This article was originally published in the November/December 1995 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online November/December 1995


Remodeling Bathrooms

Let the Energy Savings Flow

by David Johnston

  Bathroom remodeling offers a wide range of opportunities to conserve energy, from installing efficient showerheads and faucet aerators to air sealing and insulating around the bathtub.

People remodel more than 5 million bathrooms every year in the United States. Sometimes this just means replacing lighting and plumbing fixtures. More extensive remodels involve building an addition or gutting and redesigning an existing bathroom. Regardless of the scale of the project, it is usually a good opportunity to save energy and water, improve comfort, and control moisture. Unfortunately an unwary remodeler may do the opposite. A poorly insulated bathroom can mean higher heating and cooling expenses, miserable bathers, or both. Moisture buildup can create a moldy room and damage the structure of the whole house. As remodelers work to make the space aesthetically pleasing, they should also make it a priority to create a comfortable, efficient, and dry room.


Up to half the water consumed in a home is used in the bathroom. Conserving water saves money in two ways: by reducing the amount of water used (which households and communities pay for in most parts of the country) and by reducing the energy used to heat it in the home. (More energy is used for heating water than for any other household purpose, except heating and cooling.) Conserving water also saves the community money, by lowering the impact on water and sewage treatment facilities.

Many remodelers replace old worn-out faucets and showerheads with new ones. This simple retrofit can save a lot of water and energy if it is done right. An average family can save roughly 17,000 gallons of water per year (and $60-$120 on energy and water bills) with showerhead and faucet replacements. Old showerheads use up to 6 gallons of water per minute (gpm), but all new showerheads (as of January 1995) are required to have a flow of 2.5 gpm or less. The new heads come in a variety of styles, from simple fixed-position units with only one type of spray to hand-held models offering a choice of several spray patterns. Tests by the Consumers Union show that the new showerheads that provide the best shower quality are those which deliver water in a multitude of individual jets, rather than delivering a fine mist or spray.

Whether a faucet is replaced or not, simply adding a faucet aerator can save water. Faucet aerators replace the faucet head screen. They add air to the spray to lower the flow. High-efficiency aerators reduce the flow from 2-4 gpm to less than 1 gpm, which is sufficient for most bathroom sink activities. This retrofit can save from 4% to 7% of the home's total water consumption, and aerators cost only about $2 each.

Buying a new toilet will also save water. Toilets manufactured in the United States are now required to use a maximum of 1.6 gallons per flush (gpf), compared with 3.5-5 gpf for older models. To meet this low standard and still flush well, a lot of new toilets use pressure created within the household's water supply to generate a more forceful flush. These pressure-assisted toilets tend to be noisier and more expensive than those relying on gravity, but they do a better job of removing solid waste and staying odor- and soil-free.

How quickly a low-flow toilet pays for itself depends on how many times it is flushed each day and its geographic location. For instance, the Consumers Union calculated that, in Wichita, Kansas, where water and sewer rates are low, the payback period is seventeen years, whereas in North Castle, New York, where rates are high, it is only two years. To calculate the yearly savings, multiply the estimated number of flushes per year by the difference in flow (in gpf) by the water rate per gallon.

Water Heating

This is a good time to pay some attention to how the water is heated, especially if the remodel will lead to more hot water usage (for instance, adding a jacuzzi). At a minimum for existing water heaters, install an insulating jacket. These have insulating values that range from R-5 to R-11, and they cost $10-$20. They can reduce standby heat loss (the heat lost through the walls of the storage tank) by 25%-40%, lowering water heating energy costs by 4%-9%.

Especially if a remodel will make water pipes accessible or involves installing new pipes, insulating hot-water pipes is an easy and inexpensive way to reduce losses. Closed-cell foam is the most commonly used insulation, but fiberglass, either preformed or in rolls, is another option. Both are available with a slit and an integral adhesive strip to install on existing pipes. Closed cell foam is also available unslit, making for neater installation on new pipes. The R-values for either kind are R-1 to R-3 for 3/8-inch to 1-inch thickness. In addition, insulate the cold water feed to the heater for several feet, and install anticonvection valves on cold inlet and hot-water outlet pipes.

A new water heater may be appropriate if the existing one is old and inefficient, or if more capacity is needed. Quick-recovery, sealed combustion gas water heaters can save 30% over less efficient equipment. There are variations among new models--look at the Energy Factor on the efficiency label, which indicates the unit's overall efficiency. Gas units cost less to operate than electric units in most areas. For example, Rocky Mountain Institute notes that a high-efficiency gas unit will cost $2,400 to operate over its 13-year life, compared to $5,300 for a high-efficiency electric unit over the same period (in an area where electricity costs 8cents/kWh and gas costs 60cents/therm).

Instantaneous water heaters--tankless units that heat only the water needed at the fixture--may be appropriate for a bathroom that gets limited use, such as one in a single-occupant home or vacation cottage. The water is heated by a high-powered electric resistance element or a large gas burner as it flows through the unit. The electric units are usually very expensive to run. Unfortunately, most gas units have pilot lights, wasting energy at roughly the same rate as standby loss from storage-type heaters.

A different kind of demand system delivers immediate hot water from the storage tank. At the push of a button, the system pumps cold water sitting in the hot water lines into the cold water line and back to the water heater. This saves water, energy, wear and tear on the water heater, and sewage costs. The system costs about $400, and operation costs are less than $1 per year.

Water-Saving Alternatives: Reuse and Reduce

In California and Arizona, pilot programs are in place to reuse graywater from showers, sinks, dishwashers, and clothes washers for flushing toilets and watering landscapes. Total water use can be reduced 50%-75% by appropriate design and plumbing of graywater systems. Codes do not allow graywater systems in many places, but initiatives are springing up all over the country to change the codes and win market acceptance (see Graywater: An Option for Household Water Reuse, HE July/Aug '95, p. 33).

Another water-saving option is to install composting toilets, which use no water and transform human waste into humus for plants. Composting toilets are available as self-contained units or centralized systems. While these toilets aren't cheap ($1,000-$3,500), they may be cost-effective in areas with high water rates. They're an ideal retrofit for houses with problematic septic systems.


Light makes an enormous difference in the ambiance of the bathroom. People need to be able to see well while shaving or applying makeup. Limited physical space can be made to appear larger with natural and artificial lighting, whether from skylights or well-placed fluorescents.


Adding windows not only can make the room feel more spacious, but, if they are oriented to the south, can help to heat the room. Some new windows have insulating values up to five times that of a single-paned window (see Selecting Windows for Energy Efficiency, HE July/Aug '95, p. 11). Glass with a low-emissivity (low-e) coating and inert gas fill between glazings are minimum requirements for comfort and energy savings. Fiberglass, vinyl, or vinyl-clad frames should be used due to the high humidity in bath areas, which can cause wood to deteriorate. Metal frames do not insulate well (unless they have what is called a thermal break), and this can aggravate condensation problems. Efficient windows are especially important next to tubs, where cold air can cascade down the glass onto the bather.

Other types of windows, such as skylights, clerestory windows, and light pipes, can eliminate the need for artificial lighting in the bathroom during the day. However, no window insulates as well as an insulated wall or ceiling, so the remodeler should try to get the most light out of the least surface area of glass.

A skylight placed between rafters (either 16-inch or 24-inch centers) should have a light well that is insulated to the level of the walls and flared at the bottom to spread light around the bath. Clerestory windows (skylights with vertical glazing) are more energy-efficient than horizontal skylights, since the roof above them can be insulated, though they still allow some heat to escape through the glazing. Light pipes, which consist of a bubble on the roof, a light pipe to the ceiling, and a domed fixture inside, are the most efficient option for directing natural light into a room (see Figure 1).

Figure 1.Light tubes, such as the Solatube model represented here, are simple devices, which allow daylight to brighten specific areas. They consist of reflective tubing that can be fitted between ceiling joists, making this an inexpensive retrofit option.

Fluorescent Lighting

Fluorescent lamps have come a long way in light quality and fixture design. They use one-quarter to one-third as much energy as incandescents, and they can last ten times as long, making their total cost (including energy use and purchase price) half that of incandescents. Some people object to the appearance of fluorescent bulbs or, sometimes misguidedly, to the quality of their light. However, a lot of fixtures now hide the bulb, and there are many compact fluorescents on the market that provide balanced, color-corrected light. Temperature (the color of the light) can be specified at 2,700K to approach the warmer (redder) color of incandescents, 4,100K for a cooler (bluer) light, or somewhere in between. The color-rendering index (CRI) is also important; it indicates the accuracy of color of objects illuminated. Look for a CRI above 80, on a scale of one to 100.

The type of ballast used also affects lighting quality; unlike older magnetic ballasts, electronic ballasts are free of flickering at the start and strobing or noise during operation; they're also more efficient. First costs can seem high, but the light bulbs pay for themselves in reduced operating costs several times during their lifetime. Many utilities have rebate programs or other incentives for compact fluorescent light bulbs.

Many fluorescent designs are particularly well suited to bathroom applications. A 25W 3-ft tube can be placed in a soffit over the sink. Existing vanity lights can be replaced with 15W globe screwbase compact fluorescent bulbs. If central overhead lighting is desired, a ceiling-mounted diffuser containing two 13W compact fluorescent twin-tube bulbs and one ballast can provide ambient lighting.

Halogen lighting

Halogen fixtures and bulbs have come down in price over the last decade. While most halogen bulbs are only 10% more efficient than standard incandescents, they last about three times as long. Some halogens have an infrared-reflective (IR) coating that makes them even more efficient. Because halogens offer a bright white light, they may appeal to people who are dissatisfied with the quality of even the latest fluorescents.

Creating a Comfort Zone

Remodeling provides an opportunity to create a more comfortable bathroom by sealing air leaks, adding insulation, upgrading space heating, and improving ventilation. These measures will also save money on energy bills.

Insulation and Air Sealing

People are more sensitive to the temperature in the bathroom than in any other room in the house, so it is especially important to make the bathroom comfortable. Sealing air leaks and providing good insulation is the most important step remodelers can take to improve efficiency and comfort.

Energy codes for new construction in many states require R-19 insulation in exterior walls and R-30 in ceilings, but good insulation makes sense anywhere. If the room is being expanded or the walls replaced, be sure to insulate them well. If there's a chance that the existing insulation was installed badly or was damaged by moisture, gut the room to the framing and reinsulate. Either blown-in fiberglass or cellulose insulation works well; if space is an important issue, rigid foam has a higher R-value per inch than these.

Regardless of insulation type, a low-permeability vapor barrier--typically a plastic sheet--should be installed on the inside surface of the framing. This helps prevent moisture from condensing in the wall cavities, where it rots wood framing and makes insulation less effective.

Insulation should also be placed in the shower walls, as well as under the tub and in the cavities surrounding it. I once saw a cantilevered bathroom addition in Maine with ice in the bottom of the tub in the morning due to poor insulation in the floor.

Make sure all junctures in the framing are sealed to prevent air leakage. (Most insulation does not seal a space against leakage.) All plumbing penetrations through the walls and floors should be sealed with one-component urethane foam (see Urethane Foams and Air Leakage Control, HE July/Aug '95, p. 25). Don't miss the hole in the subfloor around the tub drain; it can be a major source of heat loss.

Space Heat

Cranking up the heat in the whole house to warm the bathroom is a common practice. This makes insulation and air sealing even more important. A well sealed and insulated room should not need much extra heat. If it does, it can be effective and efficient to produce heat only where it's needed.

Electric radiant heating panels can be placed on walls or ceilings to radiate heat on demand. They cost about $100 for a 4 ft2 panel and $200 for one twice as big. The smaller panel uses 375 watts (W), compared to 1,500W for a portable electric space heater. Because of their radiant nature, these panels heat people and objects, not the air. This means that people can stay warm while in the tub or drying off, though the air temperature is the same in the bathroom as it is in the rest of the house.

Infrared heat lamps can also provide spot heating. They heat up faster, have a higher temperature, and cost less than panels; but some people may find the hot, direct beam harsh.

Piping for hydronic radiant heat is less cost-effective than using radiant panels, because of the high installation cost, but it can provide warm floors for those who hate having cold feet. It's a particularly attractive option if a tile floor is to be laid, since tiles conduct heat well. Heat is radiated into the bathroom via separate hot-water lines from the water heater that have been plumbed through the concrete subfloor in a serpentine fashion. (This could be done with the supply lines to the tub and shower, but that would be less desirable for two reasons. In winter, the water would cool on its way to the bather, while in summer, the floor could get too hot.)


A bathroom exhaust fan helps remove both moisture and odors (see Bathroom Exhaust Fans). It is crucial to exhaust moisture to prevent it from entering building cavities and damaging framing, or even deteriorating a house's exterior walls.

In tight houses, vent fans, clothes dryers, and kitchen exhaust fans can create a negative pressure, so that they draw air into the house through holes in the framing, chimneys, and even exhaust flues. This can cause backdrafting in combustion appliances, a serious health hazard. While the bathroom can be maintained at a negative pressure to control odor problems, it is best if the rest of the house is kept at a slightly positive pressure. In hot, humid climates, it is best to operate the exhaust fan only when the bathroom is in use, so that the negative pressure does not draw humid outside air into the building cavities.

Heat Recovery Ventilators (HRVs), also known as air-to-air heat exchangers, exhaust contaminated indoor air and replace it with outdoor air, improving the air quality in the home. They reclaim heat (some units also reclaim humidity) and transfer it to incoming fresh air, either maintaining neutral pressure in the house or creating a positive pressure inside relative to outside. The HRV can be ducted to the bathroom fan and kitchen exhaust, so that every time the fans come on, the HRV is engaged to capture heat from the exfiltration (see Is It All a Lot of Hot Air?--Mechanical Ventilator Performance HE Nov/Dec '90, p. 25). In drier climates where indoor moisture is beneficial, enthalpic wheel HRVs capture some of the humidity as well.

Remodelers can also improve indoor air quality by using paints and finishes that do not contain volatile organic compounds (VOC). Adhesives can be a major source of toxic chemicals, so look for solvent-free adhesives and always allow the room to air out after they have been applied. Vinyl flooring is another source of VOCs to be avoided. Linoleum, on the other hand, is made from linseed oil, chalk, wood fiber, flax and other natural materials.

Bathroom Exhaust Fans

A remodel is a good time to update the mechanical ventilation system in a bathroom. The traditional bath fan is a fan or fan-light combination that moves little air and makes a lot of noise--usually about half the rated air flow and 3-4 sones of noise. The occupant typically doesn't use the fan much, if at all, because of the noise and the perceived energy loss. But we need to use bathroom fans to remove odors and moisture, and we need to run them for several hours a day, not ten minutes. A wide variety of bathroom ventilation options, ranging from quiet to nearly silent, have come on the market over the past couple of years. Leading this innovation has been the series of VQ (Very Quiet) fans from Panasonic that combine very quiet operation (0.5-1.0 sone) with low energy consumption (13W-17W) for 50, 70, and 90 CFM (cubic foot per minute) fans. American ALDES, Fan America, and NuTone have all introduced new low energy (25W-35W) and quiet (0.8-1.5-sone) fans in the last year to compete. Panasonic will introduce a fan-light combination in January that will use two 13W compact fluorescent bulbs with the VQ fan models rated at 70, 90, or 110 CFM.

A second option is to use an inline remote fan to provide the bathroom ventilation at similar or even lower sound levels. American ALDES, Broan, Continental Fan, Fantech, Rosenburg, and Tamarack Technologies all offer inline single pickup fans that are typically mounted remotely in the attic, the basement, or on the exterior of the wall. These fans are generally rated for higher flows than surface-mounted fans (100-300 CFM) at 50W-100W of power consumption. However, if they are properly mounted and sound isolated, the perceived noise level at the grille can be below 0.5 sone.

A variation on this idea replaces two to six fans in the house with a single multipoint remote fan in the attic or basement to provide ventilation from a variety of bathrooms, utility rooms, and possibly the kitchen. In a retrofit, this is easiest in a single story house that can use ceiling pickup grilles, but anything is possible. American ALDES, Broan, DEC, and Fantech all offer a range of multipoint fans with two, three, or four pickups. ALDES also offers six, eight and twelve pickup fans for large houses and apartment buildings. ALDES and DEC offer two-speed fans to give a boost when needed. This multipoint approach is similar in layout to heat recovery ventilation.

For more information on the need for ventilation and some of the new products on the market, look for an article dedicated to ventilation in the March/April '96 issue of Home Energy.

--Don Stevens

Don Stevens is a ventilation consultant in Keyport, Washington.


A multipoint exhaust fan located in the attic can ventilate several bathrooms, utility rooms, and sometimes the kitchen. Control may be manual, automatic, or continuous.

U.S. Fan Suppliers

American ALDES Tel:(800)255-7749
Broan Tel:(800)558-1711
Continental Fan Tel:(800)320-0504
DEC/Rosenburg Tel:(800)533-7533
Fan America Tel:(800)838-4074
Fantech Tel:(800)747-1762
NuTone Tel:(800)543-8687
Panasonic Tel:(201)348-7231
Tamarack Tech Tel:(800)222-5932


Bathrooms use specialized materials so intensively that we need to consider their environmental impact. By definition, 2 x 10s and 2 x 12s come from old growth trees. Wood I joists, laminated veneer lumber (LVL), microlams, and other engineered wood products are good, cost-effective alternatives and provide increased structural capability at the same time. Ceramic floor tiles made from recycled windshields, available from Terra Green in Richmond, Indiana, are beautiful and have increased durability from the glass composite. If the area is to be carpeted, use carpet made from recycled plastics (soft-drink bottles). It is more stain-resistant than typical nylon and costs the same.

Putting It All Together

Bathroom remodeling used to be a straightforward, remove-and-replace job of installing new fixtures, some tile, and paint. No longer. With careful consideration of all the energy-saving possibilities, bathroom retrofits can improve core elements of the infrastructure of the house, such as water heating and air quality. And with good design, the bathroom can be transformed into a showcase of comfort and efficiency.

Common Energy Questions
about Remodeling Bathrooms

Which uses more energy, showers or baths?

Baths usually use more energy. Of course, the opposite may be true, if a long, high-flow shower is compared to a small bath. But a 10-minute shower with a reasonably low-flow showerhead will nearly always use less energy than a bath.

I've heard low-flow showerheads deliver less hot water and have pressure problems. Is this true?

The water is just as hot when it leaves a low-flow showerhead, but it cools a little faster due to greater evaporation from the smaller droplets. So a slightly higher proportion of hot water may be needed. Since much less water is flowing through the pipes, they are indeed more susceptible to pressure variations. However, in general, low-flow showerheads compare favorably with the older models.

Do low-flush toilets work as well as regular toilets? How do I pick a good one?

The bugs have been worked out, and new low-flush toilets are just as good as the older models. There are several published comparisons of low-flush toilets in Consumer Reports and elsewhere.

I hate noisy ventilation fans; what can I do to keep humidity and noise down?

Certain new fans--such as the VQ series by Panasonic--are much quieter than old fans. Place the exhaust grille to draw from the ceiling above the shower and then install the fan remotely (through the roof) for best results.

How can my remodeled bathroom be engineered so that I don't have to wait so long for hot water to arrive?

Make sure that the pipes are located inside the heated space and insulated. Also, make the pipe as short and small as possible between the water heater and the bathroom; with normal water pressure and a low-flow showerhead, 1/2-inch pipe is plenty large enough (stay away from the 3/4-inch standard). To eliminate the wait, new demand hot water systems convert plumbing so that hot water from the storage tank is brought instantly to the faucet while standing water in pipes is recovered and no water is wasted.

Does it pay to install an electric, tankless water heater for a new bathroom?

Probably not. You save on plumbing installation costs but, over the years, you pay more for electrically heated water. Perhaps more important, few electric tankless water heaters can meet the demand of a modern household (one of the largest models takes half an hour to fill a tub).

Do infrared heat lamps use much energy?

If you use them only when toweling off, the IR lights don't use much energy. Put them on a timer, though, because they typically use about 250 watts, and leaving them on will be expensive.

What is the best lighting design for a mirror used when applying make-up or shaving?

Design the lights so that the first thing people turn on (and off) are the main, fluorescent lights. Then install a separately switched set of fluorescent lights (vanity bulbs or tubes) or, if preferred, halogen bulbs around the mirror. Put the switch near the lights to encourage their use only as needed.

Our bathroom never gets comfortably warm, even though we've installed a new high-efficiency furnace. What should we do?

Be sure ducts are properly connected. Double-check for air leakage sites at dropped ceilings, cabinets, and utility cut-throughs. Insulate the floor, ceiling, and walls, and install a low-e double-glazed window with inert gas fill.

Further Reading

Consumer Guide to Home Energy Savings, American Council for an Energy-Efficient Economy, 2140 Shattuck Ave., Suite 202, Berkeley, CA 94704. Tel: (510)549-9914.

The Non-toxic Home and Office by Debra Lynn Dadd, Tarcher Publishing, 5858 Wilshire Blvd., Suite 200, Los Angeles, CA 90036. Tel:(800)847-5515.

Green Home: Planning and Building the Environmentally Advanced House by Wayne Grady, Camden House Publishing, 7 Queen Victoria Road, Camden East, Ontario KOK 1JO. Tel:(800)387-5085.

Guide to Resource Efficient Building Elements, Center for Resourceful Building Technology, PO Box 100, Missoula, MT 59806. Tel:(406)549-7678.

Homemade Money, Rocky Mountain Institute, 1739 Snowmass Creek Road, Snowmass, CO 81654. Tel:(970)927-3851.

David Johnston is president of What's Working, a design and consulting firm in Boulder, Colorado, specializing in environmental construction technology.

This article is part of a series on energy-efficient remodeling, which is being funded by the Environmental Protection Agency and the Department of Energy.


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