Legacy practices

The building industry goes back millenia. So it should be no surprise that many of the practices in putting up a building are legacy practices—that is, they arose somewhere in building history, and they are retained because, well, sometimes just because. And this is good. Doing things the way we learned to do them, and our pappy and grandpappy learned to do them, helps keep the job going. In this regard, building design and construction is a comfortingly human endeavor; education, medicine, baby-making and child-rearing, agriculture, all of these are tradition-bound practices, where science sometimes struggles to make inroads. Any practicing scientist will tell you that science, too, deals constantly with legacy practices. Daniel Lord Smail has a word for them

Struggling with all these queries, I have come to realize that the resistance to deep history does not necessarily come from my students. It comes from me. It is rooted in paradigms, in discourse, in the nameless things that one of my advisers liked to call “ghost theories”, old ideas that continue to structure our thinking without our being fully aware of their controlling presence.

Smail, On Deep History and the Brain, p. 3.

One of my favorite tradition-bound legacy practices is the parapet. Why not have the roof simply corner into the masonry wall, improving the continuity of insulation, air barrier, and the rest? The old arguments I heard were for worker protection, and to help reduce fire transfer from one building to another. OSHA wisely ignores parapets when ensuring worker safety on roofs, and roofers walking backwards belong off the job. Parapets between townhouses may have fire benefits, but exterior wall parapets?—no. Parapets are always going bad, leading Joe Lstiburek to announce an outbreak of parapetitis. I’ve been at this practice for so many decades now that I consider myself somewhat of a brick-whisperer. What the brick whispers to me is that brick, and masonry in general, just loves compression. Can’t hardly get enough of it. When compression is lacking, like at the top of a masonry stack, joint cracking becomes easy, and widespread over time. Parapets go bad, but that’s good, because they localize the cracking up where it’s repairable and where it has little influence on the remainder of the facade. 

Gable parapets. Bruges, Belgium

Legacy practices take many forms.

  • Sometimes they are simple agreed-upon conventions, like L/360 deflection or 15 cfm outdoor air per occupant, which are arguable numbers with intriguing histories. Usually the argument is not worth it, because some number is required just to get some ball rolling.
  • Some are practices which are beneficial, but they carry misunderstandings as legacy baggage. One example is foundations to frost depth, which presumes heaving foundations are pushed up from the underside of a footing. Another is keeping a faucet dripping during cold weather, which presumes that slowly moving water carries just enough heat to preclude ice buildup (that ain’t it).
  • Some are misapplications, like a chimney smoke shelf on a fully-interior fireplace.
  • Some are contentious like radon, founded on questionable assumptions but established with a firm hand. There is a science underpinning, but it deserves a critical look.
  • Some, like indoor poly vapor barriers, do give way to new materials and understandings.
  • Many of our worries are legacy worries, that in a just world would simply vanish. “Gonna get condensation” and “that toxic black mold” are examples
  • My three favorite examples are bulging basement walls, freeze-thaw in masonry and attic ventilation (more later).

All of these legacy practices will be studied, in some depth, on this blog in the months to come.

I’m a scientist. My science world overlaps this legacy world almost everywhere. Can these two outlooks, like two religions, cohabit this same environment? Of course, just look around. The cohabitation can be fruitful–I certainly find it so. I like listening to legacy practices being defended and I am never quick to provide counterarguments. You enter arguments that are 1) worth fighting, and 2) give a chance of winning. My colleague Anton TenWolde got a big kick from hearing someone say “I believe in attic ventilation”. Humans do not change beliefs easily. The last time I changed one was when I was 20 years old. Max Planck famously stated that science advances one funeral at a time.

My health is in the hands of health professionals, and I presumed that their work on me was science-based. After dinners with real health professionals, and a ridiculous visit to a sleep clinic, I learned that health practice and building practice are very similar, in having a science-basis that does not live up to expectations.

There is an ethical principle for professionals, at least I presume there is, which states that the welfare of the client should take precedence over welfare for the provider. Doctors should reject kickbacks on prescriptions. Politicians should not be corrupt (why else invest in democracy?)

This puts building consultants in somewhat of a bind, I think. We are rooted in tradition. We rely on standards and codes. There’s validity to the claim that standards and codes protect clients, but many professionals recognize that they make their job easier. Indeed, approval of a standard or code requirement unleashes a tsunami of economic interest—products value engineered to barely comply. What if the standard or code requirement does protect the designer or builder or vendor, but its benefit to the client becomes arguable? I love the contrast between the architecture and engineering codes of ethics on regulatory compliance (more on this later).

I’m thinking of attic ventilation, which carries a strong resilience penalty, a distinct energy penalty in heating-dominated climates, and maybe an energy penalty during summer (more on this later). Here the interface between legacy practice and building science gathers friction.

Welcome to my world.

I remember reading in Eric Sloane‘s book on barns, the story of the passer-by watching an Amish builder build his barn ends of stone 3 feet thick. When asked why build the walls so thick, the builder answered “why not?” This was the southern Pennsylvania world I grew up in, where the barn gables were decorated with what were called “hexafoos” or hex signs. I say “decorated”, but for all I know they were as critical to Amish barn integrity and stability a hundred years ago as good timber framing and stout masonry. If it’s voodoo, it’s awfully handsome voodoo. A lesson for all budding building scientists is–if it ain’t broke, don’t fix it. Legacy is good. Challenge it when you have something better, otherwise hold your tongue. And when you speak up, you’d better be right.

Amish barn hex sign. Glencairn Museum, Bryn Altyn PA.

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