Simulation of the influence of an attic on the building energy efficiency in the Portuguese climate.

The thermal performance of the building envelope is of critical importance to the overall building performance. This paper presents an investigation of the influence of most common attic typologies used in Portuguese housing stock on heating/cooling loads of conditioned spaces under different weather conditions. Unused attics are part of the building envelope, which provide protection from the external environment acting as a buffer space. To improve this protective ability, some scenarios such as insulation, low emissivity, ventilation and the slant of the roof are considered. The aim of this study is to assess the influence of such scenarios by investigating through simulating the heat transfer between the attics and spaces underneath. The extent to which an improved attic steers towards low energy buildings is established where a dynamic U_d-values can be as low as 0.15 W/(m²K) and the yearly thermal reduction may surpass 20%. [ABSTRACT FROM AUTHOR]