$($b$).$ A wall is constructed using waste materials such as coconut fibres and polystyrene$/$saw dust board. The wall is $200mm$ thick made up bricks $100mm$ brickwork insulated on the inside surface by the $40mm$ coconut fibre covered with $60mm$ of polystyrene$/$saw$-$mill dust board. The thermal conductivity, in $\frac{W}{m}K,$ are: Brickwork $0\mathrm{.}75,$ coconut fibre $0\mathrm{.}04,$ polystyrene $/$sawdust board $0\mathrm{.}1.$ The internal and external thermal resistances $(m^2\frac{K}{W})$ for surfaces are: $0\mathrm{.}10$ and $0\mathrm{.}04$ respectfully. The Vapour resistivity, in GN s$/$kg m$,$ are: Brickwork $60,$ coconut fibre $5,$ and polystyrene $/$sawdust board $50.$ The inside air is at $20C$ and $59\%RH$; the outside air is at $30C$ and $100\%RH.$

$($i$)$ Using Psychrometric chart shown in Figure $1,$ calculate the boundary values of structural temperatures and dew$-$points profile.

$[10$ marks$]$

$($ii$)$ Plot a structural temperature profile and a dew$-$point profile on the same$-$scaled cross$-$section diagram of the wall.

marks$]$

$($iii$)$ Assess the wall on the possibilities of surface and$/$or interstitial condensation.

marks