Numerical analysis of heat loss from house roof and wall in winter to optimise energy consumption

The objective of this work is to estimate a transient heat loss from the roof/wall of a house during cold winter nights using transient FDM numerical method. Conventionally steady state conditions are assumed for estimating the building heating loads where the internal heat sources are neglected. However, the unsteady approach, by taking the internal heat sources into account, yields significantly small heating capacities and hence low initial costs. The solution used stability criteria using explicit method. Initially, the temperature of all nodes decreased at a faster rate and subsequently the convection, radiation, and total heat loss increased at a faster up to 400 min (or 6.67 hours) and then at a slower rate. The average heat loss estimated was 42.081 kW. The transient total heat loss varies between 16.53 kW to 60.0 kW in 12 hours. Numerical analysis provides accurate results, yields lower heating capacity and is economical for air conditioning design.