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How To Seal Your HVAC System Ducts - Part 3

  1. Environmental Protection:

    Pollution is created by the production and generation of energy. The production of energy creates a substantial portion of the air pollution that we currently face. Wasting energy in any manner has an enormous effect on overall planet's environment. Anything that any of us can do to reduce greenhouse emissions, such as sealing air ducts is to the benefit of all of mankind.

HVAC Ducting - System Problems:

Problems with forced air ducting systems are not confined just to leaks and insulation. There are numerous other criteria that makes the ducting system work properly in your home, as shown in Figure 1 and Table 1.

problems with duct work
Figure 1 - HVAC Ducting - System Problems

Table 1
HVAC Ducting - System Problems

A - Leaky duct connections

E - Fallen or damaged duct insulation

B - Return leaks

F - Supply leaks

C - Furniture blocking registers

G - Kinks in ductwork restricting air flow

D - Leaks at furnace & filter slot and sealant failure


The overall design of the ducting system plays an important factor in creating proper air flow through-out the home. HVAC ducting should always be as short as possible and designed with as few bends as possible. The longer the lengths of duct and the more bends the harder your circulation system must work in order to circulate the air within your home.

It is not uncommon, in older homes, where basements or attics have been converted from storage to living space and/or additions have been added that the duct work was not redesigned to handle the changes, but rather, additional ducting was added without consideration to the overall home's heating and cooling requirements and how the additional ducting may have created a misbalance in air flow.

Poor Duct Installation:

In areas where homes are mass produced in the hundreds and even thousands contractors do not always pay attention to detail and although he HVAC duct system is designed properly, it was installed rather poorly as installers were pushed for time and did not seal duct joints and other areas were leakage can occur. Coupled with this is poor or no insulation in crawlspaces and attics. Insulation that has been wrapped over ducts, if not installed properly will eventually become loose and possible fall off altogether.

Newer, flexible ducting comes with its own insulation. But if that ducting was installed with kinks it will hamper the free flow of air and improper sealing of joints will produce air leakage.

Unbalanced Ducts:

Very few homes have ever had their air systems balanced, even when the systems were originally installed. This means that the correct level of air flow is not going to each room as the home demands. Balancing a system may require the addition of baffles mounted in the ducts to decrease air flow in a direction or to a specific room. The proper balancing of a duct work system requires specialized measuring equipment and the ability to modify duct work. This is best left to a professional HVAC contractor.

Not Enough Air Returns:

This is a problem unto itself and we have created a separate section to deal with forced air heating circulation problems.

These problems not only create poor circulation of hot and cold air in your home, but can be the direct cause of drafts coming in through doors and windows.