The average duct system has 15 - 30% leakage. If air conditioning represents 67% of your utility bill and your leakage is 25% you could reduce your utility bill in summer by 17% (.67 X .25) by sealing your duct system. If your utility bill in summer is $400, the savings would be $67 per month. These savings could easily reach $ 400-500 a year.
Self Inspection. It is not difficult to inspect your duct system to determine if leakage is a concern. First, understand that leakage can occur on the supply side, between the blower and the grilles, and the return air side, between the return air grille and the blower.
In the New Orleans area we find two basic supply systems: flexible duct or metal duct. Let us perform a routine inspection on both:
Flexible Duct Inspection:
- Are the ducts themselves in good condition? Look for tears in the outer cover.
- Are there any severe bends that may close off air flow?
- Are the individual ducts run straight or do they meander through the attic?
- Are the ducts at the plenum (where they leave the blower section) firmly secured with nylon straps or mastic? Can you feel airflow in the vicinity of the penum?
- Is the metal collar that the duct attaches to firmly secured and sealed to the plenum box with silver (not duct) tape and/or mastic?
- Where the duct attaches to the ceiling box is the duct securely attached with straps and/or mastic? Do you feel any airflow in the vicinity of the ceiling box?
- Pull back the ceiling insulation. Is the ceiling box firmly secured to the ceiling below?
Metal Duct Inspection:
- Check the insulation. Is it in in good condition and sealed with staples and tape?
- Are the ducts in good condition with no signs of having been crushed?
- Pull back the insulation between two sections of metal duct. Is the seam between ducts sealed with silver tape and/or mastic?
- Is the seam running the length of the tube sealed with silver tape and/or mastic?
- Are the ducts at the plenum (where they leave the blower section) firmly secured with screws and tape or mastic? Can you feel airflow in the vicinity of the penum?
- Is the metal collar that the duct attaches to firmly secured and sealed to the plenum box with silver (not duct) tape and/or mastic?
- Where the duct attaches to the ceiling box is the duct securely attached with screws, tape and/or mastic? Do you feel any airflow in the vicinity of the ceiling box?
- Pull back the ceiling insulation. Is the ceiling box firmly secured to the ceiling below?
- The proper size of a return air opening is one square foot (144 square inches) per ton. Multiply the length times the width and divide this total by 144. If the answer is within 1/2 a ton of your system size, the return air is the proper size.
- Look inside the return air space behind the filter. Is the space lined in sheetrock or fiberglass ductboard?
- Are the seams in the lining sealed with tape and joint compound or mastic?
- Where the return air meets the furnace, is it sealed with tape and/or mastic?
Plenums and Transitions:
- Are the connections between the various pieces of equipment taped and sealed securely?
- Feel under the units and make sure the seams underneath are sealed as well as the visible seams.
Based on your inspection if you feel that your duct system is suspect, you should consider sealing or repairing it. Surgi's is proud to offer free estimates and a lifetime warranty on duct system repairs. If you don't feel like a do-it-yourself project and have concerns about your duct system call Surgi's at 469-4232 and schedule an inspection and discussion.
