# Heat pump ductwork in Memphis

> Crawlspace and attic ducts that choke a new heat pump: static pressure testing, bigger returns, and sealed, insulated trunks, done with your Memphis install.

URL: https://blufflinememphisheatpumps.com/heat-pump-ductwork/

Service

A heat pump can only move the air the ducts let through. We measure first, then fix returns, seams and crushed runs.

(901) 657-2200

Last Updated: November 12, 2026

1 visit

before a written estimate with load numbers, model numbers and price

95° / 20°

Shelby County design temperatures we size for

In writing

start-up readings for charge, airflow and backup heat

## A new heat pump can’t fix old ducts

A heat pump moves about 400 cubic feet of air per minute for each ton. If the ducts can’t carry that, the new system runs loud, wears its blower and never reaches its rating.

[Bluffline Memphis Heat Pumps](https://blufflinememphisheatpumps.com/) fixes ducts as part of heat pump jobs across Memphis, and we measure before we quote.

### What bad ducts feel like

- **Rooms at the end of the run** that never reach the setpoint.
- **A return grille that whistles** or pulls the filter tight against it.
- **Sweating ducts** dripping onto a crawlspace vapor barrier in summer.
- **A house that stays damp** even with a new system.
- **Higher bills** with no change in how you use the house.

## Static pressure: the number that decides

Total external static pressure is the resistance the blower pushes against, measured in inches of water column. Most residential blowers are built for about 0.5.

On the first visit we drill two small test ports and take the reading with the system running. That number tells us whether the ducts can carry a new heat pump’s air.

### Reading the result

- **Around 0.5:** the ducts are fine for the new system.
- **0.6 to 0.8:** something restricts the air, often the return or the filter rack.
- **Above 0.8:** the blower is fighting the ducts, and a new heat pump on them will be noisy and short of air.

You get the number before and after the work, so the improvement is measured, not promised.

## Returns: the usual bottleneck

Many Memphis houses have one central return, sized for a smaller or older system. A heat pump that needs 1,200 cubic feet per minute can’t pull it through one 14 inch grille.

The fix is a second return or a larger one, boxed and sealed, in a hallway or a bedroom that never cools. Where bedroom doors stay closed, a jumper duct or transfer grille lets the air get back.

## Crawlspace ducts in a humid town

Crawlspace ducts sit in humid air under the house. When the insulation is torn or thin, cold supply ducts sweat in summer, water drips onto the vapor barrier and the insulation gets wetter.

What we fix under the floor:

- **Trunk seams** sealed with mastic, not cloth tape.
- **Branch connections** that have come loose from the trunk.
- **Insulation** rewrapped to at least R-8 where it is torn, wet or missing.
- **Straps and hangers** so runs don’t sag into the dirt.

[Crawl space ductwork](https://blufflinememphisheatpumps.com/guide/crawl-space-ductwork-heat-pump/) explains why Memphis crawlspaces are hard on ducts.

## Attic ducts and flex

Attic ducts face the opposite problem: summer attic air above 120 degrees. Flex duct sags between supports and crushes where it crosses trusses, and every sag and kink cuts airflow.

We replace crushed runs, hang the new ones on straps at the right spacing and seal every connection to the plenum and the boots.

### When to replace instead of repair

- Flex that is crushed, torn or collapsing.
- Insulation that is wet or has fallen off.
- A plenum rusted or too small for the new air handler.
- Runs sized for a much smaller system.

## Leaks you can’t see

Static pressure tells you whether air can get through. It doesn’t tell you how much leaks out on the way.

In a crawlspace or attic, leaking supply air cools the space under the house instead of the bedroom, and a leaking return pulls damp crawlspace or hot attic air into the system.

### How we find them

- **A look at every reachable seam**, boot and plenum connection with the system running.
- **Temperature at the registers**, compared room to room; a cold trunk and a warm bedroom register point to a leak between them.
- **A duct leakage test** where the owner wants a number or a rebate requires one.

### Where they hide

The usual places are the plenum collar at the air handler, the return box behind the filter grille, and the boots where branches meet the floor or ceiling. All of them are cheap to seal once they are found.

## Older houses, older ducts

Ducts age with the house.

A 1990s ranch in [Bartlett](https://blufflinememphisheatpumps.com/service-areas/bartlett/) is often on its second system and its original ducts, and a 1960s house in Memphis may have ducts that were extended or patched for decades. Neither is a reason to replace everything; both are reasons to measure.

## Sizing the ducts with the system

Ducts and equipment are sized together. A load calculation sets the heat pump’s size, and the duct check confirms the ducts can carry its air.

A unit that is too big for the house is also too big for the ducts, so getting the size right often relieves a tight return.

### Related reading

The [sizing guide](https://blufflinememphisheatpumps.com/guide/heat-pump-sizing-manual-j/) covers both, and the [humidity guide](https://blufflinememphisheatpumps.com/guide/heat-pump-humidity-control/) explains why airflow matters for moisture.

## What duct work costs

Bluffline’s typical range for duct repair and sealing done with an install is $800 to $3,500. Your written estimate after the visit sets the price.

The duct line is separate from the equipment, so you can see exactly what it adds. Replacing many runs or a whole trunk is priced per house.

### Rebate

TVA EnergyRight pays $300 for qualifying duct sealing and insulation, done by a participating contractor, for MLGW customers. The [cost page](https://blufflinememphisheatpumps.com/heat-pump-installation-cost/) covers every range.

## Before or with the heat pump?

With, in most cases. Doing the duct work on install day means one visit, one permit and a static reading that proves the whole system works together.

If your heat pump is recent and only the ducts are failing, duct work can stand alone. If the system is due, see [heat pump replacement](https://blufflinememphisheatpumps.com/heat-pump-replacement/) or [air handler replacement](https://blufflinememphisheatpumps.com/heat-pump-air-handler-replacement/).

### Ducted heat pump or mini split?

Where a room has no duct at all, such as a converted garage, a ductless system can serve it. That is a different trade from ours. The [ducted versus mini split guide](https://blufflinememphisheatpumps.com/guide/ducted-heat-pump-vs-mini-split/) explains the choice.

## What's included

- Static pressure test on the first visit
- Look at the attic or crawlspace runs
- Return added or enlarged where needed
- Trunk and branch seams sealed with mastic
- Insulation replaced on sweating or bare runs
- Crushed or sagging flex replaced and strapped
- Static pressure retested after the work
- Readings before and after in writing

## Seal and repair or replace the ducts

|  | Seal and repair | Replace sections |
| --- | --- | --- |
| Fits when | Ducts sound, seams and returns weak | Crushed flex, rotten insulation, wrong sizes |
| Typical work | Mastic, new return, insulation | New plenum, trunk or runs |
| Typical range with an install | $800 to $3,500 | Priced per house |
| Usual time | Same day as the install | Extra day |

## A Bartlett return that couldn't keep up

A 1993 ranch near Stage Road gets a new heat pump. Before we quote, the static pressure reads 0.9 inches of water column, nearly twice what the blower is built for. One 14 inch return is trying to feed three tons.

Where

Bartlett, near Stage Road

The house

1993 ranch, about 1,900 sq ft, crawlspace trunk

Price

$2,900

Time on site

1 day

1. Find the restriction The return is undersized and most trunk seams have lost their tape. The back bedrooms are warm because their air leaks into the crawlspace before it arrives.
2. Add a return A second 16 by 20 inch return goes into the hall ceiling, boxed and sealed.
3. Seal, then wrap About 48 feet of trunk is sealed with mastic and rewrapped to R-8.
4. Measure again Static drops from 0.9 to 0.5. The duct work line on the estimate is priced on top of the replacement and done the same day.

## Related resources

- [Learn**How do crawl space ducts affect a heat pump in Memphis?** Humid air under the floor, cold ducts, failed tape and small returns, and what to fix before a new heat pump goes on them.](https://blufflinememphisheatpumps.com/guide/crawl-space-ductwork-heat-pump/)
- [Learn**How should a heat pump be sized for a Memphis house?** What a load calculation measures, the design temperatures it uses here, and why the right answer is often smaller than the old unit.](https://blufflinememphisheatpumps.com/guide/heat-pump-sizing-manual-j/)
- [Learn**Does a heat pump remove humidity from a Memphis house?** Why 72 degrees can still feel clammy, where the water goes, and the four things that decide how dry a heat pump keeps the house.](https://blufflinememphisheatpumps.com/guide/heat-pump-humidity-control/)
- [Decision Guide**Should a Memphis house get a ducted heat pump or a mini split?** If the house has ducts, a ducted system usually wins. If a room has none, a ductless unit can serve it. Here is how to tell which you need.](https://blufflinememphisheatpumps.com/guide/ducted-heat-pump-vs-mini-split/)
- [Decision Guide**How do you buy the right heat pump for a Memphis house?** The whole decision in the order you meet it, from the system you have now to the readings you should get at start-up.](https://blufflinememphisheatpumps.com/guide/memphis-heat-pump-buying-guide/)

## How a job runs

### Call or send the form

Tell us what heats and cools the house now and what's going wrong.

### One visit

We look at the equipment, ducts, panel and the spot outside and run the load numbers.

### Written estimate

Load figures, matched model numbers, scope and price on one page.

### Install and start-up

Permit pulled, system set, line set tested, and the start-up readings handed to you.

## Duct work: questions

### How do I know if my ducts are too small for a heat pump?

A static pressure reading tells you. Most residential blowers are built for about 0.5 inches of water column. A reading near 0.8 or higher means the ducts, often the return, are restricting the air. We take the reading before quoting.

### Why do my crawlspace ducts sweat in summer?

Cold supply ducts in humid crawlspace air hit the dew point when insulation is thin, torn or missing. Water drips onto the vapor barrier and soaks the insulation further. Sealing the seams and rewrapping the trunk stops it.

### Is duct tape okay for sealing ducts?

Cloth duct tape dries out and lets go within a few years, especially in hot attics. Mastic or foil tape rated for ducts lasts, and that is what we use on seams and connections.

### Does TVA pay anything for duct work?

TVA EnergyRight pays $300 for qualifying duct sealing and insulation for MLGW customers, done by a participating contractor. We note on the estimate whether the duct line fits the program.

### Can duct work be done on the same day as a new heat pump?

Sealing seams, adding a return and rewrapping a trunk usually fit on the install day. Replacing a plenum or many runs can add a day. The estimate gives the duct work its own line and its own time.

## Related services

- [Service**Heat pump replacement** Your heat pump is near the end and you want the next one to last. We size it from the house and match both halves.](https://blufflinememphisheatpumps.com/heat-pump-replacement/)
- [Service**Air handlers** The indoor half decides airflow, drainage and backup heat. We replace it with a matched unit and keep a sound outdoor unit.](https://blufflinememphisheatpumps.com/heat-pump-air-handler-replacement/)
- [Service**Variable speed heat pumps** Long, slow runs that pull more water out of a Memphis summer and keep two-story houses even.](https://blufflinememphisheatpumps.com/variable-speed-heat-pump/)

## Get an estimate for duct work

Tell us what heats and cools the house now, what's going wrong and roughly where the house is. Photos of the outdoor unit and its nameplate help.

(901) 657-2200