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Can You Put a Space Heater in a Crawl Space


Space heaters are not prohibited by the IRC from use in crawl spaces, but they must be approved by the manufacturer for such use. Space heaters are too small and delicate to be effective and long-lasting in crawl spaces. There is also a high risk of fire as they are not designed to be left unsupervised.

A cold crawl space can cause a homeowner no end of trouble. From frozen pipes and all the associated damage to exhaust fans that drip because their ducts run through the unconditioned space, there are many reasons why warming up a crawl space would be desirable. The most effective solution would be to encapsulate your crawl space, but as this is a rather expensive option, many people consider simply sticking a space heater in the crawl space.

I’m rather a stickler when it comes to checking the code before I do any kind of home improvement or alteration, but I’m particularly cautious of anything involving a heating unit because of the potential safety implications. While putting a space heater into the crawl space is not an immediate code violation, there are ways in which it can become non-compliant. There are also obvious drawbacks to this solution and some feasible alternatives that you should consider.

No Regulation Against Space Heaters in Crawl Spaces

The International Residential Code (IRC) doesn’t explicitly prohibit the use of space heaters in crawl spaces. Section M1305.1.3 of the IRC discusses requirements for appliances under floors, but mainly focuses on the placement and avoiding passageway obstruction. 

DIMPLEX DGWH4031G Garage and Shop Large 4000 Watt Forced Air, Industrial, Space Heater in, 11 x 7.25 x 9 inches, Gray/Black Finish

This omission is not surprising considering the fact that if the code was to specifically mention every possible scenario that could arise in building a house, it would be ridiculously long, continuously in-writing, and not at all helpful.

Instead, the code focuses on the big no-nos and more general regulations.

To prevent any problems arising from the generality of the code, there are two key phrases that crop up in almost every section. With these two phrases, the IRC has very cleverly ensured that health and safety are as protected as possible.

  1. As per manufacturer instructions/directions/specifications.
  2. Item/product/tool/appliance must be listed and labeled for use.

Firstly, a manufacturer will never recommend the use of the product in an unsafe manner because of the liability and loss of reputation that would follow. Secondly, for a product to be listed and labeled, it has to pass certain standardized safety tests, which ensure the quality of the product and legitimacy of the manufacturer.

Is Space Heater Approved for Crawl Space Use?

Whether or not the specific space heater you’re using is approved for crawl spaces depends on the manufacturer’s specifications. Check the labeling on the heater to see if it’s suitable for crawl spaces. This may require some close reading as often it isn’t specifically stated. 

Look for minimum ventilation requirements, allowable use in damp locations, and flooring/placement specifications. You’ll want to find a space heater that is safe for use in damp environments and matches the size requirements of your crawl space. 

Added safety features like automatic shut-off if the heater tips over or overheats are also important to consider to prevent a fire from starting in the crawl space because you will likely be unaware of this until it has caused significant damage. 

Floor Above Has to Be Fire-Protected

Starting a house fire is one of the main dangers of using a space heater (even outside of a crawl space). According to a Home Heating Fires report by National Fire Protection Association, 81% of home heating fire deaths from 2014-2018 involved space heaters. 

Once you’ve verified that the space heater can be used in a crawl space as per the manufacturer, according to Section R302.13 of IRC, you should make sure that the floor above it is fire-protected.

Fire blocking creates a fire barrier that prevents fire from spreading quickly in an enclosed space.
IRC Section R302.11.1 details what materials are suitable for fire blocking, including two-inch nominal lumber, 23/32″ wood structural panels, ¾” particleboard, half-inch gypsum board, quarter-inch cement-based millboard, mineral wool, glass fiber, and cellulose insulation.

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Should Space Heaters Be Used in Crawl Spaces?

Although it’s not forbidden by the IRC, using a space heater in a crawl space isn’t a long-term solution.

If you are looking to avoid dripping exhaust fans and range hoods, rather insulate the ducting of these systems.

And if you are trying to prevent your pipes from freezing, then there are other more effective and long-term solutions to this problem.

Drawbacks of Using Space Heater in Crawl Space

Not only is it seldom the best solution, but there are also distinct drawbacks to putting a space heater in the crawl space.

Space Heaters May Be Pointless in Crawl Spaces

Crawl spaces can be quite large and are also commonly uninsulated. This means a space heater is unlikely to be effective because they’re designed to heat smaller spaces and rely on insulation to make the most of the heat produced (prevent it from escaping the room). 

A space heater with enough power to heat a large space will be quite expensive (usually running between $100 and $200). On top of the initial cost, you’ll be losing money in the form of higher electrical bills. This is an even bigger waste if much of the heat is escaping through the ground, walls, windows, and doors.

To make this option cost-effective, it’s better to have a well-insulated space. Additionally, if your crawl space isn’t too large this could be a useful strategy. 

From the perspective of heating pipes or keeping an area warm while you’re working in the crawl space, other strategies may be more cost-effective in the long term. Even so, if you need a quick fix, a space heater could do the job.

Dangers of Space Heaters in Crawl Space

As previously mentioned, the main concern with a space heater is it may cause a fire. In normal rooms in the house, a space heater would not be left unsupervised for long; however, for a space heater in a crawl space, this is a more likely situation. 

Again, this is why using a space heater to avoid frozen pipes is only a temporary solution. It is very dangerous to leave an electrical appliance unsupervised. 

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One possible solution is to have a wireless/remote thermometer set up in the crawl space near the heater. This way you can check the temperature without physically going to check on the heater (if you are leaving it unsupervised).

On/Off Button Is on Heater Itself

Space heaters’ on/off switches are usually on the space heater rather than the cord or plug.

So, you will have to crawl into the crawl space to turn the heater on and off unless you:

  • Specifically buy a heater with a different setup.
  • Connect (with an extension cord if needed) the heater to a plug with an on/off switch.
  • Put it on its own circuit and manage it through a subpanel.

This is very inconvenient and impractical, while also raising the probability of leaving the space heater running too often due to the difficulty of turning it off, again making it more dangerous.

Better Option Is a Crawl Space Heater

Space heaters are normally made for offices or rooms in a house, while a crawl space heater is ideal for larger spaces. Typically, they also place more importance on durability, safety, and energy efficiency.

Often crawl space heaters are labeled for garages or commercial use.

What crawl space heater you buy will depend on the size (volume) of your crawl space, so it’s important to measure the space before purchasing a heater.

Comfort Zone 5000W Fan-Forced Ceiling Mount Heater with Dual Knob Controls, Deluxe Utility Wall, White

Crawl space heaters do tend to cost more than standard space heaters because of their more durable construction (often from steel), added safety features, and built-in thermostats.

Here are three quality options for crawl space heaters and product information to help you pick the right option for you:

Please note that all products linked in this post have not been physically tested by the HVAC-Buzz team. They have been included and recommended based on detailed research into their design and capabilities.

Crawl Space HeaterWattage (Watts)Safety Features
Dimplex heater (amazon link)4000WAutomatic overheat protection
Comfort Zone heater (amazon link)5000WAutomatic overheat protection
Power indicator light
Dr. Heater heater (amazon link)3000W/6000WTotally enclosed
Thermally protected

Best Option Is to Insulate or Encapsulate Crawl Space

As a long-term solution to keeping your crawl space warmer, insulating and encapsulating are better than space heaters. These methods involve preventing the space from getting cold in the first place by sealing the space.

Insulation is the better option if you’re working to avoid frozen pipes or a generally cold crawl space. Encapsulation is more of a waterproofing/moisture management strategy; however, it will also function to prevent air leaks.

Crawl space fully encapsulated with thermoregulated blankets and dimple boards

To seal the crawl space: close vents, ducts, doors, and other openings into the space. Use caulk or foam insulation to repair any cracks in walls, rim joists, and the foundation. Replace or install insulation in the ceiling and walls.

Install a vapor barrier (usually white plastic or Drylok) by stapling it to walls and floors. If desired, you can also install a dehumidifier like this crawl space ventilator (amazon link) if your region is particularly humid.

Sources

http://cchrc.org/crawspace-foundations/

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