Can You Use a Thinner Furnace Filter?

When it comes to furnace filters, the size matters. While a 4-inch thick filter is more efficient than a 1-inch filter, the correct size depends on the oven. If you measure the filter slot and it's large enough to accommodate the thicker filter, you can use it. However, if the slot is less than 4 inches wide, you won't be able to use that thickness. A 4-inch filter covers a higher range of MERV ratings, with a slight overlap with 1-inch filters.

With a filter of 4, you'll get at least an 8 MERV rating. With higher ratings of up to 16, you can control supermicrocontaminants, such as bacteria, viruses and dust particles. Thicker oven filters, known as media filters, almost always work better than cheaper one-inch filters. Never try to use a 1-inch filter instead of a 5-inch filter. The designers designed their oven to use a precise size, and you should always choose the filter with the correct proportions.

All forced air ovens use some type of filter, which causes air to pass through the filter before entering the main body of the system, and most heating and air conditioning systems share a filter. While many retailers sell oven filters, 5-inch filters are slightly rarer than their 1-inch counterparts. The bottom line is that size does matter when it comes to the thickness of your oven filter. However, with most HVAC systems, you should be able to modernize a media filter cabinet, either under the oven or on the side. If you have an oven in your house, the clogged filter might bother you every 2 to 6 months and ask for a new replacement. Since the designers thought that the 1-inch filters would work on their own when stacked together, the oven will push air through a barely penetrable wall.

If you have an old unit, not changing the filter often enough can cause enough damage to require the purchase of an entirely new oven. Virtually any HVAC professional will tell you that thicker filters work better than common 1-inch oven filters. It is a known fact that the standard dimensions of oven filters (length and width) have nothing to do with their efficiency. If your filter has a MERV rating that is too high, it may be inefficient because the oven has more difficulty pushing air through such a dense filter. Manufacturers design 5-inch filters to capture more contaminants over a longer period, so that if your oven works with a thicker filter, no more dust and dirt can enter its moving parts.

Ben Depauw
Ben Depauw

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