- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
This paper presents a comparative study for the determination of the most economical combination between external wall and optimum insulation thickness for energy saving into buildings. Using the degree-day's concept, the yearly cooling transmission loads of the building was determined. The P1-P2 method was used in economic analysis to find out the optimum insulation thickness, energy savings, and payback period for buildings in that locality. Expanded polystyrene was first chosen and used for five typical wall structures (sundry earth block (SEB), hollow concrete block (HCB), compressed earth block (CEB), heavyweight concrete block (HWCB), and stone). Then the investigation was extended to six other insulation materials. As results, It was found that the lowest value of optimum insulation thickness (7.6 cm) and energy savings (48 $/m2) were obtained for sundry earth block for expanded polystyrene while the payback period (3.23 years) was the highest for the same wall structure. The association of sundry earth block with extruded polystyrene was found to be more economical (23 $/m2 for minimum cost) with an optimum thickness of 9 cm and 69% of energy savings compared to other wall types.
4. Conclusion The main purpose of this study was to optimize the thicknesses of insulation layers in external walls of building in a tropical climate with respect to the wall and insulation types. The yearly transmission loads with respect to the type of external wall were determined by using the degree day concept. These loads are input in an economical model in order to estimate the optimum insulation thicknesses, the energy savings, and the payback periods using expanded polystyrene for five different wall types. The results showed that a suitable choice of the type of external wall can provide reduction of optimum thickness and energy savings. It was found that the optimum insulation thickness varies between 8.2 cm and 10 cm, energy savings vary between 44 $/ m2 and 150 $/m2 , and payback periods vary between 0.91 and 2.21 years depending on the type of wall. It was also found that energy savings are sensitive to change in the economic parameters. The energy savings are found to increase with building lifetime, inflation rate, and electricity cost; and decrease with increasing cost of insulation material, efficiency of the cooling system, and the discount rate. The calculation was extended to six insulation materials. The results showed that a suitable association of a wall type with an insulation material results to a minimum total cost. It was found that the optimum insulation thickness varies between 8.2 cm and 32 cm, energy savings vary between 58% and 86.37%, and payback period vary between 0.66 and 2.39 years depending on the type of wall and insulation material. It was also seen that the impact of the type of materials used on the total cost of cooling is more significant for SEB with extruded polystyrene. The values 9 cm and 23 $/m2 for optimum insulation thickness and minimum total cost were obtained, respectively, compared to 9.2 cm and 33 $/m2 proposed by reference . Considering the consistent impact of the wall type on optimum insulation thickness, its consideration by designer of external wall thermal insulation is fundamental for the energy efficiency of the building.