phases. Continuous Auditor Engagement: Establishing a fluent channel of communication with the certifying entity during the initial design phases helps align expectations, streamline the approval of strategies, and avoid costly mid-construction corrections. Rigorous Data Traceability: Comprehensive documentation of energy models, material properties, and mechanical efficiencies is vital. Keeping structured records of the building’s technical components is key to successfully passing the audits.

Tools and software

Cost optimisation

Prioritize High-Durability Passive Systems: Focus financial resources on the building envelope and passive strategies that will outlast the building’s lifecycle. Investing upfront in the envelope minimizes long-term operational costs; active mechanical systems will inevitably evolve technologically and can be easily upgraded or replaced over time, whereas passive systems are permanent. Design for Structural and Systemic Simplicity: Straightforward architectural geometries and uncluttered mechanical layouts significantly lower both construction and future maintenance costs. Aim for a design where functionality and simplicity go hand in hand.

Resident interaction

In our specific case, the project was driven by the end-users themselves. Nevertheless, certain steps regarding design and implementation are highly recommended: User Training and Onboarding: Being actively involved in the process has allowed the users to understand how the home's systems operate, helping them grasp best practices and the building's overall behavior. Tailored End-User Design: The project was explicitly designed for the end-users. This fact also helps optimize spaces and rooms to align perfectly with their specific lifestyle. Control Mechanisms: Incorporating real-time data tracking for both energy consumption and production empowers the users to make voluntary, informed decisions regarding responsible energy use

Performance challenges

Net-Zero vs. Extended Demands: The primary objective was to achieve a net-positive energy balance on an annual basis, which factored in standard domestic energy use. However, the main challenge arises when incorporating energy demands not traditionally linked to the building itself, such as charging stations for electric cars and motorbikes. Under this scenario, achieving a completely net-positive energy balance becomes significantly more complex.

External services

Structural Engineering: To design a sustainable building with key overall strategies and an optimized structure. HVAC and Renewable Energy: To design energy-efficient heating, cooling, and energy generation systems (e.g., photovoltaic panels and heat pumps). Sustainability Consultant: To design energy-efficient heating, cooling, and energy generation systems (e.g., photovoltaic panels and heat pumps) combined with the assessment of energy usage. Passivhaus Certification Specialist: Involved during project decision-making to calculate optimal insulation, airtightness, and thermal bridging.

Policy barriers

Grid and Energy-Sharing Restrictions: A major hurdle encountered involves the regulatory frameworks governing the distribution of self-generated photovoltaic energy.

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