Many options to consider for new heating system

  • This variable-speed WaterFurnace geothermal heat pump in James Dulley's home uses a horizontal ground loop.

    This variable-speed WaterFurnace geothermal heat pump in James Dulley's home uses a horizontal ground loop. Courtesy of James Dulley

 
 
Posted12/5/2020 7:00 AM

Q: My old furnace and air conditioning system needs major repairs. What are my options and what factors should I consider when selecting one?

A: Many factors are specific to your house, such as floor plan layout, number of floors, orientation to the sun/shade, wind conditions, etc. Others are personal such as individual room temperature control, noise level or speed to reheat after thermostat setback. Make sure to discuss these with your HVAC (heating, ventilation and air conditioning) contractor.

 

You have many fuel options for the heating portion of your new system -- electricity, oil, propane, gas, firewood, corn, wood pellets and coal. Although there are some larger gas absorption cooling systems available, typically your only option for cooling is electric-powered central air conditioning or a heat pump.

Initial installation and operating costs are usually the primary factors in selecting a new system. Often spending more initially can result is a substantial payback with lower operating costs over the life of the new system. Keep in mind, various fuel prices can vary significantly over time, so payback estimates are a guess at best.

Efficiency is the other factor in determining operating costs. Most new HVAC systems are operating at extremely high efficiencies now, so I would not expect any major design innovations to significantly increase future efficiencies. Repairing your old system in order to wait for new designs is not a wise decision.

A geothermal heat pump is still the most efficient year-round system because it heats and cools using stored energy from the ground. I installed a four-ton WaterFurnace model with a backup electric furnace in my own home four years ago.

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Select a variable-speed model for the best comfort and lowest operating costs. When coupled with a smart thermostat, the system continuously matches heating and cooling output to the instantaneous house needs. This means the compressor and blower fan run in longer cycles or almost continuously at very low speeds for extremely quiet operation and steady room temperatures.

The initial cost of a geothermal system is substantially more than other complete systems, but the utility bill savings easily pays back its higher cost. The federal energy tax credit is 26% in 2020 and drops to 22% in 2021. Also, check for some state or utility company credits.

If you plan to install a fossil fuel (gas, oil, propane) furnace for heating, install a matching heat pump with it instead of just a central air conditioner. Some manufacturers refer to this as a hybrid system. A heat pump is basically a central air conditioner with a reversing valve and other controls for heating. It costs only several hundred dollars more.

Because it draws heat from the outdoor air, a heat pump heats efficiently during mild spring and fall weather. It runs instead of the furnace burners to heat the house at a lower cost. When it gets colder outdoors, the furnace burners take over. A heat pump cools as efficiently as a central air conditioner during summer.

                                                                                                                                                                                                                       
 

If natural gas is available in your area, a condensing furnace generally is the most cost effective fossil fuel choice. With the glut of domestic natural gas from fracking, there should be an adequate supply at reasonable prices for the foreseeable future. Efficiencies are as high as 97% with sealed combustion.

because natural gas is not available in many rural areas, a propane or oil furnace provides equally comfortable heating. A propane furnace is almost identical to a gas one, but propane is typically more expensive to use and can be in short supply at times. Oil is readily available, but oil furnace efficiency is not as high, and it requires a more extensive maintenance schedule and cost.

Also consider alternative fuels such as firewood, corn, wood pellets, etc., for primary or supplemental heating. Newer models are convenient to use and the fuel is renewable to reduce your carbon footprint. For example, new dual-fuel wood furnaces automatically switch to gas or propane when the wood burns out over night.

To compare operating costs of various fuels, use the following heat contents and your local fuel costs: natural gas, 1,025 Btu/cubic foot; oil, 138,700 Btu/gallon; propane, 91,000 Btu/gallon; electricity, 3,414 Btu/kilowatt-hour; firewood, 22 million Btu/cord; and corn, 448,000 Btu/bushel. Divide your local cost per Btu by the various system efficiencies to compare operating costs.

Q: When I build an addition on to my home, I plan to use rigid foam insulated sheathing on the outside. Will it harm the efficiency to use more nails and fasteners for a stronger wall?

A: Adding more nails and metal fasteners than recommended by the manufacturer does not produce a better wall. Foam sheathing does really add much strength to a wall.

In fact, using more nails decreases the effectiveness of the rigid foam insulation. Steel nails are a great conduction of heat. Tests show that using just the recommended number of nails and fasteners (on 8-inch centers) reduces the insulation value by 20%.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit dulley.com.

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