Letters: September/October 2005
In his column,“Crawlspace Conundrum” (May/June ’05, p. 8), Brad Turk gave a solution for an arid climate but not a green-grass climate. Exhausting air from the crawlspace will load the home and the crawlspace with humid outside air. The most important measure is placing a plastic cover on the earth. Next, seal the outside vents to prevent humid outdoor air from entering the crawlspace. Dehumidify, if necessary, to maintain relative humidity at less than 60% throughout the summer.
Author Brad Turk replies:
It seems that the author of the comments and I both agree that outdoor air in crawlspaces is not desirable. My basic
recommendations for controlling moisture in crawlspaces apply to most climates and include creating a conditioned crawlspace by sealing air leaks between the crawlspace and outdoors (including closing vents), sealing the soil surface, fixing plumbing leaks and drainage problems, and using a small fan to exhaust crawlspace air to the outside while pulling conditioned replacement air from upstairs. If these measures aren’t effective or practical, then a dehumidifier may be appropriate—keeping in mind that (1) the dehumidifier should be sized properly, (2) the dehumidifier will
need to be checked regularly, (3) water produced by the humidifier must be removed from the crawlspace, and (4) a dehumidifier with a high energy factor (water removed for energy consumed) should be selected to minimize energy costs.
Sometimes We Don’t Try to Be Funny
Maybe it’s just Friday, but I have to admit that the blurbs and their placement order on the cover of a recent issue were very amusing (May/June ’05): Toilet All Stars Profiting from Sealant Strategies. The articles by the way are excellent.
Training and Technical Assistance Coordinator
Oregon Housing and Community Services
A/C and Humidity
Your article on the Web (“Behind Closed Bedroom Doors,” linked on the “Do-It-Yourself ” page) is very interesting, but I wonder if a much simpler solution in the case of an A/C system being too large (and causing excess humidity) would be a humidistat in parallel with the thermostat. This is what I have done in my system.
Irrespective of the temperature setting or the temperature in the house, the A/C system continues to run until the desired humidity has been reached. When we temporarily leave Florida, I just turn off the thermostat and set the humidistat at 60%, so the system is just concerned with maintaining the relative humidity at or below this level. I would be very interested in your comments.
Boca Raton, Florida
Author Doug Garrett replies:
Your suggested solution is one that will probably improve the humidity problem due to A/C oversizing, but it could lead to more problems. Let me explain. The air conditioning industry has introduced units controlled by thermidistats. These are a combination of a thermostat and a humidistat—much like what you have created by retrofitting your old control system. These controls are often used in conjunction with blowers with variable-speed electronically commutated motors (ECM) that slow the air flow across the indoor evaporator coil to further improve dehumidification. The thermidistat-controlled A/C units do a better job than a single-speed thermostat-controlled system at controlling indoor humidity.
The problem comes in that in trying to lower humidity, the thermidistat-controlled A/C units can cool the home below the outdoor dew-point temperature. This is especially true in very humid climates, for instance along the Gulf Coast. This can in turn lead to condensation inside your exterior walls and on the ducts. To try to stop this, the commercially available thermidistats usually have a control algorithm that keeps the system from cooling the home more than 2 or 3 degrees below the thermostat setpoint, regardless of humidity level. Your system has no such safety override.
You live in a hot and humid climate, as I do. I believe that you will find interesting a recently published report titled “Residential Dehumidification Research for Hot and Humid Climates,” written by the Department of Energy’s Building America Program. You can read and download it at www.eere.energy.gov/buildings/building_america. The report recommends the use of a stand-alone Energy Star dehumidifier over all other tested systems for first cost, operating cost, and percentage of time below 60% relative humidity.
Ice Cold Cooler?
What change in performance in an evaporative cooler could you expect by lowering the sump water temperature? For example: putting blocks of ice in the sump to lower the water temperature.
Technical Editor Steve Greenberg replies:
In general, this will have very little effect. The reason is that nearly all the cooling provided by the evaporative cooler comes from evaporation. Each pound of water evaporated into the air requires about 1,000 Btu that comes from the incoming air, hence the cooling effect. Assuming a sump temperature of 65ºF and an entering air temperature of 95ºF, that same pound of water will provide an additional cooling effect of 30 Btu (1 Btu per pound per 1ºF), so about 3% of the cooling is provided by virtue of the water’s being colder than the air.
If one dropped the sump temperature, say, to 35ºF (ice water), one would get a total of 60 Btu of cooling from each pound of water, or about 6% of the total. So the effect would be negligible. And don’t forget that the ice gets produced by a refrigeration process substantially less efficient than a conventional air conditioner.
No to Net Metering
The renewable energy listservs buzz with discussions about net metering. Renewable energy advocates spend hours, days, even years, trying to implement net metering over utility objections.Why bother? Net metering is often so limited as to be next to useless.
Of the states with net metering, only a few permit the use of any size of wind turbine that the customer chooses. In this age of customer choice, consumers should indeed have a choice about the size of the wind turbine they want to use under net metering programs. Most programs limit wind turbines to 10 kW or less. Some permit up to 50 kW. A few
go as far as permitting 100 kW. An even smaller number permit wind turbines up to 1 MW. The reason for setting limits?
Caps on wind turbine size protect utility markets. Utilities accept net metering programs with low caps because the
programs pose no serious threat.
However, utilities have little to fear—net metering is self-limiting. Only those whose consumption can absorb all the
production from a large turbine will choose to net meter. Customers such as Iowa’s Schaefer Systems and Spirit Lake
School will opt for larger turbines, because it makes economic sense to offset as much of their load as possible. Those for whom a 10-kW turbine is a closer match to their needs will choose a 10-kW machine. Artificial limits are unnecessary.
In the end, though, net metering won’t get us where we want to go—large amounts of various renewable technologies on the ground. In most cases the price offset is insufficient alone to drive renewable development. Subsidies are needed and subsidy programs have had a checkered history in North America. Most subsidy programs have led to widespread abuses that have hurt renewable energy. Even today, most subsidy programs have no requirement for metering actual generation, one of the fundamental means for monitoring the success or failure of renewable programs.
Europeans roll their eyes when North Americans speak of net metering. Or they say,“Was ist das?” How, then, can Europeans be so successful if they don’t use net metering? How can they have installed so much generating capacity that
the Danes produce 20% of their electricity with wind turbines, the Germans 9% with wind, solar, small hydro, and biomass, and the Spaniards 6% with wind?
The answer is surprisingly simple: They pay for it.They pay for renewable energy by setting a price per kWh for wind, for PV, for hydro, and for biomass. They set a price high enough to ensure that they get the kind of renewable energy they want. Germany pays, in U.S. dollars, $0.11/kWh for onshore wind, a whopping $0.75/kWh for PV, and nearly $0.15/kWh for small, farmer-owned biomass projects. The results speak for themselves.
All consumers pay for the resulting generation.There are no taxpayer subsidies involved. If you use more electricity, you pay more for renewable generation. Fortunately, the concept is beginning to catch on here in North America: Minnesota passed community-based energy development (C-BED) legislation in May for wind energy, and Washington state recently
signed its PV program, which could pay as much as $0.54/kWh for electricity produced by panels built in the state. And the list is continuing to grow as more states weigh the advantages of what the Europeans call advanced renewable tariffs or what is more prosaically known as electricity feed laws.
For more on advanced renewable tariffs and how they can benefit renewable development in North America, visit www.wind-works.org/articles/feed_laws.html or www.ontariosea.org/ARTs/ ARTsList.html.
Paul Gipe is the author of Wind Power: Renewable Energy for Home, Farm, and Business (ISBN: 1-931498-14-8), 2004.
Greening of a Home Performance Contractor
Because of a spreadsheet error, the ratio between the carbon savings for similarlypriced PV and home-performance improvements in New York reported in “Environmental Trade-Offs” (May/June ’05, p. 28) was incorrect. The corrected numbers show that the ratio between carbon savings for similarly-priced PV and home-performance jobs in New York is approximately 4 to 1. The author notes that the larger the efficiency workscope, the more the ratio will tend to drop, since you should be getting the most cost-effective improvements, and therefore higher CO2 impact per dollar, with your first dollars.
For example,comparing a $6,000 home-performance job to a similarly-priced small PV system might show close to a 7
to 1 ratio. Comparing a $24,000 PV job to a $24,000 home performance job might show a roughly 5 to 2 ratio, since the
PV output has at least doubled with the doubled investment and the home-performance output might only go up 25%, for
example, due to diminishing returns.
Guide to Training Programs
An important training opportunity was inadvertently left out of the “Guide to Training Programs for Home Performance
Professionals” (July/August ’05, p. 26). Here is that listing:
Pacific Gas and Electric Company
Energy Training Center-Stockton.
1129 Enterprise St.
Tel: (800)244-9912 or (209)932-2500
Offers hands-on instruction in the use, installation, maintenance, and testing of energy-efficient windows, insulation materials, and HVAC systems.Also teaches auditing, inspection, weatherization, and combustion appliance safety.
Participants in some classes receive AIA and NCQLP continuing education credits.
In the article “Creatively Green,” (July/August ’05, p. 40), Bob Bourguignon is mentioned as the lead designer and project manager for the Teter-Lane home.At the time the home was designed, Bourguignon was a principal of HP Architects, PC, and worked in collaboration with architect Frazer Pajak, of Converse College. Bourguignon has since founded his own company, Sustainable Architects, in Moore, South Carolina.