Systems that use Phase Change Materials (PCM) can be used to store energy. All substances store energy when their temperature changes, but when a phase change occurs in a substance, the energy stored is higher. Furthermore, heat storage and recovery occur isothermally, which makes them ideal for space heating /cooling applications.

3.8 Colour of exterior surfaces

A light colour of surfaces is an effective solution to reduce unwanted solar gains. The quantity of radiation that is absorbed by a surface depends on its colour. Light colours are effective in reducing cooling loads, whereas dark ones are more appropriate to absorb heat in thermal storage.

3. The Portuguese Passivhaus proposal

This section presents a prototype Passivhaus proposal for Portugal. Detailed results from parametric analysis as well as the other partner’s proposals for the UK, Spain, Italy and France are available in the technical guidelines produced in the project. [6]

3.1 Concept

The Portuguese Passivhaus proposal is a two-bedroom house which complies with the national building thermal regulation 2006 (RCCTE, DL 80/2006). The prototype avoids imposing a specific layout allowing the architects the freedom of design. The strategies applicable to the Passivehaus proposal were adapted to the Portuguese context, in particular those regarding the cooling season. Special care was taken to adopt commonly-used building practices to avoid an increase of the overall cost and to ease the procurement and its implementation. The current proposal, with a total useful area of 110 m2, takes into account the local climate (case study for Lisbon). It relies initially on passive strategies complemented with simple active systems, if required. Three main aspects are explored in the proposed house: relation with the sun, ventilation for cooling and high thermal mass to control temperature swings.