- ≈30%
- of final energy use in Portugal is associated with buildings
- 20.8%
- of people lived in households unable to keep the home adequately warm, 2023
- 1 system
- window = glazing + frame + seals + hardware + installation
An efficient home does not start with the machine that heats or cools it. It starts with the building itself.
A good window can make a difference. But a home is not a window.
When a home is too cold in winter or too hot in summer, the first reaction is often to look for a more powerful system: more heating, more air conditioning, or new windows.
All of those can be valid. But the order of decisions matters. According to Portugal’s Directorate-General for Energy and Geology, buildings account for approximately 30% of final energy consumption in Portugal. Comfort also remains a real issue: ADENE reports that, based on 2023 data from Statistics Portugal, 20.8% of the population lived in households unable to keep their home adequately warm.
Double glazing does not automatically mean an efficient window
A window is a system. It includes glazing, frame, hardware, seals, shutter boxes, installation and the junction with the wall.
Portugal’s CLASSE+ system allows consumers to compare window energy performance and stresses an important point: an efficient product must also be installed correctly to deliver the expected comfort and energy-saving benefits.
So asking only “is it double glazed?” is not enough. The performance of the whole assembly matters.
Solar exposure matters too
In the Algarve, this is particularly relevant. Large windows can provide excellent daylight while also introducing significant solar gains during the hotter months.
Orientation, opening size, glass specification and shading should be designed together. A good strategy may include overhangs, shutters, blinds or other forms of solar control. The aim is not to eliminate the sun. It is to use it when useful and control it when it causes overheating.
Then comes the rest of the building envelope
A home can have excellent windows and still lose energy through the roof, walls or other junctions. This is why energy upgrades should consider the building as a whole.
Roof insulation may have a major effect in one property while the main weakness in another may be the windows. An Energy Performance Certificate can support this diagnosis by identifying potential improvement measures for existing buildings.
Only then should we ask: “which system?”
Air conditioning, heat pumps, underfloor heating and other systems should not be considered in isolation. First ask: how much heat enters or leaves this home? Then: how much energy do we actually need to provide to maintain comfort?
The better the building performs passively, the lower its dependence on active heating and cooling may become. That is the difference between installing equipment and designing comfort.
