Letters: January/February 2011

January/February 2011
A version of this article appears in the January/February 2011 issue of Home Energy Magazine.
Click here to read more letters.

Defending Energy Recovery Ventilators

Energy Recovery Ventilator

Max Sherman’s editorial “ERVs Get the Yellow Flag” (Sept/Oct ’10, p. 2) makes a number of credible points. Energy-efficient ventilation makes sense in tight houses. Source control is the best solution for indoor contaminants. Dilution ventilation is a key method of reducing these contaminants. Kitchen and bath source ventilation is considered best practice by some experts and is recommended or required by other codes. However, when it comes to denigrating the “growing segment of building professionals” who are using energy recovery ventilators (ERVs) to exhaust kitchens and baths as potentially harmful, and stating that some ERVs can “recover” formaldehyde in the same way they recover water and should be used only with caution, these statements are without apparent basis in fact.

ERVs have been used in northern Europe to exhaust kitchens and baths in supertight homes over the last two decades without reports of moisture problems. This is not to say that in some climates HRVs would not serve the purpose or that spot ventilation should not be considered an option. But testing and research could be done and presented before speculating that problems occur when using ERVs. Likewise, speculating that ventilation technology and materials that recover moisture would recover formaldehyde and that “having ERVs that recover formaldehyde represents a serious risk,” based on chemical similarities and without testing, is not in the interest of building science. Since ERVs transfer only a percentage of moisture, and the off-gassing of formaldehyde is a decaying phenomenon, the anticipated result of a rigorous test protocol under conditions of air exchange and dilution would be the continuous reduction of any contaminant, including formaldehyde.

Dr. Sherman is uniquely experienced and placed to conduct broad programs of indoor environmental research. It is unclear why he chose to publish speculative hypotheses in advance of case studies. This approach increases confusion among builders who are still reluctant to accept the health, comfort, and energy-saving benefits of comprehensive ventilation strategies. We anticipate a follow-up article detailing the test protocols and results clarifying these issues.

Craig Kinzelman
Stirling Technology, Incorporated
Athens, Ohio

Max Sherman replies:

I apologize to Mr. Kinzelman or anyone else who felt they were being denigrated. It was surely not my intent to do so. My intent was to give readers a heads-up on an issue that I believe could be of health and safety importance.

While I do not yet have published data to show, I believe the concern is far more than speculative. Formaldehyde is known to be one of the major contaminants of concern in both new and existing homes. (See, for example, Logue et al., forthcoming.) It is not just a new-materials issue. Technologies such as some desiccants usable in wheels, and certain plastics usable in cores, can transmit significant amounts of formaldehyde. (See, for example, Fang, Zhang, and Wisthaler, 2008.)

As Mr. Kinzelman states, source control through exhaust ventilation is a key part of moisture control. If a code or a standard requires 50 CFM of exhaust to control moisture (that is, in a kitchen or bath), it presumes that all the moisture in the 50 CFM is being exhausted. If the ERV recovers half of it, then it is equivalent to 25 CFM exhaust. If there is truly a need for 50 CFM of exhaust, then that need is not being met. This does not require studies.

Absence of complaints does not mean absence of problems. Health and durability issues can take many years to show up and may not be obvious to occupants. I believe it would behoove anyone to consider these issues when specifying ventilation systems.


Logue, Jennifer M., et al. “Hazard Assessment of Chemical Air Contaminants Measured in Residences.” Indoor Air (forthcoming). To download this article for a fee, go to http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0668.2010.00683.x/abstract.

Fang, L., G. Zhang, and A. Wisthaler. “Desiccant Wheels As Gas-Phase Absorption (GPA) Air Cleaners: Evaluation by PTR-MS and Sensory Assessment.” Indoor Air 18 (2008): 375–85. To download this article for a fee, go to http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0668.2008.00538.x/abstract.

Readers Forum

Home Energy occasionally receives letters from readers that do not refer to previous articles but reflect a common concern of the home performance community. The editors have decided to create a new category in the Letters section, the Readers Forum. We invite readers to send letters expressing opinions and ideas for this section of the magazine.
Finding the Right Reasons for Energy Efficiency

I recently attended EEBA’s Excellence in Building conference in Portland, where I was able to see Joseph Lstiburek speak both at an educational session and as the closing keynote lunch presenter. The former session offered useful lessons on the subject of deep energy retrofits, complete with examples of lessons learned from his long career in that field. The latter was also informative and insightful, but in a very different way. He began his talk with a lengthy and detailed polemic about what he hoped to convey as the tenuous link between emissions of greenhouse gases and global climate change. This portion of the presentation was followed by personal experiences from early in his career and an explanation of how he began his work in building science. His point wasn’t that energy efficiency should be ignored, but rather that it should be pursued for the right reasons and with appropriate goals in mind.

My interest here is not to take issue with his choice of speaking material or the conclusions presented therein. In fact, I support his general premise that this is one of the least effective ways to win support for energy efficiency. His explanation that we must work to make buildings more efficient for the right reasons struck me as a very sober assessment. However, I would offer a somewhat different perspective on how best to convey this point. Rather than focusing on the flaws of arguments in favor of anthropogenic climate change, it would be more effective to highlight the points upon which we all agree: that energy-efficient buildings are of direct benefit to their occupants and represent the best investment of finite resources.

Those of us who are working to promote energy-efficient construction need to be sure that we are offering clear and effective reasons to consumers if we are to expect them to make rational choices. Energy efficiency can be a hard sell to the public, especially as people are trying to cut spending and do away with extra expenses. Building better homes often costs more up front, and this leads to trade-offs as people may be forced to decide between coveted aesthetic touches or high-performance materials. For this reason, people need to be given accurate information in a way that allows them to understand specifically why efficiency is important and how it benefits them. While everyone has heard of climate change, chances are that it means something different to most people. Exactly how it will impact our lives is a source of conjecture and uncertainty, and the issue has become politically charged. Instead of making this the primary reason to promote efficiency, why not look to more personal motivations?

The most effective messages in support of residential energy efficiency should focus on the direct benefits to homeowners. Efficient homes are generally more comfortable, offer lower utility bills, have better indoor air quality, and are more durable than conventional homes. As a result, they represent a smart investment and can offer more predictability in the face of volatile energy costs. The environmental benefits are implied in this and can certainly be offered as additional selling points. However, just promising consumers that they will be helping save the planet probably won’t be the best marketing strategy. This is partly because people have different views of what “green” and “environmentally friendly” mean. Couching them in terms of improved performance sends a clear message of exactly what homeowners can expect from your product.

The fact that consumers are beginning to expect energy-efficient homes is a great sign that the message is in fact being conveyed in this way. Building science offers a clear signal to consumers that not all homes are equal, and that they can now purchase a home with a reasonable understanding of how well it will perform. This is the most powerful way to show the value of energy efficiency and should continue to serve as the primary focus for those in support of high-performance construction. Other explanations fail to do justice to this important movement and could actually serve to hinder, rather than help, its expansion.

Aaron M. Stein
Build San Antonio Green
San Antonio, Texas

National Standard Needed for Radon

My friend Chris Peters is a trainer for NYSWDA (New York State Weatherization Directors Association), and he always seems to be thinking. Chris called up from an existing home that he planned to use for field training the next day. He had begun to look at the radon system, and it occurred to him that no one had ever really said anything in his own training about radon systems and CAZ (combustion appliance zone) depressurization.

Since Chris knows I have a bit of training and experience in this area, he called to find out what pressure radon mitigation systems run at, and what their impact is on house pressures. It was a question worth thinking about.

The answer is twofold. First, there is no fixed pressure in radon mitigation. System pressure is determined by the size of the radon fan. The pressure range that is appropriate is the one that gives an average test result for radon concentration under closed-house conditions of less than 4 picocuries per liter over a period of time. Test duration can vary depending upon the type of test being used, but readings are generally taken and averaged over a minimum of 48 hours.

Even that is just a rough metric, since radon levels can vary widely depending on any one or more of a large number of variables, including wind, rain, humidity, snow, temperature, barometric pressure, and subtle shifts in underground leakage pathways. It would come as no surprise if such considerations as the distance of the Earth from the sun over the course of the year affected radon levels due to subtle changes in the gravitational influence of the sun upon the Earth. And of course, since the Earth, like a house, is a system, a change in one condition can, and very likely will, result in changes in other conditions.

In the end, the radon mitigator will almost always try to reduce the pressure under the slab with respect to the basement to stop the flow of soil gases, including radon, from being drawn into the living space. Sometimes, although it’s rare, the depressurization simply doesn’t stop the radon infiltration. In those instances, the experienced mitigator may turn the fan over and pressurize the area under the slab. Doing so can, and sometimes does, work, and one can only attribute the cases where pressurization gets the job done to some interaction among the many variables affecting the movement of soil gases.

So what is the impact of the pressure in a radon mitigation system on combustion safety testing? Since there is nothing in the BPI standards to guide an auditor or technician, and since radon systems are designed to run continuously, their internal pressure or their effect on building pressures is simply part of the background conditions and should not be altered by the auditor unless some determination is made in the future by BPI and is incorporated into the standards.

In the meantime, radon testing as part of the scope of work when the house is significantly tightened up is an idea whose time has come. It should be part of any national audit standard.

Ed Voytovich
Building Efficiency Resources
Syracuse, New York


There is a typographical error in the article “Combustion Appliance Testing—Why, How, and When?” (Nov/Dec ’10, p. 38). The first line of the last paragraph on page 40 should read: “A natural-draft furnace works by the stack effect. In this type of furnace, assuming there is enough difference in temperature between the air outside and inside the flue, the buoyancy of warm air in the flue will cause it to rise.” The editors regret the error.

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