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Green Building Curmudgeon

Westford Building Science Symposium Raises Some Interesting Questions

Or, will my liver and my waistline survive another summer camp?

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One of the more enjoyable parts of summer camp is the band that plays every night.
One of the more enjoyable parts of summer camp is the band that plays every night. The camp serves exceptional food in copious quantities. To prove that we do more than just eat and drink, this photo captures a roomful of geeks listening to one of the presentations.

Much of the GBA team was in attendance at the 14th-annual Westford Building Science Symposium last week. More commonly known (and maybe more accurately described) as “Summer Camp,” this invitation-only, three-plus days long assembly of several hundred people involved in building science is a geek’s delight, featuring long days of lectures followed by dinner, drinks, and music until the wee hours. How we manage to get up and function each morning is one of the biggest mysteries at camp. If any Twitter fans are interested, look for #bscamp in tweets from this week to learn more.

While the festivities sometimes overshadowed the daily talks, a lot of very serious business went on between 8:30 AM and 4 PM every day, much of which really made me think.

On the first day, Bill Rose gave a great talk he called “12 Easy Pieces: Short Exercises in Building Science.” He moved through some of them so quickly that I was hard-pressed to take enough notes, but he really got us thinking.

Probably my favorite point he made was about the separation of building and architecture. I was always aware that the two professions diverged in relatively recent history, but his analysis was that in 1672, Louis XIV’s finance minister, Colbert, gave architects privileges that undermined the builders’ guilds and syndicates developed in the Middle Ages. Architects were given powdered wigs and access to kings and to academies of fine arts. After this, builders kept their knowledge to themselves, refusing to teach architects about building, leading to many of the disconnects we have in construction today.

Vapor barriers protect architects, not buildings

Rose also spoke at length about vapor barriers and retarders, and the value of prescriptive measures in building codes. He pointed out that vapor barriers don’t protect buildings; rather, they protect architects.

He also pointed out that when prescriptive measures are put into building codes, they usually develop constituencies and industries to support them. Businesses develop around these products and are financially invested in maintaining the requirement rather than assuring the highest-performing buildings.

Many of these measures don’t ever accrue as benefits to the building owner; they primarily work to reduce liability to the professional who specifies them. I particularly liked Rose’s comment that there is an “on” button for most of our behavior (one recent example being taking our shoes off at airport security), but we rarely see an “off” button. That is, no one ever questions the value of the effort, and it just stays in place forever. This relates to building science and vapor barriers as much as airport security.

Rose set some criteria to evaluate prescriptive requirements for buildings, which are good rules to live by:

  • Is it critical?
  • Is it necessary?
  • Will the building perform badly without it?
  • Is it sufficient?
  • Will compliance result in satisfactory performance?
  • Is it policed?
  • Is there a mechanism in place to revisit the questions of criticality, necessity, and sufficiency?

Challenges and questions

Rose challenged us to find people who are willing to question prescriptive measures and help make them disappear when they are no longer appropriate. This last thought leads me to a question I am going to pose—at the risk of being skewered by some of the major building science geeks that populate this site, mostly from northern climates.

Having worked in the mixed humid South for my entire career, I find the cold-climate bias of most building science a little frustrating. I don’t have any experience with most of the condensation issues that arise in severe cold, so I defer to those experts on most occasions. That said, it occurs to me that it might just be possible that the recommendation for vapor retarders in cold climates is more a response to the possibility that other things could go wrong, rather than a necessity in all conditions.

Later during the symposium, there was a presentation on spray foam insulation, and during one side discussion, the subject of open-cell versus closed-cell roofline insulation came up. Being a geek from a mixed climate, where vapor retarders generally aren’t recommended, I lean toward open-cell foam—to which the cold-climate geeks say there has to be a vapor retarder to prevent vapor from flowing through the insulation and condensing on the cold underside of the roof deck. This was not the first time I have had this conversation. I was almost beaten to a bloody pulp by some angry builders in Montana for making similar comments.

So my question is, if the moisture is adequately controlled inside a house in the winter, is the vapor retarder necessary, or is it just one of those things that is installed to protect architects and builders from liability? I hope that the cold-climate guys don’t put out a contract on my life for raising this question. I just want to start some discussion and see if my theory has any validity. I welcome your comments.


  1. SLSTech | | #1

    Per the Consortium for
    Per the Consortium for Advanced Residential Buildings / Steven Winter Associates, Inc. for Hot-Humid climates "a vapor retarder should not be added to the interior surface of the ocSPF. The exposed foam or its finish surface should remain moisture permeable to allowing drying to the interior." but the interior relative humidity contril is vital

    With all that, good luck getting this code tested & approved...

    Now as for Open Cell being best for this climate - I would have to disagree, Closed cell is the better choice as it doesn't let the moisture in to condense, or cause all those other fun little problems that are so common around here and elsewhere. If a structure doesn't get wet, does it need to dry out - nope

  2. GBA Editor
    Martin Holladay | | #2

    Interior RH and vapor barriers in warm climates
    You're quite right that controlling indoor relative humidity is a technique that can be substituted for the traditional method of installing an interior vapor retarder. The farther north you go, however, the more stringent your interior RH limitations become. The reason that builders up north haven't totally abandoned the use of vapor retarders is that we can't control how homeowners will operate the houses we build.

    It's all fine and good to say, "Keep your indoor RH at 30% or below during the winter," but once we walk away from the building, the homeowner can buy a humidifier and screw up the house.

    Down in Georgia, though, you don't really have to worry about vapor diffusion from the interior to the exterior during the winter, so you are quite right -- interior vapor retarders are unnecessary down south.

    As you probably know, the vapor diffusion you have to worry about is inward solar vapor drive -- that is, vapor diffusion from the exterior to the interior during the summer. As long as your wall and roof assemblies have been designed to address inward solar vapor drive (for example, by using exterior rigid foam and by avoiding vinyl wallpaper), you don't have to worry about diffusion.

  3. EJ Palma | | #3

    Carl, my question here
    Carl, my question here involves inclusion for all who choose to better their understanding of current concepts in the industry. I am not at all questioning the credentials, intellect, or personality of any individual. If this educational forum is by invitation only, is that not a bit exclusionary? How does one become an invitee? Evidently one has to be part of an exclusive group of "Building Science Geeks" or the "Building Science Media" to be considered. As one who is involved in community education and community service this disturbs me. These informative sessions could be a great learning tool for many in the industry who are not on the inside of the "Building Science Elite", but are interested in furthering there professional knowledge. Being a curmudgeon myself, and one who seeks to keep my education in the field current, I am a bit miffed at why these sessions would be closed. Dissemination of pertinent information can flow more easily when populations of individuals mingle with each other. In my opinion and that is all that it is, exclusion of individuals because of lack of titles, degrees, positions etc. only serves to reduce the common bond between those people working in the field and those in the upper eschelon of the industry. It can also frustrate new individuals from entering the field, while creating "Ivory Tower" impressions and fostering intellectual discrimination. I personally respect the intellects and achievements of all individuals whether they have a doctorate or not. Maybe I am being oversensitive, but in reality I feel that an open community that allows access for all that are interested, and based on the inclusion and sharing of ideas and information, provides a better and more attractive learning environment. Everyone should have access to these conferences and symposiums. Is not the community sharing of ideas coupled with the abundance of easily accessible current and relevant information, one of the strongest features of GBA, ? I believe that the community forum that GBA has built itself upon, stimulates growth in our industry, attracts interested individuals that choose to better their knowledge base, and resultantly strengthens the industry in general.

  4. GBA Editor
    Martin Holladay | | #4

    Response to Edward
    There are a great many excellent building science conferences that meet every year. I highly recommend the EEBA conference and Affordable Comfort, also known as the ACI conference.

    There are also many excellent regional conferences; here in Vermont, for example, Efficiency Vermont is the host of an annual conference called Better Buildings by Design.

    Who speaks at these conferences? Exactly the same people who show up at the "Summer Camp" in Westford: Bill Rose, Joe Lstibuerk, John Straube, and all the others.

    In the past, I have heard a few complaints about the "invitation only" aspect of the "Summer Camp" -- some people imagine that it is a secret gathering of conspirators closing the doors on the public. I pointed out that no one does more public speaking than Joe Lstiburek; every time I turn around I hear of a new opportunity to hear Joe speak. When he comes to your state, you can attend one of his events.

    There are two reasons that the number of attendees at the "Summer Camp" gathering is limited:
    1. The conference room in Westford is at capacity -- no more chairs will fit in the room.
    2. Some of the events occur in Joe and Betsy's back yard -- only so many people will fit, and the neighbors are already complaining.

    The bottom line: if you have the opportunity, you should attend EEBA or ACI or NESEA.

  5. EJ Palma | | #5

    Martin thank you for caring
    Martin thank you for caring to respond to my social criticism. My comments were only to point out that organizations can exclude people whether intentionally or unintentionally, but the results may be the same. At 58 I have witnessed many changes in the movement in the past 40 years. There were great inroads being made in the 70's, but cheap oil prices, politics and general apathy have had major effects on acceptance of green principles and lifestyle, resultantly stifling progress in the past few decades. We have become involved in wars for the control of oil and its profits, and have become a wasteful disposable society regarding resource management. In a field such as ours the influx of new blood keeps everything fresh, and aids the dissemination of information to the masses. It is extremely important with the challenges that we face regarding Energy, Climate Change , Social Issues, the future of our living world and the diversity of ideologies globally, that "new blood" is attracted to and infused into the movement. Social issues play a great part in how a movement is accepted and how it progresses. Community education on the grassroots level is going to play a major part in our future. That is why i was concerned about exclusion. I accept your explanation, and I appreciate the suggestions for conferences to attend. I have attended many NESEA conferences in the past, and have always come away with useful information and contacts. GBA has provided me with a wealth of opinions and ideas from diversified sources, coupled with the community sharing atmosphere. I believe that social justice and pertinent social issues are relevant and also need to be discussed.

  6. GBA Editor
    Martin Holladay | | #6

    Addressing social justice
    Thanks for sharing your social justice concerns. I share them as well.

    Of course, even the conferences I listed are generally only an option for the well-to-do (or those working for a generous employer). Those looking for good, rock-solid building science information who lack the funds to attend a conference should access the Internet at their local public library and visit the Web sites of and GBA.

    Local utilities and state energy offices are often an excellent source of free information and subsidized help.

    Finally, I urge anyone who needs advice or help on residential energy improvements to contact their local Weatherization agency. If your family has a low income, these services are free.

    We all need to do more to share information, to help each other out, and to widen our circles to reach out to others in our community.

  7. John Straube | | #7

    Roofs and Edward's concerns
    Roofs. The IRC has been changed to provide information on unvented foamed roofs. The south is very different than the north. See R806.4 in the IRC or BSD-102 on
    In Climate Zones 5 or higher a Class II vapor retarder is required on the interior of the spray foam layer. If a high density foam is used, a Class II vapor retarder is not required in Climate Zones 5 or higher as the high density foam itself qualifies as a Class II vapor retarder.
    A thermal barrier is usually required to separate spray foams from occupiable spaces due to the fire performance of spray foam insulations.

    The meeting in Westford is private get together that is over-subscribed. We are at more than capacity. There is no way we could open it up to everyone who wanted to come. There is no conspiracy, just practical realities. Unlike ACI or NESEA, we are not trying to make money, we are trying not to loose money. Hence, we dont move the meeting to a big hotel and try and get 600 people. It would not meet the intent.
    For people who want information, BSC provides tons of stuff for free on our website, and offers dozens of seminars per year.

  8. small d | | #8

    RH and northern climes
    Martin, your comments about subsequent occupants of buildings and their introduction of humidifiers only serves to show that the codes are designed as LCD's or Lowest Common Denominators. Here in the north that could be defined as the Lowest Canadian Denominator like so much other legislation in this country. However, as a former Building Technologies Instructor many years ago and a designer as well as builder of appropriate (now referred to as sustainable): residential and small commercial structures of some 30+ years - I am still struck by the deep corporate influence in building systems/codes that have repetitively failed us all over the past decades after having been so zealously fostered and promoted by the brotherhoods of business/manufacturer interests and with no consequence to them or their companies.
    Question: I am also concerned that on one level you are stating a) that information is essential in construction, and yet on the other b) we must compensate for the ignorance or indifference of the subsequent occupants of that structure. Which is it?
    Are not those living in a structure complicit in its failure of it's performance and the subsequent problems if they deem it to not be important to be aware of or interact with their interior environment. How much longer must our building policies/codes be determined by those who either by lack of information, total indifference or simple corporate greed.
    I am continually intrigued by your site and appreciate the many pieces of information I come across on it, although I would suggest that in many cases you are simply rehashing in scientific jargon and sanction what has been empirically proven not just over the past decades, but over millennium of human habitation.
    But, then I'm just an old guy who experimented with a lot of appropriate design and construction, as well as organic agriculture over some 40 years now and collectively worked with others to improve all of these and more within and outside the stated statutes, long before this building science, LEEDS, Sustainable (never will be) Building stuff started being really lucrative.
    Lastly, may I say how much I appreciate your inquiry, research and the dissemination of your findings, I hope it will eventually pervade the entire industry of the building 'industry'.

    Thanx and regards to everyone at

  9. small d | | #9

    How do you see it?
    A question to everyone within your organization and on the blogs. Why is it that we insist on our bodies taking up more and more space? We began by "controlling" the clothing we wore to assure our comfort in whatever environmental conditions we encountered: now we have by extension determined that our homes and structures become our external 'clothing' it that reasonable? Now the next step on the move total automation of structural environments?
    Would it or could it not be more energy, environmentally and physiologically prudent to allow our homes to once again be shelters and not external clothing?
    As the Japanese people once said - it is easy to keep warm; use clothing and site specific heating, it is keeping cool that is the challenge - I paraphrase badly, however the Mediterranean, African, and interior Chinese cultures had that cooling thing figured out many thousands of years ago.We just keep pretending we just discovered it, along with passive solar, earth berms, underground homes, transpiration cooling, green roofs, thermal mass, geothermal heating, concrete, caissons, central heating, radiant floors, rain screens, cisterns, wind scoops, xeriscaping, organic agriculture and horticulture, environmentally appropriate housing and a whole hell of a lot more that we have convinced ourselves that we have "discovered".
    Do you think that the if we collectively had the GUTS to design homes within which people had to actually and ACTIVELY participate in their comfort, within their specific climates theyt might be more aware and connected to their environment and consequently more connected to this fragile planet that 'conditionally' sustains their lives. If you don't think it's conditional look at historical and climatic history of this one and only spaceship that is so finally tuned that we call home, that we call Earth. Ain't no other spaceship coming to save you, and it would take at today's rate of progress some 120 years to just get 10,000 people of this planet onto one that could take up to 500-10,000 to make the next one even 50% as hospitable as this on is today!
    I must admit this is some questions and a bit of a rant.

    Regards to all

  10. GBA Editor
    Martin Holladay | | #10

    Response to small d
    small d,
    I'm an old hippie, so you're preaching to the converted. I have several friends who spent winters in a tipi (in Vermont), following the Asian principle that you only have to keep people warm enough to prevent hypothermia -- you don't have to heat all of your interior air. It's certainly possible.

    I remember days during my first winter in Vermont when I would wake up and put the stainless-steel cat bowl on the woodstove, because it was filled with ice. Then I would go outside with my big enamel pot and fill it full of snow; I would melt the snow for water.

    Ah, good memories. I don't know if these memories apply to today's builders, however. Builders face liability. There is a financial risk to designing a building that only works if the residents keep the indoor relative humidity below 30%. When the walls rot, the builder ends up in court. Good luck convincing the jury -- "but they ran the building at an elevated indoor humidity level!" Yeah, right.

    We need our buildings to be more robust than that. If buildings allow condensation, and if walls include OSB that turns readily to oatmeal, I don't buy the argument that the homeowner is to blame. I blame the designer and the builder.

    You ask, "Are not those living in a structure complicit in the failure of its performance and the subsequent problems if they deem it to not be important to be aware of or interact with their interior environment?" Well, maybe they are complicit. But the average homeowner doesn't want to study building science or learn about air leakage. Maybe the homeowner is a single mom with three kids. Maybe a doctor told her that a humidifier would help her sick child. So, I don't want to point my finger at the homeowner.

    Concerning your point about rehashing -- "in many cases you are simply rehashing in scientific jargon and sanction what has been empirically proven not just over the past decades, but over millennium of human habitation" -- I plead guilty. Of course all I'm doing is rehashing. That's what journalists do.

    I just hope my rehashing -- of old knowledge, folk wisdom, and recent research findings -- is presented clearly and in an entertaining way.

  11. michael anschel | | #11

    Serious business
    I can't believe there isn't more discussion about your waistline or the condition of your liver!

    As hard as this may be to believe, I agree with Martin; the homeowner is not to blame. We have to make homes idiot proof, and that means taking options off the table. My personal preference would be to see all controls locked up in a big steel box with an cable running to our office so we can monitor and control the systems for our clients.

    As for controlling our built environment, we have been doing that since the day we built our first palm frond hut to keep us dry. We modified our environment when we killed that buffalo and wore its skin. Nothing new here. Besides we will all be dead or gone long before this spaceship even notices we were here.

  12. Expert Member
    CARL SEVILLE | | #12

    Summer Camp Presentations
    Thanks for all the great comments everyone. For those of you who weren't at summer camp, here is a link to most of the presentations given there: [Removed per BSC's request]

  13. homedesign | | #13

    Thanks for posting "the Link"
    There is something about one of the presentations that still baffles me.

    Residential Construction in Hot Humid Climates (slide 72)

    What Happened!

    Is it fair to blame this on occupant behavior?

    Is Energy Gauge software THAT bad or did someone enter bad data?
    There was some mention of the actual pool equipment being far better than what was entered into the software.
    Was all of the input sloppy?

    Based on the Actual Energy Consumption this does NOT seem to be a High Performance Home

  14. homedesign | | #14

    Slide 72 is on page 18
    Noticed that not all slides are numbered... slide 72 is on page 18

  15. Daniel Morrison | | #15

    Sorry, I had to take the link down
    Building Science Corp asked me to remove the link because some of the presenters wanted those slide decks to remain in the 'private domain.'

    But it was good while it lasted, right?


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