How to Select a System
Step One
Decide which equipment should be replaced or installed
Not sure when to replace your old system? Here’s some great advice from the US Department of Energy
When is it Time for a Change?
As much as half of your household energy use goes to heating and cooling. With a few simple steps to properly seal and insulate your home, and energy-efficient heating and cooling equipment, you can stay comfortable and save on your energy bills at the same time. Review the checklist on the next page to decide whether you should consider sealing air leaks, adding insulation, replacing your old heating and cooling system, or improving the performance of your existing system. Once you’ve decided on what changes need to be made, visit page 12 “Working with a Heating and Cooling Contractor” for tips on selecting the right contractor to perform the services you need.
Page 4
You may want to consider making a change if:
- Some of your rooms are too hot or cold. Duct problems, inadequate air sealing or insulation could be the cause. Nomatter how efficient your heating and cooling system is, if your home is not properly sealed and insulated against airleakage, you will not be as comfortable and your system will have to work harder. Learn more on page 8, “Improvingyour Home’s Comfort with Home Sealing.”
- Your home has humidity problems and/or excessive dust. Poorly operating or improperly sized equipment could beto blame. Leaky ductwork can also cause these problems, so having it sealed may be a solution. Monthly maintenanceof your heating and cooling equipment’s filters may also help. See page 16, “Getting Properly Sized Equipment and aQuality Installation,” page 10, “Sealing Your Ducts” or page 6, “Maintaining Your Equipment.”
- Your cooling system is noisy. Your duct system could be improperly sized or there may be a problem with the indoorcoil of your cooling equipment. See page 10, “Sealing Your Ducts” or page 6, “Maintaining Your Equipment.”
- Your equipment needs frequent repairs and your energy bills are going up. In addition to the rise in energy costs, the age and condition of your heating and cooling equipment may have caused it to become less efficient. See page 6, “Maintaining Your Equipment” or page 14, “Choosing the Right Equipment.”
- Your heat pump or air conditioner is more than 12 years old. Consider replacing it with newer, more efficientequipment. And remember, high efficiency levels begin with ENERGY STAR. See page 14, “Choosing the RightEquipment.”
- Your furnace or boiler is more than 15 years old. Consider replacing with ENERGY STAR qualified equipment.ENERGY STAR has set high efficiency guidelines for both furnaces and boilers. See page 14, “Choosing the RightEquipment.”
- You leave your thermostat set at one constant temperature. You could be missing a great energy-saving opportunity.A programmable thermostat adjusts your home’s temperature at times when you’re regularly away or sleeping.See page 14, “Choosing the Right Equipment – Programmable Thermostats.”
- Your score on the ENERGY STAR Home Energy Yardstick is below five. That means you’re using more energyat home than most Americans and probably paying more than you need to on energy bills. Get personalized recommendationsto improve your home and/or heating and cooling system. Find the Home Energy Yardstick at www.energystar.gov. Click on Home Energy Analysis.
Pages 4 and 5 from “A Guide to Energy-Efficient Heating and Cooling”
EPA
United States Environmental Protection Agency
www.energystar.gov
Download the guide click this link.
Step Two
Chose the right equipment
The equipment is the heart of your comfort system. Just as your heart works round the clock circulating blood throughout your body, your comfort system works round the clock making your home or business comfortable. And just as your heart uses more energy throughout the year than the rest of your muscles combined, your comfort system uses the majority of the energy in your home or office. Your equipment choices have two long-term impacts. The first long term impact is on your wallet.
It might surprise you to know that the cost of operating your heating system if far more than the cost of purchasing your system!
The best way to reduce the operating costs is by choosing high efficiency equipment.
The second long term impact is on the environment:
Think of air conditioning SEER ratings like the automobile miles per gallon (mpg) rating. The higher the rating, the less fuel (energy) the unit uses. A high efficiency air conditioner will use 38% less energy than the current minimum efficiency unit (13 SEER). A high efficiency air conditioner will consume 62% less energy than a 20 year old unit!
Choosing a high efficiency system not only saves you money in the long run, it helps save the environment too! We recommend as a bare minimum, you select an Energy Star rated system.
Step Three
Sizing the equipment
Sizing the equipment is something that needs to be done by someone with the skills and experience to do it properly. Usually this job is given to a heating and air conditioning contractor. However, you can manage the process by knowing what a contractor must do to do this job properly. Here are some great third party recommendations to help educate you on the process
Department of Energy
Energy Star Program
Page 16 from:
“A Guide to Energy-Efficient Heating and Cooling”
EPA
United States Environmental Protection Agency
www.energystar.gov
Getting Properly Sized Equipment
When purchasing heating and cooling equipment, choosing energy-efficient products is a step in the right direction. However, asking the right questions of your contractor and making sure your equipment is properly sized and installed are also important elements to ensure that your new system performs at optimal efficiency. When it comes to heating and cooling equipment, bigger doesn’t always mean better. Larger capacity systems are intended to meet the needs of a larger heating or cooling load. However, if the unit is too large for your home, you will experience less comfort and increased costs. Oversized equipment will operate in short run times or cycles, not allowing the unit to reach efficient operation. In addition, oversized equipment will not run long enough to remove humidity from the air. This can leave you feeling cool but not comfortable. Don’t assume that the size of your new system will be the same as your old equipment. Changes, such as additions or insulation improvements, may have been made to the house since the original equipment was installed; or, the equipment may have been too large from the start. Expect the contractor to gather information about your house such as the level of insulation, type and size of the windows, and floor area. Your contractor can determine the right size for your heating and cooling equipment by using ACCA/ANSI Manual J®, or an equivalent sizing calculation tool that takes these and other factors into consideration.
In order to properly size a heating and air conditioning system a contractor must do the following:
- Measure the square footage of the building and note the direction it faces
- Measure the square footage of the windows and the doors and note which direction they face
- Look in the attic to estimate the value of the insulation
- Look in the walls to estimate the value of the insulation
- Look in the basement or crawl space to estimate the value of the floor insulation
- Inspect the duct system for leakage rates and insulation values
- Inspect the fireplaces for leakage
- Record the number of appliances
- Record the number of bedrooms to estimate fresh air requirements
- Find out what temperature the building is going to be kept
- Be able to provide to you a copy of his/her calculations
Department of Energy - Energy Efficiency and Renewable Energy Sizing Heating and Cooling Systems
Older space conditioning systems (more than 10 years old) are often unreliable and much less efficient than a modern system. When it's time for a new replacement, choosing one of the correct size (heating and/or cooling output) is critical to getting the best efficiency, comfort, and lowest maintenance and operating costs over the life of the new system. Some national surveys have determined that well over half of all HVAC contractors do not size heating and cooling systems correctly.
The most common sizing mistake is in over-sizing. This not only makes the new system more expensive to install, but also forces it to operate inefficiently, break down more often, and cost more to operate. Oversized heating equipment also often creates uncomfortable and large temperature swings in the house. Oversized air conditioners (and heat pumps) do not run long enough to dehumidify the air, which results in the "clammy" feeling and unhealthy mold growth in many air-conditioned houses (see dehumidifying heat pipes as one solution to this problem).
Incorrect Sizing Methods
It is the installer/contractor's job to perform the correct sizing calculation for the building. However, many installers only check the "nameplate" (the label on the unit that has the Btu per hour output among other things) of the existing system and sell you one just like it, or even worse, one that's larger. This is a not a correct sizing method and not in your best interests! Other methods include simple "rules of thumb" based on the size of your home or using a chart that accounts for a variety of factors. While these methods might provide a first estimate, they should not be used to size your system.
Why Most Older Systems are Oversized
Before the era of tightly constructed homes, it was not uncommon to install furnaces and air conditioners that had two to four times the necessary capacity. Since many people have added new windows, caulking, weather-stripping, and insulation to their homes, going by the nameplate is likely to result in an oversized system. Making improvements such as these to reduce heat loss in the winter and heat gain in the summer should allow you to install a smaller systems while still being comfortable, as well as saving large amounts of energy.
Manual J and Manual D: The Correct Way to Size a System
Correct system sizing requires considering many factors other than simply reading the nameplate of the existing unit. Key factors for correctly sizing a heating and cooling system include the following:
1. The local climate 2. Size, shape, and orientation of the house 3. Insulation levels 4. Window area, location, and type 5. Air infiltration rates 6. The number and ages of occupants 7. Occupant comfort preferences 8. The types and efficiencies of lights and major home appliances (which give off heat). Homeowners should insist that contractors use a correct sizing calculation before signing a contract. This service is often offered at little or no cost to homeowners by gas and electric utilities, major heating equipment manufacturers, and conscientious heating and air conditioning contractors. Manual J, "Residential Load Calculation," published by the Air Conditioning Contractors of America (ACCA), is the recommended method for use in the United States. There are also many user-friendly computer software packages or worksheets that
can simplify the calculation procedure. You should make sure that the procedure used by the contractor follows Manual J.
If ducts are part of the installation, they should be sized using the ACCA's Manual D, "Residential Duct Design." The ACCA also offers a comprehensive guide for choosing home heating and cooling systems, called Manual S, "Residential Equipment Selection."
A Special Case: Sizing Steam Heating Systems
One exception to the above is in steam heating systems. For these systems, the boiler should be sized to match the radiators. However, there is still room for energy savings. First of all, the original boiler may be oversized for the radiators, so the contractor shouldn't just order the same capacity boiler, but instead should match the boiler to the radiators. Second, if you've increased the energy efficiency of your home, it may have more radiators than it needs.
It may be possible to remove radiators in the core of the house and shift the others around, replacing larger radiators with smaller ones. Since radiators are modular, it is theoretically possible to downsize a radiator by removing sections; in practice, this is usually difficult to do without damaging them. In many parts of the country, used radiators are available cheaply, so you can potentially buy small radiators to replace large radiators; if you do so, be prepared to replace the shutoff valves as well, since they often won't match. Newly manufactured steam radiators are available as well.
In any case, you should work with a heating and cooling professional when downsizing your system. Your house's heating needs should be calculated using Manual J, and your radiators should be downsized appropriately. Match the new boiler to the remaining radiators. Note that balancing steam heating systems is more an art than a science; ideally, you will find a heating professional with experience in steam heating systems.
Steps a Good Contractor Should Take to Size Your System
Many factors affect a home's heating or cooling requirement, or "load." A good estimator will measure walls, ceilings, floor space, and windows to determine the room volumes, and will assess the R-value of the home's insulation, windows, and building materials. A close estimate of the building's air leakage is also necessary. A blower door test is the best way to measure air leakage.
A good estimate will also include an inspection of the size, condition of seals on joints and insulation, and location of the distribution ducts in forced air systems. The placement of supply and return registers should be appropriate for the system type and size.
The orientation of the house also affects heat gain and heat loss through windows. Overhangs can reduce solar gain through windows. Make sure the contractor uses the correct design for the outdoor temperature and humidity in your area. Using a higher summer design temperature results in oversizing air conditioners.
When the contractors are finished, get a copy of their calculations, assumptions, and the computer printout or finished worksheet. This is your only proof that they did the job right.
To summarize, when designing your new heating and air conditioning system, the contractor you choose should do the following:
- Use a computer program or written calculation procedure to size the system
- Provide a written contract listing the main points of your installation and includes the results of the heating and cooling load calculation
- Give you a written warranty on equipment and workmanship
- Allow you to hold the final payment until you are satisfied with the new system.
Click here to download "Bigger Is Not Better" Part 1
Click here to download "Bigger Is Not Better" Part 2
Other helpful information
Click this link to see a consumers guide to sizing from the DOE-EERE.
Step Four
Determine if a staged or variable speed system is right for you
Comfort - The first reason to choose a staged or variable speed heating and cooling system is comfort. Your car would be very uncomfortable if the heater or air conditioner only had one speed—HIGH. You would be constantly turning the system on and off as you became too hot or too cold. This is why your car heating and cooling system has many speeds. On days when you only need a little heating or cooling you can set the system to low so that you can be more comfortable. Maybe you have one of the newer cars that automatically control the speeds. As the car starts to heat up or cool down the fan automatically speeds up or slows down to keep you more comfortable.
Since the late 70’s and early 80.s furnace manufacturers (Trane, formerly General Electric, was the first) have been making staged furnaces that automatically adjust their capacity to meet the comfort needs of the home or office.
Even Temperatures - The second reason to choose a staged or variable speed heating and cooling system is even temperatures throughout your home or office. High speed is the only speed of a base model furnace or air conditioner. When a furnace runs at only high speed it can quickly heat up the core areas of a home closest to it and then shut off before the outer areas have a chance to heat up. Basements are particularly affected by this operation. A staged or variable speed system runs much longer at a lower speed to give the outer areas of your home or office a chance to warm up. Staged or variable speed systems help even out the temperatures in your home or office
Saving Energy (money!) – The third reason to choose a staged or variable speed heating and cooling system is saving energy (money!). When driving your car, which do you like to pay for, highway miles per gallon or city miles per gallon? Highway miles of course! You get more miles per gallon on the highway. Why? Your car doesn’t have the energy wasting stopping and starting of city driving. Your furnace and air conditioner are the same way. If your system can only run on high on those mild temperature days, it will be stopping and starting a lot. One study has shown that staged systems use as much as 12% less energy than single stage systems.
Step Five
Determine if Zoning is Right For You
Why Should I Zone My House?
No matter what the temperature is outside, keep all areas of your home comfortable! Eliminate your hot or cold rooms. Don’t pay to heat or cool areas of your home that you rarely use. Zoning has come a long way in recent years. It’s easy to install and flexible enough for any home.
What is Zoning?
Zoning separates your home into comfort areas and makes your comfort system cool or heat only the areas that need it. For example, a great room with large windows may stay too hot in the summer and too cold in the winter. A zoning system will send more hot or cold air to the great room, to make up for the extra heat gained or lost through the windows.
Why Zone?
Today's families have different lifestyles and comfort needs. Maybe you have a home office that needs extra conditioning during the day, and none at night. Or you only use the upstairs bedrooms when guests visit. Whatever your needs, zoning can keep each area of your house just right for you and each family member.
When to install zoning
When you are replacing your air conditioner, furnace or heat pump, it is an excellent opportunity to install a zoning system. When your new comfort system is paired with a new zoning system, you will have precise control in each area of your home. Zoning is also excellent for new homes, since it is installed during construction. If you are buying a new home, check with your builder about a zoning system. It could make the difference between enjoying your new house and being truly comfortable in it!
How does zoning work?
Zoning is controlled by thermostats in each zone. For example, if you have four zones in your house, you will have four thermostats. Depending on your zoning system, you may have a choice of thermostats. Each thermostat signals the heating or cooling system independently. This lets the system deliver cooling or heating only where and when it is needed. You will never have to cool or heat the whole house just to make one room comfortable.
Zoning can save you money
Zoning can lower your cooling and heating bills. Zoning systems can use programmable thermostats in each zone to make the most of energy savings. No more closing registers or shutting doors with each seasonal change. A good example of this is a guest suite on the north side of the house. You do not want to condition it like the rest of the house, but in the winter, it needs to be kept from freezing. With a zoning system, you can turn the thermostat down. Now you are not wasting money and you feel better knowing the bedroom suite will not get cold enough to freeze pipes. As you begin using your home in varying ways, such as a home office, for example, zoning will become more important. Also, the energy savings can really mean a lot with a zoning system.
Step Six
Compare systems, click on either of the charts below to download the PDF.
