ASHRAE Journal - September 2009 - 76

Screen Interior Sill Precast Unit Stucco Reflective Foil Insulation Gypsum Board Wood Furring Masonry Block Wall Figure 3a (left): Rainwater Injection System. Ridge on precast unit is designed to structurally resist wind pressures during hurricane events. Unfortunately, this ridge results in water draining inward into the building rather than outward. Notice that the reflective insulation foilfaced vapor barrier traps water in the wall. Photo 4 (right): Leakage Path. Yes, they all really do leak at the window-to-wall interface and through the window. Not extending the stucco into the ground also improves termite resistance. The little buggers can pass through tiny gaps or flaws that arise from incomplete adhesion of the stucco to the concrete slab edge of the foundation perimeter. Do we want to maximize water entry into Florida buildings? Because we do things to window openings that even surprise me. For good structural engineering reasons, but for bad water management reasons, the bottom of masonry window openings in Florida are typically lined with precast elements that are manufactured with a vertical ridge (Figure 3a) that inadvertently directs rainwater that leaks through a window unit or that penetrates the window-to-wall interface inward (Photo 4). And, the reflective foil-faced vapor barrier once again does not help matters by trapping the water in the wall. It makes you want cry. Again, it does not take much to solve this problem. Just tier the precast unit at the bottom of the window opening by adding a secondary seat, thereby draining penetrating rainwater back to the exterior (Figure 3b). Now, we come to the air-conditioning system. Almost everything that is done in Florida should be on a list of “What Not to Do.” With the exterior walls wet through, we use air conditioning to suck moisture deep into the structure and draw any associated mold into the breathing zone. We configure the air-conditioning systems in such a manner as to develop interior negative pressures, while simultaneously locating the systems in the most severe environmental conditions possible to minimize their life while maximizing energy consumption. If we want to build things wrong in Florida, here are four more ways. First, vent the attic space so that during rain events 76 ASHRAE Journal Screen Secondary Seat to Provide Backdam for Window Installation Note: Minimum 0.5 in. High Primary Seat to Provide Backing for Sill Nailing Flange Gypsum Board Wood Furring Stucco Vapor Semipermeable Rigid Insulation Masonry Block Wall Interior Sill Tiered Precast Unit Figure 3b: Drain the Rain. Tiered precast unit draining water to exterior while providing structural load resistance. when it is particularly windy, rain can enter through roof vents (a particular form of rainwater harvesting common to Florida). Note to folks who don’t know much about hurricanes; you can’t keep rain out of vented attics during hurricanes, but you can keep rain out of attics that are not vented during hurricanes. Second, penetrate the ceiling with lots of service penetrations, framing drops, trey ceilings and every conceivable change in height. Third, locate the air-conditioning air-distribution system in the vented attic. It is the hottest and most environmentally inhospitable location in a building, where surface temperatures ashrae.org September 2009

ASHRAE Journal - September 2009

Table of Contents for the Digital Edition of ASHRAE Journal - September 2009

ASHRAE Journal - September 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
Getting to Net Zero
Feature Articles
How High Can You Go? Building Height and Net Zero
Lab for Learning
Solar Hot-Water Heating System: Lessons Learned
50th Anniversary—Low Pressure Steam Heating Systems
Building Sciences
Products
Emerging Technologies
People
Classified Advertising
Advertisers Index
ASHRAE Journal - September 2009 - ASHRAE Journal - September 2009
ASHRAE Journal - September 2009 - Cover2
ASHRAE Journal - September 2009 - 1
ASHRAE Journal - September 2009 - 2
ASHRAE Journal - September 2009 - Contents
ASHRAE Journal - September 2009 - 4
ASHRAE Journal - September 2009 - Commentary
ASHRAE Journal - September 2009 - Industry News
ASHRAE Journal - September 2009 - 7
ASHRAE Journal - September 2009 - 8
ASHRAE Journal - September 2009 - 9
ASHRAE Journal - September 2009 - Letters
ASHRAE Journal - September 2009 - 11
ASHRAE Journal - September 2009 - 12
ASHRAE Journal - September 2009 - 13
ASHRAE Journal - September 2009 - 14
ASHRAE Journal - September 2009 - 15
ASHRAE Journal - September 2009 - Meetings and Shows
ASHRAE Journal - September 2009 - 17
ASHRAE Journal - September 2009 - Feature Articles
ASHRAE Journal - September 2009 - 19
ASHRAE Journal - September 2009 - 20
ASHRAE Journal - September 2009 - 21
ASHRAE Journal - September 2009 - 22
ASHRAE Journal - September 2009 - 23
ASHRAE Journal - September 2009 - 24
ASHRAE Journal - September 2009 - 25
ASHRAE Journal - September 2009 - How High Can You Go? Building Height and Net Zero
ASHRAE Journal - September 2009 - 27
ASHRAE Journal - September 2009 - 28
ASHRAE Journal - September 2009 - 29
ASHRAE Journal - September 2009 - 30
ASHRAE Journal - September 2009 - 31
ASHRAE Journal - September 2009 - 32
ASHRAE Journal - September 2009 - 32a
ASHRAE Journal - September 2009 - 32b
ASHRAE Journal - September 2009 - 33
ASHRAE Journal - September 2009 - 34
ASHRAE Journal - September 2009 - 35
ASHRAE Journal - September 2009 - 36
ASHRAE Journal - September 2009 - 37
ASHRAE Journal - September 2009 - Lab for Learning
ASHRAE Journal - September 2009 - 39
ASHRAE Journal - September 2009 - 40
ASHRAE Journal - September 2009 - 41
ASHRAE Journal - September 2009 - 42
ASHRAE Journal - September 2009 - 43
ASHRAE Journal - September 2009 - Solar Hot-Water Heating System: Lessons Learned
ASHRAE Journal - September 2009 - 45
ASHRAE Journal - September 2009 - 46
ASHRAE Journal - September 2009 - 47
ASHRAE Journal - September 2009 - 48
ASHRAE Journal - September 2009 - 49
ASHRAE Journal - September 2009 - 50
ASHRAE Journal - September 2009 - 51
ASHRAE Journal - September 2009 - 52
ASHRAE Journal - September 2009 - 53
ASHRAE Journal - September 2009 - 50th Anniversary—Low Pressure Steam Heating Systems
ASHRAE Journal - September 2009 - 55
ASHRAE Journal - September 2009 - 56
ASHRAE Journal - September 2009 - 57
ASHRAE Journal - September 2009 - 58
ASHRAE Journal - September 2009 - 59
ASHRAE Journal - September 2009 - 60
ASHRAE Journal - September 2009 - 61
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ASHRAE Journal - September 2009 - 69
ASHRAE Journal - September 2009 - 70
ASHRAE Journal - September 2009 - 71
ASHRAE Journal - September 2009 - Building Sciences
ASHRAE Journal - September 2009 - 73
ASHRAE Journal - September 2009 - 74
ASHRAE Journal - September 2009 - 75
ASHRAE Journal - September 2009 - 76
ASHRAE Journal - September 2009 - 77
ASHRAE Journal - September 2009 - 78
ASHRAE Journal - September 2009 - 79
ASHRAE Journal - September 2009 - 80
ASHRAE Journal - September 2009 - 81
ASHRAE Journal - September 2009 - Products
ASHRAE Journal - September 2009 - 83
ASHRAE Journal - September 2009 - Emerging Technologies
ASHRAE Journal - September 2009 - 85
ASHRAE Journal - September 2009 - 86
ASHRAE Journal - September 2009 - 87
ASHRAE Journal - September 2009 - 88
ASHRAE Journal - September 2009 - 89
ASHRAE Journal - September 2009 - People
ASHRAE Journal - September 2009 - 91
ASHRAE Journal - September 2009 - 92
ASHRAE Journal - September 2009 - Classified Advertising
ASHRAE Journal - September 2009 - 94
ASHRAE Journal - September 2009 - 95
ASHRAE Journal - September 2009 - Advertisers Index
ASHRAE Journal - September 2009 - Cover3
ASHRAE Journal - September 2009 - Cover4
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