Energy efficiency analysis of internally and externally insulated apartment buildings

Apartment buildings are the most common type of residential buildings in Korea, where hot water heating pipes are installed in the floor structures. An internal insulation system (IIS) has been applied to the outside walls of most Korean apartment buildings, so there are many cases in which the layer of insulation is disconnected by structural components at the wall-slab joints. These joints become thermal bridges where heat transfer increases. An external insulation and finish system (EIFS) is a possible solution to this problem. In this study, the surface temperature distributions of actual apartment buildings with an IIS and an EIFS were investigated with an infrared thermal imaging camera. Annual heat losses and gains through the wall-slab joints with an IIS and an EIFS were calculated by three-dimensional transient heat transfer simulations in which hot water heating was excluded and included, respectively, in order to evaluate not only the heating and cooling loads, but also the heating efficiency when the building is actually heated. The results show that the amount of heat transfer through the wall-slab joints with an IIS is considerable, even though additional insulation is installed under the slab, and the EIFS significantly reduces the heating and cooling loads and improves the heating efficiency.