Cool temperate versus hot humid tropical: what each climate demands of a house

1. What Section A is really testing

Section A of the Housing and Design exam gives you a choice of two passive solar design questions: one set in a Cool Temperate climate and one in a Hot Humid (Tropical) climate. The External Assessment Specifications say both relate solely to passive solar design (Unit 4) and are rated against Criterion 3: analyse and apply features and principles which contribute to environmental sustainability within design decisions. You have about 60 minutes and an A3 answer sheet, and you respond with a sketch to scale plus annotations.

The single most expensive error in this section, named in the 2023 and 2025 assessment reports, is designing for the wrong climate: putting a concrete slab, double glazing and bulk insulation into a Darwin house, or a breezy single-skin timber pavilion on a frosty Launceston block. Before you draw a line, decide which climate you are in and write it at the top of the sheet: 'Cool temperate — goal: admit, store and keep winter sun' or 'Hot humid — goal: exclude sun, catch breezes, shed heat fast'. Every later decision should be traceable to that sentence.

Choose your question by climate confidence, not by which site looks easier. A student who knows the tropical toolkit thoroughly will out-rate a student who half-remembers temperate rules, even if the temperate site seems simpler. Use the reading time to check room list, maximum floor area, scale requested, wind directions and views for both questions, then commit.

2. Thermal comfort: the purpose behind every feature

Passive solar design means using energy in its original form (sunlight, breezes) to warm or cool a home, as the course glossary defines it. The target is thermal comfort: occupants feel neither too hot nor too cold without relying on active heating or cooling. Comfort depends on more than air temperature. Four factors matter in annotations: air temperature, radiant temperature (warm surfaces such as a sun-heated slab or a cold window pane), air movement (a breeze across skin feels cooler because it speeds evaporation of sweat) and humidity (high humidity slows evaporation, which is why tropical heat feels oppressive).

This matters because it tells you which lever to pull. In Hobart in July, air movement is the enemy and radiant warmth is the friend: you want sunlit thermal mass radiating heat into the living room at night and you want draughts sealed. In Darwin in the wet season, air temperature and humidity are both high, so the only passive lever that works reliably is moving air across the body and keeping the building's surfaces from heating up in the first place.

A model annotation that shows this understanding: 'Living room floor is a dark tiled concrete slab in direct winter sun; it absorbs heat by day and re-radiates it after sunset, lifting radiant temperature so the room feels warm without the heater.' Notice the what (slab), how (absorbs and re-radiates) and why (comfort without active heating). That three-part shape earns the 'describes and justifies' language of the A standard.

3. The cool temperate design toolkit

A cool temperate climate (Hobart, Launceston, Canberra and Bendigo on the Information Sheet) has cold winters, mild to warm summers and low winter sun. The design logic runs in four steps that you should be able to recite and draw:

• Collect: orient living areas and most glazing to the north so low winter sun (Hobart 24° at noon on the winter solstice) floods in. A long east–west axis gives the largest north face.
• Store: put high thermal mass (concrete slab, brick, tiles, reverse brick veneer) inside the insulated envelope where the winter sun lands.
• Keep: insulate walls, ceiling and under the slab to at least the Information Sheet minimums (R2.8, R4.1, R1.0), double glaze, seal draughts, use heavy curtains with pelmets at night.
• Control: size north eaves so the high summer sun (Hobart 71°) is excluded, plant deciduous trees to the north, keep west glazing small and give the house a way to purge heat on hot summer days with cross-ventilation.

Notice that cool temperate design still needs summer control. Tasmanian summers have hot spells, and the marking tool for 2025 asks for cross-ventilation with the direction shown on the plan. A design that only heats will not reach the A standard. Equally, winter sun has absolute priority over views: the 2023 and 2025 reports both record weaker responses that turned the living room south to the view and lost the solar gain.

Write the four verbs on your planning area during reading time; they become a checklist that stops you forgetting insulation or landscaping when the clock is running.

4. The hot humid tropical toolkit

A hot humid tropical climate (Darwin and Townsville on the Information Sheet) is hot all year with high humidity and a distinct wet season. Night temperatures stay high, so storing heat is harmful: a heavy slab that soaks up the day's heat will release it into bedrooms at midnight. The design logic is therefore the reverse of the temperate toolkit:

• Exclude: shade every wall and opening year-round with deep eaves, verandahs, awnings, screens and vegetation. The sun is high and in Darwin is actually in the southern sky at the summer solstice (102° on the Information Sheet means 12° past vertical towards the south).
• Ventilate: elongate the plan across the prevailing breeze, keep rooms a single room deep, place large fully opening windows (louvres, casements, bi-folds) directly opposite each other, and raise the floor so air can pass underneath.
• Shed: use low thermal mass (timber frame, lightweight cladding, corrugated metal roof) so the building cools as soon as the sun goes; light colours reflect radiation; reflective foil under the roof blocks radiant heat; high-level vents and raked ceilings let hot air escape by convection.

Bulk insulation in walls and double glazing are not part of this toolkit unless the client uses air-conditioning. The 2024 report notes that weaker candidates added bulk insulation simply because the question said 'well insulated'; stronger candidates explained reflective foil and shading instead. Always use the wind directions printed in the question, because papers have given different breeze directions for the same city (south-easterly dry-season breezes in 2024, north-westerly wet-season breezes in 2025).

5. Side-by-side comparison you can memorise

Markers reward candidates who can show that the same feature is handled differently in each climate. Learn this table well enough to reproduce it from memory:

Use the table during revision by covering one column and reconstructing it. In the exam, every row should appear in your annotations at least once.

6. Reading the question before you design

Section A questions pack critical constraints into the client brief and site plan. Before drawing, annotate the question paper with these checks:

• Climate and city: which sun angles apply? Copy them from the Information Sheet onto your answer sheet immediately.
• Maximum floor area: the 2023 hot humid question set a 140 m² limit inside a 364 m² build zone; some students used the whole zone and were penalised. Calculate your room sizes against the limit (e.g. 60 m² could be 10 m × 6 m or 12 m × 5 m).
• Room list: count every space the client asked for, including deck sizes (2024 required a 16 m² deck).
• Build zone and setbacks: stay inside them; the 2024 report says some designs spilled into easements or neighbouring blocks.
• North point, winds, views, obstructions: the 2025 Launceston site had northern vegetation casting a shaded zone; strong answers placed the house clear of it. The 2025 Darwin site had a neighbouring building partly blocking the breeze; strong answers moved the dwelling south to clear it.
• Required drawings and scale: typically a 1:100 plan on the site plus a section or elevation with sun angles.

Then write a one-line resolution of the main conflict, for example 'View is south, sun is north: living room glazed to north for solar gain, with a south-facing clerestory or narrow double-glazed picture window to frame the view.' Competing factors are named explicitly in the Criterion 3 standards, so stating and resolving them is not optional.

7. Model annotations and what lifts them to A

Annotations are where the rating is won. The C standard asks you to apply and describe 'most of the key features'; B asks for 'most of the appropriate features... in a detailed and informed manner'; A asks you to apply, describe and justify appropriate features and to 'identify, analyse and seek to resolve competing factors'. Compare three versions of the same note:

• C-level: 'Big north windows.' (identifies a feature, no reason)
• B-level: 'Large double-glazed north windows to let in winter sun.' (feature plus purpose)
• A-level: 'About 75% of total glazing faces north; low 25° Launceston winter sun passes under the 600 mm eave and reaches the dark slab up to 4.5 m into the living room, where heat is stored and released at night; double glazing and pelmeted curtains stop that heat escaping after dark.' (feature, quantity, mechanism, link to site and to the other features)

For the tropics the same ladder applies: 'Louvres both sides' becomes 'Full-height adjustable glass louvres on the south-east and north-west walls, directly opposite, so the wet-season north-westerly passes straight through the single-room-deep living area; louvres stay open in rain because the 1.5 m verandah shelters them.'

Keep each annotation to two lines and connect it to the drawing with a leader line. A sheet with twenty sharp, justified notes beats a sheet with a page of prose and an unfinished plan.