$25\frac{W}{m}C$ for the external plaster

$55\frac{W}{m}C$ for the wood panel

$80\frac{W}{m}C$ for the concrete

It is known that the convection coernic and

for the interior surface is $=8\frac{W}{m^{2\text{@}}}C$ and

for the exterior surface is $=25\frac{W}{m}$ the

The room temperature is $24C$ and the

outside temperature $-15C.$

Find the thickness of insulation, L$,$ having

$=0\mathrm{.}055\frac{W}{m}C$ to reduce the heat loss from

a wall $3m$ high and $15m$ long by a factor of

$75\%?$ The thickness of the wall layers are

given in $[$mm$].$