As you can see, not all framing is known until the walls are open.

Injection foam when done in a plain box works great.  Unfortunately when doing injection foam in an existing construction project fails far more often than it works.  As you can see in this photo of an actual failed injection foam job, the foam expands too quickly, the framing is not simple and the foam did not do its job.  In this case after thousands of dollars worth of drilling and filling, this home was not any more comfortable after the foam was injected than it was before the foam was injected.

Failure with this process is due to issues with the foam rising too fast, staff not having the training or tools to ensure foam fills each cavity top to bottom and side to side.