Home Energy Rating
What is a Home Energy Rating? How is a HERS index calculated?
A home energy rating involves onsite inspections, typically including a blower door test (to test the leakiness of the house) and a duct test (to test the leakiness of the ducts). Results of these tests, along with inputs derived from the onsite inspections, are used with an energy efficiency software package to perform an energy analysis of the home's design. This analysis yields a projected HERS Index.
How energy efficient is your home? How much will it cost to operate?
A comprehensive home energy audit will provide a standardized evaluation of a home’s energy efficiency and expected energy costs. A HERS index provides a relative benchmark to compare to similar homes.
How airtight is your home? How large is the combined opening in your home?
A blower door test will depressurize the house to 50 pascals in order to determine airtightness, both absolute (CFM50, or cubic feet per minute @ 50 pascals) and relative (ACH50, or air changes per hour @ 50 pascals), as well as the equivalent “hole size” (in square inches) in your home.
How leaky are your ducts? Are you unintentionally cooling your attic and/or the outdoors?
A duct tester will depressurize the air distribution system to 25 pascals to determine the system’s airtightness (CFM25, or cubic feet per minute @ 25 pascals). Calculations will determine total duct leakage (CFM25TOT), duct leakage to outside (CFM25OUT) and normalized air distribution system leakage (Qn), which is the CFM25 normalized to the floor area of the conditioned area.
Why should I care about energy efficiency? What are the benefits of a Home Energy Rating?
- Save money on your energy bills
- Increase your comfort
- Increase your home’s resale value and marketability
- Uncover hidden problems
- Help the environment
- Take advantage of government incentives
- Invest in a sure money maker
These benefits are explained in more detail at http://resnet.us/home-energy-audit-benefits.