ARCH 262 Buildling Technology, Materials & Methods, Fall 2003, Prof. Ochshorn
Quiz #2 solutions (100 points; all questions worth 4 points each unless otherwise noted)

Part I: Names and definitions
1. Sketch a building with a steep-slope roof in the shape of a gable, and label the following: ridge, rake, eave.

See "02.steeproof.jpeg" image in "roofing: steep slope" slideshow online. Ridge is top edge; eave is bottom edge; rake is angled edge along side of steep-sloped roof.

2. (a) What does EIFS stand for? (b) Draw a section through a typical PB EIFS wall, and label all the constituent parts of the system, including the substrate. [6 points]

a) Exterior Insulation and Finish System; b) see "34.eifs.jpeg" image in "EIFS" slideshow. Note lamina (consisting of finish coat and base coat with fiberglass mesh embedded) on rigid polystyrene insulation on substrate.

3. What is tempered glass? Explain how it is made from float glass, and what it's beneficial properties are.

Tempered glass is float glass reheated and cooled to create residual stresses in the glass (compression on the outer faces; tension in the middle) that result in increased strength and breakage in small pieces without sharp edges.

4. What is low-e (low-emissivity) glass; that is, how does it work, and what is it good for?

Low-e glass is ordinary float glass with an applied surface coating that permits passage of most shortwave radiation (light and heat) but reflects most longer-wave radiation (heat). It is good for windows transparent to visible light (i.e., with no visible tint or reflective surface) that still has excellent thermal properties.

5. What is the purpose of a bond breaker in a sealant joint (we already know that it prevents a bond from forming, so explain why that is important in a sealant joint)?

Bond breakers prevent adhesion of the sealant to the backer rod (or other unwanted surfaces), allowing the sealant to stretch or contract without tearing.

6. What is the difference between a mullion and a rail in a metal and glass curtain wall system?

Mullions are the vertical or horizontal framing elements in metal-glass curtain wall systems to which the glass is fastened, and which in turn are fastened to the building structure. Rails are the horizontal metal framing members spanning between vertical mullions. [note: no points were deducted for missing the definition of "rail."]

7. What is the definition and purpose of draft in precast panels?

Draft is the slight deviation from the perpendicular angle built into precast forms (and therefore into the precast elements themselves) that facilitates the removal of the precast elements from the formwork.

8. What is the definition of dew point?

Dew point is the temperature at which water condenses from the air; i.e., the temperature corresponding to 100% relative humidity.

9. Give one example where a building separation joint should be used.

Examples: where two parts of a building have dramatically different heights, geometries, or sub-surface conditions; for especially long buildings; and also important in seismic zones, where building movement during ground shaking needs to be understood and accommodated.

10. What is a construction tolerance, and why do we need to consider tolerances of structural systems when designing cladding systems?

Construction tolerance refers to the deviation from ideal (designed) dimensions. It has nothing to do with building movement. Because cladding systems are often manufactured to extremely small tolerances (in some cases, these dimensions can be assumed to be absolutely perfect) while structure is often built with large tolerances (up to 1" out of alignment for steel, concrete frames), it is necessary to detail the building so that the "perfect" enclosure elements can be attached to the "not-so-perfect" structural elements. The basic concept here is "3-way alignment," using such things as shims, and slotted holes in clip angles.

11. In one sentence each, provide concise definitions of the three modes of heat flow: conduction, convection, and radiation.

Conduction is the molecule-to-molecule transfer of heat (energy); convection is the movement of liquids or gases carrying heat energy, for example, as hot air rises; radiation is the transfer of energy through electromagnetic waveforms, including ultraviolet, infrared, visible light, radio waves, x-rays, etc.

Part II: How big is it?
12. Draw a section through a typical 1"-thick insulated glass (IG) unit, showing dimensions of glass and air space; and labeling glass, spline, desiccant, and sealant. [5 points]

See "53.curtainwall.jpeg" in "glass, glazing..." slideshow. Typical glass thickness in this context is 1/4" with 1/2" air space.

13. To the nearest inch, how thin can thin-stone veneer be made? Choose the best answer from the following choices: a) 1"; b) 2"; c) 4"; d) 8".

1"

14. Imagine a 20' x 20' garage with an ordinary gable roof designed with a 4 in 12 slope. How many inches higher is the ridge than the eave, measured vertically? [5 points]

The roof rises 4" for each horizontal foot (12 inches), so it rises 4x10 inches or 40" in ten feet (i.e., to the centerline of the garage, or roof ridge)

Part III: What does it look like?
15. Sketch a wall section through any one of the following enclosure wall systems, assuming a reinforced concrete structure: a) precast concrete veneer; b) thin stone veneer; or c) metal panel veneer. Show the structure and enclosure system, and label all important elements in the enclosure system, any required back-up system, and any typical connections, fasteners, or supporting elements. The sketch to the left shows the assumed reinforced concrete structure consisting of spandrel girder and slab (columns are not shown). Draw the section big enough so that the various parts of the system can be shown clearly. [10 points]

a) See text, p.704 for precast example; b) see text, p.701-703 for stone veneer examples; c)See 62.metal.jpeg, 69.metal.jpeg, and 72.metal.jpeg in "metal panels..." slideshow for examples of metal panel systems. The first shows a CMU backup wall (as in a bv/cmu system) with a metal rain screen system; the second shows a "Formawall" system with each panel fastened to a backup system (not shown in the image) that could consist of either steel studs (as in Duffield Hall) or CMU; the third shows a corrugated metal panel system attached to horizontal channels spanning between column lines.

16. Draw a schematic diagram through a structure and rain-screen enclosure wall, based on Ronald Brand's ideas. The sectional diagram should have these parts labeled: structure, air barrier, insulation, and "rainscreen/sunscreen" (sorry about the forward slash here; in this case, I'm quoting directly from Brand's text). As part of the diagram, show schematically how the air barrier accommodates movement in the structure. [5 points]

See "01.insulation-b.jpeg" image in "air barriers..." slideshow.

Part IV: Theory and Practice

17. Heat loss: what is the total (a) R-value and (b) U-value for a wall section consisting of the following layers: exterior sheathing (R=0.5); batt insulation (R=19); and interior gypsum board (R=0.5). [5 points]

a) R = .5+19+.5 = 20; b) U= 1/20 or 0.05.

18. Condensation: Draw the wall section described in question #17 above, adding and labeling a vapor retarder. Assume that the wall is designed for a cold climate. Be sure to clearly indicate which side of the wall is outside and which is inside. [5 points]

See "37.insulation.jpeg" in "heat loss..." slideshow (bottom diagram shows vapor barrier location).

19. Sealant joint: The total anticipated movement at a sealant joint is 1/8". Assuming perfect alignment (that is, t = 0) and a sealant movement capability of 25%, what sealant joint width is appropriate? Choose the best answer from the following choices: a) 1/32"; b) 1/8"; c) 1/2"; d) 3-1/4". [5 points]

Joint width is (100/25) x 1/8" = 1/2".

20. Pressure-equalization: Explain how a pressure-equalized rain-screen wall keeps wind-driven rain from entering the wall's internal cavity. [5 points]

Pressure-equalized (rain-screen) walls have internal cavities that are open (vented) to the outside, allowing wind pressure to enter the cavity, thereby equalizing internal (cavity) and external pressure. With equalized pressure, no rain will enter the cavity, since such movement of rain requires a pressure differential.

21. Galvanic Action: Nails made out of what material should be used to fasten copper flashing, and why? [5 points]

Use copper nails for copper flashing (similar metals should be used wherever water may be present) to avoid galvanic corrosion (as in a battery).