Building Science

Building Science Fundamentals: Roof, Part 1: Ventilation

By Dr. Joseph Lstiburek

Dr. Joseph Lstiburek talks about the not-so-controversial ways to maximize the efficiency and airflow of your roof and attic.

Video Transcript:
There’s been so much stuff said about roofs that you sometimes lose perspective. I’m going to start off by saying what might seem controversial but really shouldn’t be.

In our last episode, Dr. John talked about How Heat Moves Through Homes and why radiant barriers work better in outer space than on earth.

In this episode, Dr. John talks about the history of insulation, how different materials work, and where they make sense.

TRANSCRIPT
The history of insulation comes about because of the history of structural engineering. Now, I’m a recovering structural engineer, which is probably why I like to think of it that way.

Today’s walls, roofs, and floors are better insulated, tighter, and made with a much greater variety of components than they used to be, making them a lot more susceptible to moisture problems when they get wet. Compared to the old days, today's walls and ceilings are more complicated and can be very slow to dry.

The weathering of wood is very different from decay; weathering is breakdown at the surface only. While there are a number of forces that contribute to weathering of wood—moisture, temperature, abrasion by wind-borne particles, air pollution—it’s the narrow band of high-energy ultraviolet light in sunlight that is the dominant force (see Image #1).

What bare wood looks like when cut or milled

In our last episode, Dr. Joe Lstiburek talked about efflorescence and the serious damage that water and salt can do to masonry. This week, Dr. John Straube explains how the three forms of heat flow work, and debunks the claims of a few common insulating materials.

Comfort is the Primary Purpose of Buildings

This podcast series is excerpted from a two-day class called "Building Science Fundamentals" taught by Dr. Joe Lstiburek and Dr. John Straube of Building Science Corporation.

This podcast series is excerpted from a two-day class called "Building Science Fundamentals" taught by Dr. Joe Lstiburek and Dr. John Straube, of Building Science Corporation.

As part of a new Master Certified Green Professional designation, NAHB worked with GreenBuildingAdvisor to develop a rigorous training course covering green home building, full of building science and quality construction details. This course premiered at the International Builders Show in Las Vegas just last week.

Once a month in Portland, Maine, a group of builders, carpenters, architects, engineers, energy auditors, insulation contractors, and other fans of building science get together for, to quote the invitation, “an informal discussion for building professionals to ask, learn, debate, knock around, support, agonize over, ridicule, flog and answer the challenges and concepts of the best building practices.”

This podcast series is excerpted from a two-day class called "Building Science Fundamentals" taught by Dr. Joe Lstiburek and Dr. John Straube, of Building Science Corporation.