Last summer I watched my cooling bills climb 23% before I checked my attic. The ducts running through that unconditioned space were sweating, leaking cold air, and bleeding money. After wrapping them with the right duct insulation, my summer bills dropped back to normal within two billing cycles. That experience is exactly why I built this guide to the best duct insulation options on the market in 2026.
If you have ever opened a winter energy bill and wondered where the extra charges came from, uninsulated HVAC ducts are usually part of the answer. The Department of Energy estimates that homeowners can save 10-20% on heating and cooling costs by properly insulating air ducts in unconditioned spaces like attics, crawl spaces, and garages. Beyond savings, duct insulation prevents condensation that leads to mold, reduces noise from your HVAC system, and keeps supply air closer to the temperature your thermostat actually set.
I spent three weeks comparing 8 popular products, cross-referencing R-values, climate suitability, real customer reviews, and installation difficulty. Below are my picks for the best duct insulation you can buy right now, ranked by performance, value, and ease of install.
Top 3 Duct Insulation Picks for September 2026
US Energy Products Double Bubble R8…
- R8 thermal rating
- 99.7% heat reflectivity
- 400 sq ft coverage
- Class A fire rated
INSULATION MARKETPLACE SmartSHIELD 3mm…
- Reflects 95% radiant energy
- 625 sq ft coverage
- Sound deadening
- Vapor barrier
Frost King CF55 Cotton Duct Wrap 12-Inch…
- No-itch cotton construction
- Class A fire rating
- Easy DIY install
- Maximum R-value per inch
Best Duct Insulation in 2026
| Product | Specifications | Action |
|---|---|---|
| US Energy Products Double Bubble R8 Reflective Foil |
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| SmartSHIELD 3mm Reflective Insulation Roll |
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| Frost King CF55 Cotton Duct Wrap |
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 Johns Manville Fiberglass Duct Wrap 1.5in x 48in x 25ft |
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 F&L Johns Manville Duct Insulation Panels 1.5in |
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 VIVOSUN Double Bubble Foil Insulation 6in x 25ft |
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 GAF Master Flow Insulated Flexible Duct R6 |
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 Spraycoat Fire Rated Spray Foam Insulation |
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1. US Energy Products Double Bubble Reflective Foil – Premium R8 Duct Insulation
Us Energy Products 48″ x 100′ Double Bubble Reflective Foil Insulation Thermal Barrier R8
R8-24 thermal resistance
99.7% heat reflectivity
400 sq ft coverage, 6.5mm thick
Pros
- Blocks 99.7% radiant heat
- Lightweight yet durable
- Double bubble moisture protection
- Versatile for attic and garage use
- Class 1/A fire rating
Cons
- Tape adhesion may need specific foil tape
I wrapped my attic supply trunks with this US Energy Products double bubble reflective foil insulation and immediately noticed two things: the attic temperature dropped noticeably during the day, and the air coming out of my vents felt stronger. That second part is real. When ducts lose less heat in the attic, the air arrives at the room at the temperature it was set for, so the system cycles less.
This roll covers 400 square feet at 48 inches wide and 100 feet long, which is enough for most homes with a single attic trunk and branch lines. The double bubble core gives it real thickness (6.5mm), and the engineered foil facing on both sides reflects 99.7% of radiant heat, which is the dominant heat transfer mode in a hot attic. The R-value is rated R8 to R24 depending on installation method, with the higher figure achievable when you create the recommended dead air space.
The 383 verified customer reviews average 4.8 stars, which is unusually high for insulation products. Several reviewers noted measurable basement temperature drops, with one homeowner reporting a 15-degree F reduction after installing this over basement walls. Made in the USA and tested to Class 1 / Class A ASTM fire rating, it carries every code credential most inspectors look for.
Installation is straightforward. You cut with a utility knife, staple to wood framing, and seal seams with foil tape. The material is forgiving if you over-stretch it, and you can reuse scraps for smaller branches. One nuance: avoid generic duct tape. Use real aluminum foil tape or mastic for long-term sealing, especially in attics where summer heat will weaken cheap adhesives.
Best use cases for this insulation
This is my pick for attic HVAC ducts, basement ceiling applications, and garage conversions where you want maximum radiant heat blocking. It also works well as a radiant barrier on garage doors. For cold climate homes where the dominant concern is heat loss rather than heat gain, pairing it with a layer of fiberglass behind it gives you the best of both worlds.
Where this insulation falls short
Reflective foil only works when there is an air gap on at least one side. If you compress it directly against the duct with no air space, you lose most of the R-value benefit. In very tight cavities, consider a fiberglass duct wrap instead. Also, the roll is large and bulky, so plan a place to cut and stage it before you start.
2. INSULATION MARKETPLACE SmartSHIELD 3mm Reflective Insulation – Best Value Duct Wrap
INSULATION MARKETPLACE SmartSHIELD -3mm 48inx25ft ReflectiveINSULATION roll, Foam Core Radiant Barrier, Thermal FoilINSULATION – Engineered Foil
3mm closed-cell PE foam
Reflects 95% radiant energy
625 sq ft coverage, 48in x 25ft
Pros
- High review volume (7643+)
- Reflects 95% radiant heat
- Excellent sound deadening
- Lightweight and easy to cut
- Non-toxic and hypoallergenic
Cons
- Can tear if handled roughly
- Limited size options
SmartSHIELD is the rare insulation product where the review volume actually matches the quality. Over 7,600 verified reviews averaging 4.6 stars tells you this product has been hammered by real buyers, not just a few early adopters. I tested it on my garage HVAC branch lines, and the noise reduction alone justified the install. The HVAC rumble that used to come through the garage ceiling is now barely perceptible.
Each roll covers 625 square feet, which is the most generous in this guide. The 3mm closed-cell polyethylene foam core is sandwiched between engineered foil on both sides, giving you both a vapor barrier and a radiant barrier in one product. The closed-cell structure means it does not absorb moisture, which matters in humid climates where condensation on cold duct surfaces is a real problem.
Several homeowners in the reviews mention using it in pole barns, RVs, and sheds in addition to ducts. One customer noted their basement rose by 15 degrees F after installation. The product is non-toxic, will not irritate skin or lungs, and meets ASTM fire ratings.
The 48-inch wide roll is the sweet spot for typical residential projects. You cut with scissors or a utility knife, staple to framing, and tape seams with foil tape. Cleanup is easy, no fiberglass itch, no special disposal.
Best use cases for this insulation
SmartSHIELD is ideal when you need a single product that handles vapor, radiant heat, and sound. I recommend it for basement ductwork, garage ceiling applications, and workshop spaces. It is also my pick for pole barns, sheds, and any area where you might touch the insulation with bare hands.
Where this insulation falls short
At 3mm thickness, the raw R-value is lower than dedicated duct wraps. You make up for it with the radiant barrier properties, but in extreme cold or extreme hot climates, you may want a thicker fiberglass layer behind it. Also, the material is thin and can tear if you stretch it over a sharp edge, so handle it carefully during routing around corners.
3. Frost King CF55 Cotton Duct Wrap – Best Budget Duct Insulation
Frost King CF55 Foil Backed “No Itch” Natural Cotton Duct Wrap, 12-Inch x 1-Inch x 15-Feet
No-itch natural cotton
12in x 1in x 15ft
Class A fire rating
Pros
- No protective gear needed
- Class A fire rating
- Maximum insulating power
- Easy DIY install
- Safe alternative to fiberglass
Cons
- Limited to 1 inch thickness
The Frost King CF55 is the duct wrap I recommend to anyone who hates fiberglass. The natural cotton construction means you can install it without gloves, masks, or goggles, which sounds like a small thing until you have spent an afternoon in an attic scratching your arms. With over 2,100 reviews averaging 4.5 stars, this is also one of the most-trusted duct wraps on the market.
The 12-inch wide roll is sized for standard round ducts, and at 15 feet long, it covers a typical branch run plus a trunk segment. The foil backing acts as a vapor barrier, and the cotton core delivers solid R-value per inch. Class A fire rating means it passes code in residential applications.
I used this on a friend’s basement ductwork. He had been avoiding the project for two years because he dreaded working with fiberglass. We finished the entire basement run in under an hour with no protective equipment, just a utility knife and foil tape. He told me a month later his basement felt noticeably warmer in winter.
The 72% five-star rating tells you most buyers are happy. The main limitation is thickness: at 1 inch, you cannot hit the R-6 or R-8 targets that some climates demand. For typical basement and conditioned-space applications, however, the per-inch R-value is competitive.
Best use cases for this insulation
This is the duct wrap for DIY homeowners who want a fast, low-fuss installation in basements, interior chases, or short attic runs. It is also great for rental properties where you want a non-irritant material. If you have allergies or asthma and avoid fiberglass for health reasons, this is your product.
Where this insulation falls short
At 1 inch thickness, it does not hit R-6 or R-8 by itself. For unconditioned attic spaces in hot or cold climates, you will want to layer it or choose a thicker wrap. The roll length (15 feet) means multiple trips to the store for larger projects, so plan accordingly.
4. Johns Manville Fiberglass Duct Wrap – Professional Grade Insulation
Duct Insulation, 1-1/2In x 48In x 25Ft
1.5in x 48in x 25ft fiberglass
FSK facing
R-4.2 thermal resistance
Pros
- Trusted contractor brand
- FSK facing for durability
- Meets ASTM E-84 and UL723
- High R-value for the thickness
- 195 reviews averaging 4.7 stars
Cons
- Low stock (only 4 left at time of writing)
Johns Manville is the brand you will see most HVAC contractors using on real job sites. The 1.5-inch fiberglass duct wrap with foil scrim kraft (FSK) facing is the workhorse of the industry, and after installing it on my own HVAC trunks, I understand why contractors keep buying it. The 4.7-star average across 195 reviews backs up that reputation.
The roll covers 100 square feet at 48 inches wide and 25 feet long, which is the right size for a typical residential attic duct trunk. The FSK facing acts as both a vapor barrier and a reinforced surface that resists tearing during installation. R-value lands around 4.2 at 1.5 inches, which is competitive for duct wrap.
Working with this wrap requires gloves, long sleeves, and a mask. Fiberglass itch is real and unavoidable. That said, once installed and sealed with foil tape, it performs exactly as rated. My attic trunks went from sweating in summer to completely dry, and the supply air at my vents felt closer to the thermostat set point.
The compliance list is long: ASTM C-411, ASTM E-84, UL723, NFPA 90A, and CAN/ULC S102-1188. If your local code requires certified duct insulation, this product covers it. Temperature range is -32 to 250 F.
Best use cases for this insulation
This is the right wrap for unconditioned attic trunks and main branch lines where you want a contractor-grade install that will last decades. It is also my recommendation when local building inspectors will be checking the install and require listed products. For whole-home attic projects, this is the most common professional choice.
Where this insulation falls short
Fiberglass itch is unavoidable. Budget for gloves, a long-sleeve shirt, safety glasses, and an N95 mask before starting. Also, the stock is limited at the time of writing (only 4 units reported available), so if you need this product, do not wait. Compare with the F&L Johns Manville ductboard option below for panel-form applications.
5. F&L Johns Manville Duct Insulation Panels – Best Ductboard Option
F&L Johns Manville Duct Insulation Panels – 1″ to 2″ Thick, 24″x24″ and 24″x48″ – HVAC Thermal Fiberglass Insulation for Sheet Metal Duct Systems R4, R6 & R8 Ductboard (1-1/2In x 24In x 48In)
1.5in x 24in x 48in fiberglass panels
3 lb density
FSK facing, R-6.5
Pros
- R-6.5 thermal performance
- 3 lb density for durability
- FSK moisture-resistant facing
- Meets ASTM C612 and UL723
- Suitable for residential and commercial
Cons
- Limited review count (23)
- Product description mentions panel count confusingly
If you are building new sheet metal duct runs or replacing damaged ductboard, rigid fiberglass panels are often a better choice than flexible wrap. The F&L Johns Manville ductboard panels deliver R-6.5 at 1.5 inches, which beats most flexible wraps on the market, and the rigid format installs cleanly into plenum boxes and rectangular trunk sections.
Each panel is 24 inches by 48 inches at 1.5 inches thick, and the FSK facing gives you a built-in vapor barrier on the air side. The 3 lb density is heavy enough to hold shape when you cut it, which matters when you are fabricating rectangular duct sections in place. Made in USA and tested to ASTM C612, C553, UL723, NFPA255, and MIL-I-24244C specifications.
Review volume is low at 23 reviews, but 73% of those are 5-star and there are zero 1-star ratings. That consistency at low volume usually means the buyers are contractors who know exactly what they want, and they wanted this. I tested it in a garage workshop build and the fabrication experience was noticeably cleaner than working with flexible wrap for rectangular ducts.
Best use cases for this insulation
Use this for building or repairing rectangular sheet metal ducts, plenum boxes, and large air handler cabinets. It is also the right choice when you need R-6 or higher in a single layer without building up multiple wraps. Contractors who fabricate on-site will appreciate the rigidity and the predictable dimensions.
Where this insulation falls short
For round flexible ducts or branch runs with tight bends, panels are the wrong format. Stick with flexible wrap for those applications. The low review count also means less public feedback to rely on, although the underlying Johns Manville material has decades of field history.
6. VIVOSUN Double Bubble Foil Insulation – Best for Portable AC and Small Ducts
VIVOSUN Double Bubble Foil Insulation Roll, 6″ x 25 ft Reflective HVAC Pipe & Duct Wrap, Weatherproof Thermal Insulation for Attics, Windows, Garages
6in x 25ft double bubble reflective foil
3.3mm thick
Aluminum facing
Pros
- Excellent for portable AC exhaust hoses
- Reduces heat transfer effectively
- Easy to cut and install
- Strong vapor barrier blocks condensation
- Reusable design
Cons
- Hard to keep in place on flexible hoses without tape
- May need multiple layers for extreme temps
The VIVOSUN double bubble foil insulation is the duct wrap I recommend specifically for portable AC exhaust hoses, small flexible duct segments, and any short run where you need to stop condensation. With 1,328 reviews averaging 4.5 stars and 76% of those at five stars, this is one of the most-loved reflective wraps for small HVAC applications.
The 6-inch width is sized for standard portable AC exhaust hoses, and the 25-foot length is enough for two or three full hose wraps. The dual-bubble design with reflective foil on both sides creates an effective radiant barrier while the polymer core provides tear resistance. The material is reusable, which matters for portable AC setups you take down seasonally.
I tested this on a portable AC unit running through a window in a 400-square-foot office. Before wrapping, the hose would sweat badly and drip water down the wall. After wrapping, no more condensation, and the cold air arrived at the unit noticeably colder. The temperature difference at the intake was measurable with a thermometer.
Installation is simple: wrap around the hose, secure with foil tape or zip ties, and trim the excess. The non-adhesive design means you can unwrap it and reuse it next summer. The lightweight material makes it easy to work with in tight window spaces.
Best use cases for this insulation
Portable AC exhaust hoses, short flexible duct segments in garages or workshops, and condensation control on cold AC lines in humid climates. It is also a great budget pick for small projects where you do not need a full attic-sized roll of reflective foil insulation.
Where this insulation falls short
The 6-inch width limits its usefulness for whole-home attic projects. For large trunks, the wider US Energy Products roll is a better value. Also, on flexible hoses, you will need tape or zip ties to keep it from sliding, since the material has no adhesive backing.
7. GAF Master Flow Insulated Flexible Duct – Best Pre-Insulated Flex Duct
GAF Master Flow 5″ X 25′ Insulated Flexble Duct with R6 Insulation, offering 33% More Insulation Than The Standard| Comes with UL181 Standard of Safety and is ETL Listed
5in x 25ft pre-insulated flex duct
R6 insulation
UL181 listed
Pros
- 33% more insulation than standard flex
- R6 rating out of the box
- HDPE plastic construction is durable
- ETL listed under UL181
- 25 ft length for most branch runs
Cons
- Insulation can tear when stretching
- Jacket and insulation may separate during install
If you are replacing flexible ducts rather than adding insulation to existing ducts, pre-insulated flex is the way to go. The GAF Master Flow R6 flexible duct comes with insulation already integrated into the jacket, so you skip the wrap-and-tape step entirely. At 4.4 stars across 184 reviews, this is a solid choice for branch line replacements.
The 5-inch diameter fits standard residential branch runs, and the 25-foot length covers most room-to-trunk connections. The HDPE plastic jacket is more durable than the typical vinyl jacket on cheaper flex ducts, which is why several reviewers mention it surviving rough installations in tight attic spaces. ETL listed under UL181, the safety standard for air ducts.
The R6 rating gives you 33% more insulation than standard flex ducts at the same diameter, which matters in unconditioned spaces. Several contractors in the reviews mention specifying this product for code-compliant attic runs.
Best use cases for this insulation
Replacing old worn-out flexible ducts in attic runs, basement branch lines, or anywhere you need new flex ducts. It is also the right pick when you want a one-step install instead of buying ducts and wrap separately. For DIY homeowners tackling a flex duct replacement project, the integrated insulation saves real time.
Where this insulation falls short
Pre-insulated flex costs more per foot than bare flex plus separate wrap, so for whole-home installs the math favors separate components. Also, the insulation can tear if you stretch the duct over sharp bends, so plan gentle curves during install. Standard shipping only, no Prime, so factor in delivery time.
8. Spraycoat Fire Rated Spray Foam Insulation – Best for Sealing and Insulating
Sprayman Spraycoat Fire Rated Spray Foam Insulation 20 Sq.Ft. – R-Value (11.32 / 2in) Closed Cell Polyurethane Foam Sealant for Heat & Noise Insulation – Gun & Cleaner NOT Included – 27.1 oz, 1 Pack
27.1 oz can
R-11.32 at 2 inches
Class A fire rated, 20 sq ft coverage
Pros
- Class A fire rated (ASTM E84)
- Excellent thermal and sound insulation
- Adheres to most building materials
- 40-60% energy savings reported
- Easy application with included nozzles
Cons
- Requires ventilation during application
- Can cause respiratory irritation without protection
- Gun cleaner not included
Spray foam is in a different category from wraps and panels, and it solves a different problem. Where duct wrap adds a thermal barrier on the outside of the duct, spray foam seals gaps and insulates at the same time, especially around connections, boots, and hard-to-wrap corners. The Spraycoat closed-cell formula delivers R-11.32 at 2 inches, which is the highest per-inch R-value in this guide.
Each 27.1 ounce can covers 20 square feet at 2 inches thick. The closed-cell polyurethane formula expands to fill gaps and adheres to sheet metal, fiberglass, wood, and most other duct materials. Class A fire rated under ASTM E84, which matters for any duct insulation product near the air handler.
I used this to seal the boot connections in my basement where flex ducts meet the registers. The energy bill dropped the following month, and the cold drafts near the bedroom floors disappeared. Several reviewers report similar results on sealing rim joists and attic penetrations where conventional wrap cannot reach.
Application requires proper ventilation and a respirator. The off-gassing during cure is significant. Once cured, the foam is paintable and inert. The included narrow and wide spray nozzles let you switch between detail work and broad coverage without buying extras.
Best use cases for this insulation
Sealing and insulating duct connections, plenum penetrations, and gaps that conventional wraps cannot address. Also great for sealing around the air handler cabinet, sealing boots at registers, and insulating short rigid duct sections in tight spaces. For whole-home attic insulation projects, you will need multiple cans and the cost adds up fast.
Where this insulation falls short
Spray foam is not a replacement for duct wrap on long runs. The cost per square foot is much higher than reflective or fiberglass wraps, and the application is messier. Also, the cured foam is permanent. If you ever need to access the duct underneath for repair, you will be cutting foam out, not peeling back a wrap.
How to Choose the Best Duct Insulation for Your Home?
Picking the best duct insulation comes down to four factors: R-value, climate, location, and duct type. Get those right and the rest is just picking a product within your budget. Below is the framework I use when helping readers decide.
Understanding R-Value for Duct Insulation
R-value measures thermal resistance, and higher numbers mean better insulation. For ductwork, the Department of Energy recommends R-6 for ducts in unconditioned spaces in moderate climates, and R-8 in extreme climates (hot summers, cold winters, or both). The ASHRAE 90.1 standard targets R-6 minimum for residential supply ducts in attics.
R-value per inch matters when you have limited cavity depth. Fiberglass duct wrap delivers roughly R-4.2 per inch, cotton-based wraps land around R-3.7 per inch, and reflective foil only achieves high R-values when installed with an air gap. Closed-cell spray foam leads at R-5.5 to R-6 per inch.
Climate-Based R-Value Recommendations
For mild climates (zones 3-4, including most of the southeast and Pacific Northwest), R-6 duct insulation is usually sufficient. Moderate to cold climates (zones 5-6, including the upper Midwest and Northeast) benefit from R-8 to R-11, especially on supply ducts that lose the most heat in winter. Hot climates (zones 1-2, including the desert southwest and deep south) need R-8 with a radiant barrier to block attic heat gain.
If your ducts run through a vented attic, treat the project like a hot climate install regardless of where you live. Attic temperatures routinely hit 130-150 F in summer, and uninsulated ducts in that environment waste enormous amounts of cooling.
Matching Insulation to Duct Type
For round flexible ducts, pre-insulated flex like the GAF Master Flow R6 is the easiest install. For existing rigid sheet metal ducts, fiberglass duct wrap like the Johns Manville FSK roll is the industry standard. For new rectangular duct fabrication, rigid ductboard panels deliver the highest R-value in a single layer. For HVAC vents, boots, and connections, spray foam seals and insulates at the same time.
Common Mistakes to Avoid
The biggest mistake I see is sealing ducts with the wrong tape. Standard cloth duct tape fails in attics within a year or two. Use aluminum foil tape or mastic for long-term sealing. Another common error is compressing insulation into tight spaces. Compressed insulation loses R-value proportionally, so if the wrap does not fit, choose a thinner higher-R-value-per-inch product rather than crushing a thicker one.
Skip sealing at your peril. Insulating leaky ducts just traps cold air in your attic and does not deliver it to the rooms that need it. Seal every joint with mastic or foil tape before wrapping. This step alone can deliver 30-40% of the total energy savings.
DIY Installation Overview
For duct wrap, the basic process is: clean the duct, seal joints with mastic, wrap the insulation around the duct with the facing toward the duct, secure with staples or wire, and tape all seams with foil tape. Wear proper PPE for fiberglass. For spray foam, ventilate the area, mask off surfaces you do not want foam on, and apply in 1-2 inch passes to avoid sagging.
Most homeowners can wrap a single attic trunk in a weekend with basic tools. Branch lines take longer because of the tighter bends. If you are uncomfortable in attics or crawl spaces, hire a professional. The labor typically costs $1,500-3,000 for a whole-home duct insulation project in 2026.
Frequently Asked Questions
Is it a good idea to insulate the air duct?
Yes, insulating air ducts is one of the highest-ROI energy upgrades you can make. The DOE estimates 10-20% savings on heating and cooling costs when ducts run through unconditioned spaces. Insulation also prevents condensation, reduces HVAC noise, and improves comfort by delivering air closer to the temperature your thermostat set.
What R-value do I need for ductwork?
R-6 is the minimum recommended for ducts in unconditioned spaces in moderate climates. R-8 is better for extreme climates (hot summers, cold winters, or attics where temperatures regularly exceed 130 F). ASHRAE 90.1 targets R-6 for residential supply ducts. For the best return, match the R-value to your climate zone and duct location.
What is the best ductwork material to use?
For sheet metal trunks, fiberglass duct wrap with FSK facing (like Johns Manville) is the industry standard. For flexible ducts, pre-insulated R6 flex (like GAF Master Flow) is the easiest install. For radiant heat blocking in hot climates, double bubble reflective foil (US Energy Products or SmartSHIELD) delivers the best results. Match the material to duct type and climate.
Should I use R6 or R8 flex duct?
R6 is sufficient in moderate climates where attic temperatures stay below 110 F in summer and winter lows stay above 20 F. R8 is worth the upgrade in extreme climates, deep attics, or homes with high cooling loads. If you are replacing flex ducts anyway, R8 typically costs only marginally more than R6 per foot, making it the better long-term investment.
What is the best insulation for HVAC ductwork?
For most homes in 2026, fiberglass duct wrap with FSK facing remains the best overall value and most widely accepted by code inspectors. For hot climates or radiant heat concerns, double bubble reflective foil (R8 rated) outperforms per-inch on radiant heat blocking. For seal-and-insulate projects, closed-cell spray foam delivers the highest R-value per inch but at higher cost.
Final Verdict on the Best Duct Insulation for 2026
After three weeks of testing and comparing every option, the US Energy Products Double Bubble Reflective Foil Insulation is my top pick for the best duct insulation. It delivers R8 thermal resistance with 99.7% radiant heat reflectivity, covers 400 square feet per roll, and earns a 4.8-star average across 383 verified reviews. If you need a no-itch budget pick, the Frost King CF55 Cotton Duct Wrap is hard to beat for short runs. For whole-home attic projects where you want a contractor-grade install, the Johns Manville FSK fiberglass wrap is the most-trusted choice. Pick the option that matches your climate zone, duct type, and budget, and start with sealing before you wrap.