Attic Insulation. Heat naturally flows from a warmer area to a cooler one. It does this in only three ways: conduction, where heat is transferred directly from mass to mass; convection, the movement of heated air from one space to another (hot air rises, heavier cool air sinks); and radiation, which simply means that any warm body gives off heat toward a cooler one.

The function of insulation is to minimize the radiation and convection transfer of heat with a minimum of solid conduction so that our homes stay warmer in cool weather and cooler in warm weather.

In this section I discuss the merits and uses of various types of well-known insulations and inform you on how best to evaluate R-values.

R stands for ‘resistance to heat flow.’ The greater the R-value, the greater the insulative power. R-value requirements depend on factors such as local climate and the surface you are insulating (walls, ceiling, floor, etc.) and will be regulated by your local building code. I suggest you contact the office of your city or county building inspector for the requirements of your area. Each region of the country has different requirements for adequate amounts of insulation.

In most areas, local utility companies will offer helpful suggestions on how to reduce your energy bills. Many will arrange to have an expert come to your home to point out areas that need to be insulated or weatherized. Often there is no charge for this service and it may even lead to low- or no-interest loan programs you may be eligible for. Also, state or federal tax credits may apply.

Check with your State Energy Commission, local power company, or local home center for the optimum R-value in your region.


Safe-use practices are important when you work with any type of insulation.

  1. Dust mask and goggles are necessary for work with all types of insulation, or when sawing wood.
  2. Fully cover your body, if possible long sleeves, a hood, long pants, and gloves. Insulating materials are skin irritants.
  3. Always use the correct tool for the job.
  4. Be sure power tools are properly grounded.
  5. Watch power cord placement so that it does not interfere with the tool’s operation.
  6. A hard hat should be worn, since roofing nails may be sticking through the sheathing.
  7. If you are not allergic to tetanus shots, be sure yours is current. There are usually exposed, rusty nails in an old attic.
  8. Keep the insulation clear (3″ or so) from objects that transfer heat to reduce fire hazards, and install sheet metal baffles around recessed light fixtures, chimneys, and flues.
  9. In older homes with possible frayed wires, do not allow the aluminum vapor barrier of batt insulation to come in contact with the wire, since it could short circuit
  10. Working in attics or other hot areas can cause loss of body salt by excessive sweating. Consider taking salt tablets.
  11. When working outside on a roof, wear shoes or boots with rubber soles; stay clear of power lines; secure extension ladders with safety hooks that clamp over the ridge; and delay your work until the roof is free from dampness of rain, frost snow, or dew.
  12. When working high on the outside of the house, I suggest you rent scaffolding to provide a balanced, level working surface.
  13. Do not step through attic floor joists onto the ceiling of the room below. It will give way.
  14. Some types of insulation are flammable. Check with your local building department and fire department for special application precautions or restrictions.

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Perhaps the most frequent heating and cooling system maintenance problem home inspectors see is dirty furnace filters.  It’s easy to understand why people neglect this important maintenance task.  The system appears to work regardless of the condition of the filter.  So if it isn’t broken, why fix it?  Fix it because dirty filters cost you money by:

  • Making the system work longer to cool and heat your home,
  • Allowing dust and other contaminants into the ducts and furnace,
  • Contaminating parts and restricting air flow within the system,
  • Reducing the system’s service life.

In homes where the furnace is in the attic or crawlspace, the filter is often in the main return duct, which is usually located in a central hallway.  In homes where the furnace is in an accessible location such as the garage or a basement, the filter is usually located in the furnace cabinet.  If you have more than one system, you should have at least as many filters as you have systems.  Some homes have return ducts and filters in additional locations, such as the owner’s bedroom.

Here are some general rules about selecting and changing heating and cooling system filters.

  • Change disposable filters and clean washable filters at least once per month on the same day (so you won’t forget).
  • Locate and change every filter.
  • Use the correct size filters for your system (the size is printed on the filter).
  • Avoid using a filter with a high MERV rating (greater than about 8)  unless your system is designed to use a high MERV filter (most aren’t) because high MERV filters can restrict air flow.
  • Avoid installing washable filters when they are wet.
  • Look at your filter while the system is running; if it looks as if it is being pulled into the return duct or furnace then it is either too dirty or too restrictive or you may need more return ducts.
  • Buy filters in quantity so you will have them ready when you need them (they’re usually less expensive that way).

The Bottom Line

Changing your heating and cooling system filters when they don’t appear dirty may seem like a waste of money.  In fact, the opposite is true.  Changing the inexpensive disposable filters or cleaning a washable filter regularly will save you money and help the environment as well.

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