QUESTION $2$

Open$-$plan office space located in a single$-$storey office building has a foor area is

$13\mathrm{.}7m18\mathrm{.}3m,$ floor$-$to$-$celling height $=3\mathrm{.}7m($no plenum between the space and

roof$).$ The desired indoor conditions are $25C$ dry$-$bulb temperature and $50\%$ relative

humidity during cooling season. The windows face west and the solar heat gain

through these windows will peak in the late afternoon when the sun is setting and

shining directly into the windows. Because of this, we will assume that the maximum

cooling load for space occurs at $5$ p$.$m$.$

The west$-$facing wall, $3\mathrm{.}7$ m high $13\mathrm{.}7m$ long. constructed of $204$ mm concrete block

$(\{$:$R=0\mathrm{.}35m^2\frac{K}{W})$ with aluminium siding $(R=0\mathrm{.}11m^2\frac{K}{W})$ on the outside $90$ mm of

insulation of froreglass $(\{$:$R=2\mathrm{.}29m^2\frac{K}{W}),$ and $13$ mm gypsum beard $(\{$:$R=0\mathrm{.}08m^2\frac{K}{W})$

inside. Additionally, there is air film on the outside of the wall $(R=0\mathrm{.}04m^2$ K$/$W$)$ moving

at $12k\frac{m}{h}$ during the summer and another air film on the inside surflace of the wall $(R$

$=0\mathrm{.}12m^{2}KW,$ still air$).$ Eight clear, double$-$pane $(6\mathrm{.}4$ mm with U$-$Eactor of $3\mathrm{.}56\frac{W}{m^2}K)$

windows are mounted in Aluminium frames with each window $1\mathrm{.}2m1\mathrm{.}5m$ high. The

roof is flat $($type $3).13\mathrm{.}7m18\mathrm{.}3m$ constructed of $100$ mm lightweight concrete $(R=$

$\{$:$0\mathrm{.}54m^2\frac{K}{W})$ with $90$ mm insulation $(R=2\mathrm{.}29m^2\frac{K}{W}).$ steel decking $,$

no dimension given$)$ and the bult$-$up roofing with $(R=0\mathrm{.}06m^2\frac{K}{W}).$ Additionally. there

is air flim on the outside of the wall $(\{$:$R=0\mathrm{.}25m^{2}KCW)$ moving at $12k\frac{m}{h}$ during the

summer and another air film on the inside surface of the wall $(R=0\mathrm{.}16m^{2}KWW,$ still

air$).$ Using the CLTD tables for sunit walls and fat roofs for ${26}^{*}$ South Latitude,

calculate:

$2\mathrm{.}1$ the U$-$factor of the wall and of the roof, respectively

$2\mathrm{.}2$ the conduction through the surnit surfaces

Note: Use only the tables supplied.

Figure $1$: Paychrometric chart $($ASHRAE$)$