Friday, October 19, 2012

Proper ventilation of high-efficiency dwellings

This is the sort of article that is both enlightening and infuriating.  Of course it is a good idea to keep indoor CO2 levels low.  More evidence that this is true is welcome.  However, there is an assumption in this article that these higher levels of indoor CO2 are an unwelcome side effect of attempts to make a building more energy efficient (see bolded sentence below).

WRONG!  This is true only if you don't do it right.

In 1982, I was fortunate to attend a two-day seminar on Swedish homebuilding methods.  Their industry had been saddled with very ridged energy-efficiency standards following the Arab oil embargo of 1973-74 and now they had newly-developed technology to market.  For me, the most interesting presentation was on why buildings needed to breathe.

Keeping expensively warmed air indoors seemed like a no-brainer.  The idea was that you insulated the structure to minimize radiant heat losses and carefully sealed all joints to minimize infiltration losses.  But the Swedes soon found out that as infiltration losses got near zero, bad things started to happen. The most annoying one was that a dwelling containing bodies exhaling warm moist air created a pressure differential that nature would redress somehow.  So the closer you actually got to creating a weather-tight structure, the harder it was to stop all the leaks.  And when you did get a building down to say, one exchange per hour, the bad air inside would grow nasty molds and other things to make you sick and destroy the house.

The Swedish answer was to create an air exchange system that would equalize the indoor-outdoor air pressure while removing the air that grew molds, etc.  These air exchange systems were fairly complex and really only worked when integrated into the original building design.  But when they worked, the results were magnificent.

In 1996, I spent part of the winter in an exurb of Stockholm in a two year-old condo built by Skanska—one of Sweden's big construction firms.  The air exchange system was remarkable.  There were exhaust pickups in the bathrooms and laundry room, as well as over the stove.  The air-to-air heat exchanger was built into the range hood and was perfectly sized to be washed in the dishwasher.  The warmed outside air was distributed into the living room and bedrooms.  The system ran whenever the kitchen or bathrooms were in use.  The fan was very quiet.  Best of all, since the condo was sited on one of Stockholm's many arms of the sea, the warmed air from outside smelled faintly of the ocean.  It was wonderful—I have never felt so healthy in the winter before or since.

So the answer to the problems caused by CO2 buildup is the same as for all the other nasty things in stale indoor air—design the building to breathe and install first-rate equipment to make it happen.  You cannot make a truly energy-efficient dwelling without actively controlling the location and rates of infiltration anyway, so why not do it right?

OCT 17, 2012

Elevated indoor carbon dioxide impairs decision-making performance

Researchers have found that moderately high indoor concentrations of carbon dioxide (CO2) can significantly impair people’s decision-making performance.

Overturning decades of conventional wisdom, researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have found that moderately high indoor concentrations of carbon dioxide (CO2) can significantly impair people’s decision-making performance. The results were unexpected and may have particular implications for schools and other spaces with high occupant density.

“In our field we have always had a dogma that CO2 itself, at the levels we find in buildings, is just not important and doesn’t have any direct impacts on people,” said Berkeley Lab scientist William Fisk, a co-author of the study, which was published in Environmental Health Perspectives online last month. “So these results, which were quite unambiguous, were surprising.” The study was conducted with researchers from State University of New York (SUNY) Upstate Medical University.

On nine scales of decision-making performance, test subjects showed significant reductions on six of the scales at CO2 levels of 1,000 parts per million (ppm) and large reductions on seven of the scales at 2,500 ppm. The most dramatic declines in performance, in which subjects were rated as “dysfunctional,” were for taking initiative and thinking strategically. “Previous studies have looked at 10,000 ppm, 20,000 ppm; that’s the level at which scientists thought effects started,” said Berkeley Lab scientist Mark Mendell, also a co-author of the study. “That’s why these findings are so startling.”

Berkeley Lab researchers found that even moderately elevated levels of indoor carbon dioxide resulted in lower scores on six of nine scales of human decision-making performance. Credit: Berkeley Lab

While the results need to be replicated in a larger study, they point to possible economic consequences of pursuing energy efficient buildings without regard to occupants. “As there’s a drive for increasing energy efficiency, there’s a push for making buildings tighter and less expensive to run,” said Mendell. “There’s some risk that, in that process, adverse effects on occupants will be ignored. One way to make sure occupants get the attention they deserve is to point out adverse economic impacts of poor indoor air quality. If people can’t think or perform as well, that could obviously have adverse economic impacts.”

The primary source of indoor CO2 is humans. While typical outdoor concentrations are around 380 ppm, indoor concentrations can go up to several thousand ppm. Higher indoor CO2 concentrations relative to outdoors are due to low rates of ventilation, which are often driven by the need to reduce energy consumption. In the real world, CO2 concentrations in office buildings normally don’t exceed 1,000 ppm, except in meeting rooms, when groups of people gather for extended periods of time.

In classrooms, concentrations frequently exceed 1,000 ppm and occasionally exceed 3,000 ppm. CO2 at these levels has been assumed to indicate poor ventilation, with increased exposure to other indoor pollutants of potential concern, but the CO2 itself at these levels has not been a source of concern. Federal guidelines set a maximum occupational exposure limit at 5,000 ppm as a time-weighted average for an eight-hour workday.

Fisk decided to test the conventional wisdom on indoor CO2 after coming across two small Hungarian studies reporting that exposures between 2,000 and 5,000 ppm may have adverse impacts on some human activities.

Fisk, Mendell, and their colleagues, including Usha Satish at SUNY Upstate Medical University, assessed CO2 exposure at three concentrations: 600, 1,000 and 2,500 ppm. They recruited 24 participants, mostly college students, who were studied in groups of four in a small office-like chamber for 2.5 hours for each of the three conditions. Ultrapure CO2 was injected into the air supply and mixing was ensured, while all other factors, such as temperature, humidity, and ventilation rate, were kept constant. The sessions for each person took place on a single day, with one-hour breaks between sessions.

Although the sample size was small, the results were unmistakable. “The stronger the effect you have, the fewer subjects you need to see it,” Fisk said. “Our effect was so big, even with a small number of people, it was a very clear effect.” more


  1. ",,,concentrations of carbon dioxide (CO2) can significantly impair people’s decision-making performance,,,"

    And especially poor performance on 'initiative' and 'basic strategy'...seems to finally explain the incredibly poor performance of oil and gas decision-makers.

    Is it finally time to exclude them in any future national energy policy-making?

    Their 1880 approach to our future, their inability to grasp even basic alternative strategies, to take and commit to even the most basic energy initiative, their lack of willingness to incorporate even minor adjustments in their tepid alternative energy efforts at the first hiccup, and their unwillingness to update their corporate energy policy is hurting America.

    Finally we know why...their suburban/exburban homes must be holding too much CO2 and their brains not receiving enough oxygen.

  2. I never quite understood how an industry that relies so heavily of folks with advanced degrees could be so clueless about the real issues affecting their industry. For example, why shouldn't all the major energy companies have serious wind and solar divisions? Why do they actually feel threatened by technology they could so easily own and dominate?

    I have some institutional answers but the aren't very satisfying. At some point, I must admit that the skills necessary to drill 20,000 ft. wells in 1000 feet of water don't translate into other activities equally as difficult—such as installing and maintaining offshore wind farms. Must be akin to the problems of switching someone who played right tackle all his life to left tackle—but I am SURE there is MUCH more to it.

  3. Well, I suppose we need to think of it more like a multinational conglomeration executive would instead. Most of 'American' energy companies are owned by a major financial firm...say Barclays, Deutsche Bank, or RBC...and run by oligarchies, many of whom strain with a pretense of being American yet regardless of their identity/location, think of America with the same concern as they do Nigeria or Iraq...that America is just a resource to use up.

    So in that regard these owners while happy to let America drift in fossil fuel malaise, already have made significant investments in solar, wind, geothermal, and the insider track on energy-efficient construction...just these investments are located in Germany, Scotland, Iceland, and Sweden (and this one global oligarchy or two in friendly competition though?) while providing those countries with serious engineering jobs for the layman worker to profit from without having to stretch themselves very far.

    So what we are experiencing is merely that the USA is in full decline, that it was once one of those chosen countries to be used while american workers were provided jobs fairly easily while we were on the risen tide and the oligarchy willing to tolerate worker rights to achieve their production goals...until roughly 1980 when the oligarchs turned away from the USA as a chosen land.

    Was this change due to
    Was this due to environmental
    Was this due to taxes or impact of
    Was this due to the rusting of our heavy factory

    It was likely due simply the fact the USA was rather fully exploited by 1975. All the easily extracted oil, minerals, copper, iron ore, gold, silver, etc was gone and that is why the ROI tipped away from the oligarchy 'caring' about America.

    Now the only wealth left to be extracted from America is held by people, so they pillage them relentlessly with predatory financial instruments, overly expensive healthcare, expanded extractive sins like gambling + alcohol + pro sport circus et al, and of course buying off any government policies to feed their special interests.

    And what follows is more rambling, so forgive me--
    It just always seems to circle back to these basics. That the rich owning class ends up appearing to be lined up versus the poor working class. They cannot help themselves, that they cannot break this cycle--generation after generation for time eternal. The workers become satisfied in achieving a simple level of comfort, become happy and complacent with next to nothing; while the owners are never satisfied, even while having incredible wealth they are unable to be comfortable with it and demand more. In truth, some individuals shift up or down, but society replaces them while remaining in the same unbalanced unease.

    And then back again to what is going on with humanity, unable to achieve a 'high society' we always fall so prey to the easy same old patterns to the point where I wonder if we have made any progress since Adam and Eve. The human flaws keep winning, the goal of goodness over evil impossible to reach, and even the most holy or the most stoic gentlemen cannot maintain their facade day in and day out.

    In their most lucid moments, they created holy books, chivalry, and religious movements to guide and support them...and then let evil in the guise of men and women undermine them. Is it out of boredom...or just a lust for the seven deadly sins.

    Grey thoughts for a grey Saturday--my apologies--there is hope, always fair hope to preserve us--that maybe society will again try to reach higher, that as your Maher quote today says...that maybe the rich pinatas will open up without having to be beaten with sticks. After all, the rich do in fact have brains and free will if they so choose wisdom and goodness over folly of lust and greed. Best wishes, thanks for your blog, it is what is left of my savings plan. :)

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  5. This is a good illustration of how people work effectively in certain environment.