b'ALEXS ADVENTURES IN BUILDING SCIENCEADVENTURES IN the facilities staff reported unusual marksold structural stuccothe 1 layer BUILDING SCIENCE #1 in the library: arc-shaped burns on theof cementitious cladding around the Years ago, a fellow named Wernervinyl flooring, and sometimes papersbottom post! And why the low moisture-Lichtenberger sent me a photo he calledon the tables would mysteriously burstcontent reading? Because the moisture riddle, implying that there was a puzzleinto flame. Thanks to Werners riddle,meter doesnt measure moisture content; to be solved (photo 1). Im sure weI knew all about the heat source thatit measures electrical conductivity. And have all seen barbecued siding, whichtravels in an arc, so it was just a matter ofif theres nothing there to conduct elec-happens when a heat source gets toodiscovering why the suns rays were beingtricity, you get a low reading.close to vinyl cladding, but this one wasconcentrated. It turned out that some of unusual because of the arcing trajectorythe children had amused themselves byADVENTURES INof the burn pattern. I knew of only onethrowing rocks at the domed skylightsBUILDING SCIENCE #3heat source that moves in an arc at thatabove the library. The skylights wereWhen called out to conduct a BECA scale, but this arc was upside-down.tough enough that they didnt break, buton a typical face-sealed stucco building, The picture only made sense if this wasdented in the process. Then, when theI noticed an odd feature on one of the a reflected image of a solar track, so Idents filled with rainwater, they actedwindows (photo 3). The mushroom asked Werner if this might be a north- like lenses to concentrate the sun ontogrowing out of the weephole of this facing wall. He confirmed, but thatthe surfaces below.aluminum-clad wood window was didnt solve the whole puzzle. It turnsfeeding on the wood sash; if left long out that a second-storey window onADVENTURES IN enough, it would rot out the window the neighbouring house had an argon- BUILDING SCIENCE #2 frame. Further investigation revealed that filled insulated glazing unit (IGU),We were conducting a building enve- this older-style cladding design simply and in those days there was a problemlope condition assessment (BECA) on awrapped a metal skin around the wood with IGU collapse that was trackedfour-storey condo with stucco claddingelements, with no standoff or air cavity back to the argon fill. Argon is a nobleand stucco-clad supports for the balconybetween the metal cladding and the gas, so the molecule is a single atom ofstacks at the front of the building. Awood. In that case, capillary pressure (or argon, whereas air is mostly nitrogenmoisture probe of the stucco-clad postsurface tension) would keep any water in and oxygentwo diatomic molecules.supporting the second-storey balcony,constant contact with the wood, which Therefore, until the primary sealant wasand therefore the upper balconies (seesupports fungal activity.modified, it was easier for the argon tophoto 2), produced a reading of six perModern cladding designs generally incor-leak out of the IGU than it was for air tocent. But how could a wooden post onporate an air cavity behind the metal leak in to replace the lost argon, and thethe southeast corner of the building withcladding to encourage water drainage. IGU would partly collapse, resulting inthat amount of exposure to wind-drivenIts effectively a micro-sized rainscreen a concave surface. This acted like a para- rain ever achieve a reading so much lowerdesign, which promotes drying of the bolic reflector, concentrating the sunsthan kiln-dried wood? I thought. Sowetted components. The older-style rays. The siding just happened to be therather than just noting the low reading,metal-clad design is appropriate for drier right distance away to feel the heat. I asked for an exploratory opening.climates, and provides good durabilitySo, puzzle solved. But it turned out thatWe discovered that the wooden postfor wood windows, but is not suitable I would need that clue to solve a similar for a predominantly wet environment had a consistency of oatmeal porridge. problem years later. We were evaluatingSo what was holding up the second-,like the west coast of British Columbia. the building envelope of a school, andthird- and fourth-storey balconies? GoodRehabilitating the design shown in photo 1. A STRANGE PATTERN OF BARBECUED VINYL SIDING. 2. FOUR-STOREY BALCONY STACKS ON STUCCO-CLAD POSTS.16 BCBEC ELEMENTSA BCBEC PUBLICATION'