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© Copyright 2007 Work-4 Projects Ltd.

Making Energy Efficiency Cost Effective

By Jon Eakes

When asked to write an article about new energy efficient building products, I was asked to avoid theory... but I can't totally. The problem is that if you just look at one product at a time, you can't possibly get it right. Payback on any individual item is dependent on the overall effect of all other energy conservation efforts. For the same capital cost, saving 20 per cent of a low energy bill doesn't pay back as well as saving 20 per cent of a high energy bill. Energy conservation measures need to be prioritized: greatest savings at least cost ratio first - and some seemingly good ideas simply left out.
Just look at insulation. Installing the first R-12 of insulation will block 93 per cent of conductive heat losses. Increasing that to R-20 only saves a total of 96 per cent of conductive heat losses and adding another R-12 to reach R-32 will only save one more percentage point: 97 per cent. There is a strong law of diminishing returns going on here. The cost of that extra insulation might be better spent elsewhere. That is why we use computer programs like Hot-2000 to judge the cost effectiveness of specific energy saving efforts in the context of a given house and the sum total of the energy saving efforts proposed.
One's first thought about this is a graph with a simple sharply rising curve - measuring capital costs against energy savings. At the beginning, you get a lot of savings for little costs, and at the end you get little more savings for astronomical costs. But when we look at the real curve, there are one or two very strange blips on the chart.
Because mechanical equipment comes in distinct sizes, there is a sudden decrease in overall capital costs when we reach a point of energy efficiency that allows us to downsize a furnace, boiler or air conditioner. The trick here is that the greatest cost efficiency is just after the point of equipment downsizing where overall costs drop even though the individual item costs more; the worst place to stop is just short of an equipment downsizing. The art to this is to reach the downsizing point while the capital costs are as low as possible.
There are really three inter-related areas where we can work on the overall energy efficiency of a house: reducing thermal losses, increasing solar gains, and augmenting heat recuperation from both ventilation and water.

Reducing thermal losses
Insulation is the first line of defense against thermal losses but keep in mind that moving from R-20 to R-32 requires a lot of insulation with very little payback. However, when we think that six inches of a wooden stud is worth less than R-8 and 20 per cent of our walls are wood structure, insulating sheathings are worth far more than thicker studs with more cavity insulation because only insulating sheathings cover the thermal bridging of the structure of the house. Metal studs can't even survive in a Canadian climate without insulating sheathing covering them.

3E Wall™ Panel System
The 3E Wall™ Panel System is an interesting new product - pre-fabricated steel stud panels - just being introduced into the US. They are probably the lightest pre-fab wall panels on the market. EPS (2-1/4 to 4-1/2 inches) bound to two steel studs with interlocking airtight edges and screw strips on the outside make this a very interesting alternative for those wanting to build with steel studs. (www.AcceleratedBuildingTechnologies.com)
The other major element working against thermal losses is air sealing. But air sealing can be labour intensive, making the old sealed poly approach to building expensive. Sealed housewraps cost more than poly but reduce the labour portion of air sealing costs.

Delta Dry
Delta Dry is a radical change in housewraps as it is totally impermeable but provides drainage layers on both sides, to drain out any moisture from inside sources and to drain out anything that gets behind the siding. Because it is impermeable, it prevents the sun from driving morning dew into the house, which can happen through permeable housewraps. The catch: It is purposefully not an air barrier with its inner drainage layer and impermeability, so you need to provide that air barrier somewhere inside the sheathing, such as with an air blocking insulation. (www.DeltaDry.com)

Increasing solar gains
Orientation of the house on the lot and the large windows to the south is the starting point of using solar energy. Shading the windows from the high summer sun with proper overhangs or awnings is important, as is the choice of leaf trees on the south side that will shade the house in the summer and let the sun in during the winter. All of these things can get you closer to that equipment downsizing point with very little cost. But even passive solar energy needs to get active; plan air circulation ducts or furnace return air ducts high up in solar heated rooms and above any mass storage walls to share that excess heat with the rest of the house.
We usually calculate passive solar energy only by what comes through windows but, in fact, when the sun warms up the outside of the walls, the temperature difference across the walls is less and the heat loss is less with no change in R-value. Reflective sheets under the siding work against this in a heating climate, preventing the sun from warming the wall and increasing your heat losses, although they do reduce air conditioning costs. Which is most important to you?

Evacuated Solar Tube
Active solar energy will soon be a part of standard housing, from evacuated solar tubes (re-read Solar Collectors in July 2006 issue for details and see www.canadiansolartechnologies.ca ) to new generations of photovoltaic collectors that are rapidly developing. The current political competition to look "green" and allow grid connection can only help this sector of the industry to finally get off the ground. Even the National Research Council will soon put up on their Web site new solar maps specifically designed to help evaluate and design photovoltaic units for every community of Canada. The Solar Energy Society of Canada is also a good Web site to keep in touch with this rapidly changing field (www.sesci.ca)

Heat Recuperation
We all know about heat recuperation with HRV ventilators and, if you have worked with the R-2000 program, you are quite aware of the tremendous contribution they make to energy conservation. Increasing HRV recuperation efficiencies is a key to reducing furnace sizing.
The hot water tank is one of those pieces of mechanical equipment that uses a lot of energy in a home, yet we throw that energy down the drain. Standard drain water heat recuperators, such as the original GFX, recycle energy in a continuous flow situation because there needs to be warm water running down the drain while cold water is flowing through the coil, like during a shower. Most homes have 60 per cent continuous flow applications, but what about the other 40 per cent?
The new GFX Star takes care of all energy flowing down the drain by using a differential temperature controller to turn on or off a pump that circulates water through the coil and then to a tank, which acts like a small capacitor. When there is a demand on the hot water tank, the extra tank is ready to provide warm water for heating. Now you can choose the inexpensive lite GFX model at about 30 per cent efficiency or the active Star model at 54 per cent heat recuperation, and maybe even reduce the power - and cost - of your hot water tank because the water coming into the tank is not as cold.
CANMET has finished testing on the GFX drain water heat recuperator. Watch for details and a savings calculator in the summer of 2007 on its Web site or at www.gfxStar.ca.

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