Friday, December 3, 2010

How do I know if I need more insulation?

Ask Ida

Dear Ida B. Green,

I've caulked around my doors and windows and I've weather-stripped all my doors. The house feels less drafty but my furnace is still working pretty hard. How do I know if I have enough attic insulation?



Dear Chilly,

Good job so far. Insulation works best when air isn’t moving through or around it, so your efforts to seal air leaks in these obvious places will help the insulation in your walls perform at its best. Insulation’s R-value defines its ability to Resist heat flow. The higher the R-value, the slower heat leaves your house. Idaho’s 2009 Energy Code recommends that attic insulation in homes being built today be R-49.

The Energy Star program recommends R-60. For your attic, Energy suggests a quick check for attic insulation. Look across your uncovered attic floor and if your insulation is level with or below the attic floor joists, you probably have less than R-49. When adding insulation, make sure you or your contractor avoids; 1) Leaving any gaps or voids in insulation coverage.
2) Compressing insulation at the ends or sides or at any obstacles.
3) Blocking soffit vents at the eaves. And just like your walls, make sure you’ve sealed air and water leaks that would reduce your insulation’s performance. Finish the job by insulating and weather-stripping your attic door or hatch.

Keep it Green,
—Elizabeth Jeffrey

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