Duct insulation: R-value, cost & how much it saves
Insulate any ductwork that runs through an unconditioned space — an attic, crawlspace, garage, or unfinished basement — because bare ducts there lose more than 30% of their heating and cooling capacity. Code wants R-8 in the attic and R-6 elsewhere; the wrap runs about $0.50 to $6.50 a foot and pays back through 10–30% lower bills. Here's exactly what to insulate, to what R-value, and why you seal first.
Uninsulated ducts are a prime cause. Call (888) 810-2291 for a licensed local contractor to seal and insulate them.
Should you insulate your ductwork?
Insulate your ducts if — and only if — they run through an unconditioned space. Ducts in a vented attic, a crawlspace, a garage, or an unfinished basement are surrounded by air that's baking in summer and freezing in winter, and bare metal there bleeds away more than 30% of the heating and cooling you paid for. Ducts that stay entirely inside your conditioned living space are already in the environment they serve, so insulation buys you nothing. The tell is simple: if you can reach up and touch cold-or-hot duct in an unfinished space, it should be wrapped.
What R-value should duct insulation be?
The 2021 International Energy Conservation Code (IECC) sets the targets by where the duct runs, not by the system. Ducts in an unconditioned attic need the most insulation because that's the harshest space; ducts in a crawlspace or garage need less; ducts in conditioned space need none. This is the defining rule of thumb:
| Where the duct runs | R-value | Notes |
|---|---|---|
| Ducts in an unconditioned attic | R-8 | R-6 in the warmest climates (zones 1–2) |
| Crawlspace, garage, unfinished basement | R-6 | any climate zone |
| Ducts inside conditioned space | None required | already in the space you're heating/cooling |
R-6 vs. R-8: which do you need?
The difference is simply how much the insulation slows heat transfer: R-8 insulates better than R-6, which is why code reserves R-8 for attics, where ducts face the widest temperature swings. R-8 is a little thicker and costs a bit more — roughly $150 versus $100 per 25-foot roll — and trims a few percent more off annual energy use. The practical call: use R-8 in the attic and R-6 in a crawlspace, garage, or basement, unless your local code or a hot/cold climate pushes you one step higher. When in doubt, more insulation in the attic is money well spent.
Ducts in a hot attic or cold crawlspace?
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How much does duct insulation cost?
Duct insulation runs about $0.50 to $6.50 per linear foot installed — the spread comes down to material and access. Fiberglass duct wrap is the least expensive and the usual DIY choice; rigid board and spray foam cost more but insulate and seal in one step. As a materials benchmark, a 25-foot roll of R-6 wrap is around $100 and R-8 around $150. Here's the breakdown:
| Approach | Typical cost |
|---|---|
| Fiberglass duct wrap (R-6, DIY-friendly) | $0.50–$2.50/ft |
| Professional wrap, labor + material | $1.50–$4.50/ft |
| Rigid or spray-foam insulation | $2.00–$8.00/ft |
| R-6 duct wrap, per 25 ft roll | ~$100 |
| R-8 duct wrap, per 25 ft roll | ~$150 |
If you're already paying for new ductwork, insulated duct or a wrap add-on is far cheaper to do during the install than to retrofit later.
How much does duct insulation save?
Sealing and insulating ducts in unconditioned space typically cuts heating and cooling costs 10 to 30%. The reason is stark: uninsulated ducts in an attic or crawlspace lose more than 30% of their capacity to the surrounding air, so the system runs longer and harder to reach the thermostat setpoint. Wrapping those runs keeps the conditioned air conditioned all the way to the register — which shows up as lower bills, more even rooms, and less short cycling.
Seal your ducts before you insulate them
Insulation and sealing fix two different leaks, and the order matters. Insulation slows heat moving through the duct walls; sealing stops air escaping through the joints — and a typical home loses 20 to 30% of its air through unsealed connections, per ENERGY STAR. Wrapping insulation over leaky ducts traps some heat but still lets the air itself blow into the attic, so you leave most of the savings on the table. Do it in order: seal the joints and seams first, then insulate the runs. Together they're the highest-return efficiency job in most homes — and often cheaper than one replacement.
Where does duct insulation actually go?
Insulate every run that lives in an unconditioned space, and skip the rest. In practice that means the attic, crawlspace, garage, and unfinished basement get wrapped; the trunk and branches inside your conditioned floors and walls do not. Pay special attention to the attic — it's the hottest and coldest space in the house, which is why it gets the highest R-value. And remember that sheet-metal duct in particular has no insulation of its own, so metal runs in an unconditioned space always need wrapping. If your ducts are older and you're weighing a wrap against a rebuild, our ductwork cost guide lays out when replacement makes more sense.
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Frequently asked questions
Should I insulate my ductwork?
Yes — if the ducts run through an unconditioned space like an attic, crawlspace, garage, or unfinished basement. Uninsulated ducts in those spaces lose more than 30% of their heating and cooling capacity. Ducts that run entirely inside conditioned living space don't need insulation.
What R-value should duct insulation be?
Under the 2021 IECC, ducts in an unconditioned attic need R-8 (R-6 in the warmest climate zones 1–2), and ducts in a crawlspace, garage, or unfinished basement need R-6 in any climate. Ducts inside conditioned space need none.
What is the difference between R-6 and R-8 ducts?
R-8 has more insulation than R-6, so it slows heat transfer better — which is why code requires R-8 for attics, where ducts face the harshest temperatures. R-8 costs a little more (about $150 vs. $100 per 25-foot roll) and is slightly thicker. Use R-8 in the attic and R-6 elsewhere unless local code says otherwise.
How much does duct insulation cost?
Duct insulation runs about $0.50 to $6.50 per linear foot installed, depending on material and access — fiberglass duct wrap is the least expensive, rigid and spray-foam more. As a materials benchmark, R-6 duct wrap is about $100 per 25-foot roll and R-8 about $150.
How much does duct insulation save?
Insulating (and sealing) ducts in unconditioned space typically cuts heating and cooling costs 10 to 30%, because uninsulated ducts there leak away more than 30% of their capacity. The savings are biggest in homes with long duct runs through hot attics or cold crawlspaces.
Should I seal or insulate ducts first?
Seal first, then insulate. Insulation slows heat loss through the duct walls, but it does nothing about air escaping through leaks — and a typical home loses 20 to 30% of its air to leaks. Sealing the joints first, then wrapping the runs, captures both savings.
Can I insulate ductwork myself?
Fiberglass duct wrap is a common DIY job in an accessible attic or basement — you cut it to length and secure it with foil tape, sealing seams. Tight crawlspaces, spray foam, and any ducts you can't safely reach are better left to a pro, who will also seal the ducts properly first.
Do ducts in a conditioned basement need insulation?
No — if the basement is inside the conditioned envelope (heated and cooled with the rest of the house), the ducts are already in the space they serve, so insulation isn't required. Insulation matters where ducts pass through unconditioned space, like a vented attic or crawlspace.