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Things have evolved considerably since the Eisenhower and Diefenbaker years. Hutcheon taught us about air flow that decade but it took more than a half century to get it right. We needed air control. We needed an air control layer – an air barrier. We started off with locating it on the inside, moved it to the middle, and finally ended up with it on the outside3. We started by combining it with a vapor barrier on the inside then we finished by combining it with a weather resistive barrier (WRB) and continuous insulation on the outside.

Thirty years ago I said the moldiest buildings in the United States were air-conditioned hotels with vinyl wall coverings that operate under a negative air pressure….they literally “sucked”…. Not much has changed. For me to point that out is amazing. Maybe we need more attorneys…we are building them wrong faster than we can litigate them. That is not meant as a joke…some of the most effective “technology transfer” to practitioners in the construction industry is through the legal profession. Some of the physics is obvious…some not so much.

Reservoir claddings are not easy especially with sun and air conditioning where it rains. Pretty much everywhere folks want to live… It is sunny in Minneapolis and we have air conditioning and it rains there. It is sunny in Miami and we have air conditioning and it rains there. It is sunny in Memphis and we have air conditioning and it rains there.

Water is weird…and I point this out in an admiring manner… Water by itself is weird…it is a “polar molecule think “tiny magnets”….but when it changes phase from a liquid to a solid or from a liquid to a vapor the weirdness goes to levels that mere mortals are left shaking their heads….or it leads them to drinking….apparently wine. More about the wine drinking later. Freeze-thaw damage, spalling and efflorescence are related in an amazing strange way. In freeze-thaw damage water changes from a liquid to a solid. In spalling and efflorescence water changes from a liquid to a vapor.

Ice dams happen when the outside temperature is below freezing, the roof deck temperature is above freezing, and there is snow on the roof. The warm roof deck causes the snow on top of the roof deck to melt, and the melt water runs down to the edge of the roof where the water freezes leading to a buildup of ice and a backup of water, hence the term “dam”.

When I was a young punk kid in my 20’s and thought I was a builder the local building official would show up on my project site before I screwed up - he kept me out of trouble - he taught me enough building science that I became hooked. I was an engineer with a big time degree from a big time school but I did not know what I did not know. I respect building officials big time. That is why I am involved in the code process…I owe the code folks..it is my way of giving back...

How about hurricanes and nor’easters? But they are not common and buildings are expected to leak during these events. Buildings are not expected to blow away and people in them are not expected to die during these events. But they are going to get wet. Get over the wet thing. Things can dry. Especially if you design and build them to drain and dry. Sheesh.

The Harvard School of Public Health is recommending that we maintain interior relative humidity between 40 and 60 percent during the winter (https://www.hsph.harvard.edu/news/hsph-in-the-news/op-ed-humidity-can-ai...). I’m not arguing with the health science basis for this, just the building science basis for this: Relative humidities this high in houses[4] are going to be a killer in cold places where we have winter[5]. Yes, bad pun…

Wood moves. Drywall does not move. Interesting problem. The more you attach drywall to wood, the more cracks you have. Easy, attach the drywall to less wood, and, in a way, that allows the wood to move. Nail pops happen because as wood dries, it shrinks. Nails do not shrink. Actually, nails do not pop. The wood shrinks away from the back face of the drywall as it dries. How about getting dry wood? Sure. Next question. Better to use shorter nails. Even better, use glue. With glue, as the wood shrinks, it pulls the drywall inwards with it.

Pests include insects and animals that have a harmful effect on humans, food or living conditions. Pests include insects, termites, ants, cockroaches, mice, rats and dust mites. We are not going to address telemarketers or lawyers… termite shield, building science, bs brief, Joe Lstibrurek, Building Science Corporation, buildingscience.com,