Different elements in every system perform different tasks and interact with each other (and the world around them) in various ways.   In a well-designed object, these elements often disappear into the whole.  Until something breaks, we stop thinking of a car as an assemblage of parts, and as one item.  A building has myriad parts, even glossing over the nails and screws that hold much of it together.   On a gross scale, it seems obvious that all of the bits and pieces are important, but as things change (and age), their relationships can become more important. 

In a building, the foundation provides a stable base for the walls and first floor, and still provides that steady base as it deals with the ground moving as it freezes, thaws, dries out, and becomes water logged.  Hopefully it was designed with a drainage system that takes into consideration the soil and local precipitation to provide a dry basement for the life of the building.   Things can change though.  A tree planted too near may shift the soil enough to crack a previously stable foundation.  Regrading part of the yard may direct more water towards the house, turning a formerly dry basement wet.  Sometimes though, a design flaw will introduce problems on its own.

On the first morning of our stay in a hotel, my wife asked me if I’d broken a glass in the tub the night before.  Reasonably certain that I had not, I went to investigate, and found several small pieces of what appeared to be shattered safety glass in the tub.  I was certain they hadn’t been in the tub the night before, but couldn’t find a source for them.  I eventually attributed them to something having broken by the cleaning staff before we checked in and the pieces being dislodged from the shower curtain or possibly a towel. 

Two days later I figured out where the “glass” had come from.   As I walked into the bathroom mid-afternoon, the sun beautifully highlighted a number of cracks in the large glass block window in the shower.   With the light just right, I was even able to find the block that had lost a few pieces of itself.   

A little research for a product number printed on the block, and examining the exterior of the window told a simple story of what happened.    The building had an exterior traditional glass window, and inside of that window, there was a false window of plastic “glass block”  for privacy and décor.   The additional insulation of an air gap between the picture window and the plastic block, and within the hollow plastic blocks, (with the relatively low thermal conductivity of the plastic) probably drastically reduced winter chill in the shower and let in really glorious light. 

The system had a flaw.  The plastic block were not designed for exterior use, and while they were not outside of the building envelope, they were exposed to a lot of high altitude sun on the south side of the building.  While the outer glass window cut some of the UV and IR hitting the plastic, the plastic block was exposed to much more solar radiation than an interior product would normally be subjected to.    To add insult to injury though, the big problem was bitter cold winter temperatures making the window side much colder than the heated interior, particularly at night.  As the sun rose and heated up the little greenhouse between the window and the block, the window side of the block would then be much hotter than the interior side.  This uneven heating and cooling added a lot of stress to the plastic blocks.  

Over time, these unexpected stresses started to cause small cracks in the plastic, which eventually knocked loose a couple of pieces while we were staying there.  This wasn’t a building collapse causing mistake on the building designers part, but it was an oversight that led to inconvenience.  It only showed up a decade into the building’s life, and it may only have manifested itself on the south facing bathrooms, but it did mean that we checked the tub before every use.

I’ll happily stay there again, but it was a very practical reminder to sift through as many impacts of outside forces as well as internal interactions within building systems as we design new structures, and work within existing ones.