What Is the Best Ductwork for Crawl Spaces?

The ductwork in your home’s crawl space plays an important role in keeping you comfortable all year long. It's important to choose the best ductwork for a crawl space to allow efficient airflow and effective heating and cooling. Your choices include sheet metal, insulated flex duct, or fiberglass duct board. 

1. Sheet Metal

Sheet metal, especially when insulated, is often considered the "gold standard" type of ductwork. Usually made from aluminum or galvanized steel, sheet metal ducts are available in rectangular or tubal shapes. They're sturdy and smooth, allowing for the free flow of air through them. 

Since metal is non-porous, it doesn't attract mold. Aluminum and galvanized steel are also known for being rust-resistant and for being the most efficient type of ductwork.

Best for: Homes with larger crawl spaces

2. Insulated Flex Duct

Insulated flex ducts are often the go-to for particularly cramped and tight crawl spaces. Since they flex and bend, they're perfect for hard-to-reach areas. Insulated flex ducts are available in two types: R6 or R8 ducts. The R-value refers to how much insulation the ducts provide. Local building codes dictate which option is needed, with R8 providing more insulation than R6.

The major downside of flex ducts is that they aren't as sturdy as sheet metal and they can tear and rip easily. Mice and other rodents, if they get into your crawl space, can also nibble through flex ducts. 

Best for: Very tight, rodent-free crawl spaces

3. Fiberglass Duct Board

Fiberglass duct board can be a budget-friendly alternative to sheet metal ducts, in some crawl spaces. They are relatively easy to install but are also considerably more fragile than flex ducts or sheet metal ducts.

Another drawback of fiberglass duct board is that it can be a magnet for mold, especially in humid crawl spaces. If the duct board breaks, it can release fiberglass particles into the air.

Best for: Budget-conscious homeowners with very dry crawl spaces

Things to Consider When Choosing Ductwork for a Crawl Space

Flex duct versus rigid metal: what should you think about when choosing the right ductwork for your crawl space? 

There are a few factors to keep in mind:

• Energy efficiency: Sheet metal ducts are the most efficient, as they have fewer nooks and crannies to trap air. However, choosing an insulated flex duct can also help to increase the efficiency of your HVAC system, leading to lower home energy bills.

• Humidity levels: In certain areas, crawl spaces can be damp and humid, creating the perfect environment for mold growth. However, it's possible to condition your crawl space, keeping moisture to a minimum. In moisture-prone areas, sheet metal is often the best bet. 

• Longevity: Sheet metal is the most durable and has the longest life span compared to other options.  

• Pests and rodents: Even with the help of an exterminator, it may be difficult to keep mice and other pests out of your crawl space. If you're at all concerned about pests, choose a material that they won't be tempted to eat.

• Size: Sheet metal can be tricky to install in a very cramped space, which is one reason many homeowners opt for flex ducts.

Can I Install Ductwork Myself?

If it's time to replace the ductwork in your crawl space, you're likely wondering who does ductwork and if it's something you can do yourself.

A professional duct installer near you is the best person to hire for a few reasons. Your crawl space is a tight area. It can be difficult to maneuver in it and even more difficult to properly assemble ductwork there, unless you really know what you're doing.

Another reason to go with a pro versus DIY is that a professional can give you expert advice on the type of ductwork to use in the area, and why. 

What Is the Cost to Replace Ductwork in a Crawl Space?

The cost to replace ductwork in a crawl space depends on the type of material you choose, the size of the area, and who you hire to do the work. Sheet metal ducts have the highest price tag, at $7 to $13 per linear foot. Meanwhile, both insulated flex ducts and fiberboard ducts start at $2 per linear foot.