R- values and air conditioners...
Ask the Energy Wiz!

Q: Dear Wiz: What is the R-Value of a 4 millimeter poly sheathing under drywall?

A: Dear Reader,

The R-value would be negligible, or zero. One millimeter is a thousandth of an inch. This product is listed in the ASHRAE Handbook of Fundamentals, as negligible.

The optimal R-value available would be polyurethane at about R-7 to R-8 per inch. So even if the poly sheathing had the R-value of polyurethane, and it does not, then 4/1000 times 8 would equal an R-value of .032, or 3 hundredths, R-0.032.

Sincerely,
The Energy Wiz

Q: Dear Wiz: On what date will air-conditioning manufacturers end production of units below the 13 SEER (Seasonal Energy Efficiency Rating)? Can equipment below a 13 SEER still be purchased after the date the regulations take effect? Will 13 SEER rated equipment be larger in size? Can the new 13 SEER equipment be used with an older furnace (air handler)? Will these higher SEER units cost more? Will the higher efficiency units save money?

A: Dear Reader,
On January 23, 2006, manufactures of air-conditioning units could no longer make units below an efficiency of 13 SEER. Those units which have already been manufactured, and are below the 13 SEER, can still be sold. Predictions are that the current inventory of 10 to 12 SEER units will run out sometime late in 2006.

The new 13 SEER air conditioners will most likely have a larger condensing unit (outdoor portion), and there may also be changes to the coil (indoor portion). These size changes should not have a substantial affect on current installation practices. If you currently have a 2 ton, 10 SEER, air-conditioner that needs replacement, the contractor would only need to check the difference in pressure drop between the existing coil and the new coil, which should be standard practice with any installation. The federal mandate to cease production of units below 13 SEER is not a big change. Manufacturers have been making units between 13 and 20 SEER for a number of years.

Based on price differences found on the internet, there appears to be between a $400 to $500 difference in price for a 13 SEER unit. Compared to a 10 SEER unit, a 13 SEER air conditioner should reduce the average air conditioning bill by 23 percent.

The Energy Wiz!
The Energy Wiz!
Sincerely,
The Energy Wiz


Q: Dear Wiz: How do convert a 1994 GMC to run on ethanol? The truck has 5.3 litre Vortec V8 engine.

A: Dear Reader,
Converting this truck to run on ethanol may be a pretty tall order. Any car dealership that does a conversion as suggested, would be required to re-certify the carís emissions. Currently, none of the manufacturers make a conversion kit for your vehicle and parts stores do not have a conversion kit either. You may want to read an article that appeared in the July 2005 Nebraska Energy Quarterly on this topic.

Sincerely,
The Energy Wiz

Editor's Note:
The staff at the Energy Office respond to many inquiries on a variety of topics from Nebraskans. From time to time, the Quarterly will share some questions — and the answers — with readers.
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