Calculations · 04 · Buildings

Enclosure assemblies & connections

The enclosure as a set of real assemblies: every layer's weight carried into the structural model as a line load, thermal performance and the argon decision, and the connection details that get each system's load into the frame.

Thesis sheetsS.3.1 · S.3.2 · S.3.3 · AP.2 · AP.3 · AP.4

CoursesAE 202 · AE 221 · AE 222 · AE 310

Sheet authorTamara Alenezi

STEP 1

Wall weights → line loads

The gravity model needs to know what each wall weighs per foot of slab edge. Tamara built each assembly layer by layer, took an area weight (psf) for every layer, and multiplied by the story height to get a line load (plf).

PLF_layer = PSF_layer × h e.g. fiber cement panel: 3.21 psf × 17.5 ft = 56.18 plf PLF_wall = Σ PLF_layer

Fiber cement rainscreen (h = 17.5 ft) · U = 0.022

Layer	Thickness (in)	PSF	PLF
Fiber cement panel	0.31	3.21	56.18
Air / rainscreen cavity	1.5	0	0
Rigid insulation (XPS)	3	0.38	6.65
OSB sheathing	0.5	2	35.00
6″ 16 ga CFM studs @ 16″	6	5	87.50
Fiberglass batt insulation	6	0.55	9.63
Vapor barrier	0.0625	0.05	0.88
½″ gypsum wall board	0.5	2	35.00
Total	17.88	13.19	230.83

Unitized curtain wall (h = 17.33 ft) · U = 0.34

Layer	Thickness (in)	PSF	PLF
Glass (¼″ + ¼″ tempered)	0.50	6.5	112.65
Argon cavity	0.50	0	0
Aluminum mullion framing	8 7/16	2	34.66
Sealant	—	0.5	8.67
Mineral wool fire safing	3	1	17.33
Vapor barrier	—	0	0
6″ metal stud wall + batt	6	5	86.65
½″ gypsum wall	0.50	2	34.66
Total	19.44	17	294.61

Punched window section (h = 17.33 ft) · U = 1.09

Layer	Thickness (in)	PSF	PLF
Laminated glass (vision PW4120A or transom AR4120A)	0.44	3.25	56.32
PVB interlayer	0.09	0.5	8.67
Aluminum frame	2.00	2.00	34.66
Sealant / gaskets	—	0.50	8.67
Mineral wool fire safing	3.00	1.00	17.33
Vapor barrier	1.00	0	0
6″ metal stud wall + batt	6.00	5.00	86.65
½″ gypsum board	0.50	2.00	34.66
Total per section	13.03		246.95

Where these numbers go. The structural loading diagrams on sheet S.1 apply the curtain wall at 0.295 klf and fiber cement walls at 0.231 klf. Those are these totals, carried into the gravity model.

STEP 2

Thermal performance

The new climate brings more cooling load and humidity, so each assembly was documented with a U-value and the thermal resistance of each layer (for example R-6/in rigid insulation, R-11 mineral wool safing, R-19 batts in the stud wall). U-values: fiber cement wall 0.022 (as calculated on AP.2), curtain wall 0.34 and punched window 1.09 (manufacturer data).

Fiber cement wall assembly layer diagram — **AP.2 · Fig. 2.** Rainscreen layers.

Curtain wall assembly table — **AP.3.** Curtain wall assembly as drawn on the sheet.

STEP 3

Argon or air in the glass?

Tamara scored typical 1″ insulated glass units from ASHRAE/NFRC data on a 0–10 scale (higher is better):

Criterion	Basis	Air-filled	Argon-filled	Air	Argon
U-value	ASHRAE / NFRC	0.48	0.28	5	9
Energy efficiency	DOE trends	Higher heat transfer	Lower heat transfer	5	9
Condensation resistance	NFRC logic	Cooler interior glass	Warmer interior glass	6	9
Acoustic performance	STC trend / gas density	Standard	Slightly improved	6	7
Cost	Industry pricing	Lower	+5% to 10%	9	6
Unweighted sum				31	40

Argon wins on thermal performance and condensation, which matter most in a humid coastal climate. Air only wins on cost. Her note says how she weighed it: "depends on how we weigh cost, but air is cheaper." The curtain wall uses a ½″ argon cavity.

Handwritten argon vs air scoring table and notes — **AP.6.** Her scoring sheet.

Bar chart argon vs air — **AP.3 · Fig. 3.** Normalized comparison.

STEP 4

Connections & load paths

Each system gets its wind and gravity load into the structure differently, and the details follow from that:

System	Supported by	Load path	Key detail
Fiber cement rainscreen	Steel stud backup wall	Panel → rivets → rails → brackets → anchors → studs	Fixed-point brackets locate each rail. Sliding-point brackets let it move thermally. Nested 18 ga studs at brackets.
Unitized curtain wall	Slab edge	Glass → frame → anchor lugs → brackets → slab	Upper mullion slips over an anchor stem welded to the lower mullion, so the stack joint takes drift and thermal movement.
Punched window	Surrounding wall	Glass → frame → anchors → stud wall	Anchors at jambs, head and sill. Hung shelf angle at the head per AISC DG 22. Kickers resist spandrel twist.

Curtain wall mullion anchor detail — **S.3.2 · Fig. 3.** Mullion anchor at the slab edge.

Wall section through punched window with hung shelf angle — **S.3.3.** Shelf angle and kickers.

Rainscreen section with fixed and sliding brackets — **S.3.1 · Fig. 3.** Fixed / sliding brackets at 49″ o.c.

STEP 5

Curtain wall vs. punched window

Her side-by-side comparison of the two glazing approaches (AP.6):

Curtain wall	PGT picture window
Unitized system	Punched opening
Hung from slab	Supported by wall
Mullion system	Single frame
Complex load path	Direct load to wall