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A Big Difference Between Physics and Building Science


You can go into just about any introductory physics classroom and you’ll see that the students learn the same stuff no matter which school they attend. They study forces and motion, momentum and energy, electrostatics, and a host of other physics topics. They do lab experiments. They observe and sometimes participate in demonstrations, as the student on the bed of nails is doing below. (I built a bed of nails when I taught at Haverford College and was even the meat in a bed-of-nails sandwich a few times.) But what about building science? Do we have that kind of uniformity?

The physics knowledge that gets passed down to new generations of students year after year is the result of thousands of years of observation, experiments, and refinement. There’s widespread agreement on the laws of physics. You have to go pretty far in the subject to find the boundaries these days.

Not so with building science. Yes, of course we all agree on the underlying physics behind building science. Conduction, convection, and radiation. Vapor diffusion and the permeance of materials. Pressure and air movement. But once you get into the applications, things change. You can ask 10 different people a question about spray foam attics and you’ll get 10 different answers. Or maybe 15.

Building science is still in its infancy. We don’t have the consensus that physics and other mature fields of study have. Some in the field have started moving us in that direction. The National Institute of Building Sciences, for example, is working to get us there. And the US Department of Energy (DOE) has a brand new Building Science Education Solution Center, whose objective is to help provide consistency.

But we still have a lot of work to do. I’m in Arizona right now about to begin my second day of the Housing Industry Boot Camp, hosted by Sam Rashkin of the US DOE. In a small group discussion yesterday, our task was to find challenges and recommendations for getting building science into the housing industry. My suggestions are:

  1. More building science research. Rashkin started the day yesterday by telling us that corporate America spends about 4% of its revenue on research and development. The housing industry spends less than 0.1%.
  2. Compilation of building science knowledge. As we develop consensus and understand buildings better, we need to get that knowledge into textbooks, websites, and forms that make it easy for the next step, which is…
  3. Dissemination of building science knowledge. That knowledge has to go from the researchers to the workers in the field and everyone in between. It has to be intelligible, relevant, and at the appropriate level for the audience.

There’s a lot of work left to do. Let’s get busy.


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Photo of student on bed of nails by COD Newsroom from, used under a Creative Commons license.


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This Post Has 10 Comments

  1. Of my graduating class of
    Of my graduating class of (five) undergraduate physics degrees (at my small school), two of us ended up going into building science, usually by stumbling into it accidentally but happily.

  2. Allison,

    I am an Architect in Missouri. Knowing the best ways to design building envelope systems etc. seems to be very valuable on a daily basis in my job. I have been thinking about this quite a bit recently, and have been considering the possibility of getting a Masters. It seems like Building Science would be an excellent masters program for architecture schools and engineering schools. To your knowledge, are there any programs out there?

    Until then, I enjoy piecing it together from your blog.

    Thank you.

  3. Having visual experiments for
    Having visual experiments for classes helps. I remember my high school physics teacher saying that if you shot something supper fast horizontally it would hit the ground at the same time as if you just dropped it. Sounded really weird at 16 but we walked to the football bleachers and had one group drop a water balloon and timed it while another group shot one horizontally with a 3-person sling shot. Everyone gets a turn and average the results. Very convincing and a nice trip out of the classroom.

    How do we convince people, either students in a class or 50 year old business owners that a building should not breathe? Our minds are visual oriented and glaze over when hit with numbers. I also think it would help as more people live in properly built homes.

    Distribution of knowledge is key. Imagine the confusion if each school had held onto their physics text books and lesson plans.

  4. I once identified with the
    I once identified with the art of building science, but more recently I have to believe using known engineering solutions is better and easier for the buildings we construct today. That’s not to say we shouldn’t value research…..just conduct the research in controlled settings and not on people’s homes they plan to live in, and especially not without their knowledge. Cause no harm is the BPI mantra.

    Over the past 20 years, building scientists postulated, tested and have demonstrated simple systems that work, and for the most part, our building codes have our basic needs pretty well defined. Engineers did that part. Follow the code. Ventilate using balanced, filtered and distributed mechanical systems and our buildings should be durable, safe and comfortable.

    Freeman Dyson on Science and Engineering:
    “A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering.”

  5. Great article. I agree that
    Great article. I agree that applying building science in the field is still a great challenge. Home Energy magazine was started 32 years ago by building scientists at Lawrence Berkeley Lab who want to transfer the technology developed at the DOE labs to the practitioners. Our articles from 1992-2000 are freely available at

  6. If physics took thousands of
    If physics took thousands of years I will not live long enough to see Home Performance mature. Although we should be smarter and it should take less time.

  7. Having worked primarily as a
    Having worked primarily as a carpenter and contractor for the past 35 years my observation of other’s (professionals in the field) building science knowledge and applications is very inconsistent. These inconsistencies obviously arise due to a variety of reasons. But it seems an argument could be made that some, if not many, of these inconsistencies stem from suppliers of the varies products used in applications, whether it’s foam, windows, structural material or fasteners. Many of these suppliers, who contractors have come to rely on for information (rightly or not) are themselves many times either ignorant, misinformed, just trying to sell particular product(s) they carry, or some combination of these.
    Contractors need to make the effort to seek out correct building source info and proper applications from the appropriate third party source (EV, BSC, DOE, etc) and not rely on just product suppliers and the product company’s themselves.

  8. Sorry, not all of us agree
    Sorry, not all of us agree that the 3 forms of heat transfer are convection, conduction, and radiation. My old books back to the 1600s seem to always have three, even before anyone knew what heat was, so I won’t try to convince anyone about the exact number, but the conventional three ignore a very important one in building science: latent transfer. For example, when wet building materials dry, the evaporating water absorbs latent heat of vaporization from nearby substances, heat which is less available as buildings get more insulation.
    And, strictly speaking, convection is not a transfer of heat from one molecule to another, but a transfer of mass from one location to another, so depending on the scale of what you are looking at, it could well be fair to not consider convection to be a form of heat transfer.
    Count as you wish, but ignore latent transfer at your peril.
    Henry Gifford

    1. Henry, I’ve never looked into
      Henry, I’ve never looked into the history of physics knowledge and its organization. But I’ve often wondered how we ended up with the big three and why the heats of vaporization and fusion weren’t included. You’re correct that those types of heat transfer are significant.

  9. Allison and all,
    Allison and all,
    every science is based on principles, which are based on physical phenomenon and material properties.
    Building enclosure is based on the Principles of Moisture Control, the only science which is relied on hazard. By checking reports like this:

    anyone can understand that principles of moisture control doesn’t contain anything based on physical phenomenon. More than this, I understand that I have to accept moisture in the envelope, in a controlled way, and I have to manage this.
    The physics of materials become virtually useless when try to use them in a science of hazard. This means that physics needs to apply to the principles of building enclosures and not only to the component elements.
    Academics will always teach Exact Sciences.

    This situation can be changed at anytime.
    I am the inventor/discoverer of a new principle of technique applied to enclosures, specifically the Building Enclosure, named the Principle of Avoiding Condensation (PAC).
    Please take the time and watch this explainer:

    Also a description can be find in the patent application:
    which is, of course, rejected by USPTO as not being an invention…

    By applying in practice the PAC and the concept of Non-Permissive insulations, the science of building enclosures become a 99.9% exact, predictable and repeatable building science, just like every other part of the building calculations, also like every other physics topics.
    The result is a zero moisture in the building envelope, one solution for all climates and seasons.
    Design and construction becomes very simple, efficient, but more important, predictable. PAC states to eliminate the cause of interstitial moisture (condensation phenomenon and intruding water) and not to reduces the effects of harmful moisture.
    Also, vapor-impermeable insulations has a precise insulation value (R-value) applied to the building and not just a theoretical number applied to materials. This is because Non-Permissive insulation eliminates convection, airflow, but more important, the in-cavity convection, which is the most responsible factor of energy lost!
    Believe me, is incredible how thermal efficient is a 3inch Non-Permissive Insulation compared to a 10inch of permeable, in-cavity insulation (see spray foam, which is vapor impermeable).

    If will not take hundreds of years to be understood such a simple principle, things can be changed at anytime, with incredible benefits for practice, meaning for designers, builders, building occupants and environment.
    The greatest impediment of implementing this principle is the mentality of thousands of years of building according to moisture control.

    Principle of Avoiding Condensation is applied to non-mineral, water sensitive walls/assemblies, such as wood structure and all cavity walls.

    There’s a lot more things to share about this new concept. Lets start somewhere!

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