I did some research and found that expanding foam insulation creates an air tight seal. It creates a barrier that keeps warm air from entering your home in the summer and warm air rom escaping from your home in the winter. I needed new insualtion, and I was trying to decide which type would be the best. I have allergies, so I had a professional install spray foam insulation in my home. I had also discovered that dust and allergens cannot enter your home through the insulation. This was good news to me, as I suffere from a number of different allergies.