Heat Transfer in Buildings ⋆ Archi-Monarch

Principles, Types, Building Envelope and Architectural Design Strategies

Introduction

A building is constantly exchanging heat with its surroundings. Solar radiation strikes the roof and walls, outdoor air exchanges heat with external surfaces, occupants and equipment release heat indoors, and conditioned spaces either gain or lose heat through the building envelope.

Understanding heat transfer in buildings is therefore fundamental to architectural design.

Heat transfer influences:

Indoor thermal comfort
Heating and cooling requirements
Building energy consumption
Envelope and insulation design
Window and glazing selection
Building orientation
Solar shading
Thermal mass
Natural ventilation
HVAC sizing
Moisture and condensation risk
Long-term building performance

The three fundamental modes of heat transfer are conduction, convection and radiation. In an actual building, however, these mechanisms rarely occur independently. A single heat-flow pathway may involve all three.

For example, solar radiation can heat an external roof surface; heat can then conduct through the roof assembly and subsequently be transferred by convection and radiation to the indoor environment.

This article explains the physics of heat transfer and connects it with practical architectural decisions.

Quick Answer: What Is Heat Transfer in Buildings?

Heat transfer in buildings is the movement of thermal energy between spaces, surfaces, materials and the outdoor environment because of temperature differences. It occurs mainly through conduction, convection and radiation, while air leakage and ventilation can also transport heat between indoor and outdoor environments.

The building envelope—walls, roof, floors, windows, doors and other enclosure components—controls a major part of this exchange.

1. Why Heat Transfer Matters in Architecture

Architects do not design buildings in a thermally neutral environment.

A building may receive:

Direct solar radiation
Diffuse solar radiation
Heat from outdoor air
Heat from occupants
Heat from lighting
Heat from electrical equipment
Heat from cooking and other processes

At the same time, heat may leave through:

Walls
Roofs
Floors
Windows
Doors
Air leakage
Ventilation
Evaporation and other environmental processes

The direction of heat flow depends on the temperature relationship between the two environments.

In a cooling-dominated situation, heat generally moves from the warmer exterior toward the cooler interior. In a heating-dominated situation, heat generally moves from the warmer interior toward the colder exterior.

The architectural objective is not to eliminate heat transfer completely. Instead, the objective is to control when, where and how quickly heat moves.

2. The Three Modes of Heat Transfer

2.1 Conduction

Conduction is heat transfer through a material or between materials in direct contact.

In a building, conduction commonly occurs through:

Concrete slabs
Brick walls
Stone
Plaster
Glass
Metal frames
Roof assemblies
Insulation
Floor assemblies

A simplified steady-state relationship for a homogeneous layer is:

Q = kAΔT / L

Where:

Q = heat-transfer rate
k = thermal conductivity
A = area
ΔT = temperature difference
L = material thickness

A material with low thermal conductivity generally resists conductive heat flow better than a highly conductive material.

Architectural example

Consider a concrete roof exposed to intense summer sun.

Solar radiation heats the external surface.
The temperature of the roof surface increases.
Heat conducts through the roof.
The internal surface becomes warmer.
Heat is then transferred to the room by radiation and convection.

Therefore, the roof is not simply a structural element. It is also part of the building’s thermal system.

2.2 Convection

Convection is heat transfer associated with the movement of a fluid, usually air in buildings.

There are two broad forms.

Natural convection

Natural convection occurs because temperature differences create density differences.

Warm air tends to become less dense and rise, while cooler air tends to descend.

This creates air movement that can transfer heat around an interior space.

Forced convection

Forced convection occurs when air is moved mechanically, for example by:

Fans
Air-conditioning systems
Air-handling units
Mechanical ventilation systems

Architectural example

A room with a large warm glazed façade can develop warmer air near the window. That air rises and circulates through the room, transferring heat by convection.

This means that the surface temperature of a building component can influence indoor air movement and thermal comfort.

2.3 Radiation

Radiation is heat transfer through electromagnetic radiation and does not require direct physical contact between two bodies.

The sun is the most important external radiant heat source for buildings.

Radiation affects buildings through:

Solar radiation
Long-wave radiation between building surfaces
Radiation between occupants and surrounding surfaces
Radiation between interior surfaces such as walls, floors and ceilings

Solar radiation can be:

Reflected
Absorbed
Transmitted

A dark roof may absorb more solar energy than a highly reflective roof, while a window can transmit part of the solar radiation directly into the interior.

3. Heat Transfer Usually Occurs as a Chain

One of the most useful concepts for architecture students is that the three modes should not be studied as completely separate processes.

Consider a flat roof in a hot climate:

Sun → solar radiation → roof surface → conduction through roof → interior surface → radiation + convection → room

Similarly, consider a window:

Sun → solar radiation → glazing → transmission/absorption → indoor heat gain

Or consider a poorly insulated wall:

Warm exterior surface → conduction through wall → warm interior surface → radiation and convection to occupants and indoor air

This way of thinking is more useful in design than memorising isolated definitions.

4. Building Envelope and Heat Transfer

The building envelope separates the conditioned interior from the exterior environment.

Typical envelope components include:

Roof
External walls
Windows
Curtain walls
Doors
Floors
Foundations
Basement walls
Skylights

The envelope has to control much more than heat. It also needs to control air, moisture, water, radiation, noise and other environmental influences.

ASHRAE identifies control of heat flow, airflow, water, water vapour and solar radiation among the major performance requirements of building envelopes. It also emphasizes coordination between envelope design and HVAC design.

The envelope should therefore be considered as a system.

A good wall is not simply a thick wall.

It may consist of:

Exterior finish
Weather-resistant layer
Structural layer
Insulation
Air-control layer
Vapour-control layer where required
Interior finish

The exact arrangement depends on climate, materials, construction method and moisture conditions.

5. Thermal Conductivity, Resistance and Transmittance

Three terms are particularly important.

5.1 Thermal Conductivity — k

Thermal conductivity describes how readily a material conducts heat.

It is commonly expressed in:

W/m·K

A lower conductivity generally indicates greater resistance to conductive heat flow for a given thickness.

5.2 Thermal Resistance — R-value

Thermal resistance describes resistance to heat flow.

For a simple homogeneous layer:

R = L/k

Higher R-value means greater resistance to heat flow.

However, an architect should not assume that adding up nominal material R-values always predicts actual building performance perfectly.

Gaps, joints, thermal bridges, compression, air movement and construction quality can reduce real performance.

5.3 Thermal Transmittance — U-value

The U-value, or thermal transmittance, indicates the rate of heat transfer through an assembly per unit area and temperature difference.

For a simplified assembly:

U = 1/R

Lower U-value generally means lower heat transfer through the assembly.

ASHRAE distinguishes between simplified “clear” assembly calculations and effective/whole-assembly performance that accounts for thermal bridges and other effects.

Simple comparison

Parameter	Meaning	General design implication
Thermal conductivity	How easily a material conducts heat	Lower is generally better for insulation
R-value	Resistance to heat flow	Higher is generally better
U-value	Thermal transmittance of an assembly	Lower is generally better
Thermal mass	Ability to store and release heat	Helps moderate temperature changes when properly designed

6. Thermal Mass and Thermal Lag

Thermal mass is often confused with insulation.

They are not the same.

Insulation

Insulation primarily slows heat transfer.

Thermal mass

Thermal mass allows a material or assembly to absorb, store and release thermal energy.

Materials with substantial thermal mass can include:

Concrete
Brick masonry
Stone
Adobe or earth construction
Water

The effectiveness of thermal mass depends strongly on:

Climate
Diurnal temperature range
Insulation location
Solar exposure
Ventilation strategy
Occupancy schedule
Whether the mass can actually exchange heat with the occupied space

Thermal lag

When outdoor temperature changes, the corresponding heat wave does not necessarily appear indoors at the same time.

The delay is commonly described as thermal time lag or phase lag.

Thermal mass can reduce temperature fluctuations and delay peak heat flow, but its usefulness is climate- and design-dependent. DOE guidance similarly notes that thermal mass can moderate indoor temperature fluctuations where the daily temperature cycle and building operation allow it to be effectively used.

Therefore:

Thermal mass is not automatically beneficial simply because a building contains a large quantity of concrete.

Its position, exposure and interaction with ventilation and insulation matter.

7. Solar Heat Gain

Solar radiation is one of the most important heat-gain mechanisms in many buildings.

Solar energy can reach the building through:

Roofs
Walls
Windows
Skylights
Curtain walls

Opaque surfaces mainly absorb, reflect and reradiate solar energy.

Glazing behaves differently because part of the solar radiation can be transmitted directly into the building.

This makes window design particularly important.

8. Solar Heat Gain Through Windows

Two important glazing parameters are:

U-value

The U-value relates to conductive heat transfer through the window assembly.

Solar Heat Gain Coefficient — SHGC

SHGC describes the fraction of incident solar radiation that enters through a window and is subsequently released as heat indoors.

Lower SHGC generally reduces solar heat gain, although the appropriate value depends on climate and heating/cooling requirements.

The U.S. Department of Energy explains that window performance depends on both U-factor and SHGC, and that lower SHGC reduces solar heat transmission.

Other important glazing considerations

Architects should also consider:

Window-to-wall ratio
Orientation
Visible light transmittance
External shading
Glass type
Frame performance
Air leakage
Internal shading
Daylight requirements
Views
Glare

A window is therefore not simply a hole in the wall. It is a multifunctional environmental component.

9. Thermal Bridges

A thermal bridge is a location where heat can flow more easily through an otherwise better-insulated building assembly.

Common examples include:

Reinforced-concrete slab edges
Balcony projections
Concrete beams
Columns
Window frames
Metal cladding supports
Parapets
Structural connections
Fasteners
Wall-floor junctions

ASHRAE notes that thermal bridges can increase heat transfer, create colder or hotter surface temperatures and contribute to condensation and comfort problems.

Why thermal bridges matter

Imagine a wall with continuous insulation.

If a reinforced-concrete balcony passes directly through that insulation, the balcony can provide a highly conductive path through the thermal envelope.

The wall may have a good nominal U-value, but the junction can perform considerably worse.

Architectural response

Thermal bridges can be reduced through:

Continuous insulation
Thermally broken connections
Improved slab-edge detailing
Careful window installation
Reduced conductive penetrations
Appropriate structural detailing
Thermal-bridge analysis for complex junctions

This is one area where architectural detailing directly influences energy performance.

10. Air Leakage and Heat Transfer

Air leakage is different from conduction.

Conduction transfers heat through materials.

Air leakage transports heat because air itself moves through gaps and openings.

Common leakage locations include:

Window frames
Door frames
Wall junctions
Roof penetrations
Service penetrations
Electrical outlets
Pipe penetrations
Duct penetrations
Construction joints

ASHRAE distinguishes infiltration as uncontrolled inward air leakage and exfiltration as uncontrolled outward air leakage caused by pressure differences. It also emphasizes the importance of a continuous air-barrier system.

Important distinction

Ventilation is intentional air movement.

Infiltration is uncontrolled air movement.

A building may need ventilation for indoor air quality, but uncontrolled leakage can increase heating and cooling loads and create moisture problems.

Therefore, airtightness and ventilation should be designed together rather than treated as opposing concepts.

11. Heat Transfer Through a Typical External Wall

Consider a simplified wall assembly:

Exterior → Interior

Exterior finish
Masonry or cladding
Insulation
Structural wall
Interior plaster/finish

Heat may move through this assembly by several mechanisms.

Outside surface

Solar radiation heats the external surface.

Exterior surface to wall

Heat is exchanged between the outdoor air, surface and surrounding environment.

Through the wall

Heat primarily conducts through solid layers.

Across an air cavity

Heat may be transferred through a combination of conduction, convection and radiation depending on cavity configuration and surface properties.

Interior surface

The interior surface exchanges heat with the room through convection and long-wave radiation.

This is why a complete building-envelope analysis is more useful than looking at the conductivity of one material in isolation.

12. Heat Transfer Through a Roof

Roofs deserve particular attention because they may receive prolonged solar exposure.

A typical roof heat-flow sequence may be:

Solar radiation → roof surface → roof assembly → ceiling → indoor space

Architectural strategies can include:

Roof insulation
Reflective or cool roof surfaces
Vegetated roofs where appropriate
Shading
Roof cavities designed appropriately
Reduced thermal bridging
Continuous insulation
Appropriate roof colour and solar reflectance
Ceiling insulation

The correct strategy depends on climate and construction system.

13. Heat Transfer and Building Orientation

Orientation affects the amount and timing of solar radiation received by different façades.

It also affects:

Window solar exposure
Shading requirements
Daylighting
Natural ventilation
Roof and wall heat gain
Outdoor thermal conditions

DOE guidance notes that orientation influences solar heat gain and that east- and west-facing glazing can be particularly difficult to shade because of low-angle solar exposure.

Orientation should therefore be considered together with:

Sun path + glazing + shading + ventilation + building form

Rather than using one universal orientation rule, architects should evaluate the actual climate, latitude, site obstructions and building programme.

14. Heat Transfer and Shading Devices

Shading can reduce solar radiation before it reaches the glazing or opaque façade.

Common devices include:

Horizontal overhangs
Chajjas
Louvres
Vertical fins
External blinds
Pergolas
Deep balconies
Verandahs
Vegetation
Adjacent buildings

External shading is often particularly effective because it can intercept solar radiation before it reaches the glass.

However, shading must be designed according to:

Solar altitude
Solar azimuth
Orientation
Latitude
Seasonal requirements
Daylight
View requirements
Ventilation
Glare

Archi-Monarch already has dedicated resources on building shading and shading according to climate; this article should therefore introduce shading as part of the heat-transfer mechanism and link readers to those deeper resources.

15. Heat Transfer and Natural Ventilation

Ventilation can either increase or reduce thermal loads depending on climate and operating conditions.

In a suitable climate, ventilation can remove:

Sensible heat
Stored heat
Indoor pollutants
Excess humidity

Natural ventilation may occur through:

Wind pressure
Cross-ventilation
Stack effect
Buoyancy
High- and low-level openings

However, opening windows in a hot, humid or extremely hot outdoor environment does not automatically cool a building.

The outdoor air must be evaluated against indoor conditions and the intended ventilation strategy.

This is why natural ventilation should be considered together with:

Outdoor temperature
Humidity
Wind
Solar radiation
Occupancy
Internal heat gains
Building thermal mass

16. Heat Transfer and Building Form

Building geometry influences the relationship between envelope area and internal volume.

Important considerations include:

Surface-to-volume ratio
Building depth
Courtyards
Compactness
Self-shading
Façade exposure
Roof area
Window distribution

A compact form can reduce exposed envelope area, while a more articulated form may provide shading, courtyards and opportunities for natural ventilation.

Therefore, there is no universally “best” building form for heat transfer.

The appropriate geometry depends on climate and design objectives.

17. Heat Transfer in Different Climatic Conditions

Hot-dry climates

Typical strategies may include:

Solar protection
High thermal mass where diurnal temperature swings support it
Controlled openings
Night ventilation where appropriate
Reflective surfaces
Insulated roofs
Courtyards and shaded outdoor spaces

Warm-humid climates

Priority often shifts toward:

Solar shading
Air movement
Reduced unwanted solar gain
Moisture-aware envelope design
Cross-ventilation
Carefully controlled thermal mass
Appropriate roof and wall protection

Composite climates

Buildings may require seasonal adaptation.

A design may need to balance:

Summer solar protection
Winter solar access
Natural ventilation
Insulation
Thermal mass
Shading

Cold climates

Typical priorities include:

High thermal resistance
Airtightness
Reduced uncontrolled heat loss
Appropriate solar gain
Thermal-bridge control
High-performance windows
Moisture management

These are general design principles rather than substitutes for climate-specific simulation or applicable codes.

18. Indian Building-Energy Code Context

For projects in India, heat-transfer decisions should be coordinated with the applicable energy code and local regulatory framework.

The Bureau of Energy Efficiency identifies ECBC 2017 as India’s commercial-building energy code framework and states that it addresses building envelope, HVAC, lighting, electrical systems and renewable energy. It considers India’s five climatic zones.

For residential buildings, BEE’s Eco-Niwas Samhita establishes envelope-performance requirements intended to limit heat gains and heat losses while also considering natural ventilation and daylighting. BEE currently also lists the ENS Code 2024 within its residential energy-efficiency resources.

The Energy Conservation and Sustainable Building Code 2024 (ECSBC 2024) includes a dedicated Building Envelope chapter and addresses matters such as fenestration, shading and envelope performance.

Important: Code applicability, adoption and mandatory requirements can depend on building type, size, state/UT notification and project circumstances. Architects should verify the current notified requirements applicable to the specific project rather than applying an isolated value from a general article.

19. Practical Architectural Strategies to Control Heat Transfer

A useful design workflow is:

Step 1 — Understand the climate

Study:

Temperature
Humidity
Solar radiation
Wind
Diurnal temperature range
Seasonal variation

Step 2 — Study the site

Consider:

Orientation
Existing trees
Adjacent buildings
Topography
Water bodies
Shading
Wind exposure

Step 3 — Establish the building form

Consider:

Compactness
Surface-to-volume ratio
Courtyards
Building depth
Self-shading

Step 4 — Control solar gain

Use:

Orientation
External shading
Appropriate glazing
Vegetation
Roof reflectance
Reduced unwanted glazing

Step 5 — Design the envelope

Coordinate:

Insulation
Wall construction
Roof construction
Windows
Doors
Air barrier
Moisture control

Step 6 — Detail thermal bridges

Review:

Slab edges
Balconies
Columns
Beams
Parapets
Window frames
Cladding supports

Step 7 — Consider thermal mass

Use thermal mass where the climate and operating strategy can benefit from it.

Step 8 — Coordinate ventilation

Decide when natural ventilation, mixed-mode operation or mechanical ventilation is appropriate.

Step 9 — Coordinate with HVAC

The envelope should be considered before finalising HVAC capacity. ASHRAE describes the envelope and HVAC system as interdependent parts of building performance.

Step 10 — Verify the design

For significant projects, consider:

Thermal calculations
Solar studies
Energy modelling
Daylight analysis
Computational fluid dynamics where justified
Thermal-bridge analysis
Hygrothermal analysis
Construction-detail review

20. Common Mistakes in Designing for Heat Transfer

Mistake 1: Treating insulation as the complete solution

Insulation is important, but solar radiation, glazing, thermal bridges, air leakage and ventilation can also dominate performance.

Mistake 2: Looking only at material conductivity

A material may have excellent conductivity characteristics while the completed assembly performs poorly because of junctions and thermal bridges.

Mistake 3: Ignoring windows

A well-insulated wall does not compensate automatically for excessive or poorly controlled glazing.

Mistake 4: Using the same shading strategy on every façade

Solar angles differ by orientation.

Mistake 5: Assuming thermal mass always improves performance

Thermal mass works differently depending on climate, insulation, ventilation and occupancy patterns.

Mistake 6: Confusing ventilation with infiltration

Intentional ventilation is not the same as uncontrolled air leakage.

Mistake 7: Ignoring construction quality

Gaps, discontinuous insulation, poorly sealed penetrations and badly detailed junctions can undermine a carefully designed envelope.

Mistake 8: Designing the envelope and HVAC independently

A change in envelope performance can change cooling and heating loads, which can affect equipment sizing and operation.

21. Simple Example: Comparing Two Wall Strategies

Imagine two external wall assemblies.

Wall A

Masonry
Plaster
No continuous insulation

Wall B

Exterior finish
Masonry/structural wall
Continuous exterior insulation
Interior finish

Wall B can provide greater resistance to heat flow and, when detailed correctly, can reduce thermal bridging by keeping the insulation layer continuous.

However, the final result depends on the complete assembly, including:

Thickness
Material properties
Junctions
Openings
Moisture
Air leakage
Construction quality

Therefore, architects should evaluate assemblies rather than isolated materials.

22. Heat Transfer, Thermal Comfort and HVAC

Heat transfer is ultimately connected with occupant experience.

A room may have an acceptable air temperature but still feel uncomfortable if occupants are exposed to:

Hot glazing
Cold glazing
Hot walls
Cold walls
Excessive air movement
Strong radiant asymmetry

This is why thermal comfort involves more than air temperature.

The building envelope influences surface temperatures and radiant exchange, while ventilation and HVAC influence air temperature and movement.

A successful building therefore needs an integrated approach.

23. Heat Transfer as an Architectural Design Tool

Heat transfer should not be treated only as an engineering calculation performed after architectural design.

It can influence the design from the beginning.

At site level

Orientation
Landscape
Trees
Adjacent buildings
Solar access

At massing level

Building compactness
Courtyards
Self-shading
Building depth

At façade level

Window-to-wall ratio
Shading
Glazing
Surface colour
Insulation

At detail level

Slab edges
Window frames
Wall-roof junctions
Parapets
Structural penetrations

At systems level

Natural ventilation
HVAC
Controls
Heat recovery
Mixed-mode operation

This is where building physics becomes architecture.

24. Key Terms at a Glance

Term	Simple meaning	Architectural relevance
Conduction	Heat movement through material	Walls, roofs, slabs
Convection	Heat transfer associated with moving fluid/air	Rooms, cavities, HVAC
Radiation	Heat transfer through electromagnetic radiation	Sun, surfaces, glazing
Thermal conductivity	Ability of material to conduct heat	Material selection
R-value	Resistance to heat flow	Insulation performance
U-value	Heat transfer through an assembly	Envelope performance
SHGC	Fraction of solar radiation admitted through glazing and becoming heat	Window selection
Thermal mass	Ability to store and release heat	Passive thermal design
Thermal lag	Delay in heat response through an assembly	Climate-responsive design
Thermal bridge	Localised high-conductivity heat path	Junction detailing
Air leakage	Uncontrolled air movement through envelope	Airtightness and energy
Thermal envelope	Boundary separating conditioned and unconditioned environments	Whole-building performance

25. Advantages of Understanding Heat Transfer

A sound understanding of building heat transfer can help architects:

Improve thermal comfort
Reduce unwanted heat gain and heat loss
Select appropriate envelope systems
Improve window design
Reduce cooling and heating loads
Coordinate architecture and HVAC
Improve passive design
Reduce thermal-bridge problems
Support energy-code compliance
Improve long-term building performance

26. Limitations and Design Challenges

Heat-transfer design is not simply a matter of choosing the material with the lowest conductivity.

Real buildings involve interacting variables:

Solar radiation
Outdoor climate
Internal gains
Wind
Air pressure
Moisture
Occupant behaviour
Building operation
Construction quality
Material ageing
Maintenance
HVAC operation

For complex buildings, simplified hand calculations may not be sufficient. Multidimensional heat flow at junctions can require simulation or specialised testing. ASHRAE specifically notes that complex thermal bridges may require multidimensional analysis rather than simplified calculations.

27. Frequently Asked Questions

What are the three modes of heat transfer in buildings?

The three fundamental modes are conduction, convection and radiation. Conduction transfers heat through materials, convection transfers heat through moving fluids such as air, and radiation transfers energy through electromagnetic radiation.

Why is heat transfer important in architecture?

Heat transfer affects thermal comfort, energy consumption, envelope design, glazing, insulation, shading and HVAC loads. Understanding it allows architects to control unwanted heat gain and heat loss through appropriate design decisions.

What is conduction in a building?

Conduction is heat transfer through a material caused by a temperature difference. It commonly occurs through walls, roofs, floors, windows, slabs and structural elements.

What is convection in a building?

Convection is heat transfer associated with moving air or another fluid. In buildings it occurs through natural air movement, stack effects, ventilation and mechanical air-conditioning systems.

What is radiation in building heat transfer?

Radiation is heat transfer through electromagnetic energy. Solar radiation is particularly important because it can heat roofs, walls and glazing and can pass through transparent openings.

What is the difference between R-value and U-value?

R-value describes resistance to heat flow, while U-value describes thermal transmittance through an assembly. In a simplified relationship, U = 1/R. Higher R and lower U generally indicate better resistance to conductive heat transfer.

What is a thermal bridge?

A thermal bridge is a localised part of a building envelope where heat flows more readily than through adjacent insulated areas. Common examples include slab edges, balconies, structural connections and poorly detailed window frames.

Does thermal mass reduce heat transfer?

Thermal mass does not simply stop heat transfer like insulation. It stores and releases heat and can delay and moderate temperature fluctuations. Its effectiveness depends on climate, construction, insulation, solar exposure and ventilation strategy.

Does more insulation always mean a better building?

Not necessarily. Insulation is important, but overall performance also depends on glazing, shading, thermal bridges, air leakage, moisture control, thermal mass, ventilation and building operation.

How can architects reduce unwanted heat gain?

Common strategies include appropriate orientation, external shading, controlled glazing, roof and wall insulation, reflective surfaces, thermal-bridge control, airtight detailing and climate-appropriate ventilation.

Conclusion

Heat transfer in buildings is the foundation of building thermal performance.

The three fundamental mechanisms—conduction, convection and radiation—interact continuously across the building envelope. Solar radiation can heat a surface, conduction can carry heat through a wall or roof, and convection and radiation can transfer that heat into an occupied space.

For architects, the important lesson is that heat transfer is not only a material-science problem. It is a design problem.

Orientation, building form, glazing, shading, insulation, thermal mass, ventilation and construction details all influence how heat enters, moves through and leaves a building.

The most effective approach is therefore to design the building envelope as an integrated system and coordinate it with climate, occupants, structure, materials, moisture control and HVAC.

When these decisions are made early, the building can respond to its climate rather than relying entirely on mechanical systems to correct problems created by the architecture.