Civil Engineering Forum Volume XXI/2  May 2012 1209 THERMAL INSULATION EFFECTS ON ENERGY EFFICIENCY OF BUILDING STRUCTURES M. Cvetkovska Civil Engineering Faculty, Skopje, Macedonia Email: cvetkovska@gf.ukim.edu.mk M. Knezevic Civil Engineering Faculty, Podgorica, Montenegro Email: milosknezevic@hotmail.com M. Rogac Civil Engineering Faculty, Podgorica, Montenegro Email: mili_5@tcom.me ABSTRACT Abstract: This paper presents the use of Finite Element Method for heat transfer analysis. Connections wallbeamfloor structure with different positions of the thermal insulation have been analyzed and conclusions about energy efficiency and energy loss are made. Keywords: heat transfer, numerical analysis, finite elements, thermal insulation, energy efficiency. 1 INTRODUCTION Energy consumption is significantly greater today than in the past decades as lifestyle changes have resulted in more consumption of energy. Now more than ever, we must find a way to build homes and buildings with greater energy efficiency. The Building Codes and state regulations require new houses to achieve energyefficiency goals. Therefore, it is important to use materials and wellestablished building technology that will help a building to use less energy over its lifetime. Taking into consideration life cycles with respect to thinking and acting is the basis of sustainable building. The more energyefficient a building is and the less energy it uses within the useful life, the more important its construction, the choice and processing of materials are. Planners and architects who want to create buildings in a sustainable way are confronted with the following questions: How recyclable are the materials used during the process of construction? How much primary energy is spent in the building? How big is the carbon footprint? Are the environmental impacts considered in planning through the whole life cycle and are they revealed correspondingly? When does a decision for a more ecological option pay for itself? Every building is unique and needs an individual analysis to illustrate the environmental impact and sustainability performance as well as to identify optimisation potentials. 2 FINITE ELEMENT METHOD FOR HEAT TRANSFER ANALYSIS The governing differential equation of heat transfer in conduction is [3],[5]: t T c z T z y T y x T x z y x ∂ ∂ = ∂ ∂ ∂ ∂ + ∂ ∂ ∂ ∂ + ∂ ∂ ∂ ∂ ρ λ λ λ ) ( ) ( ) ( (1) where: λ x , λ y , λ z are thermal conductivities (temperature dependent); ρ is a density of the material (temperature dependant); c is a specific heat (temperature dependent). The boundary conditions can be modeled in terms of both convective and radiative heat transfer mechanisms. The heat flow caused by convection is: ) ( f z c c T T h q − = (2) where: h c is coefficient of convection; T z is the temperature on the boundary of the element; T f is the temperature of the fluid around the element.