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Understanding condensation The problem of con- densation in homes can be complicated and, at times, confusing. During winter months condensation is a visible problem only when water or ice form on the in- side of windows. Condensa- tion can cause more serious problems that cannot be seen. When house air, leak- ing into exterior walls or the roof, deposits water or ice inside these areas, the result can be water-sodden insula- tion or even structural de- terioration of the home. By the time such problems be- come evident the damage is often done. Condensation -- the accumulation of moisture as liquid or ice -- occurs when warm air comes in contact with a cold surface. The air cools on contact, cannot hold as much moisture and deposits the excess. There are two types of air movement and it is es- sential to have a clear un- derstanding of what they are. Let's start with the terms infiltration and exfiltration. Infiltration is the move- ment of cold, dry outdoor air into your home through cracks and gaps in its exte- rior. Cold air cannot hold as much moisture as warm air, so when infiltrating air mixes with warm indoor air the tendency is for humidity levels to drop in the home. This is a normal condition in the majority of Canadian homes and explains why most houses need humidi- fication to keep air comfort- able. Except in humid re- gions, such as coastal areas, infiltration shouldn't cause condensation problems. Exfiltration is the flow of warm, moist room air out through gaps and cracks ina building. As this warm air contacts cool surfaces it holds less moisture and gives up excess humidity in the form of water, or, if the surface is cold enough, frost. What makes one house react differently from an- other? Basically, air move- ment is caused by dif- ferences in pressure. Higher -20°C pressure air wants to move towards lower pressure areas. Without getting too complicated it is safe to say that most older homes have high indoor air pressure. (This will vary within the house but on balance it will be higher than outdoors.) As a result, air leaves the house through chimneys and vents as well as elevated cracks and gaps. Replacement air enters the house through other cracks and_ gaps located on the lower portion of the house. As you start caulking and weatherstripping these cracks and gaps, less dry air enters the living space and |WARM POINT IN THE WALL The ideal clock thermostat for new construction or new system installation! Clock is powered by system transformer. Honeywell's multiple setback fuel saver can't be beaten for quality, value and energy saving performance Honeywell Fuel Saver Thermostats Let us show how they can save money for you! H.S. ST. AMANT & SONS LTD. P.O. Box 850, 39 Robert St., Penetanguishene LOK 1P0 Page B10, Home Energy Guide 1984 549-7227 indoor humidity levels rise.' If this reaches the point where water starts to ac- cumulate on cold window Surfaces you have to cut down humidity by venting its sources, providing con- trolled amounts of dry out- door air, mechanically de- humidifying or simply stopping the tightening up process. Where exfiltration de- posits moisture in hidden places in the building struc- ture you have a house that has higher indoor air pres- sure without an adequate seal on inside surfaces to prevent the movement of air out into hidden cavities in the wall. The reasons for this can vary, but one docu- mented cause is the closing of unused chimneys. . The absence of chimney draft in a house heated with electric- ity or a high-efficiency gas furnace, for example, can cause increased airflow through cracks in the walls and roof. None of these potential situations should be cause for distress. Dampness, peeling paint and rotting wall studs are _ easily avoided. Expert advice should be sought if you sus- pect hidden condensation or notice its symptoms. However, observing the following basic rules will prevent condensation prob- lems and save energy and money over the long term: © Seal the house well from the inside with a poly- ethylene vapour barrier UREFIRE CONVERT NOW! ...SEE SUREFIRE'S LINEUP OF DUAL FURNACES TODAY! (new construction), . vapour barrier paint, caulking and weather- stripping. This protects against exfiltration and creates a situation you can control. @ Since moisture will get through to the insulated cavities of all but the new- est houses it is important to prevent accumulation in these areas. To avoid this buildup, vent attic and roof spaces and make sure that exterior siding or cladding materials are not tightly sealed. @ Be aware of the interac- tion between the building CEILING FANS SAVE ENERGY In homes with high ceilings, a ceiling fan can be an effective way to reduce heating costs. These fans eliminate the normal layer- ing of the heated air, which can produce high tempera- tures along the ceiling while leaving the living area cool. A ceiling fan disrupts this layering by forcing heated air down, mixing and equalizing the room air temperature. In rooms with a ceiling WOOD-ELECTRIC ADD-ON-WOOD ~ possible g WOOD-OIL COMBINATION INDEPENDENT WOOD-BURNING ...and take advantage of the government's "off oil" grants of up to $800." Whether you choose our simple to install wood add-on that converts vour present furnace to an economical dual-fuel sustem. or our new wood electric or wood oil Combinations. SUREFIRE has a central wood-heating sustem for Vou Surefire manufactures a completely Canadian product... committed to seeing Canadians achieve as much heating "independence" as See cour SUREFIRE dealer for grant details. envelope and the heating system. Major alterations to the heating system that affect chimney outflow should be performed by a service technician who takes the condition of your house, with respect to airtightness, into account. Control humidity. Humid- ity can be controlled by venting bathroom, laun- dry and kitchen sources of moisture. A humidistat is a good investment -- un- der 50 per cent humidity should be comfortable -- and' having a method of monitoring humidity will pay off in convenience. height greater than 2.4m (8 ft) the savings can be considerable. With the elim- ination of heat layering, thermostat settings can be lowered, resulting in fuel savings worth up to $200 annually. The cost of operat- ing the average fan is only a few dollars per month. 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