Heat transfer between heated, partially heated and non-heated residential units in buildings

Space heating cost allocation according to actual consumption can be one possible motivating factor for saving energy in residential and other buildings. As a consequence of the exclusion of a certain number of users in collective housing units from the central heating supply system in the city of Skopje, the problem of heating cost allocation and collection of the fixed part of the heat energy payment has arosen. The subject of the analysis in this study was the heat transfer in buildings, with the main focus on the issue of heat transfer rate between residential units with different internal temperatures, such as from heated to unheated or partly heated apartments in collective building objects. The purpose of the analysis was to assess the mutual energy interaction between the completely or partially excluded apartments from the central heating system and the adjacent apartments connected to the central heating system. This is done by simulating the thermal characteristics of typical buildings that are representatives of new (insulated) and old (un-insulated) buildings. For the simulation purposes, the external average daily and monthly temperatures were obtained based on the perennial outdoor temperatures measured in Skopje and additional series of input data that are characteristic for the city were used. For the value of the internal temperature in the dwellings the value for the standard internal design temperatures are predefined. As results of the simulation, values were obtained for the annual heat gains (in kWh/year) and the specific heat gains (in kWh/m 2 year) of the excluded apartments from the system of central heating through the enclosures (internal walls, ceiling and floor) of the adjacent apartments that are connected to the system for central heating and vertical hot water pipelines for an isolated and nonisolated buildings. In order to obtain a clearer picture, in the study are considered different configurations and positions of apartments in the building. As an indicator for each considered apartment, the ratio of the received thermal energy of the disconnected apartment to the required energy for its heating is calculated. Based on the obtained results, appropriate conclusions were drawn regarding the reduction of the necessary energy for heating of the excluded apartments, as a consequence of the thermal gains through the walls of the neighboring apartments that are connected to the heating system.