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 Ud-values can be as low as 0.15 W/(m2K) and the yearly thermal reduction may surpass 20%.
ChvatalKMSCorvachoH. The impact of increasing the building envelope insulation upon the risk of overheating in summer and an increased energy consumption. J Build Perform Simul2009; 2: 267–282.
2.
KolokotsaDRovasDKosmatopoulosEKalaitzakisK. A roadmap towards intelligent net zero- and positive-energy buildings. Solar Energy2011; 85: 3067–3084.
3.
PietilaABeausoleil-MorrisonINewshamGR. Zero peak housing: exploring the possibility of eliminating electrical draws from houses during periods of high demand on the electrical grid. Build Environ2012; 58: 103–113.
4.
CarlosJSCorvachoH. Retrofit measures in old elementary school buildings towards energy efficiency. J Civil Eng Manag2010; 16: 567–576.
5.
PriantoEDepeckerP. Characteristic of airflow as the effect of balcony, opening design and internal division on indoor velocity. Energy Build2020; 34: 401–409.
6.
LechnerN. Heating, cooling, lighting: sustainable design methods for architects, 4th ed. Hoboken, NJ: John Wiley & Sons, 2015.
7.
MiranvilleFFakraAHGuichardSBoyerHPraeneJPBigotD. Evaluation of the thermal resistance of a roof-mounted multi-reflective radiant barrier for tropical and humid conditions: experimental study from field measurements. Energy Build2012; 48: 79–90.
8.
D'OrazioMDi PernaCDi GiuseppeE. The effects of roof covering on the thermal performance of highly insulated roofs in Mediterranean climates. Energy Build2010; 42: 1619–1627.
9.
LeeSParkSHYeoMSKimKW. An experimental study on airflow in the cavity of a ventilated roof. Build Environ2009; 44: 1431–1439.
10.
GaglianoAPataniaFNoceraFFerlitoAGalesiA. Thermal performance of ventilated roofs during summer period. Energy Build2012; 49: 611–618.
11.
WangSShenZGuL. Numerical simulation of buoyancy-driven turbulent ventilation in attic space under winter conditions. Energy Build2012; 47: 360–368.
12.
ToguyeniDYKCoulibalyOOuedraogoAKoulidiatiJDutilYRousseD. Study of the influence of roof insulation involving local materials on cooling loads of houses built of clay and straw. Energy Build2012; 50: 74–80.
13.
ThevenardDHaddadK. Ground reflectivity in the context of building energy simulation. Energy Build2006; 38: 972–980.
14.
GueymardCA. Direct and indirect uncertainties in the prediction of tilted irradiance for solar engineering applications. Solar Energy2009; 83: 432–444.
15.
LewisJOGouldingJRSteemersTC. Energy in architecture: the European passive solar handbook, London: BT Batsford Ltd, 1992.
16.
FerreiraJPinheiroM. In search of better energy performance in the Portuguese buildings — the case of the Portuguese regulation. Energy Policy2001; 39: 7666–7683.
17.
HongTChouSKBongTY. A design day for building load and energy estimation. Build Environ1999; 34: 469–477.
18.
AndersonTNDukeMCarsonJK. Suppression of natural convection heat transfer coefficients in an attic shaped enclosure. Int Commun Heat Mass Transf2010; 37: 984–986.
19.
OngKS. Temperature reduction in attic and ceiling via insulation of several passive roof designs. Energy Convers Manag2011; 52: 2405–2411.
20.
SahaSCKhanMMK. A review of natural convection and heat transfer in attic-shaped space. Energy Build2011; 43: 2564–2571.
21.
AsadiSHassanMBeheshtiA. Development and validation of a simple estimating tool to predict heating and cooling energy demand for attics of residential buildings. Energy Build2012; 54: 12–21.
22.
HachemCAthienitisAFazioP. Parametric investigation of geometric form effects on solar potential of housing units. Solar Energy2011; 85: 1864–1877.
23.
YannasS. Solar energy and housing design: Principles, objectives, guidelines, London: Architectural Association, 1994.
24.
ISO 6946:2007. Building components and building elements – Thermal resistance and thermal transmittance – calculation method. International Organization for Standardization, Geneva, 2007.
25.
Desjarlais AO, Petrie TW and Stovall T. Comparison of cathedralized attics to conventional attics: where and when do cathedralized attics save energy and operating costs? In: Conference on buildings IX (ed ASHRAE), Clearwater, FL, 5–10 December 2004, paper no. 62, pp.1–15.
26.
TironeLNunesK. Coberturas eficientes: guia para a reabilitação energético-ambiental do edificado, Tirone Nunes, SA: Sintra, 2011.
27.
MartinsAMTCarlosJS. The retrofitting of the Bernardas' convent in Lisbon. Energy Build2014; 68: 396–402.
28.
DuffieJABeckmanWA. Solar engineering of thermal processes, Hoboken, NJ: Wiley, 2006.
29.
Essah EA, Sanders CH, Baker P, Galbraith GH and Kalagasidis AS. Simulating the energy benefits and reduction in condensation formation that is obtained from houses with cold pitched roofs. In: Proceedings of the 8th symposium on building physics in the Nordic Countries, Copehagen, 16–18 June 2008, paper no. 025-2, pp.1365–1371.
