When looking to add heat to a crawl space, there are a few key factors to consider in order to choose the right type of heater. The main considerations are the size of the space, whether it is ventilated or unventilated, the level of insulation, and any codes or restrictions that apply. The most common types of heaters used in crawl spaces are electric resistance heaters, propane or natural gas heaters, and ductless mini-split heat pumps.
Page Contents
- 1 Ventilated vs. Unventilated Crawl Spaces
- 2 Available Space and Clearances
- 3 Heating Requirements
- 4 Applicable Codes and Restrictions
- 5 Electric Resistance Heaters
- 6 Propane/Natural Gas Heaters
- 7 Ductless Mini-Split Heat Pumps
- 8 Comparison Tables
- 9 Key Considerations by Crawl Space Type
- 10 Professional Installation Recommended
- 11 Maintenance Tips
- 12 Safety Precautions
- 13 Conclusion
Ventilated vs. Unventilated Crawl Spaces
The first factor to look at is whether your crawl space is ventilated or unventilated. Vented crawl spaces have vents along the exterior walls that allow outdoor air to circulate into the space. This air exchange helps control moisture and prevent mold/mildew growth. Unventilated or “conditioned” crawl spaces are sealed off from outdoor air and conditioned like a basement, with insulation and a vapor barrier on the floors and walls.
For ventilated crawl spaces, most experts recommend using only electric resistance heaters, as they don’t emit any moisture or gases that could build up in the space. Propane/gas units are generally not recommended for vented crawl spaces.
In unventilated crawl spaces, you have more flexibility in heater types. Electric and propane/gas units can all be effective options for sealed and insulated crawl spaces. Just be sure any fuel-burning heater is properly vented to the outdoors.
Available Space and Clearances
The physical size of the crawl space is another important factor in choosing a heating unit. Measure the length, width and height to determine the total square footage. This will help you select a heater with adequate heating capacity for the space.
Also account for any clearance requirements around the heater so it can be safely operated and accessed for service. Electric heaters often have minimal clearance needs, while propane/gas heaters require several feet of space on all sides for combustion air and ventilation.
Heating Requirements
Consider the heating needs of the crawl space based on the climate and how insulated it is. Is it just intended as a preventative freeze protection space? Or do you need sufficient heating to make it comfortable for storage or occasional access? Your heating requirements will dictate the necessary BTU rating.
Also factor in any insulation present. Heating needs will be greater for uninsulated crawl spaces compared to spaces with good floor, wall and even ceiling insulation. Properly insulating your crawl space can allow you to get by with a smaller heater.
Applicable Codes and Restrictions
Make sure to consult local building codes for any restrictions or specific requirements for heating equipment in crawl spaces. Permits are often required for fuel-burning heaters. Specific clearances or ventilation methods may be mandated. Restrictions often differ for conditioned vs. vented crawl spaces.
If you live in a condo or other building with covenants, check for any limitations on the types of heaters allowed in crawl spaces. Some associations prohibit propane tanks or units requiring exterior ventilation.
Doing your homework on codes and restrictions will ensure the heater you choose works for your specific situation.
Electric Resistance Heaters
Electric resistance units are perhaps the most common and straightforward crawl space heaters. Models are available in power levels from 500 watts up to several kilowatts. They work like an electric furnace by passing current through wires or heating elements to create warmth.
Benefits of electric resistance heaters include:
- Safe for use in vented or unventilated spaces.
- No combustion or fumes.
- Lower clearance requirements.
- Often thermostatically controlled.
- Can utilize existing electrical wiring if adequate.
Downsides to consider:
- Can be more costly to operate than gas (depending on electricity rates).
- Not powerful enough for extremely cold climates by themselves.
- Thermostat typically required to avoid overheating.
Typical costs for an electric crawl space heater range from $100-$500 depending on the power (5000W model shown below). Installation costs are minimum if existing wiring is adequate.
Overall, electric heaters provide a flexible, maintenance-free heating solution for small to mid-sized crawl spaces.
Sample Electric Crawl Space Heater
King 5,000W 240-Volt Electric Unit Heater
Propane/Natural Gas Heaters
Gas-fired heaters are another option for unventilated crawl spaces that need significant heating output. They utilize propane or natural gas for fuel. Units with ratings from 10,000 BTU to over 75,000 BTU are available.
Benefits of propane/gas crawl space heaters:
- Lower operating costs than electric in some areas.
- Very high heating capacity available.
- Can integrate with existing gas lines.
- Power vented models available.
Potential downsides:
- Not suitable for ventilated spaces.
- Venting and clearance requirements.
- More maintenance than electric models.
- May require exterior fuel tank.
Propane heaters start around $300, with installation costs varying greatly depending on venting needs. Make sure to consider ventilation requirements and clearances when budgeting for a gas unit.
Sample Gas Crawl Space Heater
Dyna-Glo 30,000 BTU Propane Convection Heater
Ductless Mini-Split Heat Pumps
Ductless mini-split systems are a great heating option for unventilated and well-insulated crawl spaces. A compact outdoor condenser is linked by refrigerant lines to an indoor evaporator air handler. Top models provide both heating and cooling.
Key benefits of mini-split heat pumps:
- Extremely energy efficient – uses 30-50% less power than electric resistance.
- Provides supplemental cooling in summer.
- Longer lifespan than other types.
- Adjustable, focused heating.
- Can be zoned for multiple areas.
Potential mini-split downsides:
- Higher upfront installation cost.
- More complex installation and setup.
- Requires annual maintenance.
- Condenser unit must be mounted outside.
Total costs for a crawl space ductless mini-split typically range from $2,000 to $4,000. While more expensive upfront, energy savings often offset the higher initial investment over time.
Sample Ductless Mini-Split System
Mitsubishi Ductless Mini-Split Heat Pump System
Comparison Tables
Here are some tables comparing key factors between common crawl space heater types:
Crawl Space Heater Operating Costs
| Heater Type | Estimated Monthly Energy Cost (for 400 sq ft space) |
|---|---|
| 1,500W Electric | $30-60 |
| 30,000 BTU Propane | $40-100 |
| Ductless Heat Pump | $20-50 |
Crawl Space Heater Output Comparison
| Heater Type | Typical BTU Output Range |
|---|---|
| Electric Resistance | 5,000 – 10,000 BTU |
| Propane/Gas | 10,000 – 80,000+ BTU |
| Ductless Mini-Split | 9,000 – 36,000 BTU |
Key Considerations by Crawl Space Type
Here is a quick recap of suitable heating solutions for different crawl space scenarios:
Vented, Uninsulated Crawl Space
Go with an electric resistance heater to provide basic freeze protection. Models from 1,500-5,000 watts are generally sufficient.
Unventilated, Uninsulated Crawl Space
A propane or natural gas convection heater in the 30,000-50,000 BTU range will provide ambient heating. Or use a ductless mini-split system for greater efficiency.
Insulated and Conditioned Crawl Space
An energy efficient ductless mini-split system is the best choice for conditioned and insulated spaces. Properly sized electric or gas heaters also work well.
Professional Installation Recommended
While it is possible for a knowledgeable DIYer to install some crawl space heater types, professional installation is highly recommended. An HVAC technician or licensed electrician can ensure the system is properly sized for the space, meets all codes/regulations, and is safely set up with appropriate clearance and ventilation (if needed).
They can also determine if your existing electrical service or gas lines can support the heater capacity needed. Upgrades may be required. Technicians have the tools and knowledge to minimize installation time and costs compared to a DIY project.
Be sure to get multiple quotes to find a competitively priced installer you are comfortable with.
Maintenance Tips
Here are some tips for keeping your crawl space heater running efficiently and safely:
- Carefully read manufacturer maintenance guidelines and perform recommended tasks like filter changes.
- Visually inspect the heater before each winter for any damage or debris buildup.
- For propane and gas heaters, annually test for gas leaks and ensure proper ventilation.
- For electric heaters, check that wiring connections are intact with no exposed copper.
- Keep the area around the heater clean and free of moisture, chemicals, flammables.
- Hire an HVAC professional periodically for a more thorough maintenance check.
Safety Precautions
Observe these important safety measures when operating a crawl space heater:
- Never leave portable heaters unattended or operate while sleeping.
- Don’t use extension cords with permanent heaters. Hire an electrician to install a dedicated outlet if needed.
- Keep all flammable materials at least 3 feet away.
- Ensure adequate ventilation for fuel-burning units.
- Install a CO detector if using propane/gas heaters.
- Check that the heater is level and stable.
- Turn off the heater when accessing the crawl space.
- Monitor humidity levels and avoid operating during extremely humid conditions.
Conclusion
Choosing the right crawl space heater involves considering your space type, heating needs, budget, and applicable codes. Electric resistance units provide a flexible, affordable ambient heating option. For greater output, propane or gas convection heaters are a powerful choice if properly vented. Ductless mini-splits offer the highest efficiency and can also provide cooling.
Carefully evaluating the pros and cons of each solution will ensure you select the ideal crawl space heater and enjoy warm, comfortable underfloor temperatures.