The ideal insulation for a masonry wall would fill every available space and leave no gaps for noise or heat to travel through. It would be noncorrosive and contribute no toxic chemicals or particulates to the building's interior. It would be easy to install and cost less than current methods. By those definitions, foamed-in-place insulation is very close to ideal. Injected into the cells of a block wall or into the cavity of a veneer wall, the foam fills all open spaces and can result in R-values as high as 20.
Currently four companies are promoting this system in the United States. They sell the equipment as turnkey systems and then train their customers to do the job right.
Doing the job right involves the following steps:
Evaluating the wall to determine where foam can be injected and how to ensure that the foam fills all empty cells, cavities, and gaps in the wall
- Drilling injection holes into one face of each wall to create openings into the block cells at the bed joints
- Injecting the foam while watching for overflow
- Testing the foam density hourly
- Cleaning and patching after about 48 hours
The foamed-in-place insulation system can fill the cells much more efficiently and completely in an unreinforced, single-wythe block wall than the alternatives can. Foam insulation can't settle and won't run out if a hole is cut in the wall, and it does not interfere with mason productivity.
Foamed-in-place insulation works equally well to improve thermal and acoustical performance in new or existing construction. The only disadvantage in existing construction is the need to repair the injection holes, but this method is much less intrusive and much more effective than any other.
The great advantage of a foamed-in-place system is that it creates a very complete insulating fill of the gaps in a wall, a huge improvement in the thermal and sound performance over a hollow wall and even a slight advantage over granular insulating fills.
Another advantage claimed by some manufacturers is an improvement in the fire-resistance rating of a foam-filled block wall.
The cost of foamed-in-place insulation varies from as low as 40 cents per square foot of wall to as high as $1.40.
One of the big advantages is that this environmentally friendly insulation emits no toxic gases either during installation or in service, and it is not an irritant like fiberglass. Also, it degrades into nitrogen in the presence of water and sunlight. But it does not work well in open spaces.
Cavity walls are another good application. A complete flashing system is still needed. Foamed-in-place insulation could create some problems with drainage, and, if the insulation is not completely closed-cell, any moisture absorbed would reduce its insulating effectiveness.
Foamed-in-place insulation is still in its infancy, having been used in masonry walls for only 10 to 15 years. As it is used more, the process will be refined and applications will be expanded. Some of the controversies will also clear up as research is conducted. For many applications, though, the process has clear advantages and should be considered one of the insulation alternatives for any masonry building.
The article includes Patrick J. Conway's discussion of "Seven Issues to Consider When Using Foam Insulation":
Not all foam insulation is equal.
- Make your selection based on quality not price.
- National or local approvals.
- Bleed-through characteristics.
- Onsite observation.
The four companies in the United States that are currently promoting foamed-in-place insulation systems are listed.