letters

Cheap Electricity III

Your editorial Cheap Electricity II (HE, Jan/Feb '95) suggests that low gas prices are the driving force behind the low reported prices for new electric generation and implies that this situation is unstable given the historic volatility in gas prices.

First, the success and dominance of gas-fired combined cycle generation is driven both by technological and market innovation (improvements in heat rates, project standardization, reduced lead times and maintenance costs) as well as low gas prices.

Second, a recent study we conducted provides some important insights on the long-term prices of new generating resources based on actual market conditions and the allocation of future fuel price risks. The average levelized price was 6.7 cents/kWh for 20 gas-fired projects, representing over 5,000 MW, with the best projects coming in at around 4.5 cents/kWh (assuming an 80% capacity factor, and gas prices escalating at 1% per year above inflation).

Claims in the trade press of independently produced power at 3.5 cents/kWh typically represent first-year prices only. We found that developers in about two-thirds of these projects signed contracts that did not tie payments from the electric utility to future gas spot prices. Developers were willing to bear much of the fuel price risk, as payments were indexed to changes in inflation rate, or fuel costs of the utility's existing plants, and so forth. Unexpected upturns in gas prices would not translate directly into rapid increases in electricity prices as you suggest.

Gas-fired combined cycle generation developed by private power producers is not too cheap to meter but it is proving to be an attractive technology against which energy efficiency must compete.

Chuck Goldman and Alan Comnes
Energy Analysis Program
Lawrence Berkeley Laboratory
Berkeley, Califonia

A Proper Foundation?

I live in a smallish 30-year-old house in Massachusetts that was a shrine to electricity. Electric baseboard heat, electric water heating, electric cooking--it all must have been quite mod in its day.

We are in the process of converting to gas hydronic (baseboard) heat, and have taken other energy- and money-saving steps as well. One problem that remains is the cold slab floor. The basement living area is half underground, with sliding glass doors to the back yard. So the foundation is in direct contact with the earth, and it is both cold in winter and moist in summer.

My question is, how can we insulate this floor without losing too much headroom and otherwise making problems with doors, and so on (I really don't want to raise the floor more than two inches, total)?

Please don't suggest radiant heat; we've looked into and dismissed that. A friend suggested one-half to one-inch rigid foam insulation, topped by quarter-inch plywood and then some floor finish material. Others have suggested radiant foils. What would your experts recommend?

Linda Cooper
Taunton, Massachusetts

Editor's Note: We forwarded this question to the Energy Efficiency and Renewable Energy Clearinghouse (EREC), operated under contract to the U.S. Department of Energy (DOE). (For answers to questions about energy efficiency and more, the toll-free number is 800-DOE-EREC.) EREC's technical specialists advised the following:

If the room feels damp or smells moldy, completely gut the walls of the space. Save nothing! All the wallboard and insulation are most likely mildewed (mold spores are hard to kill and, if given enough moisture, can become a big problem later). After the wall is open, and if you find any black or brown mold-like stuff on the foundation walls, clean it thoroughly with a 50-50 solution of bleach and water (use a good fan to ventilate the space). Re-waterproofing the foundation wall may be a good idea after this dries.

Install new studs as needed and install all new insulation (R-19 minimum) over the exposed foundation wall and a continuous vapor barrier. A layer of one-inch foam board should be installed tight to the wall, with the wall studs tight to this and high density fiberglass batts (R-13) in the stud cavities.

This would also be a good time to insulate the rim joist (which was traditionally ignored by many builders of that era). Install as much insulation in this area as you can fit.

Whatever insulating system you choose, be certain that the vapor barrier you install over the insulation is as close to perfect as possible. A good method is to run a bead of caulking over the studs (top plate and bottom plate) and down the corners of the wall. Bead the plastic sheet in it. If needed, use a staple gun to hold the plastic in place. Be sure to staple only where the caulking is and use a minimum of staples (one every three feet usually works well).

You stated that a friend suggested a one-half to one-inch of rigid foam insulation, topped by one-fourth-inch plywood. Since there are two inches to play with, we suggest something similar: Install a 6 mil poly vapor barrier over the slab. Avoid holes in it. Use a latex, silicone adhesive, or tile adhesive between the plastic and the slab to hold it down. Adhesives that stay flexible are best. Overlap the plastic up the walls and seal it to the wall vapor barrier. Now apply glue to the slab's plastic layer and install one inch of extruded foam board, tightly butt each board to one another as well as to the walls of the foundation. Apply adhesive over this and glue three-fourth inch T&G plywood on top. (All of the gluing is to prevent the floor from flopping. Lightweight floors can move up-and-down and suck air in through the edges. This sometimes makes objectionable noises inside the floor). Install the plywood over the foam board and adhesive. Do not use plywood that looks cupped. Doing so will only make your floor more difficult to glue-up. Leave a half-inch gap at the walls for expansion and then install your finished floor over this, again leaving a half-inch gap at the walls (the baseboard will hide this).

Clarifications

In the article, Where Water-Heating Energy Really Goes (Jan/Feb '95, p.5), the standby losses in Figure 3, Percentage breakdown of U.S. residential hot water energy use by end-use in 1993: natural gas water heaters are too high. What was labeled standby losses actually represents both standby losses and inefficiencies during recovery. Also, the figures in the article are for existing water heaters. Newer models will have lower losses.

Gas DSM and Fuel-Switching: Opportunities and Experiences is available free from the New York State Energy Research and Development Authority (NYSERDA) for residents of New York State only. It can be purchased from the American Council for an Energy-Efficient Economy (ACEEE) for $40 (plus $2 handling). In California, add 8.25% sales tax; In Washington D.C., add 6.25% sales tax. Contact ACEEE, 2140 Shattuck Ave, Suite 202, Berkeley, CA 94704. Tel:(510) 549-9914; Fax:(510) 549-9984. Included is a review of gas demand-side management and fuel-switching program experience throughout the United States, and an objective study of the economic savings potential for such programs for three New York utilities. Several fuel-switching measures are also analyzed (see Jan/Feb '95, p. 42).