1. Final Project - Building Envelope Flashcards
What properties of a material intended to be exposed to the weather or used in a humid environment should be considered? (2)
- Water resistance
- Water vapor resistance.
What properties of a material that will be used in the construction of the outer envelope should be considered? (2)
- Conductivity
- Thermal resistance
What properties of a material that will be used to finish the surfaces of a room should be considered? (3)
- Transmission capacity…
- Reflection capacity…
- Absorptive capacity…
… visible light and radiant heat
Name the 4 factors on which the evaluation of building materials must be based.
- functional
- economical
- aesthetic
- environmental consequences of their use (life cycle estimation)
What properties determine the durability and maintenance costs of a material?
- The density or hardness of a material determines its resistance to wear and abrasion; the durability of this material and the costs of its maintenance depend on it.
3 broad aspects which impact window performance
- Physical characteristics of window assembly (window as system of elements)
- Physical interference with the enclosure (component of build. envelope)
- Effects of windows on quality of indoor space (part of indoor environment)
Function of cap bead & heel bead. What do these components prevent?
Cap: keeps rain out
Heel: air tightness (inside joint seal) * prevents air leakage
3 Ways to mitigate condensation on windows.
- Add air space with plastic or glass
- Circulate warm air towards glass
- Remove obstructions
4 Ways to mitigate sound transmission in a window system
- Large glazing caps
- Thicker glass
- Separate frames / sashes (int / ext)
- Completely airtight (fixed often perform better than operable)
Functions of films & coatings on windows
- reflect solar heat back out
- reflect radiant heat back in
- reduce transmission of UV rays
What type of window frame is best for high rise & commercial & why?
Aluminium
they can be designed to meet specific structural requirements
3 Types of strengthened glass - pros & cons
1 - FULLY TEMPERED (surface in compression & core in tension)
+ 3-5x more resistant to fail due to bend, impact, heat
- impact along edge will shatter sheet
2 - HEAT STRENGTHENED (lower level of surface compression compared to fully tempered, same process)
+ stronger than annealed glass & less susceptible to shatter due to edge impact
3 - LAMINATED (bonded together with intermediate layers of plastic)
+ holds together if broken
+ can be used for solar heat control, sound control, bullet-resistance, blast resistance
- not stronger than regular annealed glass
2 pros / 3 cons of PVC windows
+ low maintenance
+ stable in saline / polluted air
- steel in sash / frame for stability = increased thermal conductivity
- risk of cohesive failure at the joint
- limited light tones because of fading, expansion due to direct sun
1 pros / 2 cons of unsealed windows
+ no need to be replaced due to condensation
- cannot accommodate any films, coatings, gases
- separate sash option typically only available in sliding windows
3 pros / 2 cons of sealed windows
+ 2 surfaces to clean rather than 4
+ no condensation between the glass
+ability to incorporate films, coatings, gases
- metal spacer = thermal bridge (can cause condensation along cold perimeter of glass)
- deflection due to change in temp. & wind pressure = compression and tension cycle on sealant (can cause failure)
As a point of reference, know the typical R value of single and double glazing (w 5mm air space).
single R = .88
double R = 1.61 *Approx
List the 5 main forces of moisture transfer in a building envelope.
- KINETIC ENERGY OF RAIN (impact)
-
SURFACE TENSION (drip edges)
- water clings to horizontal(ish) surfaces
-
CAPILLARY (gaps <5mm)
- water drawn into permeable materials & small openings (cracks, joints & junctions)
-
GRAVITY
- moves rain down surface and into sloped openings (holes cracks flashing)
-
AIR PRESSURE DIFFERENCE
- rain driven in direction of lower pressure
What are the 4 ‘D’s of preventing rain pentration?
- deflection
- drainage
- drying
- durability
List & describe the 4 main strategies for preventing moisture infiltration.
-
Integral Sills & Drip Edges on Flashings
- typ. projection of 10mm beyond cladding
- 25mm may be rqrd
-
Drainage Holes in Permanent Cladding
- needs to slowly dissipate/evap water
- min. 10mm to prevent capillary bridging
- Sealants/ Gaskets reduce openings
- Joints:
-
Locked Joints (open)
- manage gravity driven
- rqr 10mm overlap
-
Lapped Joints (closed)
- rqr 5mm gap btwn to prevent capillary action
-
Locked Joints (open)
Describe the 2 lines of defence in a rainscreen system.
- CLADDING
- a DRAINED CAVITY
- intercept all water that passes cladding
- dissipate water to exterior:
- evaporation
- drain via flashing
2.b or WATERPROOF MEMBRANE
A rainscreen should also be protected, what are 3 ways to do so?
- ROOF OVERHANGS
- CORNICES
- BALCONIES
What is the primary purpose of thermal insulation?
Control the flow of heat through an exterior assembly.
List the 4 most common types of insulation and their r-value per inch of thickness
Batt = 3.3 (same fiberglass or rock wool)
Rigid board
= 2.5 (cellular glass)
= 3.6 - 7.2 (the various polys - polyisocyanurate highest)
Foamed in Place
= 6.2 (polyuerethane)
Loose fill
= 2.1 -3.7 (vermiculite to cellulose)
The steady state method of measuring thermal resistance of a construction assembly is useful,
but these 4 factor also influence heat/loss gain:
- Surface colour / reflectivity
- Mass (time lag)
- Orientation (solar /wind)
- Latent Heat (occ. etc)
Masonry elements that are bonded together with mortar are stronger in ________________ than wood.
A) shear
B) compression
C) shrinkage
D) bending
E) tension
B) compression
What are the nominal brick sizes for:
1 - modular
2 - norman
3 - utility
1 - modular 100 x 68 x 205 (3.937”x2.677”x8.071”)
2 - norman 100 x 68 x 305 (3.937”x2.677”x12”)
3 - utility 100 x 100 x 305 (3.937”x3.937”x12”)
**nominal brick sizing includes mortar joints
What are these 3 types of face brick:
1 - FBX
2 - FBS
3 - FBA
1 - FBX = perfect/high degree of uniformity
2 - FBS = wider range of acceptable colour
3 - FBA = desired non-uniformity
What is efflorescence?
Powdery deposit on face of brick, due to leaching and crystallization of soluble salts within material
Best defence: reduce moisture absorption
List and describe the 6 main varieties of brick.
(example: soft mud)
1 - SOFT MUD
• form brick w wet clay (20-30% moist)
2 - SANDSTRUCK (matt texture)
• form w form lined w sand to prevent sticking
3 - WATERSTRUCK (smooth dense surface)
•form lubricated w water
4 - STIFF MUD
• extruding stiff but plastic clay (12-15% moist)
5 - DRY PRESS (sharp edge smooth surface)
• form relatively dry clay (5-7% moist)
What are brick grades a measure of?
Brick grades measure durability when exposed to weathering.
According to: • compressive strength • max H20 absorb • max saturation coefficient
What do the 3 brick grades below indicate:
1 - SW
2 - MW
3 - NW
These grades indicate suitable weather regions
1 - SW = Severe Weather
(min. comp. str. 2500psi)
2 - MW = Moderate Weather
(min. comp. str. 2200psi)
3 - NW = Negligible Weather
(min. comp. str. 1250psi)
In order of highest strength to lowest, list the 3 types of concrete used in concrete masonry units.
- Normal
- Medium
- Lightweight
What do CMU grades indicate?
Suitability for load bearing:
N = Loadbearing below and above grade
S = Loadbearing above grade only
How can you identify if CMUs have been manufactured to have a certain moist. content to prevent shrinking & cracking?
Type 1 = manufacture to have certain moist content
Type 2 = not manuf. to have cert. moist. content
What is the nominal size of a typical CMU block?
8 x 8 x 16”
(205 x 205 x 405mm)
