Introduction to Building Envelope

Question 1

Define “Building Envelope”

Answer 1

A building envelope also referred to as the ‘skin’ of the building, is the element of the building that separates the interior from the exterior.

Question 2

How to ensure a building envelope that is functional with a long lifespan?

Answer 2

Good quality materials.

Question 3

Name the elements of a building envelope. There are 5.

Answer 3

1. Exterior walls
2. Roof
3. Openings
4. Flashings
5. Foundation walls

Question 4

What is the typical composition of an exterior wall?

Answer 4

• Cladding
• Insulation
• Vapour Barrier
• Air Barrier
• Sheathing

Question 5

What are the most common building envelope problems? Name at least 5.

Answer 5

• Rain penetration
• Infiltration of groundwater at grade and basement level
• Infiltration of snow in attics via soffits and grilles
• Frozen pipes
• Heating costs
• Efflorescence
• Spalling masonry
• Ice build-up
• Condensation in the wall cavity
• Mould
• User discomfort

Question 6

What is ‘efflorescence’ in building envelopes?

Answer 6

Water/air transfers through the brick/mortar leaving a salt deposit, formed from calcium that is found within the material.

Question 7

What is ‘spalling masonry’?

Answer 7

Spalling masonry is when the exterior surface of the masonry appears to chip off.

Question 8

What causes ‘spalling masonry’?

Answer 8

Due to the freeze/thaw cycles, the moisture content in the brick/masonry expands when frozen, and then cracks.

Question 9

How to prevent ‘ice-build up’ or ‘ice-damming’?

Answer 9

Good quality insulation

Question 10

What causes ice to build up?

Answer 10

• Caused by a flaw in ( or inadequate ) roof insulation
• Snow melts
• Resulting water freezes in a cold area
• Creating a dam allows water to back up and penetrate shingles, also creating icicles

Question 11

Condensation in a wall cavity will lead to what?

Answer 11

Mould growth

Question 12

What are the 3 elements that create mould growth?

Answer 12

• Mushroom spores
• Humidity
• Organic material

Question 13

What are methods used to detect mould growth?

Answer 13

• Air sampling detection equipment
• Trained dogs

Question 14

What are building envelope design considerations and requirements? Name at least 5.

Answer 14

• Structural performance and movement
• Rain penetration
• Air infiltration and exfiltration
• Condensation control ( controlling water vapour )
• Thermal control
• Sound and pollution control
• Natural light
• Fire resistance
• Durabiity
• Green design
• Aesthetics
• Cost

Question 15

What forces does the building envelope have to withstand?

Answer 15

Gravity:
- Must support its own weight
- May have to support an additional weight of building ( load-bearing wall )

Wind loads:
- Minor impact loads ( birds, airborne debris, etc. )

Question 16

How is wind pressure influenced? Name at least 5 factors.

Answer 16

• Height of building
• Shape of building
• Direction of prevailing winds
• Position of building on site
• Relative location to neighboring buildings
• Topography

Question 17

What is negative pressure?

Answer 17

Negative pressure generally refers to a place where pressure is smaller in one place relative to another place. ( ex. blowing into a water bottle )

Question 18

What is ‘Deflection’?

Answer 18

In structural engineering, deflection is the degree to which a part of a structural element is displaced under a load. It may refer to an angle or a distance.

Question 19

What is a ‘Creep’?

Answer 19

The permanent sagging of a material over time.

Question 20

What is ‘Differential Settlement’?

Answer 20

Differential settlement is the uneven or unequal settling or sinking of a home or building’s foundation. This occurs when the soil under your foundation contracts, expands, or shifts irregularly, causing the structure to settle unevenly.

Question 21

Explain ‘Thermal expansion and contraction’.

Answer 21

All materials expand in heat and contract in the cold. Thermal expansion/contraction is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of a substance’s average molecular kinetic energy.

Question 22

True or False. Swelling due to moisture, humidity and temperature can cause movement. To accommodate all types of movement, we have to provide mechanisms for movements including control joints and expansion joints.

Answer 22

True.

Question 23

Define ‘CCR’

Answer 23

Convection
Conduction
Radiation

Question 24

Name a few building envelope design considerations.

Answer 24

• Air infiltration and exfiltration
• Condensation control
• Thermal control
• Sound and pollution control
• Natural light
• Fire resistance
• Durability
• Green-design
• Aesthetics
• Cost
• Life-cycle cost

Question 25

True or False. Infiltration of unconditioned air or exfiltration of conditioned air may cause higher energy costs, drafts, and localized temperature differences, and may even lead to condensation and damage in a wall.

Answer 25

True.

Question 26

True or False. Vapour barriers help to keep moist air from penetrating walls; it may cause condensation and damage in the wall.

Answer 26

True.

Question 27

What are some factors that cause sound pollution? There are 3.

Answer 27

- Air Infiltration - Orientation of the building with respect to its surroundings. - Quality and amount of windows exposed to noise.

Question 28

Define 'Fire Resistance Rating'

Answer 28

Fire resistance rating (FRR) is the time in minutes or hours for which the construction materials or assemblies have withstood a standard fire exposure. How to measure the FRR of a material? Fire resistance ratings are calculated based on the time taken by a given material or structure to fail during a fire

Question 29

What is a 'combustible' material?

Answer 29

Combustible material means a material that, in the form in which it is used and under the conditions anticipated, will ignite, burn, support combustion or release flammable vapors when subjected to fire or heat. Wood, paper, rubber, and plastics are examples of combustible materials.

Question 30

What is a 'non-combustible' material?

Answer 30

Non-combustible means that the material will not ignite, burn or release flammable vapors. when exposed to fire or heat. Examples of non-combustible materials include steel, masonry, ceramics and certain insulating materials (such as fiberglass or mineral wool insulation).

Question 31

What makes a material durable?

Answer 31

Resistance to corrosion, rusting and rotting. The ability to withstand wear and tear through weathering and corrosive attack.

Question 32

What are some advantages to Green Design?

Answer 32

- Durability; long lasting ( less replacements, low maintenance ) - Provides better thermal control; less energy loss - Natural light

Question 33

What is Green Design?

Answer 33

Environmentally sustainable design is the philosophy of designing physical objects, the built environment, and services to comply with the principles of ecological sustainability and also aimed at improving the health and comfortability of occupants in a building.

Question 34

True of False. Aesthetics involve image and context.

Answer 34

True.

Question 35

True of False. Initial costs include materials and installations.

Answer 35

True.

Question 36

Define 'Life-cycle cost' (LCC)

Answer 36

LLC refers to the total cost of ownership over the life of an asset. ( + includes planning, design, construction and acquisition, operations, maintenance, renewal and rehabilitation, depreciation and cost of finance and replacement or disposal )