Except for electric models, fireplaces, stoves, and inserts need to be vented to the outdoors. Venting helps remove combustion gases, some of which are unsafe for the home’s occupants.
Complete venting also allows the fire to draw combustion air (oxygen needed for burning) from outside the house. This, too, is critical as using indoor oxygen for the burning process may deprive people in the room of oxygen. Low oxygen often results in carbon monoxide, a poisonous and often fatal gas.
Nevertheless, some gas fireplaces aren’t vented. They don’t have any mechanisms purposefully built-in to eliminate combustion gases or draw fresh air for combustion. These units are known as vent-free fireplaces.
Unfortunately, you cannot vent a ventless gas fireplace. If you have a vent-free gas fireplace but wish to add some ventilation, your only alternative is to replace the ventless model with a vented gas fireplace.
What is a Vent Free Fireplace?
A vent-free fireplace is precisely what the name says – it’s a fireplace without a venting system. Vents are small, special pipes fitted to some fireplace systems to serve as a pathway out of the house for combustion gases.
A category of fireplaces, known as direct vent models, even has two of these vents, with the second vent opening helping to draw fresh air into the fireplace to aid combustion.
Vent-free fireplaces don’t have any vents at all. Instead, they vent all the combustion gases inside the home and draw from the room the oxygen necessary for burning.
Since the chimney and vents aren’t necessary for a vent-free fireplace’s functioning, installing such fireplaces is a much simpler process compared to installing a vented fireplace.
Moreover, unlike vented models, the ventless fireplace can work even in rooms where fireplaces simply weren’t an option, such as small dens.
How Does a Ventless Fireplace Work?
The ventless fireplace works on a fairly simple principle. The fire is designed to burn at optimal efficiency, with minimal carbon dioxide output. It also produces very little moisture.
Indeed, most ventless fireplaces are considered 100% efficient, though, practically, they are around 99.99% efficient. The result is a comfortable, clean-burning fire that’s generally safe for your home and the people in it.
Two things are critical for complete safety when using the ventless gas fireplace, however. First, you need plenty of ventilation. Since the fireplace draws combustion air from your home, you must replenish the lost air continually.
For this reason, it’s important to open the windows after every hour of heating to allow fresh air into the room. Leaving the windows open for 5-10 minutes after every hour of heating is the recommended rate.
Additionally, never run the ventless heater for more than four straight hours. After, say three hours, shut off the heater and open the windows to allow fresh air into the room.
Secondly, pick the right size heater. A ventless gas fireplace too big for the room means you end up with more combustion gases in the small space.
Also, you’ll be drawing a lot more oxygen and at a higher rate. This could leave your room full of combustion gases and simultaneously depleted of oxygen in no time – a dangerously unsafe living environment.
Pros and Cons of Vent-Free Fireplaces
If you’re still interested in ventless heaters, though, understanding the pros and cons will help you make an informed decision on whether to buy one or not.
Ventless Gas Fireplace Pros
- Very affordable: In general, vent-free gas heaters are much more affordable than their vented counterparts. If you’re shopping on a budget, they are a worthy consideration.
- Very silent: Ventless gas heaters are also extremely quiet. Even at peak operation, you may not hear a sound. This makes an ideal choice when you need quiet.
- Use propane 0r natural gas: Depending on where you live, one of the two (propane or natural gas) may not be readily available. A ventless gas heater can use either.
- Easy to install: Compared to vented models, vent-free gas heaters are simple to install. The easy installation often means even lower upfront costs.
- Extremely efficient: Ventless heaters are very efficient. The majority are 99.99% efficient, meaning only about 0.01% of the fuel isn’t converted to useful heat.
Ventless Gas Fireplace Cons
- Oxygen depletion: The first major drawback of ventless gas fireplaces is oxygen depletion. These fireplaces use up the oxygen in your home for the combustion process. If you’re not careful, this could leave your home short on oxygen. Low oxygen levels in breathing air can cause asphyxiation.
- Carbon monoxide risk: Low oxygen levels in a confined space can also lead to carbon monoxide. Whenever there aren’t enough oxygen molecules to form stable O2 compounds, the single oxygen (O) molecules easily bond with carbon, creating CO. Carbon monoxide is a poisonous, even fatal gas.
- Vent-free fireplaces are highly regulated: Owing to the safety risks associated with them, ventless fireplaces are highly regulated throughout the world. In states such as California and many municipalities, ventless heating is completely prohibited. Therefore, you may not be able to have one even if you want to.
Differences Between Vented and Ventless Gas Fireplaces
The first major difference between vented and unvented gas fireplaces is the venting. Vented fireplaces have a vent system to guide combustion gases outside the house.
This effectively reduces the risk of excess carbon dioxide and water vapor. Extended exposure to excess carbon dioxide can cause drowsiness, while too much moisture is harmful to your walls and furniture.
Some even have a second vent to bring in fresh air for the combustion process. In fireplaces where this second vent is missing, the heater uses indoor oxygen for combustion, a situation that can leave occupants in the home short on oxygen supply.
Other key differences are as follows;
The flames of vented and unvented aren’t the same. Vented gas fireplaces tend to have bigger, more realistic flames creating the impression of a fully functioning wood-burning fireplace.
The flames have enough yellow, which is what anyone really wants. Ventless gas fireplaces, by comparison, produce much smaller flames. Also, since the burning is a lot more efficient, the flame is mostly blue, thus less realistic.
The vent-free gas fireplace is a lot more efficient than the standard vented gas fireplace. Nearly all ventless models are rated 99.9% efficient or higher, with a few rated at over 99.99% efficient.
This is near-flawless for heating appliances. Vented heaters aren’t as efficient. Many lose about 20% to 30% of heat via the vents, thus are only 70-80 percent efficient.
The vented gas fireplace also burns a lot more fuel compared to the standard ventless gas fireplace. Most 18 to 30-inch vented gas fireplaces burn between 70,000 and 90,000 BTU per hour.
Ventless units, being more efficient, burn less fuel to produce the same amount of heat. The average, the standard vent-free gas fireplace burns 20,000 to 40,000 BTU per hour.
Given the efficiency differences, ventless gas heaters are slightly cheaper to run compared to their vented counterparts.
The figures aren’t easy to come by, but you’re likely to spend $36 to $46 per month using a vented heater four hours per day. If you switched to a ventless model, the costs come down to $10 to $20 per month for the same amount of use.
How to Vent a Ventless Fireplace
Unfortunately, it’s impossible to vent an unvented gas fireplace. It doesn’t matter the fuel type – propane or natural gas. It may seem like all you need to do is cut a hole or two into the fireplace, fitting pipes into the holes, and having the pipes vent outside. But it’s a lot more complicated.
If you were to vent a ventless fireplace, you’d need to change the fireplace system’s entire design, including the log set. Any HVAC expert would tell you it’s not worthwhile.
If you’re serious about switching to a vented gas fireplace from a ventless model, the best solution is to buy a new vented unit from the store.
Vent-Free Gas Fireplace Safety
Considering the many health and safety risks associated with ventless gas fireplaces, it’s imperative that you use them with extreme caution. Observing the following safety tips would be a great start;
Check your Local Codes First
Before you head out shopping, check your local laws to determine what they say about ventless gas fireplaces. Most states and municipalities allow the use of these units, but with strict regulation. Other states, such as California, meanwhile, ban them altogether.
Buy for the Right Application
The ventless gas fireplace is best suited to large, open spaces with plenty of ventilation. If you’re looking to add supplemental warmth to your reading room in the basement, a ventless gas heart would be the worst possible solution. Bedrooms are also not the right application for ventless gas heaters.
Buy the Right Size (BTU)
Ventless gas heaters produce substantial amounts of water/moisture and carbon dioxide. Moisture might be harmless to people, but it can be damaging to the home.
Excess moisture damages walls (including paint and wallpaper) and can destroy your furniture and books. Too much carbon dioxide causes drowsiness. A ventless gas fireplace too big for your room will produce more moisture and CO2 than your room can handle.
Always Install an ODS
The oxygen depletion sensor (ODS) is a small electrical device that monitors levels of oxygen in the home and gives an alert if dangerously low levels of oxygen are reached. Even if your ventless gas heater comes with an inbuilt ODS, it’s always better to acquire a second one.
Always Burn the Unit with the Door Open
Many ventless fireplaces have a door. The purpose of this door is to let out combustion gases and let in fresh air for the combustion process. Therefore, you must never have the fireplaces working with the door closed.
Doing so causes the burner to produce excess amounts of soot and carbon dioxide. The potential build-up of heat also creates a significant risk.
Consider a Fireplace Screen
Gas fireplace fires are still fires. The logs might be fake, but the fire is very real and can get extremely hot. This poses a risk to kids and pets who may be tempted to get too close.
A fireplace screen, such as a glass panel with a mesh behind the glass, allows you to burn the fire with the fireplace door open – without creating a burn risk for your kids.
Never Leave the Fire Unattended
This is perhaps the biggest tip here. As long as the ventless gas fireplace is running, you must be around. If you’re leaving the house, even for 30 minutes, shut it off. Also, shut it off when you go to sleep.
Vent-Free gas Fireplace Danger Signs
Even after taking the necessary safety precautions, you need to remain vigilant throughout the heating process. Be wary if you notice the following signs;
- The ODS sensor alert: Whenever the oxygen depletion sensor (ODS) sends a warning of low oxygen levels, don’t want any longer. Turn off the fireplace and open the windows.
- Excessive condensation on the windows: Although moisture isn’t a safety risk for humans, it can destroy your walls, books, furniture, etc. Open the windows to allow in the fresh air.
- Drowsiness among home occupants: Too much carbon dioxide causes drowsiness. If you feel drowsy or notice that some of the people around the fire are drowsy, it might be a sign of too much carbon dioxide.
Ventless Gas Fireplace Maintenance
Proper maintenance can help ensure greater safety when using the ventless gas fireplace. We especially recommend the following tips;
- Ensure the unit is professionally inspected and maintained by a licensed technician at last once a year.
- The existing firebox or masonry fireplace and damper area must be cleaned thoroughly before use.
- Replace the batteries, often twice a year, when you replace the smoke detector and carbon monoxide detector.
- Clean the glass by wiping gently but firmly with a soft cloth sprayed with household window cleaner.
- Clean the interior by vacuuming dust and debris from the fireplace and cleaning the logs by gently brushing them with a paintbrush.
Ventless gas fireplaces are an economical alternative to vented models. They are also more efficient, thus less costly to run. If your local codes allow it, you should at least consider them for a few applications.
Just make sure to use them safely. Ventless gas fireplaces vent combustion gases into your home and use up indoor oxygen for the burning process.
These two processes can leave your indoor air extremely unsafe. So, if you decide to go the vent-free route, arm yourself with a carbon monoxide detector, and be vigilant.