7 Minutes of BS (Building Science)

Science explains the natural world with a disciplined method of repeatable—and verifiable—questions, experiments, and answers

You can't simply go down to the hardware store and buy a box labeled air barrier

HOLY COW! If you blow hard enough, you can blow through OSB!

Stack effect is relentless: it is always working, when you’re awake or asleep, even during blackouts. And it feeds on itself.

As houses are built tighter, they exchange less air between inside and outside. This saves energy, but the inside air can get stale if you don't have a fan and a plan

Houses cannot expand and contract with changes in pressure like balloons can. Instead, they need paths for air to balance the pressure

A three-pronged solution to indoor pollution: Isolate, eliminate, and ventilate

Moving air keeps unwanted heat and moisture out of your roof system

Like an out-of-plumb wall, an insulated and unvented roof can work well—or not.

Drip edge is another water-shedding tool

Dew point differs from relative humidity in that it measures exactly how much vapor is present. With relative humidity, it's all relative.

Old Building Details That Work

A snowball effect of physics vs. physical structures: water carries salt to the surface of masonry, which crystallizes and can blow apart its masonry host.

Vapor barriers cause a lot more harm than good in many parts of North America. Understanding vapor barriers begins with knowing what it means to be one

This chart explains how moisture behaves in the air as temperatures rise and fall—rainstorms, flooding, and glaciers in wall cavities are distinct possibilities.

Siding is supposed to shed water away from walls; so what's the deal with siding that absorbs water?  

Vented roofs are often called cold roofs because they are—(theoretically) cold from ventilation air

Three mechanisms usually work together to move electrons from more to less. These three mechanisms can conspire to move heat AROUND your insulation.

Thin foil can block massive amounts of heat transfer, but it needs a massive temperature difference to be effective. So, insulation sort of makes radiant barriers irrelevant.

A thermal bridge is an area of the building enclosure—whether it be the walls, roof, or foundation—that has significantly higher heat flow than intended.

Can a wall plummet from R-50 to R-12 because of the studs?

If you can't build to stay dry, build to tolerate wet

Choosing hail-resistant roofing is as simple as looking at a chart and choosing a color

Too much of a good thing can kill you. Including sunny weather

With 100 years of fuel on the floor and a hotter climate, wildfire resistance and resilience matters almost everywhere

Wind damage is not restricted to hurricane zones, so why does wind-resistant construction limit itself?

PVC trim expands and contracts with temperature. But it never expands as much as it does that first time, so install it tight and fasten it right

Extreme heat and humidity can drive moisture deep into framing cavities which can cause mold, rot, and structural damage

Stucco is supposed to keep water out, but it is a reservoir cladding, so it also keeps water in. Sort of.

The science of stickiness: a molecular look at tape's adhesive and cohesive properties

In short, mortar is a mixture of some or all of the following materials: Portland cement, sand, lime clay, and more modern additives.