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1.2 Background <strong>and</strong> literature review 25<br />

Fig. 1.3 presents <strong>the</strong> best location <strong>of</strong> insulation inside a ro<strong>of</strong>.<br />

glass wool<br />

concrete block<br />

glass wool<br />

concrete block<br />

glass wool<br />

Fig. 1.3: Configuration <strong>of</strong> insulation selected by Ozel <strong>and</strong> Pihtili (2007) as <strong>the</strong> best solution.<br />

Dombayci <strong>and</strong> co-workers (Dombayci, et al., 2006) investigated <strong>the</strong> optimization <strong>of</strong><br />

external wall insulation thickness for Denizli (southwestern Turkey) wea<strong>the</strong>r conditions.<br />

The effects <strong>of</strong> <strong>the</strong> energy source types (coal, natural gas, LPG, fuel oil, electricity) on<br />

energy savings <strong>and</strong> <strong>the</strong> use <strong>of</strong> different insulation materials (exp<strong>and</strong>ed polystyrene, rock<br />

wool) were analyzed. The difference between <strong>the</strong> buildings’ heating costs, with <strong>and</strong><br />

without <strong>the</strong> insulation <strong>of</strong> external walls, was used in a life-cycle cost <strong>analysis</strong> (LCCA).<br />

Results <strong>of</strong> <strong>the</strong> calculations revealed that <strong>the</strong> life cycle savings are $ 14.09 per square metre<br />

<strong>of</strong> wall surface area <strong>and</strong> a very short payback period <strong>of</strong> 1.43 years for <strong>the</strong> optimum<br />

insulation-thickness. These results were obtained with coal as <strong>the</strong> energy source <strong>and</strong><br />

exp<strong>and</strong>ed polystyrene as <strong>the</strong> insulating material.<br />

Khaled (Khaled, 2003) comprised two types <strong>of</strong> ro<strong>of</strong> insulation (polystyrene <strong>and</strong> fiberglass)<br />

for warm <strong>and</strong> cold climate conditions. Energy <strong>analysis</strong> was carried out for a 108 m 2 house<br />

in two USA locations: College Station (Texas) <strong>and</strong> Minneapolis (Minnesota). The<br />

RENCON simulation program (Degelman, et al., 1991) was used to determine annual<br />

heating <strong>and</strong> cooling energy consumption. Six different insulation resistance levels <strong>of</strong> <strong>the</strong><br />

ro<strong>of</strong> (R5, R10, R15, R20, R25, R30) were examined. In Khaled’s opinion, <strong>the</strong> most costeffective<br />

<strong>the</strong>rmal resistance for polystyrene is R5 <strong>and</strong> for fiberglass is R10. Besides this,<br />

<strong>the</strong> author remarked that <strong>the</strong> payback time <strong>of</strong> using insulation in a cold climate is shorter<br />

than that <strong>of</strong> a warm climate <strong>and</strong> that <strong>the</strong> best solution for <strong>the</strong>rmal insulation design is <strong>the</strong><br />

use <strong>of</strong> a life-cycle cost <strong>analysis</strong> ra<strong>the</strong>r than <strong>the</strong> construction budget limitation.<br />

The problem concerning <strong>the</strong> best insulation level <strong>of</strong> <strong>the</strong> envelope <strong>of</strong> new residential<br />

buildings in 6 Italian climatic zones was studied by Lollini (Lollini, et al., 2006).<br />

Economical <strong>analysis</strong> was based on two main parameters <strong>of</strong> investment efficiency: <strong>the</strong> net<br />

present value (NPV) <strong>and</strong> <strong>the</strong> payback rate (PBR). The methodology used in this project<br />

included <strong>the</strong> following factors: calculation <strong>of</strong> <strong>the</strong> optimal insulation thickness, analyses <strong>of</strong><br />

market <strong>and</strong> cost, energy calculation <strong>of</strong> <strong>the</strong> reference buildings, calculation for different

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