Principles of Heating and Cooling

Principles of Heating and Cooling

Understanding how heat is transferred from the outdoors into your home and from your home to your body is important for understanding the challenge of keeping your house cool. Understanding the processes that help keep your body cool is important in understanding cooling strategies for your home.

Principles of Heat Transfer

Heat is transferred to and from objects -- such as you and your home -- through three processes: conduction, radiation, and convection.

Conduction is heat traveling through a solid material. On hot days, heat is conducted into your home through the roof, walls, and windows. Heat-reflecting roofs, insulation, and energy efficient windows will help to reduce that heat conduction.

Radiation is heat traveling in the form of visible and non-visible light. Sunlight is an obvious source of heat for homes. In addition, low-wavelength, non-visible infrared radiation can carry heat directly from warm objects to cooler objects. Infrared radiation is why you can feel the heat of a hot burner element on a stovetop, even from across the room. Older windows will allow infrared radiation coming from warm objects outside to radiate into your home; shades can help to block this radiation. Newer windows have low-e coatings that block infrared radiation. Infrared radiation will also carry the heat of your walls and ceiling directly to your body.

Convection is another means for the heat from your walls and ceiling to reach you. Hot air naturally rises, carrying heat away from your walls and causing it to circulate throughout your home. As the hot air circulates past your skin (and you breathe it in), it warms you.

Cooling Your Body

Your body can cool down through three processes: convection, radiation, and perspiration. Ventilation enhances all these processes. You can also cool your body via conduction -- some car seats now feature cooling elements, for instance -- but this is not generally practical for use in your home.

Convection occurs when heat is carried away from your body via moving air. If the surrounding air is cooler than your skin, the air will absorb your heat and rise. As the warmed air rises around you, cooler air moves in to take its place and absorb more of your warmth. The faster this air moves, the cooler you feel.

Radiation occurs when heat radiates across the space between you and the objects in your home. If objects are warmer than you are, heat will travel toward you. Removing heat through ventilation reduces the temperature of the ceiling, walls, and furnishings. The cooler your surroundings, the more you will radiate heat to the objects, rather than the other way around.

Perspiration can be uncomfortable, and many people would prefer to stay cool without it. However, during hot weather and physical exercise, perspiration is the body's powerful cooling mechanism. As moisture leaves your skin pores, it carries a lot of heat with it, cooling your body. If a breeze (ventilation) passes over your skin, that moisture will evaporate more quickly, and you'll be even cooler.

Home Heating Systems

Heating your home uses more energy and costs more money than any other system in your home -- typically making up about 29% of your utility bill.

No matter what kind of heating system you have in your house, you can save money and increase your comfort by properly maintaining and upgrading your equipment. But remember, an energy-efficient furnace alone will not have as great an impact on your energy bills as using the whole-house approach. By combining proper equipment maintenance and upgrades with recommended insulation, air sealing, and thermostat settings, you can save about 30% on your energy bill while reducing environmental emissions.

Heating Tips

• Set your programmable thermostat as low as is comfortable in the winter and lower the setpoint when you're sleeping or away from home.

• Clean or replace filters on furnaces once a month or as recommended.

• Clean warm-air registers, baseboard heaters, and radiators as needed; make sure they're not blocked by furniture, carpeting, or drapes.

• Eliminate trapped air from hot-water radiators once or twice a season; if unsure about how to perform this task, contact a professional.

• Place heat-resistant radiator reflectors between exterior walls and the radiators.

• Turn off kitchen, bath, and other exhaust fans within 20 minutes after you are done cooking or bathing; when replacing exhaust fans, consider installing high-efficiency, low-noise models.

• During winter, keep the draperies and shades on your south-facing windows open during the day to allow the sunlight to enter your home and closed at night to reduce the chill you may feel from cold windows.

Select energy-efficient products when you buy new heating equipment. Your contractor should be able to give you energy fact sheets for different types, models, and designs to help you compare energy usage. See the efficiency standards for information on minimum ratings, and look for the ENERGY STAR

 when purchasing new products.

What is the Inflation Reduction Act?

Signed into law on August 16, 2022, the federally funded Inflation Reduction Act (IRA) gives you an opportunity to save on the cost of replacing or upgrading your HVAC system with higher-efficiency equipment that can reduce energy consumption and lower utility bills. The purpose is twofold:

• To help homeowners obtain higher-efficiency equipment that helps reduce energy consumption and lower utility bills

• To reduce the environmental impact of carbon emissions across the United States by 40% by 2030

Whether you’re thinking about installing a heat pump in the future or you installed one in 2022, the Inflation Reduction Act includes rebates you can use:

• The Energy-Efficient Home Improvement Credit (also known as the 25C Federal Tax Credit) took effect on January 1, 2023, and covers:

• Up to 30% or $1,200 annually for qualifying equipment

• A $2,000 annual limit for heat pumps

• The High-Efficiency Electric Home Rebate Act (HEEHRA) offers rebates up to $14,000 per household for the installation of high-efficiency heat pumps and other efficiency improvements

• The HOMES rebate program, a $4.3 billion program that is part of the IRA, isn’t restricted by income level and is based on the actual performance of your whole-home energy efficiency and electrification improvements; the HOMES rebate program cannot be combined with the HEEHRA program, so talking with your tax consultant is important to determine which program works best for you

What the Inflation Reduction Act means for you

The IRA includes cost-saving credits and rebates when you purchase qualifying energy-efficient equipment for your home. By making improvements that electrify and/or reduce energy use, you may qualify for these tax credits and rebates while improving your home’s overall energy efficiency. Qualifying improvements include weatherization efforts, installing new electric appliances and installing electric heat pumps.

These benefits go beyond improving your month-to-month heating and cooling bills — many new, efficient heat pump systems that qualify for the IRA have features that improve indoor air quality through built-in humidity control.

Forget The Weather

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It’s National Energy Awareness Month

Take control of your energy usage and energy costs by getting a home energy audit.

What’s more, tax credits are available for professional audits. Go to the “Home Improvement” tab at energy.gov/save/homeowners.

Dual Fuel (Hybrid) Systems in Cold Climates

Can heat pumps work in cold climates? Check out these 4 different climate modes that demonstrate how a dual fuel (or hybrid) heating and cooling system takes the best qualities of a heat pump and gas furnace to provide a comfortable home climate.

OVERVIEW: While heat pumps provide both heating and cooling, they have to work overtime at extremely low temperatures, which isn’t always the most cost or energy efficient solution. A dual fuel system is a great solution for colder climates with four seasons. Dual fuel systems take the best qualities of a heat pump and gas furnace to provide you with energy-efficient home comfort no matter the temperature outside.

• Heat pump as the primary source of heat

• Indoor Furnace only runs when heat pump cannot meet the current heating demand (Usually 40 degrees or less)

• Utilizes existing ductwork and refrigerant line sets

MORE ON HEAT PUMPS: What Is A Heat Pump?

In all climates, including those with very cold weather, heat pumps offer an energy-efficient alternative to running an air conditioner with a gas furnace. Like your refrigerator, heat pumps use electricity to transfer heat from a cool space to a warm space, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house. During the cooling season, heat pumps move heat from your house to the outdoors.

Pump Up Your Savings with Heat Pumps

Heat pumps are increasing in popularity; as of 2020, over 17 million housing units had them installed. Because they provide cooling in the summer as well as heating in winter, heat pumps are helpful year-round. Now, they already account for more than half

of all residential heating equipment sales across the United States. Today we’re going to break down how they work, why Americans are upgrading to them, and how they can help save you money — via tax credits and rebates!

How They Work

Heat pumps are an energy-efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to transfer heat from a cool space to a warm space. During cold seasons, heat pumps move heat from the cool outdoors into your warm home. During warmer seasons, they move heat from your home into the outdoors. Because heat pumps transfer — rather than generate — heat, they are significantly more efficient than traditional heating systems.

There are two main types of heat pumps connected by ducts: air-source and geothermal, which differ in where they collect heat from (air, water, or the ground outside your home) and concentrate it for use inside.

Air Source

The most common type of heat pump is the air-source heat pump, which transfers heat between your home and the outside air. Modern air-source heat pumps can reduce your electricity use by 50% compared to furnaces and baseboard heaters. Until recently, they haven’t been used in areas that experience subfreezing temperatures for extended periods of time; now, they're a legitimate option for colder regions due to advancements in air-source heat pump technology.

Air-source heat pumps are also now available for homes without ducts, using a ductless version called a mini-split heat pump. Another kind of air-source heat pump is called a “reverse cycle chiller,” generating hot and cold water instead of air and compatible with radiant floor heating systems in heating mode.

Geothermal heat Pumps

Geothermal (ground-source or water-source) heat pumps transfer heat between your house and the ground or a nearby water source. They cost more to install but have low operating costs because they take advantage of relatively constant ground or water temperatures.

Sturdy and reliable, geothermal heat pumps can reduce energy use by 30%-60%, control humidity, and fit in a wide variety of homes. Compared to other types of heat pumps, they can also be used in more extreme climates.

You can learn more about the different kinds of heat pump systems — and which one might be best for you — at our Energy Saver site.

Why should you upgrade to a heat pump?

Minimizing Environmental Impact

Heat pumps use electricity to transfer — rather than create — heat, making them much more efficient than traditional HVAC systems. Depending what heating equipment you’re upgrading from, you could save up to 7.6 tons of carbon emissions per year. With millions of households choosing a heat pump each year, those tons add up to a meaningful impact for our climate. Show your appreciation to our Earth by choosing the clean energy option!

Lower Energy Bills

Less energy usage = lower utility bills. Depending on the size of your home, local climate, and how energy efficient your home is, savings can average over $500 per year. Pairing weatherization measures such as insulation with a heat pump can help you save even more – you can learn about incentives for insulation and other technologies in our Energy Savings Hub. When you’re shopping around for a heat pump, make sure to reference EnergyStar.gov for government-certified products to maximize your energy savings.

Tax Credits & Rebates

Through President Biden’s Investing in America Plan, homeowners are now eligible for tax credits when they install an air-source or geothermal heat pump: up to 30% federal tax credit on the total cost of buying and installing a heat pump. Soon, states will be able to provide residents with additional rebates to save money off the cost of heat pumps — with low-income residents eligible for particularly high savings.

Where Do I Start?

Upgrading to clean technology without first ensuring that your home is properly weatherized, or protected against energy loss, can undercut your efforts and eat into your potential savings. A home energy audit will give you a personalized roadmap, tailored to your home and environment, that will help you get the most bang for your buck.

Through President Biden’s Investing in America plan, you may be eligible for a 30% tax credit (up to $150) on your professional home energy audit. To claim this credit, simply submit IRS Form 5695 when filing your 2023-2032 taxes.

Learn more ways to save money while also saving the planet at our Energy Savings Hub, and check out our blog post addressing misinformation on DOE appliance standards.

Benefits Of Communicating HVAC Systems

Communicating HVAC systems, like our Affinity™ systems paired with Hx™3, help speed up installation and set-up since the thermostat and system can communicate information rapidly. That means optimized comfort, constant reporting on issues and faster maintenance checkups for contractors. Learn more about our communicating-capably systems: https://on.jci.com/45Yo243

• Faster Installation

• Optimized comfort technology

• Real-time error reporting for faster diagnosis and repair