This article was originally published in the March/April 1994 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online March/April 1994
The Landlord-Tenant Quandary
As a residential energy auditor for a western New York utility, and with several hundred audits completed, it has become obvious to me where the greatest energy savings potential exists. Time and again, I respond to tenant requests for energy audits and discover little or no ceiling or wall insulation, leaky windows (often without storms), drafty doors, leaky ducts, and so on. Usually, the utility payments are the tenant's responsibility.
What we have is a circumstance that fosters inaction. The landlord has little incentive to improve energy efficiency when the tenant is the benefactor, and the tenant feels they shouldn't have to improve property they don't own--especially when occupancy is a month-to-month uncertainty.
And then we have tenant irresponsibility when the rent includes utility cost. This includes doors and windows left open, lights left on, electric heaters used unnecessarily, and on and on.
This is not news, yet I have not heard of or seen any programs that address this problem. I would like to know what has been done in other parts of the country. Surely there must be some experience in solving this problem that warrant publication.
Richard D. Smith
Keuka Park, NY
Editor's Note: Reader Richard Smith brings up an important point. Renters, who represent over one-third of the nation's population, are often overlooked in the quest to conserve energy. We invite readers to share their experiences helping tenants save energy for possible publication in a future issue of Home Energy. Photos and artwork are strongly encouraged!
Blower Doors and Rules of Thumb
I disagree with your assertion that the eight-year old article, Infiltration: Just ACH50 Divided by 20? is fresh and valuable (see HE Jan/Feb '94 p.35). A number of developments since 1986 supersede the rules of thumb embodied in that article.
Air changes per hour at 50 Pascals (Pa) is a crude measurement that combines the uncertainty of not knowing the house volume with the ambiguity of using a reference pressure above most of the measurement datapoints and far above physically meaningful pressures. In 1988, ASHRAE came out with a Standard (119) that not only defined a normalized leakage but set tightness limits for different climates. Rules of thumb are given in that standard that have passed the consensus process.
The 1986 article does not recognize that air changes have different values at different times, and that they are involved with two functions: ventilation for air quality, and energy transfer due to convection. Recognizing this, ASHRAE has written a standard (136) on how to calculate infiltration for indoor air quality purposes. Heating and cooling season ventilation rates are usually quite different, as are the demands on the HVAC system necessary to condition such air. It is important, therefore, to separate them.
Even if one were willing to ignore the advances and be constrained by the limitations of the original article, a single divisor to get some average infiltration rate is no longer very useful. There can be an enormous difference between such an average and a divisor calculated for a more specific purpose.
To exemplify the point, I made two plots similar in spirit to the original figure, but for two different cases. First, I calculated the divisor for heating-season, energy-loss purposes (if one were using the calculated air changes per hour [ACH] with average heating season temperatures to determine heating loads). Although this looks similar to the original in the severe heating climes, it begins to differ as the climate improves.
A more extreme example is in the second plot, which displays the divisor for the purpose of estimating effective ventilation for indoor air quality purposes (to meet ASHRAE Standard 62). In this case the divisor is larger than the original in all locations, and significantly so in many.
Even crude rules of thumb can be out of date and should be allowed to go gently into the night.
Lawrence Berkeley Laboratory
Figure 1. Climate factor for indoor air quality. This plot shows the value of the factor (C) from the original article for winter energy consumption purposes. The shaded regions represent the range of values between the labeled C contours of 16, 20, 24, and 28.
Figure 2. Climate factor for energy. This plot shows the value of the factor (C) from the original article for annual ventilation (air quality) purposes. The shaded regions represent the range of values between the labeled C contours of 20, 24, 28, and 32.
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