In the Great Flood of 1993, more than 10 million acres were inundated by floods that caused more than $12 billion of property damage in the nine states of North Dakota, South Dakota, Minnesota, Nebraska, Kansas, Iowa, Wisconsin, Illinois, and Missouri. More recently, flooding took 32 lives and inundated more than 6 million acres, some of it prime cropland, when a tropical storm stalled and drenched Georgia, northern Florida, and Alabama with torrential rain in the early summer of 1994. In the middle of October, more than 12,000 people were displaced from their homes in a Texas flood.

In the wake of such devastation, victims are quick to repair and rebuild their homes. It is natural to want to return to "normal" as quickly as possible.

This noble trait, however, often results in an approach that robs individuals of the rare opportunity to improve upon what they had before the disaster. Many energy-efficiency options may not have been widely available when the house was built, even if that was only a few years ago. The incremental cost of more efficient materials is likely to be paid back in energy savings, since nature has already made the decision that appliances or insulation must be replaced anyway.

In the fall of 1993 and into 1994, under contract to the U.S. Department of Energy (DOE), we participated in an effort for the National Center for Appropriate Technology to identify the best measures to incorporate energy efficiency technologies when rebuilding flood-damaged homes. We conducted dozens of interviews with weatherization field staff, state energy offices, HVAC specialists, architects, builders, manufacturers, disaster response personnel and many others working in the region.

Most of the measures identified in the course of these interviews were not new. What was surprising was the lack of energy-efficiency information available to flood victims and the lack of consensus among those dispensing advice directly to victims about what should be done. The best practices gathered from the field in these interviews contributed to the report Rebuilding Your Flooded Home: Guidelines for Incorporating Energy Efficiency prepared by Oak Ridge National Laboratory. This article is condensed from that report.

What a Flood Does to a Home

Flooding damages a building in many ways. Materials submerged in flood water can decay, swell, and warp. Electrical equipment and components can corrode and may cause fires or electrical shock if not replaced after a flood. Wet surfaces encourage mold growth, which discolors surfaces, leads to odor problems, deteriorates building materials, and may cause allergic reactions and other health problems in susceptible individuals.

A flooded home must first be carefully cleaned, dried, and decontaminated before it can be retrofitted. Because flood water and mud contain sewage, and other hazardous and toxic materials released upriver, along with micro-organisms, and other contaminants, it is essential to both dry and decontaminate the home. Controlling and preventing decay is easier to accomplish and reduces the potential for ongoing damage to the structure. Control and prevention of the effects of mold and other contaminants is more difficult to accomplish, but the stakes are higher, because the health of the occupants is involved.

Dry and Decontaminate

Ventilate a flood-damaged building as soon as possible. Open doors and windows, as well as cabinets, drawers, and closets. Circulate as much air as possible through the building and its cavities, such as walls and attics. Also, heat the building as soon as heating equipment can safely be used--moisture will move from inside the home if the indoor temperature is warmer than the outside. Ventilating and heating are more effective when done together than when either is done alone.

Depending on the extent of flooding and the weather, drying the home after a flood can take anywhere from several days to several months, or even longer. To determine whether a house is adequately dried, ask a local contractor, county extension agent, or building inspector about recommended moisture levels for your area, and use a moisture meter to test the wood in the structure.

Clean the home of mud and silt immediately to remove any sewage and microorganisms that may have been deposited on building surfaces by flood water. However, removing mud and debris is only the first step. Surfaces that have been cleaned will still be wet and will require time to dry. As these surfaces dry, they will become hosts for mold and other biological growth. Therefore, a home may have to be decontaminated again once it is dry.

To decontaminate, apply a solution of diluted chlorine bleach on surfaces that have come in contact with flood water or mud. Experts suggest a solution of 5% to 10% bleach. If you can respond right away, the 5% solution will be enough. The higher concentration is recommended for surfaces that have heavier contamination. In all cases, repeat the treatment at least twice within a 30-minute period. Be sure the area is well-ventilated as you work, and wear a mask and latex gloves to protect yourself when doing any cleaning or decontamination.

Repair or Replace?

Probably the most difficult decision when retrofitting a flooded home is deciding whether to repair or replace flood-damaged materials and equipment. Most experts recommend replacement to avoid a long list of potential problems later and to gain the maximum benefit from new energy-efficient technologies. New furnaces, air conditioners, refrigerators, and other appliances have to meet stricter efficiency standards than they used to, and in many cases the energy savings can be dramatic. Switching from an electric appliance (like a clothes dryer) to one that uses natural gas can also reduce utility bills. That said, appliances should be considered individually. The following are guidelines for replacement or repair of materials and equipment.

Costs of repairing or replacing equipment that has been exposed to flood water will likely be extensive. Homeowners should first contact their insurance adjuster to determine coverage for repair versus replacement, especially for heating and air-conditioning equipment. They should also check their warranties. Repairing flood-damaged equipment may void the warranty for future problems.

In the United States, several federal and state flood-relief assistance programs are available to flood victims that can help augment the benefits of individual insurance policies. To find out more about eligibility requirements for these programs contact the Federal Emergency Management Administration (FEMA).

Building Envelope

Framing and Walls

Wood construction is durable and will normally be structurally sound even after being in water. But once the water recedes, a moist contaminated environment may promote decay. If the environment persists, the decay will cause structural damage. Kiln-dried or well-seasoned wood used for residential framing can absorb water and will swell as a result. However, as the wood dries it will often return to its original shape and strength.

Generally, good-quality brick masonry can withstand flooding over long periods. Most types of brick will dry out and show no permanent water damage. But if the mortar is old or of poor quality, damage can occur from strong water currents or wave action. In addition, a disturbance or subsidence of the foundation can cause cracks in brick masonry. Even tiny cracks may be evidence of much larger and more costly problems with the foundation.

In most homes, ceilings and walls are covered by either plaster or drywall. Wet plaster should be removed and discarded. Although plaster can regain its strength when dried, it cannot be easily decontaminated.

Drywall acts like a sponge drawing water up above the flood level. It becomes very fragile if it stays wet for a long time, and it will fall apart when bumped. Like plaster, drywall can't be easily decontaminated, and wet sections should be discarded. Because new drywall will usually be installed horizontally, it's good to remove old drywall to a line about 48 inches above the floor (if the flood water in the home was less than 48 inches deep). Check to make sure that the insulation above this line is dry and hasn't wicked water any higher--insulation can pull water up much higher than the point of contact with flood water.

Wallpaper and other wall coverings inhibit drying, so they should be removed and discarded, even in homes where the flood water has not actually reached the walls. New wall coverings can be installed once the building has been dried and decontaminated.

If flood water reached a drywall ceiling, you should remove and replace it. If the ceiling is plaster, it will dry eventually but will likely sag or crack, so it should also be removed and replaced. Remove all ceiling insulation to allow the rafters or trusses to dry.

A ceiling may not have been touched by flood water, but it can still be damaged by humidity. Check to see if drywall has swelled or pulled away from the framing. If it has, replacement will probably be necessary. If sections of the ceiling are sagging, carefully punch a few small holes at the low spots to drain collected water. (Don't drill them with a power drill! Be very cautious--hard hats are a minimum requirement, since wet and sagging ceilings can easily collapse.)

Floors

Most floor coverings will not survive a flood and should probably be replaced. By removing them you will also help the house to dry. If the flood water reached wall-to-wall carpeting, discard the fabric. (To make this job easier, cut carpet and padding into strips that are small enough to carry.)

Tile, vinyl, and linoleum should be removed to speed the drying of the floor. Tile, vinyl, and linoleum are usually installed over an underlayment, which in turn sits on a structural subfloor. Water can loosen these materials directly or through swelling of the underlayment so it may be necessary to replace the flooring material and even the underlayment.

Structural subflooring is usually plywood or oriented-strand board. Older types of plywood made for interiors are especially susceptible to damage since they may not have waterproof glue between the plies. Water penetrates the unfinished edges and surfaces of the plywood causing the plies to soften, swell, and delaminate. If this has occurred, you may need to replace the structural subfloor as well.

Wet or flooded foundations will be a continuous source of moisture, and can increase the time needed to dry the rest of the house. If the house has a crawl space, remove and discard all wet insulation and plastic sheeting there, then dry out the crawl space with a fan if necessary.

Homes with basements require special attention in the aftermath of a flood. Do not rush to pump water out of a basement. Water in the ground outside the house is pushing hard against the outside of basement walls. At the same time, the water inside a basement is pushing back. It is important to keep these two forces balanced as the water subsides. If the forces become unbalanced due to pumping too rapidly, the basement floors or walls may crack.

Doors and Windows

Solid wooden doors that swell will tend to return to their original size when dry. Give them time to dry thoroughly before making adjustments. Check for warping or other structural damage if the doors have been exposed to flood water. If an exterior door is not very airtight, weatherstrip it and consider installing a storm door to reduce heat loss.

Solid core doors have a wood veneer over pressboard (essentially glued sawdust) and the veneer will often come right off the pressboard. Many hollow core wood doors are made from hardboard or contain hardboard spacers. Unfortunately, these wood products (hardboard, plywood and oriented-strand boards) will not regain their original shape when dried after substantial wetting. Plywood and oriented-strand boards may delaminate. Hardboard swells when wet and can lose its strength. Replace the door with a solid or insulated model with good weatherstripping.

Windows should be checked and, if damaged, replaced with newer, more-efficient ones. Windows can account for as much as 25% of a home's heat loss, and the technology of energy-efficient windows has substantially improved in the past few years. New windows with low-emissivity coatings, for example, can cost 25% more, but they can save 50% to 67% of the heat loss through the window.

Insulation

If insulation in walls, floors, or ceilings comes into contact with flood water, it must be replaced. Some sources say that fiberglass insulation can be dried and reused with no loss of thermal performance. However, once any type of insulation has been exposed to flood water, there is potential for mold or mildew growth and resultant indoor air quality problems.

Replacing insulation is relatively inexpensive, and provides an opportunity to select a product with a higher insulating or R-value. For example, many homes with standard two-by-four framing have fiberglass insulation batts rated R-11 in the walls. Within the same stud cavity, you can boost the insulating value to R-13 or R-15 by installing medium- or high-density fiberglass batts. For a greater gain in R-value, you can add insulating foam sheathing to the outside of the exterior walls, particularly if the siding has been severely damaged in the flood and must be removed for replacement anyway.

If attic or crawlspace insulation needs to be replaced, take the opportunity to raise the R-value at least to DOE's recommended minimum levels. While replacing insulation in the crawlspace, check for and seal air-leakage paths to the house from underneath. Also seal attic by-passes and holes around chimneys, flues and plumbing penetrations.

As you replace insulation, you may discover that additional drywall and wood framing are also wet. While you'll want to install the new insulation and drywall as soon as you can, be aware that it can take weeks or months for a house to completely dry out. The house must be completely dry before it is re-insulated, to avoid later damage to building materials and serious health problems that may develop if moisture, mold, and mildew are allowed to go untreated in a house.

Electrical Wiring

Electrical wiring in walls may suffer damage from wetting. The damage will depend on how well-sealed and impervious the shielding is. In many homes, wiring is plastic coated, and it is fairly waterproof. Plastic-coated wiring will probably not need to be replaced after a flood. If the walls are open and all the connections are being redone anyway, a qualified electrician can replace any aluminum wiring with copper and increase the size of wiring to heavily-loaded circuits.

Any outlets, switches, lighting fixtures and all connections that have been under water for any period, may corrode. It is much cheaper and safer to replace them and to redo connections than to try to repair them.

Equipment and Appliances

Residential heating and cooling systems, refrigerators, water heaters, and other appliances in contact with flood water can be extremely dangerous. For safety reasons alone, it is essential to restore heating and cooling systems and appliances to proper operating condition, through repair or replacement, before restoring power.

In addition to safety, there are health concerns associated with equipment and appliances affected by floods. Always assume that flood water brings contaminants. If equipment in the home has been in contact with flood water, it may contain harmful bacteria and organics from the flood water.

Eliminate these substances from appliances, particularly those used for food storage and preparation, and from any equipment in contact with potable water. While thorough cleaning of all surfaces with a disinfectant is necessary, you need to do more to return equipment to safe operation. The general procedure involved is cleaning, disinfecting, drying, and having a qualified professional inspect equipment.

Motors

Whether each of the many electric motors in a home should be replaced depends on the length of time the motor was under water, the age of the motor, the type of bearings involved and how they are lubricated, and the type of contaminants in the flood water. Manufacturers usually recommend that all motors, electrical components, safety controls, and (for gas appliances) gas valves be replaced. A detailed and thorough cleaning and disinfecting of all remaining components is also recommended. Given the likely expense of attempting to have equipment repaired, replacement may be the best option, especially when new equipment is much more energy-efficient.

Heating Systems

Furnaces, space heaters, and boilers fueled by natural gas or propane all have gas valves and controls that are especially vulnerable to water damage from floods. Even if the outside of the device is clean and dry, corrosion begins inside the valves and controls, and damage may not be readily visible. At a minimum, this damage can result in reliability problems. More severe consequences could be fire or explosion. In all cases where you have decided to try to salvage the unit, you will need to replace gas valves, pilot and burner orifices, controls, and the filter.

Even if a furnace has been cleaned of debris and mud, and disinfected (often at great cost), and seems to be working properly, parts may later corrode or malfunction and you may also lose your warranty coverage. The older a heating system is, the more likely it is to be inefficient, so you may be better off replacing it even if it hasn't sustained much damage.

Propane systems also require attention to their gas-pressure regulator. This regulator contains a small vent hole in its body to sense outside pressure. For effective gas regulation, this hole must always remain unobstructed. During a flood, debris can easily plug the hole, causing dangerous corrosion and malfunction.

Do not try to salvage duct insulation that has been in contact with flood water. It is impossible to decontaminate. Remove the wet insulation; then clean, dry and disinfect the ductwork. A thorough job will require disassembling the ductwork. Since many ducts are leaky and uninsulated, this is another opportunity to eliminate wasteful heat loss. Carefully seal all joints in the ductwork, and insulate all ducts located in unconditioned spaces such as attics and crawl spaces. Often when ductwork is located under the flooded house, the ducts will be so compacted with mud, bent up, collapsed and/or dented that it is not worth the time and effort to repair and clean them--they should just be replaced.

Baseboard-mounted electric-resistance space heaters have no moving parts, and unless they are damaged by an electrical short, they will withstand flood conditions. Before returning these systems to operation, disconnect electrical power to each unit by switching off the main breaker (the main panel, meter, and breakers may need to be cleaned, disinfected, and dried, or even replaced). All connections at the heater and control thermostat should be allowed to dry carefully and thoroughly. Check for shorts on all heating circuits before restoring electrical power. You can then use the heaters to help dry out the interior of the house.

As in a gas forced-air furnace, an electric forced-air system is susceptible to corrosion and damage, resulting in reliability problems or safety hazards. In all cases, if you try to salvage the unit, all controls, safety interlocks, and probably motors will need to be replaced.

Heat Pumps and Air Conditioners

Some heat pumps (the unitary type) are simple wall- or window-mount, and some (split systems) are more elaborate, with part of the components indoors and part outdoors. Of the various types of split-system heat pumps in use, two things they have in common are the power and control wiring between the indoor and outdoor parts of the system, and the piping that carries the refrigerant from inside to outside the home and back. The refrigeration circuit of virtually all residential heat-pump (and air conditioning) systems is sealed at the factory. In a split system, it is sealed by the contractor during installation.

Even if the system is in contact with flood water for a long period, the sealed system of the unitary type is likely to remain intact. However, if flood water has repositioned either the indoor or the outdoor units of a split system by even a small amount, there is the potential for a breached refrigerant system. The heat pump (or air-conditioning system) may then require major repair or full replacement.

If the refrigerant system remains intact after the flood, the entire system should be cleaned, dried, and disinfected. A qualified electrical or refrigeration mechanic should check all electrical and refrigeration connections for both indoor and outdoor units, including all control circuits.

If an electric heating system is damaged by flooding, consider a switch to gas heating, which is less expensive in most areas of the country. If electricity is the only energy source available and the climate requires considerable cooling and heating during the year, a heat-pump system can be more cost-effective than electric resistance heating with a separate air-conditioning system. If you are replacing an old flood-damaged air conditioner or heat pump, a model with a high efficiency rating (SEER) can use 20% less energy. Have a professional size the unit properly, taking into account the air-tightness and insulation levels in your house.

Other Appliances

Ovens and ranges are often salvageable. First disconnect the electricity to the stove and remove the back cover to expose portions of the insulation. Allow the insulation to dry thoroughly before turning on the stove. If the controls are wet, replace them. With gas stoves, always replace the pilot orifice and any valves that may corrode if water was present. The interior surfaces must be cleaned and disinfected. Once the stove is operable, an extended "bake out" period is recommended. The high operating temperature of a stove will help eliminate residual moisture that could cause later problems. Self-cleaning settings should be used when available.

Any refrigerator or freezer that was submerged in flood water should be replaced. Refrigerators and freezers contain insulation that will be wet if the units were under water. This insulation is difficult to get at without destroying the cabinet of the unit. It will dry very slowly since the cabinet walls remain relatively cool while the appliance is on. Further, the slow dry-out of the insulation in refrigerator/freezers is conducive to the growth of bacteria carried between the walls of the cabinet by the flood.

Refrigerators alone can easily account for as much as 15% or more of a home's energy budget, so replacing an old unit with a newer energy-efficient one can save considerable amounts of energy and money. A typical new refrigerator with automatic defrost and a top-mounted freezer uses only about 800 kilowatt-hours (kWh) per year, while a typical 20-year-old model uses about 2,000 kWh per year.

If flood water covered only a few inches of the kitchen floor, it is likely that the insulation in refrigerators and freezers is dry, and you will only need to check the refrigeration system along the bottom and back of the unit. Like heat-pump and air-conditioning units, the refrigeration system is sealed in refrigerators and freezers. Unless punctured during the flood, they should be in good shape. If the unit has a bottom-mounted condenser, the fan motor should be checked and may need replacing. Check all electrical controls including the defrost timer, thermostats, and other safety interlocks in refrigerators. Replace them if there is significant water damage.

As with other appliances, clean, dry, and disinfect the washing machine and clothes dryer and have an electrician or appliance technician check all electrical contacts and connections. Replacement of the timer controls of these units will likely be necessary. If you decide to replace the washer, look for machines that offer several water temperature selections for both the wash and rinse cycles. The most efficient new washers are horizontal-axis models that save both energy and water.

If you want to replace the clothes dryer, newer models are able to sense dryness and automatically shut off. Compared with the older models, which have only a timer, these new models can save 10% to 15% on energy costs. If your old model was electric, switching to a gas model should pay back the extra investment relatively quickly, depending on local utility costs.

Smaller appliances like microwave ovens and TVs should be unplugged, cleaned, dried, and disinfected inside and out. Examine them carefully to determine whether to repair or to replace them. In some cases, simply drying the entire unit with careful attention to the electrical parts will be enough. Allow an extended drying time before testing the appliance.

Water Heaters

If a water heater, whether gas or electric, was exposed to flood water, it should be replaced. A new water heater is a relatively small investment, and replacing it is fairly easy. Switching from electric water heating to gas is usually one of the most cost-effective retrofits you can make. Electric heat-pump water heaters will also save energy compared to electric resistance types.

Valves and controls in a gas water heater will likely corrode after coming into contact with flood water. In an electric unit, the thermostat and controls will likely corrode. In both types, the insulation surrounding the unit will be contaminated and will be nearly impossible to disinfect. Additionally, the insulation would take a long time to dry, leading to corrosion of the tank from the outside.

Even if water heater components have been cleaned and the unit seems to operate properly, parts may corrode in the future. Both gas and electric water heaters have a pressure-relief valve that can corrode and stick after being exposed to flood water. Be sure, then, if the unit is only repaired and not replaced, to replace this valve as well (or add one, if the water heater had none).

Decisions about salvaging or replacing damaged equipment and materials will be influenced by the length of time and level of flooding in the home, and the amount of coverage allowed by insurance and flood-relief programs. But if the rebuilding of a home is seen as an opportunity to improve it, it is almost always better to choose more efficient replacements over repair.

Further Reading

Repairing Your Flooded Home. For a free copy, write to FEMA Publications, P.O. Box 70274, Washington, DC 20024, or contact a local Red Cross chapter and ask for ARC 4477.

Rebuilding Your Flooded Home: Guidelines for Incorporating Energy Efficiency, U.S. DOE, Office of Building Technologies, DOE-EE-0019, May 1994. This publication contains a reference section for additional information. For free copies write to U.S. Department of Energy, Office of Scientific ad Technical Information, P.O. Box 62, Oak Ridge, TN 37831.

Bob Corbett is president and director of research and George Everett is director of communications at the National Affordable Housing Network in Butte, Montana.

The publication of this article in Home Energy was supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.