By Katherine Salant
George and Martha want their new house to be more energy efficient.
George argues for a more expensive, more efficient furnace because they use it eight months of the year. Martha argues for a more expensive, more efficient air conditioning unit even though they only use it three months of the year.
They are both on the right track. But to make a sizable dent in their energy consumption and utility bills, George and Martha need to look at the entire heating and cooling system, not just the two biggest pieces.
For example, in most houses the ducts that carry the conditioned air leak at their connection points. On average, about 25 percent of the energy used to heat and cool a house is wasted in this way (only Florida building codes require that all ducts be sealed).
When the unsightly ducts are put in an attic or a crawl space, a common practice in much of the country, this leaking air is lost to the great outdoors. Thanks to the laws of thermodynamics, additional heat or cold is lost through duct walls.
Even worse, some of the air may not be ducted at all. In some areas it's a common practice to route the air back to the heating or cooling unit through wall cavities between wood studs and the space between floor joists.
Sending all the conditioned air through ducts and sealing them with mastic (a gray, goopy glue) or foil tape is the obvious first step.
Duct tape, as it turns out, is ideal for the quick fix or the emergency repair, but lousy when used for its stated purpose -- sealing ducts. Tests at the Lawrence Berkeley National Laboratory in Berkeley, Calif., have shown that it falls off ducts as it ages.
An added benefit to sealing the ducts with the right material: the time to cool down a house that has been empty all day can be reduced by more than one hour.
The next step, and some would say the first order of business, is moving ducts out of the attic or crawl space and into the conditioned envelope of the house, thereby capturing that otherwise lost air.
Since many people don't like the aesthetics of this solution -- furred out ducts running along the ceiling line could derail plans for crown moldings, for example -- another possibility is to leave the ducts where they are but seal up and insulate the attic or crawl space so that it will be inside the thermal envelope of the house.
This is easier said than done, however. Sealed up, fully insulated attics and crawl spaces that do not have any vents contradict established building practices that are more than 100 years old, and most building codes do not allow it.
A number of intrepid and persuasive builders and researchers in Nevada and Florida fought city hall and succeeded in building sealed-up, fully insulated attics, but this approach has yet to catch on.
Another attic strategy now being tried in Florida is to box in and insulate a small portion of the attic and put the ducts in there.
Over the strenuous objections of contractors, other research/builder teams in California and Arizona simply put the flimsy, round attic flex ducts on the attic floor and covered them with insulation. This also works, but reservations about potential moisture problems limit its application to the few areas of the country that do not experience summer humidity.
If George and Martha lived in an area where the furnace, air handler and ducts are put in a basement, they could avoid the attic/duct headache.
In this case, the air leaking from the ducts will find its way back into the living areas above, but the rooms that are farthest from the furnace may be uncomfortable. Sealing and insulating the ducts, which is not commonly done when they are in a basement, will help insure that the air is more evenly distributed.
Moving on from the ducts, there's the outside air coming into the house through the walls. This also affects energy consumption. When this air infiltration is excessive, it causes the furnace or air conditioning to run unnecessarily, which runs up the utility bills.
All those points of entry need to be plugged up. Heat can also pass through the window itself, making a house colder in winter and hotter in summer; getting the right window -- a dual paned one with a low emissivity coating -- will help to staunch this flow.
Even the roofing material and color will affect the heat load in the house below; in the south, as near to white as prospective buyers can stand and tile if they can afford it is the best.
When George and Martha address all the other things in their new house that will affect how much energy is needed to heat and cool it and finally get back to the furnace and air conditioner, they should be pleasantly surprised.
In all likelihood they will be able to purchase less expensive models that would ordinarily be installed in a smaller house because they're reduced the heating and cooling loads.
When their new system is up and running after they move in, they'll find that it is significantly less costly to operate and it delivers a noticeably higher level of comfort than their old one did because the heating and cooling is more evenly distributed through the house.
Such a comprehensive and systematic approach to heating and cooling has been advocated for at least 20 years by building science engineers, but it has finally captured the imagination and attention of home builders through the Department of Energy's Building American program.
Started in 1996, this program has two ambitious goals: 1)devise strategies that will make new houses 30 to 50 per cent more energy efficient than conventionally built ones, and 2) accomplish this through a series of tradeoffs and substitutions so that the dollars saved by some of the changes will cover the added cost of others.
In the past, energy efficiency has been a hard sell to both builders and buyers because it nearly always made the houses more costly to build and buy.
Few people got very excited about a more efficient furnace, for example, and buying one usually only made financial sense if the buyers planned to be in the house five to ten years, long enough to exceed the "payback period," the length of time required for the savings on the utility bills to equal the extra money spent the furnace.
And the immediate tangible benefits -- a much greater level of comfort because the house was evenly heated and cooled were often unrealized because the rest of the heating and cooling system was unchanged.
With the Building America approach, however, buyers pay a minimal amount extra to get energy efficiencies and get greater comfort and savings from day one. It is a win-win for everyone.
Pulte Homes in Las Vegas, for example, has found that with the Building America systems approach, the buyers of one of their 2,400 square foot houses save about $660 a year on their heating and cooling bills, compared to what they would be paying in a conventionally built house. The added cost to get the savings and comfort: about $1,000.
To locate a builder who participates in the Building America Program, check its website, www.eren.doe.gov/buildings/building_america/index.html.
Another federal program that also promotes energy efficiency in new houses is the Energy Star Homes program, which is jointly sponsored by the Department of Energy and the Environmental Protection Agency.
To locate a builder who participates in the Energy Star Homes program, check its website, www.energystar.gov and click on homes.
Many of the participating builders in these two programs are small, but some divisions of the larger, national firms including Centex, Brookfield, Beazer and Ryan are also involved.
If you don't find a participating builder in the area where you want to build, you can still ask any builder that you are considering about duct sealing, duct location, windows, air infiltration, and insulation.
Two other websites that have useful information about energy efficiencies in housing: http://ducts.lbl.gov and www.fsec.org--browse the homes and buildings pages.
Sidebar story:
When trying to make a house more energy efficient, sealing the ducts, locating them so that less energy is lost to the great outdoors, buying good windows, and plugging up the air leaks will make a huge difference.
But other refinements will also affect comfort and lower those utility bills; here are some additional questions to ask any builder you are considering:
1. Who designed the heating and cooling system?
It looks deceptively simple, but designing a good one is part art and part science; you need an experienced mechanical engineer, not a heating and cooling contractor who did it on the fly.
Large heating and cooling contracting firms generally have several mechanical engineers on their staff, but you should ask.
A poorly designed system can produce uneven air distribution (some of the rooms are too hot or too cold), unhealthy indoor air (some rooms get too much fresh air and others not enough), and unwelcome noise (poorly installed and/or wrongly sized duct work).
2. Where is the air handler?
This is the fan that sends the hot and cold air through the ducts. In some areas, it is routinely put up in the attic space; in others it is put there only in larger houses that require two heating and cooling zones.
Either way, this location will cause additional energy losses, which can range from 10 to 25 per cent of the total consumed to heat and cool a house. The obvious solution in this case is to bring the air handler down and put it in a closet inside the conditioned space.
3. Was the mechanical system tailored to the orientation of each new house in a subdivision, or calculated for the worst case and then installed in all the houses?
If the calculations are based on the worst-case scenario, you could be paying for a larger system than your house requires.
If the major living areas of your house face east or west -- the worst-case scenario -- and this was not taken into account when the system was designed, you will be uncomfortable to miserable, especially if you live in an area with a humid climate such as Houston.
4. Does the builder offer additional windows as an option?
In many cases, a buyer can add as many as six or eight windows to a production builder's standard floor plan. This may greatly enhance the interior spaces, but it also adds to the heating and cooling load, so ask if the mechanical system has been appropriately modified.
5. If you are buying the end unit in a row of town houses, the house will have a large exposed end wall. Was the mechanical system designed to take this into account?
If your heating and cooling system is the same size as the interior unit next door, you will be very uncomfortable, especially if your end wall faces east or west.
6. Does the builder offer a whole house exhaust fan?
When the outside temperature cools off in the evening, you can open your windows and bring this cooler air into the house, cooling it off for the night and reducing the use of your air conditioner.
7. Where are the filters located?
All hot and cold air systems have filters that must be periodically changed or cleaned. When the filter is at a return grill, this is easy. But when the filter is in the attic or somewhere else that is fairly inaccessible, this becomes an odious chore that is often left undone.
Ask the sales agent to show you where the filter is and judge for yourself how often you will change it.
You should also ask if the builder offers any filter upgrades. Standard issue in a production house will almost surely be the "dollar filter" type that only removes the largest dust particles -- about 7 to 10 per cent of what comes through the ducts. It's definitely a Yugo.> /P>
The Cadillac of filters is the electronic type that removes about 80 per cent of the dust that comes through. Between these two extremes are several intermediate grades of filters that cost less than the Cadillac filter but more than the Yugo.
Because some of the filters are sizable and can affect the installation of the air handler, you need to discuss any filter upgrades with the builder and his heat and air conditioning contractor before the sales contract is finalized.
Katherine Salant can be reached at salantques@aol.com
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