In recent years the popularity of vent free gas heaters to heat residential garages and small shops has grown steadily. Heatstar (by Enerco of Cleveland, Ohio) manufacturers a small gas fired vent free heater designed specifically for such spaces. The heater is small – just 25,000 BTU’s (natural gas model HS25N) or 22,000 BTU’s (propane gas model HS22L) and lightweight. It is the only residential garage heater of its kind approved for residential garages in North America.

Compared to other types of heaters, customers seem to like the fact that, since the Enerco heater is designed to be "vent free", it does not require a flue to the outside. Here are some pros and cons to consider:

The pros -

1. 99.9% efficiency. Nearly all products of combustion are emitted to the space. Heat is not lost through a flue to the outside, making the Enerco heater inherently more economical to operate compared to a vented forced air heater, for example, which can lose from 25 to 30% of its total BTU capacity through a flue to the outside.

2. Easy installation. Heater comes with a mounting bracket and hardware, which simply bolts to the wall. The heater head suspends from the bracket. Installation time: about 30 minutes to an hour.

3. Comes with a millivolt wall thermostat and thermostat wire. No electrical power is required. The owner lights a pilot light, which stays on all winter. When the thermostat calls for heat, the heater turns on. When satisfied, it turns off. Continues to operate during power outages.

4. Quiet operation. No fan or other moving parts to create noise. No drafts.

5. Infrared. Comfortable radiant heat.

6. Inexpensive to buy. $285.00 to $375.00 (US)

The cons –

Ironically, most negative feedback about the Enerco vent free heater surrounds the fact that the heater is, well, vent free. After-all, "vent free" means "unvented". Therefore all of the heaters’ products of combustion are emitted to the indoor space. This could pose problems if the space is too small or too tight. Therefore, the heater manual recommends an air displacement equivalent of 1 square inch of free outside air per 1000 BTU’s. For example, the model HS25N (25,000 BTU’s) requires 25 square inches of outside air. This can be accomplished with a wall louver (supplied with the heater) or may exist naturally through cracks around overhead door(s), window(s), etc.

Two primary reasons for providing outside air dilution are:

1. To ensure proper combustion of the gas by providing sufficient oxygen levels.

2. To dilute water vapor.

Incomplete combustion of a fossil fuel (in this case natural or LP gas) can produce dangerous carbon monoxide if oxygen levels are too low. While a typical 2-car garage would normally have enough natural combustion air to provide proper heater combustion, some smaller well sealed garages and shops may require a wall vent or slightly opened door or window to supply the needed air.

Water vapor (humidity) is one of the primary by-products of fuel combustion. Vent free heaters in very tight and well-insulated garage/shop structures may produce and excessive amount of humidity to indoor air, which can condense on cold surfaces, such as overhead door rails tools, etc. This problem can be solved by simply installing a wall vent or by slightly cracking open an outside window. The heater manufacturer (Enerco) prefers that customers use the vent louver that comes in the heater packaging. We find that most homeowners choose not to install it, seeking other sources for outside air instead.

With all of the discussion about vent free heater safety, it is remarkable that millions of Enerco garage heaters have been installed throughout North America for at least 25 years with a stellar record of safe and reliable operation.

It’s important to note that the HS25N and HS22L Enerco heaters are not CSA approved for dwelling spaces of the home (ie, living rooms, bedrooms, etc.). Vent free heaters approved for use in those areas must have an oxygen depletion sensor (ODS)., a safety device that shuts the heater down if too much oxygen in the room is consumed.

In summary, when used for their intended purpose of heating garages, shops and commercial spaces, in accordance with the manufacturer’s guidelines, The Enerco HS25N/HS22L is as safe as any other type of heater. It’s benefits seem to outweigh any negative aspects of owning and operating a vent free garage heater. Overall, this author believes Enerco vent free heaters to be a safe, affordable and economical choice for most average garages and small shop spaces.