Energy Efficient Building Design Questions and Answers

Answer: C

Still air is a good insulant, and an unventilated cavity adds perhaps 0.18 to the resistance before any insulation is put in it. Filling the cavity multiplies that severalfold, which is the commonest retrofit on such a wall.

Answer: D

A concrete slab edge, a steel lintel or a balcony carried through the wall lets heat past the insulation and may cost a substantial share of the notional performance. It also creates a cold spot where condensation and mould follow.

Answer: A

Reflecting most of the incident radiation rather than absorbing it keeps the roof surface tens of degrees cooler, and the roof is the surface that receives most sun on a low-rise building. A high emittance in the infrared helps it shed what it does absorb.

Answer: B

Correct answer: evaporation from the planting and the soil's insulation

The soil and vegetation add thermal resistance and store heat, and the water they transpire and evaporate carries away a great deal more as latent heat. Together those keep the roof surface tens of degrees cooler than a dark membrane, and the effect extends to the surrounding air.

Answer: C

A horizontal surface takes the midday sun at normal incidence while walls take it obliquely, so the roof is the largest single gain in a single-storey building. Its area may be smaller than the walls' and it certainly carries load.

Answer: D

Correct answer: the gross wall area of that facade

The ratio is per facade and is taken against the whole wall, glazed and opaque together. Computing it per facade matters because the right value differs with orientation - generous on the north, restrained on the west - and a whole-building average would conceal exactly that.

Answer: A

Even good glass admits a substantial fraction of the incident radiation, and on a sunny facade that dwarfs the conduction through it. Reducing the ratio, shading the glass or specifying a lower coefficient are the three remedies.

Answer: B

It lets visible light through while turning back the long wave radiation, so a heated building keeps its warmth and a cooled one rejects the re-radiated heat. Which side of the pane it is placed on depends on whether heating or cooling dominates.

Answer: C

Glass itself is a poor insulator whatever its thickness; the still gas layer between the panes is what provides the resistance, and argon does better than air. It reduces the conduction and does comparatively little about the solar gain.

Answer: D

Correct answer: south, where the summer sun is high

At midday in summer the sun is high in the south, so a modest projection above the window intercepts it. In winter the sun is low and passes beneath the overhang into the room, which is precisely what is wanted. The geometry does the seasonal switching with no moving parts.