| New government programs are encouraging | | | | Covering ventilation openings may change the air |
| people to make their home more energy efficient | | | | flow and temperature in an area. These changes |
| and green. Insulation is an important part of an | | | | can allow water vapor to condense into liquid |
| energy efficient home, but more is not always | | | | water. |
| better. Adding it in previously uninsulated and | | | | Changes to air flow and temperature in the attic |
| under-insulated spaces can waste money and | | | | can contribute to ice dams. Ice dams form when |
| may damage your home. Understanding the | | | | snow melts on a roof over a warm attic. The |
| potential problems will help you avoid costly | | | | water flows down to the cooler eaves where it |
| mistakes. | | | | freezes and forms ice. If this cycle of melting and |
| When adding insulation, use the same type as the | | | | freezing occurs, the liquid water can't flow off the |
| existing material. If this is not practical, then add | | | | roof because of the ice dam. The water can flow |
| new material that is similar in weight and density | | | | under the roof covering and into the home. |
| to the existing material. This is because heavier or | | | | Some batt insulation has a paper backing on one |
| denser material may compress the existing | | | | side. This is the vapor retarder. Do not install a |
| material. Compressed insulation does not have its | | | | vapor retarder over existing insulation. Moisture |
| full R value, so the combined R value could be less | | | | can collect on the vapor retarder and condense |
| than the R value for each type. For example, | | | | into damaging liquid water. |
| installing loose fill cellulose over loose fill fiberglass | | | | Some homes built during and before the 1930's |
| will often compress the fiberglass because | | | | still have live knob and tube electrical wiring. This |
| cellulose is heavier and denser than the fiberglass. | | | | wiring consists of two insulated wires supported |
| Adding insulation in attics, crawl spaces, and walls | | | | on porcelain spacers and uses porcelain tubes |
| changes the conditions within those areas. For | | | | where the wires pass through wood. Do not |
| example, adding it to an attic should reduce the | | | | cover these wires. Any covering can cause the |
| attic temperature in the winter because less heat | | | | wires to overheat and cause a fire. |
| from the home flows into the attic. Water vapor | | | | Adding insulation in an attic can increase the |
| that moves from the home into the attic can | | | | weight on the home's structural supports beyond |
| condense into liquid water if the reduced attic | | | | the design capacity. This situation is unusual, but it |
| temperature falls below the temperature at which | | | | can happen with older homes and when using |
| water vapor condenses. Liquid water can damage | | | | heavier material such as loose fill cellulose. |
| the home and provide moisture for mold growth. | | | | More insulation is usually better for improving a |
| This same problem can occur in crawl spaces and | | | | home's energy efficiency. If you are going to add |
| in wall cavities. | | | | it, take some wise precautions to understand the |
| Take care not to cover any attic or crawl space | | | | potential problems and to avoid unintended and |
| ventilation openings when adding insulation. | | | | damaging consequences. |