Manufactured Home Ductwork Guide: How To Find A Suitable Replacement

Manufactured home ductwork is usually part of the larger HVAC system, but it is purchased and installed separately. As part of the HVAC system, the job of the ductwork is simple – to distribute airflow from your cooling or heating installations throughout your home.

The job can also involve the suction of stale air from rooms back into the A/C system where it is cooled or heated and returned in the ductwork for redistribution.

So, a typical home needs two sets of ducts –

  1. the supply and
  2. the return duct.

As such, the ductwork is one of the most critical parts of your home’s heating/cooling system meaning you wouldn’t compromise on quality.

Manufactured Home Ductwork – 6 Shopping Factors

Consider these factors when shopping if you want to select the best ductwork for your manufactured home:

  • Type of ductwork
  • Efficiency
  • Maximum Temperature Rating – MTR
  • Fire Safety
  • Acoustical Control Features
  • Size of Your Project

1. Type of The Ductwork

The first thing to consider the type of ducts that will work perfectly with your HVAC system and one that suits your needs. There are numerous types of ducts used in homes, but we’ll focus on just five popular types:

Round Pipe

This is the most popularly used type of duct in residential settings. It comes in a range of shapes and sizes to route airflow in a variety of locations. It is standard for round pipe ducts to come with a crimped end to ease the process of fitting them into adjoining pieces.

Rectangular Pipe

As you would expect, they are rectangular and come in a range of sizes too. They are normally made to be short and narrow to permit installation in wall cavities and other cramped crevices.

Oval Pipe

If you want a duct that combines the features of rectangular and circular pipes, consider oval pipes. Just like round pipes, they come crimped at ends for easy like with joints. They too can fit in limited spaces, just like rectangular pipes.

Spiral Pipes

Spiral pipes are very much like round pipes except that they feature spiral seams on their outer surface.

This design makes them especially desirable ducts to accompany any HVAC system because they are leakproof and are lightweight to most other options.

Another advantage is that airflow is streamlined with the spiral, meaning you will hear less noise air rushes from the A/C system. Plus, the spiral design appears nice to the eye.

Insulated Flexible Duct

This is a unique type of duct made from a flexible material (often plastic) and a layer of insulation material around it.

So, if you are not a big fan of metal-based and often inefficient ducts (which constitute a majority of the ducts you will find in the store, by the way), then you should limit your choices within this type of duct.

To choose the right type of duct, start by evaluating your needs and then determine which type of pipe would work well with your HVAC system.

For example, if you are looking forward to cutting your energy bills, you are more like going to settle for insulated flexible ducts because they reduce heat loss.

Also, unlike the uninsulated metallic ducts, they don’t require you to spend extra money on insulation.

2. Cost v/s Budget

Replacing ductwork in your manufactured home will relate to its size and the state of the crawl space (whether this space needs some changes to be done to accommodate the ductwork).

Mobile homes often require greater linear feet of ducts because they have a single trunk for every unit. For example, if your property is a double-wide then you will be dealing with two trunks. The traditional home usually comes with one.

As you’ve probably guessed, the cost of installing new ductwork can vary widely based on the layout (more on this later), extent of the job, and your specific cooling and heating needs.

With that said, you should understand that pros calculate ductwork installation costs differently, but will factor in all the things that need to be considered.

Most pros charge their installation cost by linear foot. An average manufactured home will require 30 to 90 linear feet of the duct at an average installation cost of $35 to 55 per foot. This brings the average installation to $1,000 – $5,000 for full home installation.

According to Home Advisor, the cost of replacing or installing ductwork in a small home is in the region of $1,130, with a range between $467 – $1,930. This translates to about $1 – 10 per linear foot. This cost increases with the size of the home and can depend on the type of duct as well as the material used to make the duct.

  • Flexible Polyester ducts costs between $1 – $4 per linear foot
  • Galvanized Steel ducts cost between $3 – $10 per linear foot
  • Flexible Steel ducts cost between $2 – $5 per linear foot.

3. Efficiency

Many homeowners like to think of the efficiency of the HVAC system as a thing reserved for the A/C.

However, the ductwork too has a big say on the general efficiency as it is responsible for distributing warm air throughout the home.

For this reason, you want to buy ducts that are, firstly, insulated so that you don’t spend extra money on insulation, and secondly, tough and durable so that they don’t develop leaks which might affect the efficiency of the system if it occurs.

You still can choose to buy uninsulated pipes and add the insulation later if they bring an advantage you may want to take full advantage.

The buyer is normally left to choose between two types of ducts as far as efficiency is concerned –

  • the flexile insulated ducts and
  • the uninsulated ducts.

Insulation isn’t a universal HVAC necessity in ductwork anyway, so you may choose the uninsulated ducts.

You can install uninsulated ductwork if – only if – your home is serviced with forced-air systems with offshoots, in which case the most rigid uninsulated ductwork will be recommended especially for the truck.

Insulated ducts, besides being thermally insulated, are flexible enough to bend around obstacles that can’t be removed.

And because they are mainly plastic, they are less prone to accumulation of dirt on the inside compared to metallic options.

Note that the materials used for insulation in ductwork varies between locations. Glass wool is the most often used type of insulator used in ducts sold in the United States. In Canada and parts of Europe, polyester is a popular insulator.

4. Maximum Temperature Rating – MTR

The maximum operating temperature is the temperature point beyond which the ductwork won’t function perfectly. It is easy to forget or even overlook this important aspect of ducts even when it is apparent that it contributes to the effectiveness of the entire HVAC system.

There are two reasons why you need to consider the maximum:

  • The attics can get hot sometimes especially during the summer. If these temperatures go past the maximum temperature rating of the ductwork, significant damages may occur.
  • The suction of warm air from the room may cause heat to build up in ducts, more so in the event of malfunctions on the part of the A/C unit, causing some damages on the ductwork.

You want ductwork with a higher Maximum Temperature Rating if your home is more likely to experience these scenarios. Sometimes it is better to have the most heat tolerant ductwork installed just in case.

Most ductworks are designed to work at temperatures in the range of 40°F (or 4°C) and 250°F (or 121°C).

The MTR seldom surpasses 250°F (or 121°C), whether you are thinking of the common fibrous glass insulated flexible ductwork or polyester-based options.

So, if your attic’s normal operating temperature is within this range (most likely is) then you need to limit your choices of ducts within it.

5. Fire Safety

Installing a duct with flammable parts is one of the riskiest things you can ever do in your home.

If it is made from any material other than black, consider determining the flammability of that material.

If it is insulated, then check whether the thermal insulation layer is fire resistant. There is a shortcut to that though – just check if the duct passed fire resistance tests from these fire safety agencies:

  • ASTM – American Society for Testing and Materials
  • UL – Underwriter Laboratories
  • NFPA – The National Fire Prevention Association (they publish over 300 consensus standards and codes and intended to minimize the effects and possibility of fire and an array of other risks in homes and commercial spaces.

6. Acoustical Control Features

Ducts without acoustical control features can be a real headache when the HVAC is left to operate to its full potential. You need peace and silence.

In most cases, it boils down to the type of material that was used to make the duct, but other things like the presence of an insulator, the manner of installation, and the presence of striations on the pipe can contribute to noise problems.

Metal pipes are more prone to noise generation than any other type of duct unless they come with proper acoustical mitigating add-ons.

Plastic and fibrous glass options are normally silent.

Fibrous glass (particularly) is an important contributor to the production of comfortable acoustically satisfying indoor environments by absorbing most of the noise generated by even the most chaotic central air systems, by contraction and expansion of duct parts, and from noise created by air movement within the ductwork.

Another reason why you may consider fibrous glass ducts is that they contribute to personal productivity and privacy by preventing the ducts from transmitting any unwanted conversations from your room to other rooms in the home. Few other ductworks come close to beating the acoustic insulation properties of fibrous glass ducts, including reflective and elastomeric foams products.

7. Material of Construction

Most HVAC ducts you will find in the store are made from these materials:

  • Aluminum
  • galvanized steel

More commonly referred to as sheet metal, metallic ductwork is considerably strong compared to other ducts made from other materials.

However, it is not the easiest ductwork material to add insulation. Plus, it is inflexible.

Fiberglass duct board

Fiberglass ducts bare made from compressed fiberglass boards that are excellent for creating square-shaped vents. It comes insulated, is easy to cut, and seals with adhesive tape.

Typical applications of fiberglass duct boards are between floor joists, rafters, or along with a pre-existing ceiling.

Polyurethane

The best thing about polyurethane is its great strength. It is basically an insulated plastic molded rolled panel, then molded into the ductwork.

Flexible, non-metallic ductwork materials

These groups of ductworks can be made from a range of materials, including plastic, polyester, and PVC.

  • These pipes fold like accordions, making it super fun and easy to install. They also come in a range of diameters to cater for a range of needs.
  • If you are looking for the best material for foldable ducts, materials from this category are the best. They are perfect for projects that involve snaking through crevices and difficult spots.
  • The bad side of these ducts, however, is their tendency to tear easily owing to their delicate foldable nature. For this reason, you will need to be extra careful when installing them to prevent punching holes.

Why do you need to be choosy about materials used to make the ductwork?

Well, such duct attributes as efficiency, durability, ease of installation, and even the quality of air can be determined by the kind of material used to make it.

8. Size of Your Project

The length of the duct is directly proportional to the size of your project – the bigger your home the longer the ductwork you’ll need.

You should measure the entire length and width of channels that will contain your ductwork before buying the ducts.

Of course, you need to buy slightly surplus ducts to spare extra materials for errors and future repairs.

HOW TO REPLACE YOUR DUCTWORK

A badly installed ductwork may end up to be prone to malfunctions and leakages. The common sign of leaking ductwork is foul smell immediately when you turn on your A/C system.

If your ductwork is too old or is prone to malfunctions, it is probably about time you replace it with a brand-new installation. Here is a step by step guide how:

Firstly, a few necessary tools and materials:

  • Scissors
  • Paintbrush
  • Measuring tape
  • Aluminum tape
  • Duct tape
  • Plastic rib

Step 1 – Remove the Old Ductwork

Start by removing your old ducts where needed. You will need to remove the resultant debris and dust from the attic or basement to create a clean and spacious area for the new ducts.

Be careful not to damage the plenum or metal vent boxes unless you want them removed as well.

How you proceed past Step 1 can depend on the type of ductwork you plan to use. If it is the uninsulated type, you have an option to install the insulation first (strongly recommended) in the attic along the line or install the uninsulated pipes as they are (not recommended).

If the pipes are insulated, you can proceed to step 2. Let’s assume you are using insulated pipes.

Step 2 – Secure and Seal Your Ductwork

Having installed your ducts neatly in the right channel in the basement or attic, taking your plastic ties to attach the whole length of pipes to the joists – seals an inch apart is just about right.

Remember that the ductwork needs to stay lifted slightly above the surface.

Seal the new ducts to the new box with plastic ties and keep the connection between your box and ducts as airtight as you can.

Once you have ascertained that everything is in proper working, seal the ductwork with aluminum tape or any other tape you wish to use. Complete this step by burnishing the ducts with a tight plastic rib.

Now let’s proceed to vents.

Step 3 – Create Housing for Vents

The new vents need to be held in place. The best way to hold them firmly in one position is to create housing or wooden vents and put a vent in each housing.

So, measure the opening, cut the wooden boxes, and put your vents in them.

Each housing should be 2″ x 4″. Note that we are using rectangular boxes because most vents come with rectangular bases.

Time to make final sealing

Step 4 – Gas and Sealing

Everything is installed and fastened as required.

Fill in the gaps left between the surface of the attic or floor of the basement and the frame complete with its insulated duct board.

Proceed to cut your board to the right size and make sure it can side in and fit snuggly.

If needed, consider sealing the vent even further with mastic adhesive/cement which, when applied properly, ensures no air leaves around the vent.

Conclusion

The materials of construction and the type of ductwork will have a considerable effect on the function of the functioning of the ducts.

To ensure that you don’t spend a lot of money on energy, choose the most energy-efficient ducts you can find.

Maximum Temperature Rating (MTR) is a temperature beyond which your ducts could be damaged by heat.

Ensure your ducts are fire-resistant. Some ducts come with acoustical control features to cut sound transmission and production of noise. The bigger your project, the more ducts you will need.

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