Regulations & Installers · Vayron

Ventilation in Spain: the CTE and RITE regulations every installer needs to know in 2026

Updated September 2026 · 8 min read

Fir forest in the mist

If you install ventilation systems in Spain, knowing the current CTE and RITE regulations is not optional. The Código Técnico de la Edificación (CTE, the Spanish Building Code) and the Reglamento de Instalaciones Térmicas en Edificios (RITE, the Spanish regulation on thermal installations in buildings) set the minimum requirements that any installation must meet, and failing to comply can mean anything from a rejected project to legal liability towards the customer.

In this guide we go over the key regulatory points that directly affect your day-to-day work as a professional installer: minimum airflows, IDA categories, when VMC (mechanical ventilation) is compulsory, the grants available in 2025 and the mistakes that come up most often on site.

The CTE and basic document HS3: indoor air quality

The Código Técnico de la Edificación (CTE) is the reference regulatory framework for construction in Spain. Within it, the Documento Básico de Salubridad, section HS3 (basic document on health, indoor air quality), specifically regulates ventilation conditions in residential buildings.

The DB-HS3 sets the minimum ventilation airflows that any residential installation must guarantee, and these vary depending on the type of room:

  • Dry rooms (living rooms, bedrooms): the minimum outdoor airflow is calculated on the basis of the number of occupants and the floor area of the room.
  • Wet rooms (kitchens, bathrooms, toilets): specific extract airflows are set, regardless of occupancy.
  • Storage rooms and garages: have their own requirements depending on their floor area and use.

A common mistake among installers is sizing the system below the airflows required by the DB-HS3, especially in renovations where the customer asks for "something small and cheap". The customer needs to understand that regulatory compliance is not negotiable, and it is always best to document it in the quote and in the technical report.

The RITE: when it applies to ventilation installations

The Reglamento de Instalaciones Térmicas en Edificios (RITE) comes into play when ventilation is linked to an air conditioning system or when dealing with non-residential buildings (offices, hotels, retail premises, healthcare centres). In these cases, the RITE establishes:

  • Indoor air quality categories (IDA): from IDA 1 (optimum quality air, for hospitals and operating theatres) to IDA 4 (low quality air). Most offices and retail spaces require IDA 2 or IDA 3.
  • Minimum airflows by IDA category: the higher the quality category required, the greater the outdoor airflow needed per person or per square metre.
  • Air filtration: the RITE also regulates the filtration levels required according to the IDA category and the outdoor air quality (ODA).

For installations in existing buildings with a nominal output above 70 kW, the RITE also requires periodic inspections, and maintenance must be documented in a maintenance log book.

Ventilation in new-build homes vs. renovation

The regulations do not apply in the same way in every scenario. As an installer, it is worth being clear about the difference:

  • New build: the project must fully comply with the CTE DB-HS3 from the design stage. If you find that it is incorrectly sized, you must report it in writing.
  • Renovation or refurbishment: the resulting installation must not worsen the previous conditions and, wherever technically feasible, should come as close as possible to complying with the DB-HS3.
  • Change of use: if commercial premises are converted into a home, or vice versa, the requirements of the new use category apply — an increasingly common scenario in cities such as Madrid or Barcelona.

VMC and mechanical ventilation: compulsory in new builds

Since the 2019 update of the CTE, new buildings must guarantee that the ventilation system works regardless of outdoor weather conditions. In practice, this has driven the adoption of VMC (mechanical ventilation) systems, both extract-only and heat recovery (double-flow).

For installers, this translates into:

  • Greater demand for VMC installations in new residential builds.
  • Better-informed customers who specifically ask about heat recovery (double-flow) systems.
  • The need to technically justify the chosen system to the owner and the project management team.

Heat recovery VMC systems, in addition to complying with the regulations, offer a solid sales argument: they cut the heat losses associated with ventilation by up to 80%, which translates into direct savings on the end customer's energy bill.

Grants and subsidies available in 2025

This is one of the areas where you can really set yourself apart from the competition: knowing which grants are available and proactively offering them to your customers.

  • Plan de Recuperación (Recovery Plan, Next Generation EU funds): through the home energy renovation programmes (PREE and its regional successors), improvements to ventilation systems are subsidised when they form part of a comprehensive renovation.
  • IRPF (personal income tax) deductions: energy efficiency improvement works on a main residence qualify for deductions of up to 60% of the investment. A heat recovery VMC system contributes directly to that improvement.
  • Regional grants: regions such as Catalonia, the Basque Country and Madrid have their own energy renovation grant schemes. It is worth knowing the ones in your region.

Common regulatory mistakes you need to avoid

  • Insufficient airflows in kitchens: the DB-HS3 requires a minimum extract airflow of 50 l/s in kitchens with an extractor hood. Many installations fall below this value.
  • Poorly positioned air valves: the regulations set distance criteria between supply and exhaust air valves to avoid air short-circuiting.
  • Lack of documentation: the CTE requires the installer to hand the owner a document with the characteristics of the installation and the operating and maintenance instructions.
  • Not checking the airtightness of the ducts: leaks in the network can significantly reduce the performance of the system and mean the required minimum airflows are not reached.

Conclusion

Ventilation regulations in Spain are more demanding than many customers — and some installers — assume. Knowing them in depth not only protects you legally, but also makes you a go-to professional capable of advising beyond price.

Technical contact: tecnico@gtsystems.es · Web: https://vayron.es/