Passive Design & Thermal Comfort – Week 2 Comprehensive Notes

Administrative & Course Logistics

  • Introduction of co-coordinator Adrian Chu; absent Week 1 due to overseas commitments, now present.
    • Handles Canvas announcements, tutorial allocations, email queries.
    • Encourages students to “keep pestering” if emails not answered; will finalise tutorial groups after today’s lecture.
  • Group Assignment
    • Short in duration; possible to complete even if you missed Week 1.
    • If still unallocated, simply attend your scheduled tutorial and speak with the tutor.
  • Lecture Quizzes
    • In-class quiz (5 Qs, contextual to lecture).
    • Alternative online quiz opens ~5 p.m. today for ~24 h.
    • Same 5-question length, open book, but questions randomly drawn from whole week’s materials (incl. readings).
    • 5-minute time limit; requires prior study.
    • Harder and less “contextualised” than lecture version.

Week 2 Focus & Structure

  • Theme: Passive Design principles for health, wellness & energy efficiency.
  • Four theoretical components followed by practical demonstration:
    1. Rationale for shelter that exploits free solar energy.
    2. Climate analysis: “location, location, location”.
    3. Climate-responsive design in Melbourne context.
    4. Intro to materials as segue to later topics.
  • Guest architect Ben Gallery invited to showcase built examples (40 min after lecture start).

Heat Transfer Fundamentals

  • Three modes of heat flow
    • Radiation: energy exchange without contact (e.g.
      sunlight).
    • Conduction: heat flow through materials; dependent on thermal conductivity and expressed via R-value.
    • Convection: heat carried by moving air; “warm air rises”, wind can accelerate heat loss or support cooling.

Building Envelope & “Micro-Meso-Macro” Environments

  • Building envelope = boundary separating interior micro-environment from macro climate via a meso (buffer) zone.
  • Goal: maintain occupant comfort (~36! -! 37^\circ\text{C} core temp).
  • Metabolic heat augments space heating load; more occupants ⇒ higher internal gains (important in offices vs dwellings).

Thermal Comfort Variables

  • Air (dry-bulb) temperature T_a.
  • Mean radiant temperature T_r (influenced by cold windows or sun patches).
  • Relative Humidity (RH).
  • Air velocity v.
  • Clothing insulation (clo):
    • 1\,\text{clo} \approx business attire at 21^\circ\text{C}/50 % RH.
    • T-shirt ≈ 0.5\,\text{clo}; heavy sweater adds ~0.3\,\text{clo}.
  • Activity level (met): 1\,\text{met}=58.15\,\text{W}/\text{m}^2 body area.
    • Human heat gain approximation: Q=MET\times A_{body}\times58.15 (e.g.
      1\,\text{met} \times 1.6\,\text{m}^2 \times 58.15 \approx 100\,\text{W}).

Comfort Metrics & Standards

  • PMV (Predicted Mean Vote) scale −3 (cold) → +3 (hot).
  • PPD (Predicted % Dissatisfied) target ≤20 %; commercial buildings aim for ≥80 % occupants satisfied.
  • ASHRAE Standard 55 referenced for interview & practice credibility.

Psychrometric Chart Essentials

  • Axes: dry-bulb T_a (x) vs moisture ratio (y); curved RH lines.
  • 100 % RH line gives wet-bulb equals dry-bulb.
  • Dew-point: move horizontally left to saturation line; key for condensation control and NCC code updates.
  • Evaporative cooling potential: example Ta=20^\circ\text{C},\ RH=50\%\Rightarrow T{wb}\approx13.5^\circ\text{C} (max theoretical cooling).
  • Chart knowledge not examinable but underpins later topics.

Humidity, Health & Indoor Air Quality

  • RH
  • Melbourne often very dry; aged-care thermostats set ≈23.5^\circ\text{C} to offset.

Solar Geometry & Key Dates

  • Terminology to memorise:
    • Summer solstice (≈21 Dec, highest sun).
    • Winter solstice (≈21 Jun, lowest sun).
    • Equinoxes (≈21 Mar & 23 Sep): sun rises/sets due east/west.
  • Roofs as collectors: daylighting, heating, cooling potential; colour affects absorptance (light vs dark roofs).

Site Orientation & Urban Form

  • Plot choice for Melbourne passive solar: prefer long east-west lot exposing long north facade.
  • Example lecture quiz asked students to choose best block.
  • Corner blocks provide more façade freedom.

Wind, Night-Purge & Ventilation

  • Prevailing summer southerlies in Melbourne; harness for cross-flow cooling.
  • Night-time purge:
    • Open windows at night to cool thermal mass when diurnal range is high.
    • Very effective passive cooling strategy (quiz emphasised).

Thermal Mass

  • Acts like a “heat battery”.
  • Materials: concrete, brick, mud; water has highest specific heat.
  • Strategy: expose to sun in winter, shade in summer.
  • Must be insulated (underslab, walls) to prevent unwanted losses/gains.

Shading Strategies

  • Fixed: deep eaves sized for solstice angles; louvres calibrated (as on Melbourne School of Design façade).
  • Vegetation: deciduous trees/vines give summer shade, winter sun (e.g.
    grapevine pergola at lecturer’s home).
  • Devices: external venetians, folding-arm awnings, perforated metal screens; external > internal blinds for heat control.

Passive Cooling Options

  • Cross-ventilation & stack effect (solar chimneys).
  • Evaporative cooling (limited by T_{wb} drop).
  • Reduce indoor RH within healthy band.

Sample Quiz Questions (Lecture)

  • North-facing plain window photo: illustrates “passive space heating in winter”.
  • Preferred Melbourne block orientation for passive solar.
  • Sun rises due east/west only on equinoxes.
  • Night-purge identified as best cooling where high diurnal swing.
  • Comfort requires considering “all of the above” (air temp, velocity, humidity).

Building Fabric Metrics

  • R-value (thermal resistance) inversely proportional to conductivity.
  • Airtightness critical; uncontrolled wind (“wind-washing”) accelerates heat loss.

Guest Lecture – Architect Ben Gallery

  • Practises passive solar principles in Melbourne climate; 10 years collaborating with subject.
  • Benefits of Passive Design
    • Reduces energy, improves comfort, health, finances, and supports biophilia (nature connection).
  • Key Toolkit
    • North light capture; external shading (venetians, blinds, pergolas).
    • Natural cross-ventilation; selective use of louvre windows (ventilation priority over double glazing).
    • High insulation in walls, roofs (e.g.
      On-deck insulated roof panels), floors (insulated slabs or “decoupled” topping slabs).
    • High-performance glazing: double glazed timber frames, thermally-broken aluminium, lift-and-slide doors, tilt-and-turn windows.
    • HRV (Heat-Recovery Ventilation) for airtight homes.
    • Integration of PV arrays, battery storage, electric vehicle charging, rainwater tanks.

Case Study Highlights

  1. Personal Northcote House
    • Single-fronted terrace; two-storey rear; north side windows & deciduous grapevine for summer shade.
    • Double-height void admits winter sun.
  2. Brunswick “Laneway” House
    • Living upstairs; monopitch roof oriented north; pop-up roof with motorised louvres harnesses southerly breezes.
  3. High Camp Off-Grid House
    • Remote site, extreme winds; square plan with decks north/south enabling shelter.
    • 29 kWh batteries, roof-mount PV; solar DHW; inline fans move fireplace heat to bedroom.
    • Deep eaves, minimal west glazing.
  4. “Oculus House” (Melbourne)
    • Large family home; north side glazing almost entire façade with hoods & blinds.
    • Extensive insulation, HRV duct network concealed under dropped ceiling.
    • Insulated topping slab over structural slab; lift-and-slide doors, external venetians.
  5. “House for Life” (Northcote)
    • Two-storey on tight block; stair light-well with north clerestory penetrates to rear kitchen.
    • West pergola + deciduous vines; thermally-broken aluminium windows.
  6. Park-Edge Extension
    • Timber slats angled to block views & summer sun but admit low winter rays.
    • Void brings north light over neighbour; folding awnings & blinds manage west.
  7. “Habitat House”
    • Compact extension prioritising quality of space; sliding cavity doors open corner to garden.
    • High clerestory over meals; louvre + slider pairing for cross-vent.

Practical Insights from Q&A

  • Skylights used only when highlight windows impossible; higher heat loss/gain.
  • Thermal mass must be shaded in summer to avoid heat dump.
  • External blinds vastly outperform internal blinds (prevent solar heat entry).

Melbourne Climate Particularities

  • “Four seasons in one day”; 8-season Indigenous calendar offers richer nuance.
  • Victoria has among highest residential space-conditioning energy use; moving off gas to efficient electric (heat-pump) systems encouraged.

Ethical / Sustainability Context

  • Built environment ≈39 % global CO₂; Paris Agreement demands reductions.
  • Passive design = first, low-cost, low-carbon lever before active HVAC.

Connections to Future Content

  • Upcoming tutorials will apply vernacular precedents, solar geometry, PMV/PPD calculations.
  • Winter (February) intensive subject will delve into advanced solar cooling & chimneys.