Modern Wood Heat vs. Cold Climate Heat Pumps, Which is Better?

Home heating updates should always start with energy conservation. Energy audits are excellent for learning how to reduce energy needs. Insulation and air sealing can yield large benefits for comparatively low costs. Simple practices like turning thermostats down or using programmable thermostats can also have a sizeable impact on fuel use and carbon dioxide emissions.

Three Easy Steps to Start Weatherizing Your Home

Still, a heat source will be required unless a home requires zero net energy, like passive houses. Furnaces and boilers generally last about 20 years, which means for many of us, a heating system swap is around the corner. End-of-life for outdated technology also presents a perfect opportunity to stop using fossil fuels.

Modern wood heat and cold climate heat pumps provide the ability to eliminate fossil fuels while staying toasty with all of the convenience of gas, oil, and electric resistance heat. What technology should be considered when it is time to replace the furnace or boiler? This article will address comfort, convenience, cost, and carbon + environmental factors for each option.

Wood Pellet Boilers and Furnaces aka. Modern Wood Heat

Comfort
Modern wood heat provides exactly the same heating comfort as fossil fuel heating systems, responding to conventional thermostats automatically. The quality of the heat is unchanged from fossil fuel heat.

Further easing the transition to renewable heating, existing ductwork, radiators, in-floor tubing, and domestic water are heated no differently than while using fossil fuel furnaces and boilers. Unfortunately for some homeowners with antiquated heating systems, there are currently no residential wood pellet boilers that produce steam.

There is another type of comfort that modern wood heating provides, which is knowing that fuel purchases support the local economy and retain wealth in our communities. Using wood pellet fuel helps provide markets for waste wood. Using waste wood helps economically upstream by creating higher value for wood and therefore forests. That in turn provides more reasons for forests to stay forested rather than being sold for development. In New England, where we are losing 65 acres of forest per day to development; providing tangible, market-based incentives to retain our forestland is important.

Convenience

Modern wood heat takes advantage of the consistency of shape, size, and hardness of pellets to provide conveniences that are difficult to impossible with other wood fuels. Wood pellet boilers and furnaces respond to room thermostats and make hot water all while filling, igniting, and de-ashing automatically. Fuel is delivered through hoses from delivery trucks directly into a holding bin. Homeowner involvement is only required to order more fuel and to remove the ash box about once every 6 weeks depending upon fuel consumption. Internet connectivity is standard with push notifications indicating when it is time to take ash out and to notify if there are any problems. Modern wood heat becomes practically forgettable.

Cost
Wood pellet fuel is typically substantially less expensive than oil, gas, and electric heat. On average, wood pellets cost 30%-50% less than fossil fuels. Fuel savings add up quickly and typically more than pay for higher up-front costs of modern wood heat. The more oil and gas consumption that is replaced with wood pellets, the greater the savings can be. While modern wood heat generally has higher maintenance costs than oil and gas, those costs are almost always offset by fuel savings over time. State rebates, tax holidays, and other incentives can offset large portions of installation costs. As this is being written, there is also a federal tax credit of 26% available for new installations of residential modern wood heat.

Carbon + Environment

Wood pellet fuel is part of our terrestrial carbon cycle. While trees grow, they absorb carbon from the atmosphere. After harvest, some trees become lumber, which when turned into long-term products such as homes and furniture, lock carbon away for a long time. Other forest products like bark mulch, sawdust, and paper may have shorter life spans and typically release carbon back to the environment quicker. Wood that has no higher use is often used for energy, such as wood pellets. When wood pellets are used for heating, about 80% of the available energy becomes heat. Almost all of the carbon in the wood is released into the air as carbon dioxide during combustion. As long as forests are not losing more wood or are gaining wood as wood pellets are used, the carbon cycle remains virtually neutral. In many regions, particularly in Northeastern United States forests, this neutral carbon cycle has been in place for decades. The biggest threat to the neutral carbon cycle today is not using wood for heating, but rather human-caused development and other complete losses of forests due to invasive species and climate change.

When wood pellets are burned, other gases and particulates (aerosol-sized particles) are emitted. While no exhaust is benign, due to advanced controls used in modern wood heaters, particulates are low in toxicity compared to fossil fuels and old-fashioned wood burning. Due to their cleanliness, modern wood heat can also be considered an excellent choice for replacing older cord wood boilers, furnaces, and stoves that were made prior to the EPA approval process.

Often unheralded, the benefits of using non-toxic, natural wood are real and beneficial. Harvesting fuel from the communities we live in, transporting, processing, and storing wood fuel is far safer than with fossil fuels.

The Role of Forest Biomass in Addressing Climate Change - Webinar Presented by Dr. Robert Malmsheimer

Cold Climate Air Source Heat Pumps

Comfort

Cold climate air source heat pumps can replace existing fossil fuel furnaces, boiler, and electric heat pumps with some limitations. Using electricity, ASHP captures and concentrates heat in the air (even very cold air) by the use of refrigerants and compressors. Think of heat pumps as reverse refrigerators. They can be ducted like a traditional furnace, can make hot water like a boiler, or can be un-ducted point-source heaters, often called mini-splits. In modern homes, small homes, and older homes with good insulation and air sealing, cold climate heat pumps can excel. Some heat pumps convert heat from the ground and/or groundwater for home heat. These are typically called Ground Source Heat Pumps (GSHP). This article does not address GSHP's due to their relatively slow market adoption rates compared to ASHPs.

Introduction to Heat Pumps Video

Mini-split ASHPs can be installed with one or more wall-mounted "heads", which blow hot air into rooms or areas of a home. Mini-splits may be used to keep heavily used areas of a home such as a living or family room warmer than other home spaces, such as bedrooms so that the furnace or boiler can run less often.

However, ASHPs may struggle in some applications. Temperature output from heat pumps is lower than oil, gas, and electric resistance heat, so heat distribution that is designed for low temperatures, such a radiant floor heating, is beneficial for heat pumps. In older homes, or in homes designed for high-temperature heat distribution, ASHPs may not keep homes comfortable on colder days. Current technology limits ASHP hot water output to about 140 degrees F, whereas traditional boilers operate at 180 degrees F. A paradox of ASHP technology is that as outdoor temperatures drop, particularly below 10 degrees F, heat output decreases while at the same time efficiency decreases. It costs more to make less heat. For that reason, often, cold climate heat pumps are supplemented with another form of heat for the very coldest weather.

By eliminating fossil fuels and combustion, the hazards of toxic fuels, exhaust, and fire danger are eliminated by using ASHPs. That surely adds to peace of mind.

Convenience

ASHPs are the ultimate in heating convenience. They respond to conventional room thermostats. Operation is completely automatic. There is no on-site fuel storage, so there is potentially one less energy provider to deal with. Some maintenance is required, but it is minimal compared to combustion appliances.

Cost

Heat pumps use electricity to produce heat. Operational costs depend upon outdoor temperature, house size, insulation, and the cost of electricity. Generally speaking, heat pumps should save money compared to oil and gas, but the degree of savings varies. Part of the popularity of heat pumps is the ability to provide power from solar and other renewable sources such as wind and hydroelectric. Because cold climate heat pumps may work hardest when there is no sun and colder temperatures, the use of the power grid and therefore utility billing policies will impact savings.

Cold climate heat pumps can range broadly in price depending upon the type of installation. As with wood pellet boilers, heat pumps may receive tax credits, rebates, and other incentives that can reduce up-front costs. Mini-split heat pumps can be relatively inexpensive compared to a new boiler or furnace. When heating small and/or, well-insulated spaces, a mini-split may provide all of the required heat, making for a very affordable heating transition. Installing ducted or air-to-water heat pumps can be expensive, potentially twice as expensive as a conventional boiler or furnace.

Operationally, because heat pumps use no combustion, service, and maintenance costs are low compared to oil and gas heating.

Carbon + Environment

ASHPs are not renewable energy. Heat pumps require significant amounts of electricity to produce heat. In ideal installations, ASHPs can produce on average three times as much energy as they consume, which means heat pumps use electricity to produce heat very efficiently. If heat pumps are supplied with electricity from renewable sources such as wind and solar, it is fair to say that they are nearly carbon neutral.

Household solar arrays are typically not adequate for supplying renewable electricity for heat pump use, especially at night, when heating loads are highest. When ASHPs are connected to the power grid, then the emissions associated with heat pump use are likely to involve carbon emissions from fossil fuels. As the power grid is supplied by more renewables, ASHPs use will produce fewer carbon dioxide emissions. The local grid operator in New England, ISO- New England is predicting that 18 percent of home heating will be produced by heat pumps by 2030. It is less well known what the renewable power segment of the grid will be in 2030, but there seems to be a future gap between renewable power production and power use.

Heat pumps do not use any combustion to make heat, so there are zero emissions at the point of use. This makes heat pumps environmentally friendly.

Heat pump refrigerants are toxic and can be powerful contributors to the greenhouse effect if they leak. ASHP refrigerants must be handled by licensed experts.