Choosing the right outdoor furnace is key to saving money and keeping fuel consumption down. Here’s how you pick the right size for your home and shop.
Important Factors When It Comes to Picking a Furnace
Boiler furnace capacity is measured in BTUs, which stands for British thermal units. One BTU is the amount of energy needed to increase the temperature of one pound of water by one degree Fahrenheit. Every home and building has a unique requirement. For instance a greenhouse that is all glass is going to have a different BTU requirement than a well insulated home of the same size. Let’s break down some things to consider when choosing an outdoor furnace.
Square Footage of the Building You Want to Heat
Square footage alone is not enough to determine the size of your outdoor boiler but it is a practical place to start. A typical rule-of-thumb for BTU calculations is that in cold areas, you will need about 30 to 40 BTUs for every square foot of space, while moderate climates will need about 20 to 30 BTUs and warm areas will only need about 10 to 15 BTUs. For example, a 2,000 square foot house in a moderate climate would need an outdoor boiler that can produce about 40,000 to 50,000 BTUs.
How Well Insulated Your Home or Building Is
Heat moves towards cooler areas, with hot particles bumping into cold particles and transferring some of their heat until the whole room is the same temperature. Insulation works to stop heat transfer to cold areas. By acting as a barrier, insulation prevents heat loss to the outside of your home.
How well your home or building is insulated is a key factor in how many BTUs you will need from your outdoor boiler to keep the ideal temperature. Obviously, well insulated buildings are going to need less BTUs and fuel to stay warm. Poorly insulated homes allow heat loss and cause higher fuel consumption. Windows and doors are also factors in this. If you have lots of windows, then you will likely lose more heat and will need more BTUs to maintain your ideal temperature.
Determining the Average Temperature You Want to Maintain
As hinted at above, geographical location and weather is another key factor to consider. This is important because you will need to know how to keep your home or outbuilding the ideal temperature. Consider the worst case scenario of temperature swing. If the coldest temperature of the year is 15 degrees and your ideal temperature is 72 degrees that is a 57 degree difference!
Other Household Appliances to Consider
When making your boiler size calculations, consider if you have other outbuildings, pools, hot tubs or garages to heat. For other buildings, the same factors of square footage and insulation apply. Using an outdoor furnace to heat your pool or hot tub is a great option. If you are planning to hook up a pool or hot tub to your outdoor boiler, consider the size and what temperature you want the water to be at for your family to enjoy.
Building Heat Loss Calculations
For a more exact heat loss calculation, you need to know some basic information about your building and climate conditions. Here is what you need to know about your building:
- R-values of walls, ceiling, floor, windows, and doors.
- Area of the above items in square feet.
- Quality of construction (How drafty is the building?)
Here is what you need to know about your local climate:
- The outdoor “design” temperature for the building location. This number can usually be found by obtaining local weather data for your area.
- Determine ground temperature. Ground temperature is fairly constant in most areas at about 45 F but water table levels and soil types can change the floor heat loss dramatically.
Infiltration or building air leaks will also determine how many BTUs are needed to keep your barn or outbuilding at the desired temperature. A well-insulated building, for example, would have a vapor barrier in the walls and good seals on the doors and windows. A building like that may exchange about half of its air volume every hour. In a poorly insulated building that number can easily double or triple.
In the end, you would come up with a total heat loss as the sum of all the totals. For example, adding up all of the heat loss calculations below, you would find a shop building that is 40’ x 60’ with an 18’ high ceiling, heat loss would equal 62,009 BTU/hour. See below:
- Walls – 13,166 BTUs
- Windows – 2,916 BTUs
- Doors – 2,244 BTUs
- Ceiling – 4,860 BTUs
- Floor – 7,680 BTUs
- Infiltration – 31,143 BTUs
In this case, a HeatMasterss G4000 furnace, which puts out approximately 68,000 BTU per hour would be a great fit.
Other Variables to Consider
This calculation changes dramatically based on how the area is heated. A building that is heated from the floor would keep the air temperature at the ceiling very close to the air temperature at the floor. If the building is heated with a radiator and fan unit heater the figures would change considerably because heat from the floor has less heat loss than heating from the walls, ceiling, and overhead.
For example, if the thermostat was set for 65 F in a livestock barn that has fan heat, the ceiling temperature could actually be anywhere from 75 to 85 F. Combined with the added heat loss from the air turbulence created by fans can increase the overall building heat loss by 30% – 70% over the same building with radiant floor heat.
HeatMasterss Outdoor Furnaces
HeatMasterss has a variety of outdoor furnace solutions for residential and commercial applications. Our C, G, and B Series work with almost any heating system and are the standard for quality.
HeatMasterss C Series is an outdoor coal furnace that is compact but will heat anywhere from 3,000 to 20,000 square feet. As a coal burning outdoor boiler, it comes with convenient features that makes heating your home simple.
Our wood burning HeatMasterss G Series is easy to operate and gives maximum comfort for buildings 4,000 square feet to 10,000 square feet. Built to last, our G Series has a larger firebox for burn rates up to 24 hours, an ultra efficient heat exchanger and EZ clean handle for quick cleaning.
The HeatMasterss Multi-Fuel Biomass B Series is excellent for large spaces and commercial applications. With a highly efficient design, our B Series put out anywhere from 200,000 BTUs per hour to 1,000,000 BTUs per hour. You can use wood chips, wood pellets, coal and more, giving you fuel flexibility and freedom from fluctuating fossil fuel prices.
Heat Your Home With HeatMasterss Today
HeatMasterss furnaces are made with titanium stainless steel that resists corrosion, can withstand higher continuous temperature and transfers more heat to save you fuel. By combining the best materials with expert engineering, HeatMasterss has created the most rugged and longest-lasting furnaces available.
We are committed to creating products that offer our customers long term energy independence with a rapid return on investment. All of our outdoor furnaces come with automated features that keep every step of the process efficient, safe, and easy. Talk with our team about finding the right size for your home or applications — find a local HeatMasterss dealer near you today.
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