Energy simulation in building sector was an important issue which can eliminate energy use and improve energy efficiency. The building, which is located at Ringvägen 18 in Ljusdal community in Sweden, was chosen to be the main mission of this research and it was one of eleven objects which were involved in EKG project. First step was to create the model and simulate it to reach heating value of 117 MWh which was reached by EKG project. After getting validation value, many renovations were implemented and the heating value was reduced by 58.7% and the heating demand by 55.2%. Improving of energy use through prefabrication gave reduction of heating value of 70.4% and heating demand of 65.8% The LCC part was important issue because it gave clear vision and judgment about the economic and investment issue. The acceptability of the investment decision was decided by 198 answers which were responsible to judge if the investments were good or not. There were 22 types of different renovation and every type included 9 cases which depended on interesting rate and energy price factors. The result was 198 answers which were divided to 100 answers as “YES” for good investment and 98 answers as “NO” for good investment.

ROT är förkortning till ” Reparation, Ombyggnader och Tillbyggnader ” som ä avsedd för skatteavdrag för vidtagna energibesparande åtgärder inom byggnadsektorn. Syftet med det här examensarbetet är att undersöka olika slags besparingar med hänsyn till dagens befintliga flerbostadshus omständigheter. Byggnadens energianvändning skulle generellt kunna minskas genom att förbättra klimatskal som exempelvis byggnadstekniska åtgärder och utnyttja nya installationstekniska åtgärder bl.a. som FTX ventilation system eller värmepumpar. Med hjälp av IDA ICE energisimuleringsprogram ska två flerbostadshusmodeller byggas. Resultatet från energiberäkningen med IDA ska analyseras och jämföras med bostadshusets energistatus idag. Avsikten med jamförelsen är att anpassa byggmodell för att representera den befintliga byggnaden så gott som möjligt. Förbättringsåtgärder som tillförs i byggmodellen ochberäknas med IDA skulle kunna påvisa olika potentialen av energibesparing. i olika förslagen .Även en ekonomiskbedömning av förbättringsåtgärder med valda åtgärder ska genomföras med ur livscykelkostnadssynpunkt som tar hänsyn till alla kostnader under kalkylperioden. Genom dessa kan fastigheter ägare få överblicka energikostnader för att avgöra ett rimligt och lönsamt beslut om energieffektiviseringsåtgärder. Nyckelord : åtgärder,befintliga flerbostadshus, IDA simulering, livscykelkostnad analys / The building sector accounts for almost one third of total energy use in Sweden. A large amount of residential buildings which were built one half century ago are in urgent need of renovation in order to reduce energy consumption meanwhile improving the inhouse comfort. This paper demonstrates that the heating need of apartment building from 1950s could be lowered by carrying out suggested measures. These include increasing the insulation layers on the roof and external wall, upgrade of windows in the building and reinstallation of ventilation system with heat exchange function. How much heating energy could potentially be cut down by implementation of each measure were examined by constructing and operating the model in the simulation program IDA Indoor Climate and Energy, which takes not only the indoor factors into account but also the external parameters like solar radiation , geographic location and surroundings. Finally the analysis on life cycle cost of each method has been performed based on reasonable assumptions in order to compare these measures in the term of costeffectiveness and give a more complete and sensible picture of energy effective means in the long run. Keywords : apartment building, heating energy reduction buildings envelop, model simulation, life cycle cost analysis, cost effectiveness.