Direct vented space heaters and room furnaces by Rinnai = save money on your heating bills and keep your loved ones warmer!

Direct vented room furnaces: What the HVAC contractors and forced air furnace companies don't want you to know about! Compare January to March energy usage.

In January, we solely used the central furnace, March was only the Rinnai Energy Saver. After installing Energy Saver furnace, setting the house temperature higher! (70F instead 65F), with an average outside temperature that was 2 degrees lower, gas usage went down by 28 therms ($42 dollars)! Furthermore, electricity usage was down by 81 KW/H ($12) most likely due to the furnace blower not running.

Forget the 96% AFUE furnace, the most efficient way to heat your house could be with space heaters. Not what you think of when you think of a space heater, power hogging light dimming electric space heater. These are gas, heating oil or kerosene fired direct vented room furnaces with 84%+ efficiency. Direct vented means two things:
  1. The exhaust will go directly out of a hole in the wall, meaning no chimney is required and no potential of harmful carbon monoxide (CO) gasses entering your home (combustion chamber is actually entirely sealed from the living area). Without a chimney, you can please these on any outside facing wall. In addition, there are window kits, and extension kits giving you just many placement options.
  2. Cold air for combustion will also come through the same hole in the wall, meaning that the furnace will not be "sucking" air through the cracks in your walls and windows to get oxygen to burn. Most people do not think about it but your monster 100,000+ BTU furnace needs oxygen to burn. Most furnaces do not have an "intake" to allow cold air to come in from the outside, so the furnacs will "suck" air in through any cracks it can find. This usually means cold air coming in through cracks around your window.
How is 84% more efficient than 96%?

Central forced air heating systems are by design full of loss and inefficiency. In a perfect world you have a 96% AFUE furnace (but you probably don't...) and in a perfect world, you are still looking at 15% duct losses.

Somebody asked me "If the heat is lost, where does it go?". They go wherever the ducts run. So if that is unconditioned space, it's for all intents and purposes completely lost. These losses come from heat either leaking out or being dissipated from the furnace to the point where the air is conditioning a room. In a real world, if you deliver heat from point A to B, the temperature is going to drop to some extent. If your ducts are running through conditioned space, then you are better off, of course because you are only losing heat to space that you want to be conditioned anyway.

And if you have not looked very carefully at every single supply and return duct then these losses could be 2x that (if you plan on keeping forced air, I would highly suggest having the system pressure tested which will identify leaks). So assuming the perfect forced air scenario, you've got a 96% AFUE efficient furnace and 15% duct losses. That means that only 81.6% of heat from burning natural gas, propane or heating oil conditions your living area. With the direct vented room furnaces, a minimum of 84% of gas or oil is turned into actual space heat. The oil fired heaters are more efficient, but oil here costs more.

Gas around these parts is around $1.45 per 100,000 BTUs delivered. This is a very reasonable price per therm of natural gas. If you think about it, a gallon of heating is maybe 140000 BTU and costs $3.30/gallon. We are paying $1.45 for 100000 BTU. Equiv. price for 100000 BTU with oil is $2.35. So here, gas is the answer. But in other parts of the country heating oil or even kero might be the answer.

So if you compare the Rinnai (brand of best direct vented natural gas or propane heater, also very well known for their tankless water heaters) to the perfect world of forced hot air, the Rinnai is 2.4% more efficient. But most people do not have 96% furnaces, or 15% duct losses.

Rinnai direct vented heaters are 84% out of the box and are easy to install (If I did it, then you definitely can!) and basically maintenance free. Now the fun part, with space heat, you can only heat the areas where you are. When you go to bed, only heat the bedrooms. This way you are not paying to heat the kitchen, living room, etc. all night while you sleep. The Rinnais are so powerful and efficient that you will not wait long at all for the room temperature to come up. I close my office door at night to save energy and it gets down into the 50s at night. In the morning I turn on the Rinnai and it is up to 70 within minutes. Furthermore, you can program them very easily so it's already warm when you get up to make your morning coffee.

Another wonderful aspect of the Rinnai heaters is that they are seven stage. What on earth does this mean? Most furnaces are single stage. It means they are either on or off. 100k BTU or nothing. The Rinnais have 7 different levels of power so they can regulate heat comfortably and efficiently. On a very cold day, the Rinnai may stay on indefinitely, but will regulate the heat so that it maintains a consistent temperature.

The importance of picking the CORRECTLY SIZED heater

It is very important that you pick the right sized heater. If you pick a heater that is too small, the heater will run on full power all the time, causing metal fatigue and shortening the life of your heater. If you get one that is too big, it will short cycle from being in an area too small. Sizing chart coming soon...

Why have I never heard of these heaters?

If you live in areas like Canada, Maine and Alaska, you have heard of these heaters and probably rely on them. Those of us in slightly more moderate climates have been brainwashed into thinking forced heat, steam, hot water and baseboard heat are the only and best choices with which to heat our homes. You can imagine why HVAC contractors would not want to promote something so reliable and efficient and easy to install... because you won't need them ever again!

The importance of heater placement

It is very important that you not just stick the heater in some unused corner and think it is going to heat your entire house. The fewer heaters you have, the more this comes into importance. If you purchase a single large heater and expect it to comfortably heat your entire house, consider placing it in the space where you spend the most time, and wish to be the most comfortable. For us, this would be our family room. As you go further away, the heat will indeed lessen. There is no magic that is going to make the entire house the same temperature with a single heater.

In our bedroom when we sleep, we prefer temperatures in the very low 60s, wherever while relaxing, we enjoy in the upper 60s. The heater placed in the living room makes perfect sense for this arrangement because the bedrooms are further away from the living room.

Another scenario would be a medium sized heater inthe living room and the smallest model heater in each bedroom. This way you could shut off the heater at night and each individual would be able to set the bedroom heat to their own comfort level. Obviously, everything is going to depend on your scenario, your lifestyle and your home. Please feel free to ask me for advice on heater placement and sizing.

Don't forget the bathroom! Most people's bathrooms are probably too small to fit a heater, but there is nothing comfortable about getting out of a shower to a freezing bathroom (or waking up to a cold toilet seat!!!). If you can't fit a Rinnai into your bathroom and really enjoy a warm bathroom, consider other options such as a radiant floor or small space heater for the bathroom. Even if you have to use electric heat in the bathroom, the efficiency of the direct vented heater will most likely make up for the high cost of electric heat. Another great option to consider is a heated toilet seat. No, I am not joking! Kohler makes wonderful heated toilet seats. They use only an average of 15 watts, and keep the toilet seat heated to 25 degrees warmer than the ambient bathroom temperature. Not cheap, but you get what you pay for with Kohler.


I would be lying if I said these heaters had no disadvantages. I have one and therefore I know how it works. You need to take everything into consideration when deciding if it's right for you or not.
  1. First of all, they are not the prettiest things in the world. This is a personal thing of course. They are modern and sleek, but they are no work of art, unless you're referring to their burn technology! If you really love the idea of direct vented heaters but hate the look of these heaters, consider a gas, pellet or wood stove. More information about these items to come. In the meantime, check out
  2. They do take up floor space. Anywhere from 16" to 36" wide. We feel that you can usually find a good ununsed nook to place the heater. Again they only require 2" of clearance on either side.
  3. These heaters somewhat rely on an "open" floor plan. If your house is full of hallways, turns, walls and doorways, you may need to consider multiple heaters. But you could realistically purchase three Rinnai heaters for less than the cost of a single 96% AFUE gas powered furnace, and the Rinnai's will give you true zoning power.
  4. Most importantly, these furnaces simply may not be "right" for your living style, home layout, fuel availability, etc. They are not right for everyone...

Rinnai 556WTA is 21,500 BTU and is easily programmable, has a built in humidifier and has a child safety lock. Very low clearances to combustibles. Yellow wire is thermostat probe and can be hidden.

3" intake and exhaust. All you need to install the Rinnai is a 1/2" gas line (natural or propane) 3" hole saw, drill and screwdriver. The combined intake/exhaust pulls cold air in from outside for combustion instead of sucking it through the cracks in your windows. Yes furnaces need oxygen to burn, and if you don't give them a path to intake that oxygen, they will find a way!!! Direct vents can be installed almost anywhere on an outside wall. In this picture, we are running just 9" underneath a window. This is completely legit and passes code.

If all of this is not a consideration, check out this surprisingly valuable (surprising because it comes from a .gov) spreadsheet about how to insulate and seal your central HVAC system. Unless you did it yourself, I would not trust that your central HVAC system was installed properly.

All Rinnai heaters come in both natural gas and propane versions. Do not hestitate to contact me if you have questions about sizing or anything, please feel free to leave a comment! For oil fired heaters, look for Toyotomi brand.

If you need help running a gas line, see here for more information on that.