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ARCH TECH
LECTURE 3 INFO
| Question | Answer |
|---|---|
| What is the rainscreen principle? | A design approach that controls rain penetration using two lines of defense: one to minimize water entry and another to manage and drain any water that gets through. |
| What is the First line of defense in a rainscreen wall? | Blocking outside rain and minimizes water penetration |
| What is the second line of defense in a rainscreen wall? | Intercepts and drains water back outside by accepting the water infiltration but allowing drainage. |
| What factors determine moisture load on a wall? | Precipitation intensity, duration, frequency, wind, building heigh and shape, and facade features. |
| How does wind affect rain penetration? | It drives rain onto surfaces and increases pressure that forces water into openings. |
| Why must climate be considered in wall design? | Because wall performance varies by region, a system that works in one climate may fail in another. |
| What is the role of the first line of defense? | To reduce the amount of water entering the wall. |
| What are the three main design goals of the first line of defense? | 1. reduce moisture load 2. minimize holes 3. manage driving forces |
| Name three ways to reduce moisture load on cladding. | - Roof overhangs - Drip edges and window sills - Proper drainage design |
| How do overhangs help reduce moisture load? | They direct water away from walls, reducing wetting. |
| Where do most water entry points occur? | Joints, junctions, windows, doors, and penetrations. |
| Why are joints critical in cladding design? | They are primary pathways for water penetration. |
| What forces drive water through walls? | Gravity, capillary action, air pressure difference, surface tension, and kinetic energy of rain. |
| Which forces move the water? | Gravity and air pressure difference |
| How do permeable materials behave? | Absorb and store water |
| How do impermeable materials behave? | Resist absorption but rely on joints for protection. |
| Why is stored water in permeable materials a concern? | It remains after rain and must be safety drained or evaporated. |
| What is the purpose of the second line of defense? | To catch and remove any water that passes the first layer |
| What are the second line of defenses two main function? | 1. intercept water 2. Drain or evaporate it |
| What is free water? | Water moving through openings due to gravity or pressure. |
| What is bound water? | Water held in materials or small pores by capillary forces. |
| How is free water controlled? | With drainage cavities or waterproof membranes. |
| How is bound water controlled? | With capillary breaks like air gaps. |
| What is the most effective way to remove water? | Drainage |
| Why is evaporation less reliable? | It depends on climate humidity and temperature. |
| What cavity depth is typically needed for drainage for masonry? | 25 mm |
| What cavity depth is typically needed for drainage for most walls? | approx. 10 mm |
| Why is continuity important in the second line of defense? | To ensure water cannot bypass the system through gaps or joints. |
| Where must continuity be maintained? | Across joints, penetrations, windows, and wall connections. |
| What is the role of the air barrier system? | It reduces air pressure differences that drive water into the wall. |
| Besides rain what other moisture sources must be controlled? | Interior moisture (vapor diffusion and air leakage) |
| Why is integrated design important? | Because heat air and moisture control systems interact. |
| Why should designers assume the first line of defense will fail? | Because of construction imperfections, aging, and material deterioration. |
| What is the key principle of rainscreen design? | Redundancy with multiple layers of protection. |
Created by:
averylumgair