Every homeowner should know how to seal and insulate ductwork.  However, the truth is few people are aware ductwork requires sealing and insulation.  Most people assume ductwork will function without flaw after installation.  Below, we explain how to seal and insulate ductwork and why it is so important.


Save Money With DIY Ductwork Sealing and Insulation

There is no sense paying another person to seal and insulate your ductwork when you can do the work on your own.  Embrace this challenge, learn how to seal and insulate ductwork on your own and you will never have to pay another person to do the work on your behalf.  There is no reason to be intimidated by ductwork sealing and insulation.  This process is easier than expected.  Once your ductwork is sealed and insulated, you will spend less on utilities.  So don’t worry about spending your time, money and effort to perform a DIY sealing and insulation.  The minor investment necessary to add sealing and insulation will pay massive dividends down the line.


Insulation Types

The exterior of ductwork can be insulated by blanket wraps or sleeve insulation.  The blanket variety wraps around the entirety of the ductwork.  The installation of sleeve insulation requires the disassembly of the ductwork.  The sleeve insulation slides on prior to the point at which the ducts are reassembled.  In fact, you can slit sleeve insulation and warp it around the insulation similar to a blanket.


The Sealing and Insulation Process

Sealing and insulating ductwork will be slightly messy.  Take a close look at the ducts for holes, rust, damage, missing portions and other flaws.  Mark these problem spots with chalk or a marker.  Run a broom or damp cloth across the ducts to ensure the surface is completely dry.  A dry surface makes it easier for the sealant to bond to the ducts.  Though mastic is the most popular sealant, there are duct sealants sold in caulk tubes or cans that are specially formulated for such a project.  You will also need a foil tape or mastic tape.  Refrain from using duct tape as it probably will not stick long.  Spread the sealant or duct mastic along the duct seams, holes and joints.  The mastic should be applied in layer form.  However, it is a mistake to apply the mastic in a layer beyond the thickness of a nickel. 

Use a paintbrush with stiff bristles to apply the sealant.  Avoid getting mastic on your clothes as it will prove difficult to wash out.  Be sure to seal the duct connections, holes and joints by the furnace.  The duct/register connection must be sealed as well.  Apply sealant at all points of intrusion and all joints.  When in doubt, apply more seal than you think necessary as it is better to have additional protection rather than insufficient protection.  Seal along the furnace/air unit back toward the last register.  This approach ensures the most important parts are properly covered.  Protecting the area that is closest to the HVAC unit is of the utmost importance as gaps and holes near the unit are subjected to elevated air pressure compared to those positioned farther away. 


Adding Insulation

Give the sealant some time to dry.  Once the sealant is completely dry, it is time to add the insulation.  Insulating air ducts is fairly easy, especially if you are using the wrap version of insulation.  Just be sure to read the insulation product’s instructions prior to performing the insulation.  When measuring and cutting the duct insulation, leave some extra so it can overlap at the seams.  Wrap the insulation around your home’s air ducts, ensuring it is turned in the proper direction.  The vapor barrier must face outward.  The fiberglass should be pressed against the duct.  Staple and tape the seams between pieces and lengthwise.  The joints will prove secure if overlapped with a couple extra inches to spare and secured with tape.