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Ask This Old House general contractor Tom Silva discusses the options for insulation with host Kevin O’Connor.


  1. Fiberglass insulation is sold by wall thickness and that should be adhered to so the insulation doesn’t get compressed and lose effectiveness.
  2. Open cell spray foam has the same R-factor as fiberglass, but it goes around any penetrations and acts as an air infiltration barrier.
  3. Closed cell spray foam has a higher R-factor per inch, but it is more expensive.
  4. When retrofitting, cellulose, made from recycled newspaper, can be dense packed into the stud bays. It’s treated with borate for insect and fire resistance.

Tom showed Kevin 3 types of insulation: Spray foam, fiberglass and blown-in cellulose. Insulation specialists can be contracted to install spray foam and blown cellulose. Fiberglass insulation can be found at the home center.