Insulation, Radiant and Vapor Barriers - Hardwood Floor Gaps-insulation

I have recently moved into a house built in 1950 in L.A. California.
I removed the very old carpet and moulding and in a few areas, found gaps where the hardwood meets the wall. Below the hardwood subfloor is the crawl space and I could feel air come up through these gaps. What is the best way to insulate or seal these gaps? Would spray-foam insulation be a consideration? I plan to refinish the hardwood floors and replace the moulding. Thx, NancySue

This gap at the edges of your floor is there to allow for movement of the wood floor. Usually anything you put there fails because of this movement, including caulk, foam and similar products.

I found that natural fiber rope, like hemp, is best for this application. The reason for this is you can stain rope or if you prefer dye it to match the color of the floor. I buy rope that is larger than the gaps in thickness and twined. I untwine the rope to fit into the gaps. Once I adjusted the thickness, then I put the rope into a bucket of stain until it is the desired color, let dry and install it into the gap.

The trick here is to install the rope compressed into the gap if done during the summer. This will allow the rope to expand when it gets cold because the floor will contract. If you install it in the winter, you don't compress the rope. This will allow the rope to compress when the floor expands in the summer.