7/31/2019 2_ Calcul coeficientului global de izolare termica G

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II - The general factor of thermal insulation G

This factor of thermal insulation reflects the sum of all thermal loss trough all the buildingenvelope elements for a thermal difference of 1 Kelvin ( ∆θ ) plus the losses because of ventilation and airinfiltration.

G≤ GN

The minimal values GN are given in the following table:

7/31/2019 2_ Calcul coeficientului global de izolare termica G

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Where:V – represents the inside volume of the building V[m3] ;R’m - represents the average corrected thermal resistance of the building element,

[m2K/W];

;1∑∑ ′

==′

j

j

j

med m

R A A U R

[W/m3K];

A – The area of the element with the specific main thermal resistance R’ m;A[m2];

n – represents the ventilation rate (the number of volume changes per hour.n=0,7; 0,8; 0,9 [h-1] according to the degree of win exposure of the building);

– The temperature correction factor

;)()(

e i

u i

T T T T

−−=τ

Ti=+20°CT e – represents the external temperature and it is in function of the zone.T u= +5°C;T u – represents the temperature for indoor un-wormed spaces;

A l

R R U ∑ ⋅

+=′=′)(11 ψ

;where:Ψ – represents the linear coefficient of temperature losses trough thermal bridges and

depends on the constructive detail of the linear thermal bridge.l - represents the length of the linear thermal bridge where the specific Ψ measure the heat

losses (l is determined for one floor and than multiplied with the nr. of similar floors).

One requirement for the thermal resistance of each type of envelope element is :

R o,ef ≥ R nec

Where the corrected mean resistance for building envelope elements are :

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C u r r e n

t n u m

b e r

B u

i l d i n g

E l e m e n

t

B r

i d g e

D e

t a

i lLinear

heat lossLinear bridge

length AreaThermalresist.

Correctedthermal resist.

Temp.

Correct.factor

Specificpower

Ψ l Ψ*l A R ∑(Ψ*l) R' (A· )Rm'

_ Wm*K m W

K m² m²*KW

WK

m²*KW

1 2 3 4 5 6=4*5 7 8 9=∑6 11=1/(1/8+7/9) 13 14=7*13/12

1 External Wall _1

1 Ψ1Ψ2

12465

1 External Wall _2

1Ψ1Ψ2

124

65

2Floor over the

basement5

8

3 Roof 5 1

4 Windows & Doors 90.5

1

Need for G ∑ . . . . . ∑ . . . . .