Water, Ice & Steam Everywhere

posted Mar 3, 2010, 7:54 PM by Thomas Skrodzki

Heavy wind during snowstorms or rain storms can carry snow or rain through attic vents at times. This is normal. Often, the moisture will evaporate before you notice it. However, if there are water stains on the insulation or ceilings, you should have a roofer move or modify the vent.

Placing a pan below the vent is a good option for an occasional small leak. See the the Figure at the end of this paragraph. The water in the pan will evaporate without damage to your home. Don't try to get by using a pan for a large leak, though—it could lead to a large problem.

Ice Blocking the Gutters

In winter, ice can build up in the gutters, forming a condition called an ice dam.

The process is triggered by excessive heat in the attic. The heat warms the roof deck, causing rooftop snow to melt. The slushy melted snow flows down the roof and into the gutters. Since gutters aren't warmed by the escaping heat, they remain cold, and the slush refreezes there. As the process continues, the ice gets thicker, forming a dam.

Eventually, water ponds behind the ice (the same way water pools behind a river dam), and this water can leak through an asphalt shingle roof. Roof shingles are designed to shed water but will not resist ponding water. The leaks will occur just above the ice dams, penetrating the overhangs.

Your best defense against ice dams is to keep the attic cool with good ventilation and adequate insulation. The attic should have about R-40 (about 15”) of insulation. Close all air leaks into the attic, and insulate and seal all access doors.

Check ventilation openings. There should be about one square foot of ventilation per 150 square feet of attic floor space. Half the ventilation openings should be high in the attic and half should be in the overhangs. For homes with a vapor barrier below the insulation, the ventilation ratio is 1 per 300.

If ice dams persist even when there are no obvious problems with attic insulation and ventilation, you may need the help of a professional insulation contractor. Ventilation can be tricky with complicated roof designs. Air leaks from the heated space to the attic are a common cause of attic problems, but often they are hard to find.

Moisture on the Windows

Often, moisture (“steam”) condenses on windows in the fall with the start of the winter heating season. As long as moisture condenses only occasionally and disappears after several weeks, you don't need to do anything.

Condensation requires a cool surface and moisture in the air. Inside your home, when the temperature of the glass drops below the dew point of the inside air, invisible water vapor in the air condenses on the cool glass. More condensation occurs when there is more water vapor in the air and/or when glass surfaces become colder.

Over the summer, moisture slowly accumulates in furniture, walls, woodwork, cloth and other surfaces. In the fall, as the exterior temperature drops for the first time, some of this moisture condenses on cold window glass. Most moisture leaks out of your home as your furnace runs and vent fans are used. Eventually, all the materials in your home dry out, and moisture stops condensing on the windows. This normally takes a few weeks.

If condensation continues to form on windows after several weeks, your home may have excessive moisture. Most moisture problems can be solved by limiting sources of moisture and improving ventilation.

Reducing Severe Dampness Throughout the House

Some homes have problems with excessive moisture. It's most noticeable as condensation on windows. If moisture is excessive and stays on your windows for several days…if water runs off windows and damages wood surfaces…if ice forms on windows and frames…or if storm windows remained fogged up and icy all winter, you need to reduce the humidity level inside your home.

Condensation requires a cool surface and moisture in the air. Inside your home, when the temperature of the glass drops below the dew point of the inside air, invisible water vapor in the air condenses as water on the cool glass. More condensation occurs when there is more water vapor in the air and/or when glass surfaces become colder.

Evaluate changes you have made to your home—any effort to tighten up a home and reduce air infiltration will increase humidity levels. A high-efficiency furnace vented with two plastic pipes draws combustion air from outside and reduces ventilation. Weatherstripping, better windows, caulking, and any other measures you have taken to reduce air leaks will increase the amount of moisture retained inside your home.

Try to increase ventilation by running kitchen and bath exhaust fans whenever steam is produced by cooking or bathing/showering. In the bathroom, keep the fan running until the bathroom is dry. Add timer switches to the fans if necessary.

Limit the number of plants in your home. Look for plumbing leaks or damp areas in the basement. If basement crawl spaces have bare soil, cover the soil with a vapor barrier.

There are many other sources of moisture and ways to eliminate excess moisture. Often your local natural gas utility company can provide information on moisture problems. University extensions often have good booklets on solving moisture problems.

Excessive Winter Dryness Indoors

Humidification of air inside the home has been the subject of many articles and investigations. Manufactures of humidifiers have claimed that humidified air would protect us from health hazards, but there are no firm facts that humidified air is better for us. In fact, humidifiers can cause problems with excessive moisture and even mold or bacteria.

To decide on the need for a humidifier, evaluate the comfort of your home during the dead of winter. Many of today's tighter, energy-efficient homes don't need additional moisture. Condensation on windows indicates excessive humidity; in that case, you don't need a humidifier. However, if your nose and skin are dry, and static electricity is a problem, you may need a humidifier.

The best type is a central humidifier that mounts on a forced-air furnace. Look for one that flushes water over a panel and drains away excess water as it operates. It should be mounted on the return duct to prevent water leaks into the furnace, and it should have a humidistat control that automatically turns the unit on as needed.

Aprilaire is a quality brand of furnace-mounted humidifier. See Figure on right. Its newer models have a removable plastic cover that makes the unit easy to maintain. This type flushes water over a panel and doesn't require a water reservoir.

Portable humidifiers can operate with a reservoir and evaporative panel. To create mist, some use ultrasound, others use a spinning wheel (for a cool mist), and others use heat (making steam). I consider all of these types hard to maintain and difficult to control. Any unit with a water reservoir is a potential source of mold or bacteria and must be meticulously cleaned and disinfected on a routine basis.

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