# Solve the following problem.The PasivHaus standard for low energy building requires that the U-values of all outer shell materials be no more than 0.15 W/ m^2*K. If the area of a PassivHaus...

Solve the following problem.

The PasivHaus standard for low energy building requires that the U-values of all outer shell materials be no more than **0.15 W/ m^2*K**.

If the area of a PassivHaus standard wall is ** 18 m^2**, how much energy **En** flows through the wall over a week if the inside temperature is **10 ℃ **warmer than the outside?

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### 1 Answer

I believe you want to know the energy that flows through a PasivHaus standard wall.

Now the U-value of the standard PasivHaus low energy building for all outer shell material is to be less than 0.15 W/m^2*K.

So the rate of energy flowing out can be a maximum of 0.15 W/m^2*K. The standard area of the wall is 18 m^2. The temperature difference inside and outside the house is 10 degree C or 10 K.

Therefore the rate of flow of energy is 0.15*18*10 W

= 27 W.

In a week there are 24*7= 168 hr.

Therefore the energy flowing through the building is 168*27 W*hr

= 4536 W*hr

= 45.36 kW*hr.

**The required energy flow over the week is equal to 45.36 kW*hr.**