How to Blow Insulation into Existing Walls
Cellulose; Greener, More Effective than Mineral Fiber or Fiberglass
Dec 28, 2008
In new construction, spray insulation can be applied while the walls are open, using green, sustainable building materials like closed-cell spray foam soy-based insulation. But many older homes were built with no exterior wall insulation at all.
No Central Air Conditioners or Heaters
Why were exterior walls uninsulated? In many cases it was seen as an unnecessary expense. In many cases, central air conditioners and heaters hadn't gained popularity, so what was the point?
Also, it wasn't until heating and cooling costs rose so high that manufacturers had an incentive to work on perfecting their product.
Using Green, Sustainable Cellulose Insulation
Cellulose insulation is the product of choice for this retrofit procedure.
- There's really no realistic way to get fiberglass batts into the the finished wall.
- Mineral fiber is undesirable because it's produced in natural gas fired furnaces that release greenhouse gases into the atmosphere; it's environment-unfriendly.
- Cellulose is made using electricity and takes 15% - 20% less energy to produce than mineral fiber, given the same R-value. The Canadian Standards Association reports that making mineral fiber, on a pound for pound basis, takes 59 times more energy than cellulose production.
- Cellulose can be made from recycled newsprint to which a flame retardant is added.
Blow-In Insulation from the Interior
Blowing insulation into finished walls means creating an opening to insert the nozzle. There are two places this can be done, on the inside and on the outside. If the home has a brick veneer, it must be done from the inside.
Framing studs are generally16” on center by local building codes. This means at least one penetration must be made near the ceiling between consecutive studs, below the top plate.
This is a job best done by a professional insulation company. Why?
- They have the proper equipment, although it can be rented by the intrepid DIYer.
- There are obstructions in the wall such as Romex electrical cable, plumbing pipes, and firestopping (horizontal noncombustible members between studs). The pros have the experience enough to find all these and cut additional holes as needed.
After all the insulation has been blown in, the holes are plugged with drywall and the texture and paint must be matched.
Blow-In Insulation from the Interior
This is the preferred method because it eliminates the additional interior steps of matching the drywall texture and paint after the holes are plugged. Also, the mess and work site clean-up isn't as much of a concern. This method works well when the exterior has vinyl or wood siding. One or two courses of siding are removed prior to cutting the holes.
The Financial Benefits of Adding Insulation
This is the most economical way to lower utility bills. Wall and attic insulation, along with a foil or painted radiant barrier, will pay for itself quickly. Additionally, in the US, homeowners can claim an energy tax credit of up to $500 for 10% of qualified energy efficiency improvements including insulation.
And that's a credit, not a deduction. Take advantage of it before the end of the tax year.
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