Converting an 18×20 filter box to a 20×20: How To Boost your HVAC Performance 

Introduction 

Proper air filtration is essential for HVAC systems to maintain good indoor air quality and protect the unit from dust and debris buildup. However, filter boxes sometimes come in sizes that are less common or more expensive, like an 18×20 filter box. Converting an 18×20 filter box to a 20×20 filter box can make filter replacement easier, reduce costs, and improve airflow in your HVAC system. This guide will walk you through why this conversion might be necessary, the benefits it provides, and each step involved in converting an 18×20 filter box to a 20×20.

Why Convert an 18×20 Filter Box to a 20×20?

There are several reasons why homeowners and HVAC technicians consider converting an 18×20 filter box to a 20×20. Here are the primary motivations:

1. Increased Airflow: A 20×20 filter offers more surface area for air to pass through compared to an 18×20. This increased airflow can make your HVAC system more efficient, reducing strain on the fan motor.
2. Easier Filter Replacement: Standard filter sizes like 20×20 are more widely available than 18×20 filters. Converting to a 20×20 filter box means you can find replacements more easily and often at a lower cost.
3. Improved Filtration: A larger filter area can trap more particles and dust, leading to cleaner air circulating in your home. For families with allergies or respiratory issues, this can make a noticeable difference.
4. Reduced Costs: Standard 20×20 filters are typically less expensive than less common 18×20 filters. Over time, the savings on replacement filters can add up, making this a cost-effective upgrade.

Tools and Materials Needed for Converting an 18×20 Filter Box to a 20×20

Before you begin, gather the following tools and materials to make the conversion process smoother:

• Measuring Tape: For precise measurements of the filter box and ductwork.
• Sheet Metal: Used to modify the existing filter box size.
• Metal Snips: Essential for cutting sheet metal.
• Screws and Drill: For securing new components to the HVAC system.
• Weatherproof Sealant or Tape: To ensure the modified box is airtight, preventing any leaks.
• 20×20 Filter: The replacement filter that will fit the new dimensions of your filter box.

Step-by-Step Guide to Converting an 18×20 Filter Box to a 20×20

Step 1: Measure the Existing Filter Box

1. Remove the 18×20 Filter: Start by taking out the current 18×20 Filter from the box to get an accurate view of the interior space.
2. Measure Interior and Exterior Dimensions: Use a measuring tape to measure the height, width, and depth of the current 18×20 filter box. Record these measurements for reference.
3. Check Duct Compatibility: Measure the duct opening as well to ensure that it can accommodate the slight size increase to 20×20.

Step 2: Cut the Filter Box to Fit a 20×20 Filter

1. Mark the New Dimensions: Using the measurements for a 20×20 filter, mark out the areas on the filter box that will need to be expanded. Mark these carefully with a permanent marker.
2. Cut the Sheet Metal: Using metal snips, carefully cut away sections of the filter box to match the size required for a 20×20 filter. Be cautious when handling metal edges, as they can be sharp.
3. Attach New Metal Sections: Add extensions if needed, cutting sheet metal to the new size and securing it with screws or rivets to expand the box.

Step 3: Ensure an Airtight Seal

1. Apply Sealant or Tape: Once the box has been adjusted, apply a weatherproof sealant or duct tape along the seams to create an airtight barrier.
2. Test for Leaks: After sealing, run the HVAC system to check for any air leaks around the modified box. Adjust seals if necessary to prevent air from escaping.

Step 4: Install the 20×20 Filter

With the box now converted, slide in the new 20×20 Filter. Check that it fits snugly and covers the entire opening without any gaps. The 20×20 Filter should improve airflow and filtration in your HVAC system, helping it to operate more efficiently.

Benefits of Converting an 18×20 Filter Box to a 20×20

Improved Efficiency

One of the primary benefits of converting an 18×20 filter box to a 20×20 is the increase in efficiency. By allowing more air to flow through the Filter, the HVAC system can operate without working as hard, potentially reducing energy consumption and prolonging the lifespan of the unit.

Enhanced Air Quality

Larger filters trap more dust and airborne particles, which is beneficial for indoor air quality. For homes with pets, smokers, or allergy sufferers, upgrading to a 20×20 filter box is a smart move to enhance the filtering capacity of the system.

Lower Maintenance Costs

Since 20×20 filters are standard and widely available, they’re often cheaper and easier to find than 18×20 filters. Over the years, the reduced cost of replacements can lead to significant savings.

Common Issues When Converting an 18×20 Filter Box to a 20×20

Size Incompatibility

Not all HVAC systems can handle an increase in filter size. Before converting an 18×20 filter box to a 20×20, consult your HVAC manual or speak with a professional to confirm that your system can accommodate a larger filter.

Leaks and Airflow Problems

If the filter box isn’t properly sealed after conversion, it can cause air leaks, which affect efficiency. Ensuring a tight seal is critical when you convert an 18×20 filter box to a 20×20 to prevent any airflow issues.

Improper Fit of Filter

If the modification is not precise, the new 20×20 Filter may not fit perfectly, leading to gaps that reduce the Filter’s effectiveness. Taking accurate measurements is essential to ensure that the new filter box dimensions align with a 20×20 filter.

Tips for Maintaining Your New 20×20 Filter Box

1. Replace Filters Regularly: Even with the larger 20×20 Filter, it’s important to replace it as recommended (typically every 3 months) to keep the HVAC system running smoothly.
2. Check for Leaks Annually: Perform an annual check on the seals and fittings to ensure no air leaks have developed around the converted filter box.
3. Use High-Quality Filters: Investing in quality filters can improve air quality and reduce the need for frequent filter changes.

Frequently Asked Questions

Why would I want to convert an 18×20 filter box to a 20×20?

Converting an 18×20 filter box to a 20×20 can improve airflow, reduce costs, and make filter replacements easier, as 20×20 filters are more commonly available and often cheaper.

Can I convert an 18×20 filter box to a 20×20 myself?

Yes, with the right tools and instructions, most DIYers can complete this conversion. However, if you’re uncomfortable with HVAC modifications, consulting a professional is recommended.

Is there any downside to converting an 18×20 filter box to a 20×20?

The main concern is ensuring that your HVAC system can accommodate the increased airflow of a larger filter. Checking compatibility with your system and sealing the new box can prevent potential downsides.

Conclusion

Converting an 18×20 filter box to a 20×20 filter box offers several benefits, including improved airflow, easier access to filters, and lower costs. By following this guide carefully, you can make this conversion with minimal hassle, upgrading your HVAC system for better performance and enhanced indoor air quality.

With a larger 20×20 filter, your HVAC system will likely enjoy a longer lifespan, fewer maintenance issues, and reduced energy costs over time. Always take your time with measurements and ensure a proper seal to avoid problems with air leaks or improper filter fit. This upgrade is a worthwhile investment, bringing cleaner air, greater efficiency, and peace of mind to your home’s HVAC system.