The Top 4 Ways to Insulate Closed Walls

Insulation in Closed Wall
Insulation in Closed Wall. Hans-Peter Widera / Getty Images

Most new construction homes have insulation contained in the wall recesses.  Walls of older homes built before the 1970s and even as late as the 1980s often will not be insulated, unless a retrofit project already took place.

Having uninsulated closed walls in a harsh climate results in discomfort and high energy costs.  It means an overworked heating or cooling system that diligently blows hot or cold air, yet the house envelope is not holding up its end of the deal.

 All of that expensive warm or cool air seeps through hollow wall cavities and ceilings.

Retrofit wall insulation is a touchy subject because there is no single right answer for all situations.  Only by making a cost/benefit analysis in relation to your own situation can you arrive at the right answer.  Here are your alternatives: 

Injection Foam

Foam has advantages over fiberglass insulation, chiefly because it resists mold and mildew better than fiberglass.  Unlike blown-in cellulose, its strong expansion properties mean that it can force its way into difficult areas (around wires, boxes, protruding nails and screws) that tend to hang up gravity fed cellulose.

Professional installation is best, but several manufacturers offer do it yourself kits costing $600 for 600 square feet of coverage at 1" thick.

It IsLike those individual Great Stuff cans of foam insulation but on a much larger and more efficient scale.
ProsFoam expands to work into difficult areas that blown-in insulation may ignore.
ConsHoles in your walls that need to be filled, patched, and painted.
Great For Retrofit?A good retrofit insulation choice, but professionally applied foam is recommended over do-it-yourself.
DIY Brands

Remove Drywall and Install Roll Fiberglass

In a perfect world, you would be able to unscrew invisible bolts, remove wall panels, install insulation, and reinstall the panels.  

Our less-than-perfect world of permanently attached wallboard means time consuming hacking away of gypsum, individually removing drywall screws or nails, installing the insulation, and re-installing the drywall.

Still, for all the pain and effort involved, the remove-and-reinstall method is simple and straightforward.  Anybody with rudimentary home remodeling skills can figure it out.

It IsRemove drywall and install fiberglass roll R-13 or greater.
ProsEnsures maximum wall cavity coverage at low cost.
ConsMessy and labor-intensive.
Great For Retrofit?Pretty much the antithesis of a clean retrofit.  However, it is a basic solution that uses simple tools and materials, no special rental equipment required.

Loose-Fill Blown-In Insulation

A paper product insulating your walls?  Sure.  With boric acid added for fire resistance, shredded, recycled telephone books, tax forms, and newspapers all contribute to make cellulose insulation.

Blown-in cellulose is injected into the wall cavities by a series of holes drilled into either the inside or outside of the walls.  

Blowing-in attic cellulose is conceivably a do-it-yourself job.  But wall cavities are more difficult; DIY installation is not recommended.

It IsLoose cellulose (wood product) or mineral wool injected into walls with a blower.
ProsWith no shortage of companies offering blown-in cellulose, competition keeps prices lower for this type of insulation.
ConsCellulose insulation tends to settle, resulting in hollow spaces above the cellulose.  Also it can hang up on inner-wall obstructions.
Great For Retrofit?Blown-in insulation is one of your best bets for retrofit insulation.

Blow-In-Blanket System®

Blow-In-Blanket (or BIBs) is a new-construction method of insulating walls that can also be used for closed walls.  

On open walls, fabric sheath is attached to studs, providing a "cage" that contains blown-in fiberglass (not cellulose) pellets.  Unlike loose fill, BIBs pellets form a tight, dense, seamless "blanket" that is highly effective at stopping air infiltration.

It IsFiberglass wool pellets that are injected with a blower.
ProsBIBs pellets do not settle.  The initial volume you fill will remain at that volume.
ConsBIBs is a fairly specialized system and is not widely available.  
Great For Retrofit?BIBs can also be used as a retrofit system for closed up walls.

Blow-In-Blanket System® by Service Partners LLC