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Ventless Gas Log BTU Calculator!

December 11, 2009
By: Greg Tillotson
Gas Log Expert & Webmaster for Hansen Wholesale

Recently, a visitor asked if there was a formula for determining how many BTUs a ventless gas log should put out depending on the size of a room. Now this is certainly not the first time we have been asked this question. So after answering this same question over and over, I decided to create the very first online BTU calculator for Ventless Gas Logs.

Ventless Gas Log BTU Calculator!

Ventless gas logs MUST NOT exceed a certain BTU rating based on the size of a room. The formula for calculating the maximum BTU allowed is: Room Width x Room Length x Ceiling Height x 20. You can use this tool below to perform the calculation. Find out why it is important to limit the BTU output of ventless gas logs based on the size of the room!

Enter your ROOM DIMENSIONS:
Width x Length x Height x =
????? BTUs Max
Important Note: Professional Installation is required for all ventless products. Vent Free gas logs are not recommended for use in elevations over 2,000 feet. We advise that you install a high quality Carbon Monoxide Detector if you install a ventless gas log. Some cities do not allow vent free gas logs to be installed in bedrooms, bathrooms or other confined spaces, others do not allow ventless gas logs to be installed at all (California for example). Check local building codes for any restrictions or conditions regarding ventless logs before you purchase or install them. You may also view this: USA Map of Ventless Code Status.

Why must you limit the BTUs a ventless gas log burns in a room?

I'll first use a quick scientific approach, then we'll put it in layman's terms:

The scientific formula that represents the combustion of Natural Gas in its pure form which is methane:

CH4[g] + 2 O2[g] -> CO2[g] + 2 H2O[l] + 891 kJ

This formula shows that every molecule of Methane gas consumes 2 molecules of oxygen when it burns and creates 1 molecule of carbon dioxide and 2 molecules of water... while generating 891 kilajoules of energy.

Layman's terms: The natural byproduct of burning natural gas is Water Vapor and Carbon Dioxide. The beauty here is that neither of these is harmful to us. The downside is that if there is not enough oxygen in a room, it makes it difficult to breath and if there is too much water vapor, it can cause mold and mildew to grow. So, naturally, you want to make sure that you do not burn too much oxygen or create too much water vapor in any given area. Hence, the limitation on the BTUs allowed based on the cubic feet of space in a room.

Also of concern are lower levels of other byproducts that come from impurities in the gas. Also, when natural gas does not burn perfectly, carbon monoxide is produced instead of carbon dioxide. This is referred to as incomplete combustion. For the most part, ventless gas logs burn the gas almost completely, but they are not 100% perfect, which means that there are other potentially harmful byproducts that enter your home and must be controlled. That being said, it makes sense that smaller areas must use lower BTUs so that the percentage of carbon monoxide and other byproducts remains at a safe level. For example, even the small movement of air created by walking past the fireplace can cause a few molecules of Carbon Monoxide to be produced. Of course, when I say molecules, this is insignificant...but this happens often and the room is very small, it could then become significant..

The chemicals that are added to natural gas that make it smell like rotten eggs are also introduced into the room. It is typically the combustion of these additives that produce the odor which many people complain about when burning ventless logs. So, it is also important that there is enough ventilation to dilute the smell.

How does burning Ventless gas logs compare to burning Vented Gas Logs or Wood?
When you burn a wood fire or vented gas log in a wood burning fireplace, you have far more incomplete combustion of either the gas or gasses created by burning wood. This is what creates the lofty yellow flames that are taller and more alive than the flames you see on a ventless gas log. So burning wood or vented gas logs does in fact create a lot of smoke and emissions that you simply cannot have in your home, which is why you must have a chimney. Now because you have a chimney, the heat rises from the fire creating a draft that draws the smoke and other particulate matter up the flue, including the carbon dioxide and water vapor produced during the combustion process. The strong draft creates negative pressure, so fresh air literally gets sucked into your home through spaces between windows and doors, thus replenishing the oxygen without introducing water vapor or carbon dioxide.

Since vent free gas logs do not create such a draft (because the chimney is closed), the negative pressure is not created in the home and fresh air is not drawn in to replace the oxygen that has burned. For this reason, you will find that ventless gas log manufacturers recommend that you crack a window open when you are burning your logs.

I hope this helps clarify why it is so important to purchase the right gas logs for your fireplace.


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Answers to Recent Gas Logs Questions Posted To This Page
  1. Question #9272 - Posted: 1/28/2012 11:04:54 AM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/gaslogfaqs.asp

    we have direct vent gas fireplace, has on-off switch - will fireplace work when the power is out?

    Answer: We do not sell or support direct vent fireplaces. I would suggest that you Google the make and model of your fireplace to see if you can come up with an owners manual so you can learn how it operates. If you use the advanced search feature for Google you can select to search only for .pdf files, which will make it much easier to refine your search.

  2. Question #9267 - Posted: 1/12/2012 2:40:29 PM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/default.asp

    Why do gas logs smoke up a room?

    Answer: Gas logs should NOT smoke up a room, so if that is what is happening with your gas log set, then something is definitely wrong. If you are burning the logs with your damper closed, that would explain it. But I assume that you are not doing that. It is possible that something is blocking your chimney, so you may need to have a chimney sweep come take a look. Some fireplaces are poorly designed and simply do not create enough draft, so both gas logs and real wood will smoke up the house. If your house is tightly sealed, your fireplace may not be able to create a draft, in which case you will need to open a window. It could be the gas log set you own is poorly made or installed incorrectly.

    If you email me some pictures of your fireplace and gas logs, I may be able to give you more direct input. Email your pictures to: gregt@hansenwholesale.com

  3. Question #9266 - Posted: 1/8/2012 10:09:18 AM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/burners.asp

    My fireplace does not have a damper but I want vented logs in it . What will I need to do in order to have vented gas logs in it?

    Answer: You do not have to have a damper to use vented gas logs since they are supposed to be burned with the damper open anyways. But, you must have a chimney. So, when you say you do not have a damper, do you actually have a chimney that vents the fireplace to above the roof line, or is it sealed off at the top inside your fireplace where the damper should be? If you email me some pictures of your fireplace so I can see what is inside...including how it looks at the top inside the opening, I may be able to offer you more information. Email pictures to: gregt@hansenwholesale.com

  4. Question #9263 - Posted: 1/7/2012 11:13:21 AM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/default.asp

    We want to be able to leave ventless gas logs on low setting all night to supplement our heat pump when it is going to be very cold (in teens to single digits) overnight, are these made to withstand this type of use?

    Answer: Ventless gas logs are not supposed to be burned for more than 6 continuous hours per day or more than a total of 40 hours per week. The owners manual on every ventless gas log will state this quite clearly. This is a national building code standard for your safety. The reason is that they produce a lot of water vapor, which can certainly lead to the production of mold and mildew if they are over-used. They also deplete the oxygen in the air and replace it with carbon dioxide, which is not healthy. They should NEVER be operated when you are sleeping or not in the room for extended periods of time.

  5. Question #9262 - Posted: 1/4/2012 10:32:34 PM

    Gas Logs Question - R.H. Peterson Model PL-CHFRG10-30-15P

    View  model PL-CHFRG10-30-15P
    PL-CHFRG10-30-15P - http://www.hansenwholesale.com/gas-logs/model.asp?SetModel=PL-CHFRG10-30-15P

    I have a G10-30-15P unit. Can I have the 15P control replaced by the 01VP control? If so, what is the cost?

    Answer: You cannot just replace the control and value, you must replace the entire burner system. This is part of the safety regulations for ventless products. There is no allowance for field conversions of ventless gas logs.

  6. Question #9261 - Posted: 12/31/2011 12:41:59 PM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/remote-gas-logs.asp

    I have gas logs in my original fireplace. I want to increase the heat output and want a remote control. What are my options? Thanks, Elizabeth

    Answer: Very little can be done to increase the heat output of an existing gas log, so you are most likely going to have to replace it with one designed for heat. Since you apparently are not getting much heat from your gas logs right now I assume you have a vented gas log set that must be burned with the damper open, so the heat goes up the chimney. If you really want heat, you need to replace the entire burner and log setup with a new Ventless gas log that can be burned with the damper closed. Ventless gas logs are not for everybody because they produce an odor that some people just do not like. My suggestion would be to read this article: Vented -vs- Ventless Gas Logs. I would also suggest that you email me some pictures of your fireplace and gas logs so I can see what you have as well as what could potentially be installed. Email pictures to: gregt@hansenwholesale.com and include your fireplace measurements (front width, front height, depth, rear width).

  7. Question #9260 - Posted: 12/31/2011 12:35:35 PM

    Gas Logs Question

    http://www.hansenwholesale.com/recommendations.asp

    Hello, I need 30" fireplace logs but want some with a great flame. I have logs but flame is very small,what set do you recommend that looks like a blazing fire?

    Answer: Without knowing how much flame you are getting right now it is difficult to compare to what you might expect to get from the best logs on the market today. Can you possibly take some pictures of your gas logs both on and off so I can see what we are up against?

    I will say that often times people buy logs that are simply too large for the fireplace. The larger the log set, the lower the flame is...which is just the nature of the beast. The reason being that there are building code restrictions on the amount of gas a burner can use, so the wider the burner is, the less height the flame can be. You might find that switching to a 24" gas log will produce the flame you desire without compromising the appearance in your fireplace. There are some 24" sets that are rather massive and may look better proportioned in your fireplace than the 30" set you have.

    So if you can email me some pictures, I will be able to give you more pertinent advice. I would also like the following measurements of your fireplace:

    Front Opening Width:
    Front Opening Height:
    Back Width:
    Depth front to back:

    Email pictures and info to: gregt@hansenwholesale.com

  8. Question #9259 - Posted: 12/31/2011 10:08:31 AM

    Gas Logs Question - R.H. Peterson Model PL-CHDG4-24

    View  model PL-CHDG4-24
    PL-CHDG4-24 - http://www.hansenwholesale.com/gas-logs/model.asp?SetModel=PL-CHDG4-24

    Hi, We moved to a house in the ATL area w/Marco model 7928626 (solid wood fuel only). Dimensions are 30" Front X 15" Depth X 25" Rear width. Gas logs were already installed. We get major soot when lighting so we called out a local sweep. The sweep cleaned/inspected the chimney and quoted new charred oak logs for $821 (not sure if incl burner). Reading your site it looks like our soot problem may be related to having a gas starter which he never mentioned. What kind of setup can we get?

    Answer: Can you email me some pictures of your fireplace? Show me the entire fireplace as well as some shots of what you have inside. I'm sure I will be able to give you a second opinion as well as save you some money on the log set. Email pictures to: gregt@hansenwholesale.com

  9. Question #9257 - Posted: 12/31/2011 9:59:53 AM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/why-ventless-gaslogs-smell.asp

    My Peterson gas logs are about 4 yrs old. The remote worked fine for two years but now does not. What could the problem be? Could it be the battery and can that be replaced?

    Answer: It is most likely the batteries. There is a battery in both the transmitter and the receiver. You should be able to find the battery easily. Replace both batteries, and if it does not solve your problem then email me directly and I'll help you get in touch with someone who can troubleshoot your burner.

  10. Question #9254 - Posted: 12/31/2011 9:29:27 AM

    Gas Logs Question

    http://www.hansenwholesale.com/gas-logs/how-safety-pilot-works.asp

    I have a gas fireplace with on pilot valve is this legle in California or should I install a pilot failsafe valve?

    Answer: Can you please restate your question...it does not make sense to me. Also, can you email me a picture of your fireplace and gas logs? That might help explain what you are trying to ask. Email pictures to: gregt@hansenwholesale.com

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