What is a good, cheaper prefilter upstream of a more expensive HVAC filter?

A dry filter serves as an effective and economical prefilter for HVAC systems, primarily because it captures larger particles from the air before they reach more advanced and costly filters. By trapping dust, lint, and larger allergens, dry filters help to prolong the life of the more expensive filters downstream, which are designed to catch finer particles and need to be replaced less frequently as a result of this preliminary filtration.

This approach not only ensures the efficiency of the HVAC system but also reduces overall maintenance costs, making it a practical choice for many applications. Dry filters are typically less expensive than other types, such as HEPA or activated carbon filters, which are designed for specific filtration needs — like removing very small particles or odors, respectively. While fiberglass filters can also be an option for certain situations, they may not be as effective in providing a strong first line of defense against debris, compared to dry filters.