Best Horizontal Venting Garage Heater Options for Garages and Workshops

Choosing the right horizontal venting garage heater depends on fuel type, venting category, BTU output, and installation needs. Below is a short comparison table of the most relevant products reviewed in this article to help you assess features at a glance.

Product	Fuel / Type	Venting / Notes	Output
Mr. Heater Big Maxx MHU80NG	Natural Gas	Category 1 vertical, Category 3 horizontal	80,000 BTU
DuraVent Vent Unit Heater Kit – 4in. Horizontal	Venting Kit	4″ Horizontal design for compatible units	Accessory (fits specific units)
Reznor UDXC-150 Commercial Natural Gas Heater	Natural Gas	Horizontal Cat 1 B-Vent Kit	150,000 BTU (two levels)
Reznor UDXC-45 Natural Gas Heater	Natural Gas	Horizontal Cat 3 Z-Vent Kit	45,000 BTU (two levels)
CTSC 10000W Electric Garage Heater	Electric (Hardwired)	No venting required (alternative to vented units)	10,000W

Mr. Heater Big Maxx MHU80NG Natural Gas Unit Heater

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This Mr. Heater Big Maxx MHU80NG is a natural gas unit rated at 80,000 BTU and designed for larger garages and workshop spaces. The purchase includes the heater with two angle brackets and a liquid propane conversion kit. Thermostat, hose, and regulator are not included. Unit dimensions are 29.33” L x 15.50” W x 26.37” H.

Key technical points: it runs on 120 V with 2.3 amps, and coverage is listed around 2,000 sq. ft. Clearances include a minimum 8 ft. from floor to base of unit. The unit supports Category 1 vertical and Category 3 horizontal venting, which makes it suitable for installations requiring a horizontal vent exit in many garage configurations.

When evaluating this model for a horizontal venting installation, confirm local codes for Category 3 installations and the required clearances. The included LP conversion kit may be useful for certain installations but verify that any gas conversions are performed by a qualified technician.

DuraVent Vent Unit Heater Kit – 4in. Horizontal

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The DuraVent 4in. Horizontal Vent Unit Heater Kit is an accessory designed to enable or simplify horizontal venting for compatible unit heaters. It fits specific DuraVent-compatible units including several item numbers listed by the manufacturer.

Use this kit when a unit supports a 4-inch horizontal vent exit and you need a purpose-built, sealed path for combustion exhaust. Because ventilation components are sized and rated, matching the kit to the heater model is important to maintain combustion safety and performance.

Installation notes: the kit is intended for use with particular unit models, so verify compatibility before purchase. Proper sealing, slope, and support are essential for a reliable horizontal vent run. Local building and mechanical codes can affect allowable vent routing and termination details.

Reznor UDXC-150 Commercial Natural Gas Garage Heater

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The Reznor UDXC-150 is a high-capacity natural gas heater suitable for commercial garages, large workshops, and warehouses. It is rated at 150,000 BTU and provides two heating output levels: a low-fire setting and a higher output for colder conditions. The unit achieves approximately 83% thermal efficiency.

Venting details: this model is offered with a Horizontal Cat 1 B-Vent Kit option. Its design includes threaded-nut retainers at four suspension points for ceiling mounting, and it can be ceiling- or wall-mounted depending on the bracket used. Mounting hardware may be sold separately.

For horizontal venting, ensure the B-vent assembly rating aligns with the unit’s category and that clearances to combustibles and termination locations meet code. The UDXC series emphasizes forced-air distribution with a low-static propeller fan suitable for spaces that require broad heat dispersion.

Reznor UDXC-45 Natural Gas Unit Garage Heater

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The Reznor UDXC-45 is a compact natural gas unit heater rated at 45,000 BTU with two output levels for milder and colder conditions. It also advertises an 83% thermal efficiency and uses a low-static propeller fan for quiet, broad air distribution.

Venting compatibility: this unit is supplied with or compatible with a Horizontal Cat 3 Z-Vent Kit, making it suitable for applications where a Category 3 horizontal vent termination is required. The unit includes suspension attachment points for ceiling mount installation (mounting hardware may be sold separately).

Consider the UDXC-45 for medium-sized garages where a horizontal vent is preferable due to roof or wall constraints. Confirm vent category and termination clearances, and check compatibility of the Z-vent system with local codes and manufacturer installation instructions.

CTSC 10000W Electric Garage Heater, 240v Hardwired

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The CTSC 10000W Electric Garage Heater is a hardwired, fan-forced electric heater that does not require combustion venting. It features a digital thermostat, remote control, timer, and an innovative voltage display screen intended to help troubleshoot common voltage-related issues during installation.

Safety and operation: built from SPCC cold-rolled steel, the unit includes overheating protection and ETL listing for electrical safety. It offers three heat modes (10000W, 7500W, and fan-only) and a digital control interface for precise temperature management.

As an alternative to horizontal venting systems, electric heaters avoid combustion exhaust routing and required vent clearances. Consider electrical service capacity, hardwired circuit requirements, and the relative operating cost difference between electric and gas heating in your area when evaluating this option.

Buying Guide: Choosing A Horizontal Venting Garage Heater

This buying guide covers critical considerations when selecting a horizontal venting garage heater, with perspectives on fuel type, vent categories, installation, capacity, safety, and long-term operation.

Fuel Type And Venting Implications

• Natural Gas And Propane Units Require combustion venting. Horizontal vent kits are available in different categories (e.g., Category 1, Category 3, B-Vent, Z-Vent). Match the heater’s vent category with appropriate vent components.
• Electric Heaters Do not require combustion venting and avoid exhaust routing, making them simpler to install where venting is restricted. They require adequate electrical service and may have higher operational costs depending on electricity rates.

Understanding Vent Categories And Compatibility

• Category 1 Vents Typically for atmospherically vented appliances; confirm allowable horizontal runs and clearances for the specific unit.
• Category 3 Vents Often for mid-efficiency condensing appliances or units with different exhaust temperatures and materials; these may use Z-vent or special connectors.
• Always use vent kits and components specified by the heater manufacturer or approved equivalents. Mixing incompatible vent categories can create unsafe exhaust conditions.

Heat Output And Space Sizing

• Calculate required capacity using space volume, insulation level, and desired temperature rise. For garages, common guidance ranges widely; professional heat loss calculations offer the most accurate sizing.
• BTU ratings for gas units and wattage for electric units should align with the area to be heated. Oversized units can short cycle; undersized units may not maintain comfort.

Installation Considerations

• Mounting Location: Ceiling- or wall-mounted units require clearances and structural support. Verify suspension points and required mounting hardware.
• Venting Path: Horizontal vent runs must maintain proper slope if required, be supported, and terminate to code-approved locations. Penetrations through walls may require flashing and weatherproofing.
• Gas Hookup & Electrical: Gas units require properly sized gas lines and qualified connections. Electric units require correctly rated breakers and hardwiring.

Safety, Codes, And Compliance

• Follow local building and mechanical codes, which dictate vent termination distances from openings, combustible clearances, and vent materials.
• Install carbon monoxide detection when using combustion appliances in attached garages or enclosed spaces.
• Use ETL/UL listings and manufacturer installation instructions to ensure compliance and safe operation.

Durability, Maintenance, And Serviceability

• Look for robust construction materials and accessible service panels for routine maintenance like filter cleaning or fan inspection.
• Periodic inspection of vent joints, seals, and termination caps helps prevent exhaust leakage and corrosion-related failures.
• Consider availability of replacement parts, conversion kits, and authorized service networks.

Operational Costs And Efficiency

• Natural gas heaters typically list BTU and efficiency ratings; higher thermal efficiency reduces fuel usage for a given heat output.
• Electric heaters convert nearly all electrical input to heat but may be more costly to operate depending on local electricity rates.
• Factor in climate, usage hours, and fuel costs when comparing lifetime operating expenses.

Vent Termination And Exhaust Location

• Horizontal vent terminations must be positioned clear of doors, windows, air intakes, and property lines per code. Consider prevailing wind and nearby openings.
• Terminations for Category 3 or B-Vent systems can have different clearances and cap designs; follow manufacturer guidance exactly.

Comparing Forced-Air Distribution Versus Radiant/Direct Warmth

• Forced-air vented units use fans to distribute warm air and can heat larger volumes quickly. Consider fan noise and draft when in occupied spaces.
• Other systems provide radiant or direct heat without a blower; assess which delivery suits your workspace activities and comfort preferences.

When To Consult A Professional

• Complex vent runs, gas line sizing, or code interpretation merit consultation with a licensed HVAC technician or mechanical inspector.
• Professional installation reduces the risk of improper venting, which can create safety hazards such as back-drafting or carbon monoxide infiltration.

By considering vent category compatibility, fuel type, capacity, installation constraints, and long-term operating costs, you can identify the horizontal venting garage heater that best meets the needs of your garage or workshop. Prioritize matching the heater’s venting requirements to the correct vent kit and ensure all work conforms to local codes and manufacturer instructions.