Describe when and where overheating happens
Record the hottest rooms, window orientation, floor level, roof exposure, existing shading and the times when discomfort is worst. Note indoor and outdoor conditions, occupancy, cooking and equipment use. A west-facing living room with afternoon sun is a different problem from a top-floor bedroom under a poorly performing roof.
Spain does not have one summer climate. Night-time cooling opportunities, humidity, urban surroundings and noise differ between locations. Ask the assessor to explain the main heat gains and constraints for this apartment. An energy rating provides useful information, but do not treat a single letter as a room-by-room overheating diagnosis.
Reduce unwanted sun before choosing a new window
IDAE’s household guidance includes using awnings and shutters to reduce summer heating and ventilating during cooler hours. Establish which windows actually receive direct sun and at what time. External shading, where permitted and correctly designed, can intercept radiation before it enters; an internal blind serves a different position in that path.
Compare the shading geometry, usable daylight, wind exposure, maintenance and how it will be operated. An awning that must stay retracted during common local conditions may not provide the planned protection. Check whether existing persianas can be repaired or controlled more effectively before assuming every opening needs replacement. Do not promise a universal temperature reduction from a product label.
Treat glazing, frame and installation together
Ask for the whole window specification: thermal performance, solar characteristics, frame, seals, shutter box and the perimeter installation detail. A quoted glass value alone does not describe the installed opening. Solar control and winter heat retention are related but different decisions; choose with orientation, shading and daylight in view.
IDAE’s insulation guidance treats the building envelope as a connected set of elements. Replacing windows while leaving a weak shutter box or unresolved junction can limit the result. Interior insulation also needs an assessment of moisture, thermal bridges, space loss and detailing. Have the professional assess the applicable requirements rather than choosing thickness from a generic online example.
Preserve ventilation when making the flat tighter
Cooler-hour airing can help only when outside conditions and the dwelling make it useful. Check temperature, air quality, security and noise, and whether a genuine airflow route exists. Leaving a window open to hotter outside air is not a universal cooling strategy. Night ventilation may be constrained in a noisy street or during a warm night.
CTE DB-HS3 sets out a ventilation strategy for indoor air quality, including the relationship between air admission, passage and extraction. Have applicability and the existing system assessed when changing windows or room layout. Background ventilation is not the same as occasional window airing; a recirculating appliance is not a substitute for the whole dwelling’s ventilation system.
Match the intervention to the problem
| Observed problem | Proposal to investigate | Check before ordering |
|---|---|---|
| Direct afternoon sun through glass | Suitable external shading or solar-control strategy | Orientation, daylight, wind and facade conditions |
| Heat exposure below the roof | Roof/envelope assessment | Ownership, condition, moisture and building-wide works |
| Weak openings or shutter boxes | Coordinated window and junction upgrade | Whole opening specification and air supply |
| Little useful night airflow | Ventilation/comfort assessment | Outside conditions, noise, security and possible routes |
| High heat gains from use or equipment | Controls and suitable efficient equipment | Actual loads, maintenance and installation needs |
These are routes for investigation, not automatic prescriptions. A fan can improve perceived comfort without removing accumulated heat from the building. Where active cooling is needed, have the system sized and installed for the assessed conditions. A promise that passive work will always eliminate cooling is not a dependable design criterion.
Resolve the facade and shared-property route
Awnings, external blinds, changed windows, roof work and outdoor cooling units can affect common elements or exterior appearance. Under the LPH framework for the Madrid example, establish the ownership boundary and required community decision. Obtain the applicable colour, position and installation conditions before a non-returnable order.
Check heritage protection and the municipal route separately. An energy-saving purpose does not by itself permit a facade alteration. Coordinate proposed equipment with drainage for condensate, access for maintenance and any shared systems. If a community envelope project is already planned, ask whether private work now would be compatible or would later be removed.
Phase a budget around evidence
Start with an assessment and price complete options, including access, removal, making good, electrical work, controls, documents and any permissions. Separate a low-disruption improvement from a later envelope intervention. Do not compare an awning’s supply price with a fully installed window contract and call the difference a saving.
The energy-certificate framework provides for technically viable improvement recommendations and their sequencing. Use those recommendations as an input to a specific design, not a promise that a historical national aid scheme remains available. Keep proposed, approved and actually received support as different states.
Check the result over a comparable period
- Record the starting conditions and agreed performance intent.
- Confirm the final products and installation details before payment milestones.
- Have the installer demonstrate controls, ventilation and maintenance access.
- Keep manuals, records and the agreed defect list.
- Compare later room conditions with weather, occupancy and operation noted.
One cooler day after installation cannot establish the saving for a year. Keep observations and any next-stage decisions with the budget. Reno Pro can organise stages, costs and notes; the assessor establishes the technical solution. The aim is a coordinated improvement to the flat you occupy, with a clear reason for each investment and realistic limits on what it will achieve.
Sources, date and scope
- IDAE — Recomendaciones para el ahorro energético en hogares
- IDAE — Guía práctica de la energía para la rehabilitación de edificios: aislamiento
- BOE — Real Decreto 390/2021: certificación energética, artículo 8
- Ministerio de Vivienda / Código Técnico de la Edificación — DB-HS Salubridad: HS3, HS4 y HS5
- BOE — Ley 49/1960 de Propiedad Horizontal: artículos 7, 9, 10 y 17
- Ayuntamiento de Madrid — Guía para conocer el nivel de protección del patrimonio
Sources checked on 19 October 2026. Local procedures and examples concern the city of Madrid unless stated otherwise. IVA explanations concern the territory where that tax applies, rather than the separate tax systems of the Canary Islands, Ceuta or Melilla. Original worked calculations are teaching examples for the stated scope, not market averages or contractor offers.