The Best Attic Insulation for 24-Inch Centers

Start by Eliminating Air Leaks

• A key task when re-insulating existing homes is finding and fixing air leaks and moisture problems.  Uninsulated kneewalls, recessed light fixtures and gaps where exterior walls meet the attic floor can create large heat losses.  Before adding new insulation, make sure these holes are properly plugged.  Look for places where warm air from the house is infiltrating the attic space by noting dusty, damp or frosty places in the attic insulation.  Use expandable foam to fill and seal gaps.
  
   
  
  

Using Rolled Fiberglass Bats

• Rolled bats can be difficult to get into an attic space, but are very efficient.  They have fewer seams than cut bats and are relatively easy to deploy.  Simply secure one end, then unroll the entire bat, taking care to keep the bat at right angles to attic floor joists.  Position the bats so that they butt up against each other very snugly, without actually compressing the material.  Use only unfaced fiberglass bats.
  
   
  
  

Using Blow-In Insulation

• Blow-in insulation comes in several varieties.  It can be made from cellulose, fiberglass or rock wool.  Blow-in insulation requires a special machine for application.  A large hopper unit is positioned on the ground either below or outside the area to be filled.  Because it takes one person to keep the hopper full of insulation and one to wield the hose in the attic space, you'll need at least one helper to tackle this job, but two would be better.  The bundles of compressed insulation can be very heavy.  Insulation supply companies, tool rental yards and big-box home stores often rent the machines on an hourly or daily basis.
  
  

It Only Insulates If It Stays Dry

• A good DIY insulation job has to take ventilation of the attic space into account.  Blocking ventilation with insulation can result in the formation of condensation in the attic, with disastrous results.  Trapped moisture can create indoor air quality problems, promote the growth of mold, stain walls and ceilings and even do structural damage.  Make sure rafter vents, soffit vents and ridge vents are correctly installed, positioned and clear.