sentences:  Subsequent real world surveys have cellulose performing 20-30% better at reducing energy used for heating than fiberglass.Compared to closed cell, Polyurethane foam insulation (R=5.5 to 6.5 per inch), cellulose has a lower R-value per inch, but is much less expensive; foam has a higher cost per equivalent R-value.Annual savings from insulating vary widely and depend on several factors, including insulation thickness, original wall performance, local climate, heating/cooling use, airtightness of other building elements and so on.