Heating, Ventilation, and Air Conditioning (HVAC)

 accounts for 48% of the energy use in a typical U.S. home (US Department of Energy). Upgrading or commissioning your HVAC systems can significantly decrease your home's energy use. The goal of this webpage is to provide resources and strategies to decrease your HVAC energy use.

  1. HVAC System Components to help familiarize you with all of the pieces that make up an HVAC system
  2. HVAC Improvements presenting regular maintenance that can help increase the efficiency of your existing system
  3. Distribution Improvements that can be done to reduce your overall energy demand
  4. Thermostat Control System improvements that can be implemented in order to reduce your energy usage
  5. Selecting a new HVAC system to present the primary considerations in selecting a new energy efficient system, which includes: energy efficiency ratings, types of heating fuels, and types of cooling systems

HVAC System Components

A typical HVAC system includes the following components

Furnace or alternative heating source

provides heating for distribution into your home.

Air conditioner or heat pump

works with evaporator coil to provide cooling.

Distribution systems

air ducts, fans, pumps, and hydraulic pipes that circulate the conditioned air or other fluids throughout your home.

Control systems

control your HVAC system, such as the thermostat.

Air quality control system

humidify or filter air before circulation throughout your home.

Terminal units

used in radiant heating and cooling systems, serve as the heat exchanger to the internal environment.

Typical HVAC Systems

Forced Air Systems

Forced air systems heat or cool air for distribution into your home. These systems consist of a air handler, air distribution ducts, vents, and return grill. These systems are cheaper and easier to install, and deliver conditioned air to rooms quickly. Additionally, since forced air systems incorporate an air filter in the air handler, they eliminate the need for a separate air filtration unit.

The cons of a forced air systems are that they may deliver uneven heating, have a lower efficiency due to heat loss in ductwork, require more regular maintenance, can be noisy during operation, and can introduce dust and debris into your home through build up in the ductwork.42

Radiant Systems

Hydronic radiant distribution systems rely on a boiler to heat a fluid which is then distributed throughout the home using a pump. Radiant systems heat and cool surfaces which condition the surrounding air in the room for occupant comfort. Older systems typically use standalone radiators, while modern systems are built into the floor or the ceiling of a home. Typically these systems are used for heating in residential applications but not for cooling. They can use air or water in pipes or electrical coils to heat the surfaces, though water is most commonly used.43 Radiant systems are known to be more efficient for distributing heat, since there are no duct losses. Other advantages of radiant systems are that the heat is delivered lower in the room where the occupants are, they don’t introduce dust to the environment (hypoallergenic), and you can control room temperatures individually.

The disadvantages of radiant systems are that they can cause condensation in humid environments when cooling a home which can lead to mold and rot, they require a higher capital cost, and take longer to heat or cool your home. Radiant systems shouldn't be placed underneath carpet, acoustic panels, or any other thermally resistive materials as they reduce the overall efficiency of the system.4

HVAC Improvements and Maintenance

It is important to maintain the heating and cooling unit and the distribution system for efficient operation.

Forced Air systems

As your forced air heating and cooling system ages, it becomes less efficient. To maintain the best performance, you need to:

Replace your air filter every three months18
Maintain all electrical connections, lubricate moving parts, check the condensate drain, and ensure that the controls of the system are properly operating.6

It is recommended to contact a professional HVAC contractor for troubleshooting any HVAC problems.

Radiant Systems

Issues for radiant systems typically arise from improper installation. Some more common issues include:16

Insufficient insulation – radiant flooring requires insulation to minimize heat loss to the foundation or lower floors.
Improper insulation – on top of the radiant piping some people opt to have carpeting or padding. This reduces the efficiency of the system.

If you believe your radiant system has one of these issues, we recommend you contact the contractor that installed the unit to check for these issues. If it turns out that the unit was installed correctly, you may want to check the distribution system for issues.

 

Distribution improvements

After heat is generated, it must be distributed throughout your home. Most commonly, forced air systems use fans and ducts, and radiant systems use pumps and pipes.

Forced air systems

In forced air systems 20%-30% of the energy may be lost through the duct system due to leaks, holes, and poor connections between ducts. This will result in a higher utility bill and an uncomfortable home.

How do you know if your ducts can be improved?

  • High summer and winter utility bills
  • Individual rooms are more difficult to heat and cool than others
  • Rooms are stuffy and not comfortable
  • Ducts are located in attic, crawlspace, or the garage
  • Ducts appear tangled or kinked in some spots
  • High dust and allogenic levels in your home

If you notice any of these issues, we recommend you hire a professional contractor to improve the duct performance. Check out homeadvisor.com to find local contractors in your area.

If you choose to do it yourself, check out the ENERGY STAR brochure on duct sealing.24 If you’re running new ductwork, GAF has a how-to video series on running new ductwork.23

Hydronic radiant distribution

In hydronic radiant systems, some common distribution issues include: 14   

1.     Leaks – this is the biggest concern for radiant systems. Typically leaks are a result of poor plumbing connections, but can also result from other installations puncturing a tube (such as flooring or drywall). For this reason, it’s important to tell any contractors working in your home that you have a radiant floor system.

2.     Uneven heat distribution – uneven radiant heating typically means that there is an issue with the water pump or that there is air built up in the circulation system.

For any of these issues, we recommend contacting a trusted local contractor that installs and repairs radiant systems. Homeadvisor.com can help you find contractors in your area.1

Selecting a new HVAC system

If your HVAC system is becoming outdated or having regular issues, it may be time to replace it.25 To select new heating and cooling equipment, you must first understand the energy efficiency ratings, the heating sources and cooling sources available in your area, and the advantages and disadvantages of each type of system.

Energy Efficiency Ratings Systems

There are several efficiency ratings available to compare HVAC equipment. The most common efficiency measurements are the Annualized Fuel Utilization Efficiency (AFUE), Seasonal Energy Efficiency Ratio (SEER), and the Coefficient of Performance (COP).

Annualized Fuel Utilization Efficiency (AFUE)

is a measure of how well your furnace converts gas or oil energy into warm air for your home. It is typically used for furnaces with outputs less than 150,000 BTU/hr. The higher the AFUE rating, the more efficient the furnace.8

Seasonal Energy Efficiency Ratio (SEER)

is the average ratio of annual cooling output to the system’s total energy consumption. A higher SEER rating indicates a more energy-efficient air conditioner.26 Heat pumps use SEER for their cooling cycle performance.

Coefficient of Performance (COP)

 is the ratio of the energy transferred by a heat pump to the electrical energy consumed by the heat pump. Typically, commercially available heat pumps have COPs between 3 to 4.

 

Types of Heating Systems

Heating can be accomplished using various energy sources to keep your home comfortable during the cold times of the year. Heating systems include furnaces and boilers, heat pumps, radiant heaters, active solar, wood and pellet heating, portable space heaters, and others.32

Furnaces and Boilers

These systems are commonly referred to as central heating systems. They are the most commonly used system in the United States. Furnaces heat air for distribution throughout the home using ducts. Boilers heat water that is then distributed to radiant heating terminal units.8 Steam boilers are inherently less efficient than hot water boilers. The efficiencies of these systems are measured by their annual fuel utilization efficiency (AFUE) rating, which can be found on all new furnaces and boilers.9

Heat Pumps

Heat pumps use electricity to heat or cool a home by transferring heat to/from the room air, and dissipate the energy to the outside environment.39 These systems can come in various configurations, and can both heat and cool your home. Heat pumps operate at a lower cost than electrical resistance heating equipment. Heat pumps are also able to provide heat for a home's water heating system, and may be integrated into geothermal systems if desired.  For more information, check out heat pumps in water heating and geothermal. Check out the DOE’s Heat Pump Water Heating40 and Heat Pump Heating39 webpages for more information about heat pumps

Electric Resistant Heating Systems

Despite their 100% efficient conversion of electricity to heat, these systems are an expensive way to heat a home due to the high price of electricity. These systems vary from electric baseboard heaters, electric wall heaters, electric radiant heaters, to electric space heaters. If electricity is the only option, heat pumps are typically more preferable as they use less electricity.29

Radiant Heating

Heats your home using a fluid in pipes. Radiant heating is more efficient than baseboard heating and forced air heating. It also reduces introduction of allergens into the air.29

Active Solar Thermal

Active solar thermal systems harness the sun's energy to heat a home using a heat transfer medium. Typically, these systems provide supplemental heating to a home.27 These systems are discussed in more detail in solar thermal page.

Wood and Pellet Heating

These systems burn natural biomass to heat your home. Current wood and pellet burning appliances are more efficient than older models. However, they still produce air pollutants, thus some municipalities restrict the use of these systems. Be sure to check your local building codes before implementing one of these systems.30

Portable Space Heaters

These systems are small heating units to heat specific locations in a home. Though less efficient, space heaters can heat up a small space where the occupants spend most of their time, ultimately saving money and energy that would otherwise be used to heat up the entire home.31

Click Here for Home Advisors website which provides a great discussion on the cost of each of the above systems. 

Types of Cooling Systems

 Although air conditioning is the most commonly used cooling system, there are other alternative cooling systems that can reduce your home's energy demand.33

Air conditioner

the most common cooling system. Air conditioners operate similarly to refrigeration units by using electricity to remove heat from a home. Typical air conditioners are central air conditioners and room air conditioners. High efficiency air conditioners can reduce your electricity usage by 20%-50%.17

Ventilation for Cooling

ventilation introduces cooler outdoor air into a home to provide cooling. It can be the most energy efficient and cost effective way to cool your home. This strategy is most effective in climates where temperature swings are large throughout the day, and least effective in hot humid climates where temperature swings are small throughout the day. In Ohio, ventilation during summer nights with low humidity can reduce the cooling demand.34

Fans for Cooling

Fans can be used to move air within a home to produce a wind chilling effect. With a ceiling fan in operation, your thermostat set-point for cooling can be about 4°F higher than normal with no reduction in comfort.35 When purchasing ceiling fans, look for the ENERGY STAR® label as these fans can operate 20% more efficiently than fans without the certification.36

Evaporative Cooling

works by removing air heat through a water evaporation process to create cooler humid air. These systems can reduce air temperature by 15°F-40°F. They should not be used when outdoor humidity is high, which makes them less effective in Ohio's summer months. Another concern is that these systems require a continuous water supply, thus they may not be completely sustainable in many parts of the country. 37

Heat Pumps

Heat pumps can also be used to cool a home. See above Heat Pumps section for details.

 

Thermostat Control Systems

Thermostat is typically used to control operation of HVAC systems in homes for occupant comfort. It can be used to save energy by (1) thermostat setback, (2) occupancy sensing, (3) zoned temperature control. A thermostat setback is a setting that allows you to change the temperature of your house when you are sleeping or away from your home. By doing so, the HVAC system is only in operation when you are active in your home. This can be done by you manually each time you leave the house, or it can be done automatically by a newer programmable thermostat.20 According to the DOE, you can save up to 10% on heating or cooling using a set-point of 7-10 °F higher or lower than your normal temperature setting for 8 hours per day.

More recently, occupancy or door sensors have been incorporated into smart home control. These sensors can be used to determine whether the occupants are active, sleeping, or absent. Historical data can also be used to pre-condition the home based on previous occupancy patterns. When the sensors detect the home is vacant, they can change the temperature set-point to save energy without sacrificing occupant comfort.44

Some newer home control systems also incorporate zoned temperature control, which uses individual thermostats in each room or temperature zone.  All of the thermostats are wired to the central control panel, which controls valves (in radiant systems) or dampers (in forced air systems) to heat or cool a room more or less according to specific thermostat set-points. When used properly, the DOE estimates that zoned temperature control can save up to 30% on heating and cooling.45

 


Resources

1 http://www.nrel.gov/docs/fy12osti/52991.pdf - “Strategy Guideline: HVAC Equipment Sizing” by Arlan Burdick, prepared for the U.S. Department of Energy

A comprehensive overview of HVAC sizing including: design conditions, preliminary equipment selection, manufacturer data tables, cooling equipment capacity sensitivities, estimated volumetric air flow, and efficiency considerations. This resource is most useful for professionals in the field.

2 http://www.hvacopcost.com/equipsize.html - “VAC Equipment Size Finder” by hvacopcost.com

Rough estimate for sizing your HVAC heating and cooling system. This resource intended for an energy usage comparison. Contact a licensed HVAC contractor or engineer before designing your system.

3 http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/75898/How-to-Determine-the-Size-of-Your-Central-Air-Conditioner - “How to Determine the Size of Your Central Air Conditioner” by Allison Bailes of energyvanguard.com

Resource for sizing your Air conditioning system including how to read the labeling on AC units.

4 http://energy.gov/energysaver/heat-and-cool “Heat and Cool” by Energy.gov

Space heating and cooling links provided by the Department of Energy.

5 https://www.acdoctor.com/compare-hvac-systems.php - “Compare all HVAC Products” by acdoctor.com

Source for comparing air conditioners, ductless splits, furnaces, heat pumps, and a discussion of SEER, rebates, and advantages of R-410A.

6 https://www.energystar.gov/index.cfm?c=heat_cool.pr_maintenance “Maintenance Checklist” by ENERGY STAR

Typical maintenance points for heating and cooling systems.

7 https://www.wbdg.org/resources/hvac.php - “High-Performance HVAC” by Whole Building Design Guide

In depth design recommendations for all HVAC systems.

8 http://energy.gov/energysaver/furnaces-and-boilers - Furnaces and boiler options, including their efficiencies.

9 http://energy.gov/articles/energy-saver-101-infographic-home-heating - infographic on heating via energy saver

10 http://www.energystar.gov/index.cfm?c=heat_cool.pr_hvac - ENERGY STAR Heating and Cooling Efficiency Information

11 http://ducts.lbl.gov/HVACRetrofitguide.html - Best practices for HVAC improvements for contractors (if you're very serious about understanding all target values for contractors)

12 http://www.nrel.gov/docs/fy14osti/62539.pdf

“Insulated Concrete Form Walls Integrated With Mechanical Systems in a Cold Climate Test house” by U.S. Department of Energy

13 https://www.energystar.gov/ia/partners/publications/pubdocs/HeatingCoolingGuide%20FINAL_9-4-09.pdf?b0ad-0550

14 http://www.theearthheating.com/blog/3-maintenance-tips-radiant-heating-systems/

15 http://www.homeadvisor.com/tloc/Cleveland-OH/Radiant-Floor-Heating-System-Install/

16 http://www.hydronicheating.net “Hydronic Heating” by hydronicheating.net

Includes an introduction to hydronic heating, and the benefits, issues, costs, tax credits and rebates associated with the heating technique. 

17 http://energy.gov/energysaver/air-conditioning

18 https://www.energystar.gov/index.cfm?c=heat_cool.pr_hvac “Heat and Cool Efficiently” by ENERGY STAR

Steps that can be taken to improve the efficiency of your current heating and cooling system.

19 ftp://ftp.panasonic.com/heatairconditioner/brochure/ahri-certified_brochure.pdf “Integrated Energy Efficiency Ratio” by Panasonic.com

IEER background material.

20 http://energy.gov/energysaver/thermostats

21 https://www.energystar.gov/index.cfm?c=home_improvement.hm_improvement_ducts_contractor

22 http://www.gaf.com/Video_Library/0_5wn7ji0r - “Ductwork 101” by GAF

HVAC ductwork installation videos

23 http://www.perfect-home-hvac-design.com/hvac-for-beginners.htmlhttp://www.perfect-home-hvac-design.com/hvac-for-beginners.htm

24 https://www.energystar.gov/ia/products/heat_cool/ducts/DuctSealingBrochure04.pdf?697f-4eb9

25 https://www.energystar.gov/index.cfm?c=heat_cool.pr_checklist_consumers

26 https://energy.gov/energysaver/central-air-conditioning

27 http://energy.gov/energysaver/active-solar-heating

28 http://energy.gov/energysaver/radiant-heating

29 http://energy.gov/energysaver/electric-resistance-heating

30 http://energy.gov/energysaver/wood-and-pellet-heating

31 http://energy.gov/energysaver/portable-heaters

32 http://energy.gov/energysaver/home-heating-systems

33 http://energy.gov/energysaver/home-cooling-systems  - Overview of all cooling systems by the Department of Energy

Great overview for all cooling systems.

34 http://energy.gov/energysaver/ventilation-systems-cooling

35 http://www.nrel.gov/docs/fy01osti/29513.pdf - Cooling your home with Fans and Ventilation http://www.nrel.gov/docs/fy01osti/29513.pdf - Cooling your home with Fans and Ventilation

36 http://energy.gov/energysaver/fans-cooling

37 http://energy.gov/energysaver/evaporative-coolers

38 http://energy.gov/energysaver/radiant-cooling

39 http://energy.gov/energysaver/heat-pump-water-heaters

40 http://energy.gov/energysaver/heat-pump-systems

41 http://www.lennox.com/buyers-guide/guide-to-hvac/glossary “HVAC Glossary” by Lennox

Common terminology associated with HVAC systems.

42 http://www.commonwealthhvac.com/blog/radiant-and-forced-air-heat-pros-and-cons “Radiant and Forced-Air Heat Pros and Cons” by Commonwealth Cooling and Heating L.L.C

A short discussion of the advantages and disadvantages of forced air and radiant heating systems.

43 “Radiant Heating and Cooling” by Autodesk Sustainability Workshop

http://sustainabilityworkshop.autodesk.com/buildings/radiant-heating-and-cooling

A short discussion of radiant heating and cooling.

44 The Smart Thermostat: Using Occupancy Sensors to Save Energy in Homes by University of Virginia
http://www.alice.virginia.edu/~stankovic/psfiles/sensys10-final169.pdf

45 “System Zoning” by howstuffworks.com

http://home.howstuffworks.com/home-thermostat4.htm

A discussion of residential system zoning.

46 http://www.mnshi.umn.edu/kb/scale/hrverv.html