Home Energy Ratings (HERS)
What is a Home Energy Rating?
A Home Energy Rating, completed by a Certified Home Energy Rater, is a comprehensive evaluation of the efficiency of a home which is not specifically related to the occupants or the structure alone.
The evaluation results in a written report which includes the rating of the home, generally given as both a numerical and “star” score. Knowing your home's energy rating is similar to knowing the fuel efficiency, or miles per gallon rating of your car. It is, in effect, the fuel efficiency of your home.
Having a rating completed, based on the standards of the Home Energy Rating System (HERS), will provide you with a comprehensive report that:
- provides detailed information on each area of your home and its energy use
- provides detailed heating and cooling load calculations for equipment sizing
- gives insight as to what areas of your home would benefit the most from improvement
- shows how your home compares to those built to the International Energy Code, and
- is transferable to subsequent occupants of the home.
What is Involved?
All ratings are REQUIRED to start by the rater providing you with a copy of their disclosure statement. The disclosure statement shows you any outside interests the rater might have in providing you with a home energy rating. Those interests might disclose that the rater also works for an insulation company or a window company, companies that might benefit by providing improvements to your home as a result of your rating.
If the rater does not provide you with a copy of their disclosure statement, ask for one. Raters are required to provide a disclosure statement to each client by their HERS Provider, and by the Residential Energy Service Network (RESNET), the national governing body of the Home Energy Rating System.
The next steps in providing a Home Energy Rating are for the rater to take pictures of your home, and to make detailed sketches that include floor plans and outside elevations.
The information developed from these sketches includes the square feet (area) and cubic feet (volume) of the homes “envelope,” and the location and square feet of the windows and doors; and the locations and types of various items such as vents, ducts, lights, and heating, cooling, and hot water equipment.
Other items, such as shading from trees and adjacent buildings or overhangs, and the orientation of the home with respect to sunlight are also considered. All of this information is important and is needed to obtain an accurate rating.
A rating will generally include completing a blower door test to evaluate the home's air infiltration. The blower door consists of a calibrated fan and several pressure gauges, or a digital pressure sensor which are used to test the air infiltration rate.
The air infiltration rate is the amount of air that can enter the home through cracks and gaps around doors, windows, trims, moldings and penetrations. The blower door is used to pressurize the home, making it possible to measure the amount of air that is escaping or entering. The pressure created by the blower door is typically 50 pascals, or roughly ¼ inch of water column, and is equivalent to having a 15 mile per hour wind blowing past the outside of your home (the blower door does not create any appreciable wind inside your home).
This measurement is termed the air infiltration rate, air exchange rate or air changes per hour and, depending on the tightness of your home, can have a sizable effect on your heating and cooling requirements.
The rating might also include a duct blaster or pressure pan test of the ductwork. This duct blaster or pressure pan test can determine how leaky the ductwork is and how much, if any, of your conditioned air might be escaping to the outdoors. Blower door and duct testing, and in some cases a visual inspection of the insulation during construction, is required for certain ratings, such as for *ENERGY STAR® homes and for certain tax credits.
Other issues which affect the energy use of the home, and must be documented for the rating are:
- the type and amount of insulation in the walls, floors, ceilings and other areas;
- the size and efficiency of the heating, cooling and water heating equipment;
- the insulating value, or U-value, of windows and doors in the home;
- other types of energy using equipment;
- the number of occupants in the home and
- how the energy using equipment is controlled.
After the information is gathered and all relevant testing completed, the Rater inputs the information into the Home Energy Rating System approved rating software program. The program then calculates the home's energy usage information.
If the owner has the actual energy usage history for the house (copies of electric, gas, and/or other utility bills for one or more years), the real usage and costs can be compared to the results of the software for accuracy. It is important to note that the results of the Home Energy Rating will vary from actual use due to variations in energy usage by occupants.
What Does the Rating Mean?
The cost of heating a home is the largest cost of home ownership after the mortgage. An efficient home can save on your utility bills and provide you and your family with greater comfort for years to come.
The homeowner will receive a detailed report which will help to show the home owner where they will benefit the most from energy efficiency improvements. The rating consists of a star and a numeric rating. The numeric rating is associated with a percentage of the energy the home would use compared to a home built to minimum energy code standards. The more efficient the home, the lower the number (percentage) and the more stars of the rating score. The following chart provides general information regarding the overall efficiency and the numeric and star rating scales.
| Star Rating | Numeric Rating | Energy Efficiency |
|---|---|---|
 + | 0-70 | Extremely Efficient and ENERGY STAR® |
| 71-85 | Very Efficient and ENERGY STAR® |
 + | 86-90 | Above Average |
| 91-100 | Average |
 + | 101-150 | Below Average |
| 151-200 | Poor Efficiency |
 + | 201-250 | Extremely Poor Efficiency |
| 251-300 | Homes in these categories show the greatest need for improvement, using 250% to 500% (2½ to 5 times) more energy than the reference home, a home built to minimum energy code standards. |
 + | 301-400 | |
| 401-500 |
Your HERS Report
The HERS report will pinpoint specific areas of your home which are wasting energy and money. By comparing improvement costs to possible benefits, a home owner can determine which improvements will be the most cost effective. Most raters will be able to help in this decision making process, and may provide a report outlining which improvements they expect will result in the most savings for the least cost.
How Should I Prepare My Home for the Rating?
The Rater will have all of the necessary paperwork and tools required to complete the rating.
Additional considerations:
- You should make sure that the Rater has clear access to the basement, attic, crawlspace and all energy using equipment
- If there is a fireplace or wood burning stove, the ashes should be removed to avoid the possibility of blowing onto the floor
- Once again, you will notice very little air movement in the home due to the effects of the blower door, usually no more than a slight draft in areas of high leakage
- The rater will need to close all exterior windows and doors, and open all interior doors to perform the blower door test
*Note that for ENERGY STAR® ratings, a separate thermal bypass check list must be completed on new homes. This will require an inspection of the insulation prior to the application of the interior wall finish.
If available, you should also have the actual energy usage history for the house including the real usage and costs. This would consist of copies of utility bills for a typical year or up to three years if available. This is not a necessary part of the rating, but does help with evaluating possible improvements. You should also talk to your rater about any specific areas of the home you are concerned about, or possibly prepare a list of energy items that most interest you.
How Much Does the Rating Cost?
The cost of a rating can vary depending on the degree of complexity, travel distance, size of a home, accessibility, whether the rating is for an existing or new home, and of course, the pricing structure of the individual rater.
The simplest rating may only involve a physical inspection to check insulation levels, equipment efficiency and other readily available efficiency factors, and then to make minimum recommendations for possible energy savings. The most complex rating would include a blower door test for infiltration, a duct blaster test for duct leakage, physical inspections during different phases of construction, completion of ENERGY STAR® checklists, HVAC load calculations, participation in design decisions, multiple software input changes to compare possible designs and submittal of calculations and verification of compliance with requirements for ENERGY STAR®, energy codes or other efficiency programs.
Because of wide variation of rating complexity, costs will also vary from a minimum of $250 to $2,500 or more.
It is recommended that perspective customers check with community service agencies, utilities and other providers of energy efficiency programs, as some may provide these ratings for free, or at a reduced costs. Regardless of possible incentives, the customer should always check pricing from multiple providers to compare like costs.
Who Can Provide the Ratings?
For a list of certified HERS raters across the nation, please visit the ENERGY STAR® website; or the Residential Energy Services Network (RESNET) website under the consumer information link.
Questions or comments regarding the quality or actions of raters, or the program itself, can be directed to:
Residential Energy Service Network
P.O. Box 4561
Oceanside, CA 92052-4561
Phone: 760-806-3448