These days, energy-efficiency is the name of the game when it comes to home building. Today's high-efficiency homes utilize a wide variety of building techniques and materials to create an energy-efficient, cost-effective and ultimately sustainable environment for homeowners. So how do gas-fired furnaces figure in this picture? As it turns out, using a traditional gas furnace in a high-efficiency home could offer more drawbacks than you'd think.
A Big Fish in a Small Pond
Tighter building envelopes and increasing use of insulation have helped reduce energy losses in the modern home. In turn, this reduces the amount of heating capacity that's required to keep it comfortably warm. But while modern homes require less energy to stay warm, the heating capacity of the average gas furnace has pretty much remained the same. According to HVAC expert David Butler, it's not uncommon to see furnaces that are oversized by 400 percent or more.
For homes built with high-efficiency in mind, the vast majority of gas furnaces are vastly oversized for the task at hand. A typical 15-minute run cycle that would adequately heat an ordinary home could cause temperatures to overshoot your desired set point in a high-efficiency home, creating noticeable comfort issues for you and other occupants. Butler notes that nearly all gas furnaces feature electronic controls that enforce similar minimum run times, making temperature overshoot inescapable, in many instances.
Even furnaces that offer multi-stage variable-speed controls are not enough to mitigate overcapacity issues. Multi-stage heating can help mitigate some of the undesirable effects, but the units themselves can cost significantly more than an ordinary gas furnace.
Heat Pumps and Hydronics May Offer a Better Solution
In short, the main problem with a gas furnace in a high-efficiency home is that its heating capacity far exceeds what's actually needed. Heat pumps and hydronic forced air systems offer a more reasonable heating capacity that's more in line with what your high-efficiency home actually needs.
Heat pumps are ideal for homes located in warm climates with reasonable electric rates. In most cases, heat pumps can prove more economical to operate than a typical gas furnace. But what makes a heat pump truly stand out is its lower heating capacity. While this would normally be a drawback, this particular aspect actually results in increased comfort in a well-insulated home.
In colder climates, you can combine your heat pump with a natural gas-fired hydronic coil as a reliable form of supplemental heat. A hydronic system takes some of the hot water generated by your hot water heater and passes it through a coil located within an air handler. The blower passes air over the coil, heating the air that passes over it and eventually enters your living spaces.
If high electricity rates are a concern, it may be possible to rely solely on hydronics as a primary source of heat. However, that depends on a broad range of factors, including average outdoor temperatures, the quality and amount of insulation in your home and your access to natural gas.
Are There Other Options Available?
If access to natural gas poses an issue, there are a number of other alternatives to explore:
- Propane offers a compelling alternative for powering hydronic forced air systems, but the costs are often on par with electric heating.
- Fuel oil is highly available in most Northeastern locales, but average costs can also be more volatile than natural gas or electricity.
- Geothermal heating via ground source heat pump is a viable option, but it requires a significant upfront investment.
- Electric resistance heating is exceptionally convenient and requires no preexisting gas or oil infrastructure, but it could also prove expensive to use in areas with high electric rates.
These alternatives still provide a compelling advantage over traditional gas furnaces in high-performance homes. Not only will you enjoy better comfort, but you'll also be able to enjoy energy and operating cost savings as well
For more information, contact a company like Allied Air Conditioning & Heating Corp.