1. The problem statement, all variables and given/known data A single roomed building measureing 12.0m x 12.0m x 2.5m is maintained throughout the day at a temperature of between 18-23°C. Each wall is to be constructed from 2 layers of common brick, an internal particle board and a layer of insulation. The building is heated using standard space heaters that will run on natural gas. The gas currently costs 7p/kWh and is burnt at an efficiency of 70%. During heating calculations it is assumed that the same thickness of insulation is applied to floor, wall and roof and that mineral wool at a current price of £55/m3 is utilised. Calculate the the optimum thickness for insulation over a 12 months period. 2. Relevant equations q = ΔT/∑Rth therefore: q with insulation/q without insulation = 0.3 = ∑Rth (with)/∑Rth (without) Thermal resistance Rth = Δx/k 3. The attempt at a solution So far I've assumed that due to it being over 12 months, there will be a change in outside temperature during the different seasons. Also assumed that there is no air gap between the wall. The k values I have found so far are: brick = 0.7, particle board = 0.15 and k for wool is 0.04, so I can calculate the Thermal resistance and heat loss. R wool = L/kA = x/0.4*1 = x/0.4 °C/W R brick = L/kA = 0.1/0.7*1 = 1.429*2 = 0.2858 °C/W R P.board = L/kA = 0.01/0.15*1 = 0.067 °C/W I just need help in finding the equation for calculating Energy cost.