Install Blown-In Fiberglass insulation over your existing insulation to bring your attic up to a minimum of at least an R-38. Keep in mind this is the minimum you should have. Unfortunately, most homes today do not have anywhere near this much insulation in the attic. Blown-In Fiberglass represents the cheapest option for the homeowner. While good, this product is limited in its effectiveness as it still allows air to flow through it helping to perpetuate the stack effect in most homes.
If no HVAC units or air ducts are located in the attic, Virginia Foam Insulators recommends the removal of the existing insulation and the spraying of a minimum of at least a 1″ average of Closed-Cell Polyurethane Spray Foam onto the attic floor (also known as down spraying).
With this application all recessed lighting fixtures, fan exhausts, and other fixtures that pierce the ceiling are covered with hard spray foam or mineral wool boxes and then the attic floor is then sprayed with Closed-Cell Polyurethane Foam insulation. This application is then followed up by installing Blown-In Fiberglass over the foam insulation to bring the attic to an R-38 code level or higher. This approach results in a significant improvement over just Blown-in Fiberglass because an air barrier is reached and it is less expensive than spraying 2 inches of foam.
If HVAC units or air ducts are in the attic space, we recommend the removal of the existing insulation and the installing of at least a 2.5 inch average depth of Closed-Cell Polyurethane Spray Foam or for a cheaper option the homeowner can have installed at least a 5 inch average depth of Open-Cell Polyurethane Spray Foam. These products are applied to the roof deck (or the underside of your roof) as well as over all soffits, ridge vents, fans, etc. resulting in the attic being sealed airtight. Consequently, this eliminates the stack effect in your home, addresses the 20-25% leakage that most homes have in their duct work connections and allows your air ducts and/or HVAC unit to operate in a conditioned space that will vary no more than 10-15 degrees from the internal temperature of your home.
Remember, if you have a gas/propane furnace in your attic it must have a fresh air intake and be vented to the outside. If you do not have this in place it will need to be done prior to installing the insulation by an HVAC company. A customer should expect to pay somewhere between $300-$500 for this service.
If no HVAC units or air ducts are present in the attic, Virginia Foam Insulators recommends the removal of the existing insulation and the installing of between 1 to 2 inches of Closed-Cell Polyurethane Spray Foam to the attic floor. With this application, since we are spraying the attic floor, all floor boards must be taken up to gain access to the attic floor. We then cover all recessed lighting fixtures, fan exhausts, and other fixtures that pierce the ceiling with hard spray foam or mineral wool boxes. The entire attic floor and boxes are then sprayed with Closed-Cell Polyurethane Spray Foam providing a monolithic air barrier. If a homeowner chooses to go with less than 2 inches of Closed-Cell Polyurethane Spray Foam, technically no additional insulation is required, but we do recommend that homeowners overlay the spray foam with additional blown-in fiberglass to pass a home inspection in the event the home is ever to be sold.