Boiler Buying Guide
All About That Boiler in the Basement

One of the most common home heating systems is a boiler, and that’s especially true for older houses in the Northeast and other cold-climate areas. Boilers heat water, and then distribute hot steam or hot water to rooms through a series of pipes to heat the home. Steam is sent to radiators, while hot water flows to radiators or radiant heating systems. Boilers are fueled by natural gas, heating oil, propane, electricity or a biodiesel-oil blend. New systems are very energy efficient, with efficiencies as high as 98.5 percent.

1

What Type of Boiler do You Have?

Boilers are called central heating systems because the equipment is in a central location, and the heat is spread throughout the home. However, unlike other heating methods, there is typically a lag time between the boiler turning on and the heat being dispersed.

Most boilers produce steam or hot water using natural gas or heating oil, and all are either condensing or non-condensing (see below). Boilers are required by the federal government to be at least 80 percent efficient, and can have efficiencies as high as 98.5 percent. Some boilers can be expensive to install, but all types typically last 15 to 30 years.

Illustration of a gas-fired boiler.

Gas-Fired Boilers

Gas-fired boilers are fueled by either natural gas or propane, and are highly efficient. However, natural gas is not available everywhere, and some homeowners at the end of a gas pipeline pay higher fuel prices. Propane typically is more expensive than natural gas, but it’s available throughout the U.S.

Illustration of an oil-fired boiler.

Oil-Fired Boilers

Oil-fired boilers are common in areas that have limited access to natural gas. If you buy a oil-fired boiler, you’ll need heating oil delivered and stored in tanks like the one above, and your operating costs will be affected by the rise and fall of oil prices.

Some boiler manufacturers now offer models that use biodiesel fuel, which produces less pollution than regular heating oil. Depending on oil prices, biodiesel heating oil can be cost-competitive with standard oil. However, because it burns cleaner and lubricates the system, biodiesel fuel can reduce your boiler service and cleaning costs.

Illustration of an electric boiler.

Electric Boilers

Electric boilers are highly energy efficient. However, they typically are not economical because electricity costs more than other fuel types in many parts of the country. If you are interested in electric heating, consider a heat pump.  

2

How the Heat Is Distributed

    

Illustration of a steam radiator.

Steam Radiators

Steam heating is one of the oldest heating technologies, and upright metal steam radiators positioned along walls in older homes are common. They can provide consistent, comfortable heat.

Steam radiators need some simple maintenance to work properly and efficiently. In addition, a radiator can warp or create a groove in the floor. If that happens, the radiator may tilt, causing it to make loud banging noises. Plus, steam radiators on exterior walls can radiate some heat to the outdoors, and limit your ability to position furniture around the room.

Illustration of a hot water radiator.

Hot Water Radiators

More common in newer homes, hot water radiators run along a room’s baseboard or stand upright like a steam radiator. Hot water radiators can reduce your home’s energy consumption because they allow you to control the temperature of each floor or a large space. A heating professional can install automatic valves on the radiators, and connect them to separate thermostats.

The most common problem with hot water radiators is unwanted air in the system. Plus, like steam models, upright hot water radiators can limit your ability to position furniture.

Illustration of hydronic radiant floor heating.

Hydronic Radiant Floor Heating

Hydronic (water) systems are the most common radiant floor heating systems. A boiler heats water and flows it to tubing under the flooring, which acts as a giant radiator. Hydronic systems can heat a whole house, but they’re mainly used to heat a single room or area, and some can be zoned so thermostats regulate each space.

Hydronic radiant heating is more efficient than baseboard heating and usually more efficient than forced-air heating, too. It also doesn’t distribute allergens like forced-air systems can, and uses little electricity. However, hydronic systems can be expensive to install and to repair, and may not be as efficient if the floor is covered with thick carpeting.

3

Key Boiler Features

Condensing vs. Non-Condensing
All boilers are either condensing or non-condensing. A condensing boiler concentrates water vapor produced in the heating process, and uses waste heat to preheat cold water entering the boiler. Condensing boilers are extremely energy efficient because they can provide ample heat while operating at lower temperatures.

Non-condensing boilers typically operate at higher temperatures, and some heat ends up being vented outside. Non-condensing boilers are 80 percent to 88 percent efficient, while condensing boilers have efficiencies greater than 88 percent.

Sealed Combustion vs. Non-Sealed Combustion
Boilers are either sealed-combustion or non-sealed combustion units. You should buy one that is sealed combustion because it brings outside air into the burner and directs exhaust gases outside. Non-sealed combustion boilers draw heated air in and then send it up the chimney, wasting the energy used to heat the air. Also, sealed-combustion boilers won’t introduce dangerous gases into your home.

4

What to Consider Before You Buy

Climate
If you live you in a cold climate, a boiler may be a good choice for your home. But if you live in a warm climate, you may not need a central heating system. In that case, consider a heat pump, which can satisfy your air conditioning needs as well as moderate heating requirements.

Fuel Type
Gas-fueled boilers may cost less to operate than oil-fueled ones if heating oil prices are high. However, the fuel type you choose will depend on what’s available in your area.

Sizing
The boiler’s size is as important as its efficiency. If the boiler is undersized, it won’t work efficiently; if it is oversized, it will cost you more to heat your home. Work with a heating and cooling professional, who should use an Air Conditioning Contractors of America (ACCA) Manual J calculation to determine the right boiler type and size. The calculation will take into consideration your home’s foundation, wall thicknesses, insulation values, windows, air filtration and more.

Cooling
Boilers only provide heat; so you’ll need a cooling system, too, if you want to air condition your home.

5

Energy Efficiency

Boilers are rated with an annual fuel-utilization-efficiency (AFUE) score, which tells you how much energy is being converted into useable heat. New boilers must have an AFUE rating of at last 80 percent, and high-efficiency models are 90 to 98.5 percent efficient. The higher the rating, the higher the equipment cost, but the lower the operating cost.

For example, say your current boiler’s AFUE score is 65 percent and you pay $1,300 a year for fuel bills. If you install a high-efficiency natural gas system with an AFUE of 90 percent, your total yearly savings should be about $364.

Illustration showing the efficiency of combustion heating appliances (furnaces and boilers).
6

Boosting Your Boiler’s Efficiency

Don’t buy a new boiler until you make the rest of your home as energy efficient as possible, because reducing your home’s heating load will allow you to buy a smaller, less expensive system. If needed, you should:
• Add insulation to your attic and walls.
• Add weather stripping around doors and caulk around windows to keep heat from escaping.
• Properly insulate cooling system ducts in crawl spaces and attics.
• Clean your chimney.
• Set your ceiling fans to spin clockwise to blow rising heat down.
• Install and set programmable thermostats to automatically lower the temperature at night and while you are away. Programmable thermostats can save you 10 percent annually on your heating bills.

7

How to Maintain Your System

Boilers should be serviced annually by a heating professional to ensure efficient heating. The technician should:

Hot Water Boilers
• Test the pressure-relief valve and high-limit control.
• Inspect the pressure tank.
• Clean the heat exchanger.

Steam Boilers
• Drain some water to remove sediments.
• Check the safety controls.
• Analyze the water and add chemicals if needed.
• Clean the heat exchanger.

Both Systems
• Check the vent connection pipe and chimney to see if they are deteriorating.
• Check the heat exchangers and pipes to see if they are leaking.
• Adjust the water and air temperature settings for optimum efficiency and comfort.

Upright and Baseboard Radiators
• Make sure radiators are not obstructed by furniture, carpeting, rugs, and drapes.
• Be sure to release trapped air from hot water radiators at the beginning of the heating season and possibly one more time during the heating season. If you are unsure how to perform this task, contact a heating professional.
• Place shims under the radiators so they are pitched slightly toward the pipe in a one-pipe system or toward the steam trap in a two-pipe system.
• Place heat-resistant reflectors between radiators and exterior walls to keep heat from escaping.

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