The R-value depends on the type of insulation and includes it’s material, thickness, and density.  When calculating the R-value of a multilayered installation, add the R-values of the individual layers.   Installing more insulation in your home increases the R-value and the resistance to heat flow.

The effectiveness of an insulation’s resistance to heat flow also depends on how and where the insulation is installed.  For example, insulation that is compressed will not provide its full rated R-value.  The overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself because some heat flows around the insulation through the studs and joists.  Therefore, it’s important to properly install your insulation to achieve the maximum R-value.

The amount of insulation or R-value you’ll need depends on your climate, type of heating and cooling system, and the section of the house you plan to insulate.

Air ducts supply conditioned air from your space heating and cooling equipment to your living spaces. They also return an equal volume of air back to the equipment to be conditioned again.

Ducts are typically made out of thin metal materials that easily conduct heat. Therefore, uninsulated or poorly insulated ducts in unconditioned spaces can lose through conduction 10%–30% of the energy used to heat and cool your home. The heating and cooling equipment then has to compensate for the heat loss and gain by conditioning additional air. This added conditioning raises a homeowner’s energy bills. In addition, when ducts lose heat through conduction, rooms served by long duct runs can experience “cold blow” during the winter because they usually have lower heating-supply temperatures.

Ducts in conditioned spaces experience minimal conductive losses and gains since they are exposed to indoor air temperatures. However, these ducts may also require some insulation to prevent condensation on duct walls and to ensure that conditioned air is delivered at the desired temperature.

HVAC contractors typically insulate ducts using rigid fiber board insulation. Below is a table showing the recommended  R-values by climate for duct insulation in unconditioned spaces.

The most common sizing mistake is in oversizing. 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:

• The local climate
• Size, shape, and orientation of the house
• Insulation levels
• Window area, location, and type
• Air infiltration rates
• The number and ages of occupants
• Occupant comfort preferences
• 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.

For both new and existing homes, it’s important to first maximize the energy efficiency of your home. This is the most cost-effective means of keeping your home comfortable, no matter what climate you live in. After doing so, be sure to do what you can to make use of passive solar heating in your home and consider whether ventilation can keep your house cool on warm days, or if you really need artificial cooling. Only after exploring these topics should you decide on the type of system you want and work with a contractor to figure out the optimum size for it. To learn more on these topics, see the following resources:

• Limitations When Replacing Existing Systems
• Selecting Fuel Type and Type of System
• Sizing Your Heating and Cooling System

Even the most energy-efficient heating and cooling system will fail to save you money if it is installed incorrectly or improperly adjusted. To verify the qualifications of your heating and cooling contractor, ask if they have been certified by North American Technician Excellence, Inc. (NATE).

Here are some further tips on choosing contractors:

• Ask neighbors and friends if they have worked with a contractor they would recommend
• Focus on local companies
• Look for licensed, insured contractors
• Ask about previous experience
• Check references
• Inquire with the Better Business Bureau.

A digital setback thermostat is designed for people with fixed schedules that take them in and out of the home. With it, you can program the temperature to ‘set-back’ when you are not at home. This feature keeps you comfortable when you’re home and saves you money when you’re not by reducing the energy needs to heat and cool your home.

Digital setback thermostats are available in what are called 5+2 day configurations and 7-day configurations. The difference is flexibility. A 5+2 day configuration allows you to set Monday–Friday as a group setting with up to four different time settings. This configuration also allows you to set Saturday and Sunday as a separate group with up to four different time settings per day. The 7-day configuration thermostat allows you to program each day differently with up to four different time settings per day.

Have you ever been in your attic in the middle of the summer? It’s HOT! That’s why you need an attic ventilator. Assisting your air conditioner in cooling your home and in lowering your utility bills, an attic ventilator exhausts the hot air from your attic and brings in cooler air from the outside. This circulation of air greatly reduces the heat load on your home allowing your air conditioner to work more efficiently and to cool your home faster. Adding an attic ventilator to your home will save you money and make you more comfortable.

Lack of return air is a very common problem for those systems that were either poorly designed or originally planned for heat only applications. Adding additional returns to your system allows for greater supply air into your home, resulting in better airflow and comfort for your family. The benefits you will receive by taking care of this problem include: quieter operation, better airflow, fewer repairs, longer life of your equipment, lower utility bills and, best of all, greater comfort.

Most heating and cooling systems still use a basic air filter. These filters were originally designed to protect the equipment and not the people served by the equipment. The average air filter is only capable of removing 3–5% of the particles that pass through it. Today, however, there are several types of permanent air filters available in various efficiencies that can help you filter the air in your home. If you suffer from allergies, asthma, hay fever or other breathing difficulties, there is an air filter that can help you. We can even provide you with the same type of air filter used in hospital operating rooms.

Within a few years, however, complaints started to arise, due to health, and excessive moisture issues caused by indoor pollution, and associated moisture problems within these homes.

In the late 1980s and early 90s, indoor air quality became a nationally recognized issue. Even today, newer and more energy-efficient homes seemed predisposed to the problem. In addition, they retain more humidity and airborne pollutants, which causes longer life-spans, and more productive cycles of microbial activity within the home, such as mold, germs, bacteria and viruses.

This greater activity and concentration of these airborne contaminants, equates to more allergic reactions, and sickness within families, for longer periods of time.

MOLD: A SURVIVOR

Why is mold so difficult to control? Mold is at the bottom of the food chain. It thrives on very little, grows rapidly, and produces spores, volatile organic com-pounds, and other toxins. One organism can multiply to trillions in less than three weeks. When given the right conditions, mold can occur anywhere; in homes, schools, workplaces, entertainment centers, vehicles, etc.

The interior of your ductwork and air conditioning equipment, provides an ideal environment for mold growth — especially in the air conditioners inside drain-pan where it is dark, damp, and filled with nutrients. The result can be like blowing air over a swamp or through a sewer and then into your home, vehicle, and workplace.

According to the World Health Organization (WHO), 60% of Indoor Air Quality (IAQ) problems and allergies may be mold-related. Some IAQ diagnosticians and practitioners today say the figure may be as high as 80%. The increased usage of air conditioning systems almost directly parallels the increase of allergies and IAQ problems.

As mold and bacteria grow on coils and in drain pans, they are disseminated through the ducts to occupied spaces. Some mold products (toxins) produce serious and sometimes life-threatening reactions, including allergy, asthma, hypersensitivity, pneumonitis, and in some extreme cases even bleeding lung disease.

Additionally, mold creates a troublesome maintenance problem. Its activity results in dirty coils, a loss of air-flow, loss of heat exchange efficiency, dirty and sometimes plugged drain pans, and excessive energy use.

USING UVC TECHNOLOGY

Our company has found that the most successful way to handle system mold is through Ultraviolet (U.V.)germicidal lights. These U.V. systems are a recent breakthrough in protecting the health of a home.

Ultraviolet light in the “C” band (UVC) has been used for more than 65 years to kill microorganisms in hospitals, barber shops, laboratories, pharmaceutical plants, and at the nation’s Center for Disease Control. Residential ultraviolet units have been independently tested and proved to be effective in the constantly moving air environments of heating and cooling systems, killing mold and bacteria quickly and effectively. The UVC energy attacks the organism’s DNA and either destroys it immediately or prevents it from reproducing.

For most people, the original motivation for installing the lights is to abate IAQ complaints and/or allergies. However, they are also pleased to learn that many hidden odors are also eliminated with U.V. technology.