We wanted to write about energy audits because they’re required by the City of Austin when homes are sold. Some sellers want to know when they’re required to have one, others want to know how they are performed. Some buyers like to know what to do with the results once they receive them. In this blog, local expert, Andy Pell with Earth Energy Audits helped us understand the process.
ABOUT ENERGY AUDITS
Energy Audits have been required by the City of Austin (in most cases) when a home is sold since 2009. The primary goal is to reduce energy consumption in existing homes. The idea is to promote buyers to make basic, energy saving upgrades and to incentivize them with rebates from Austin Energy and TX Gas. Sellers are not required to do any upgrades; only provide the energy audit report to the buyers. The audit results note the areas of the home that could use improvement and if rebates are available. Energy Auditors, like Earth Energy Audits, are looking for the key contributors in home energy savings like attic insulation, duct sealing, window shading, and other basic weatherization measures as they have a fast return on investment.
HOW THE AUDIT IS PERFORMED
- An auditor will place seals on all the vents in the house to prevent air from entering through the vent opening.
- Everything is based on pressure so a duct blaster is attached to the return air vent.
- While the system is off, the duct blaster de-pressurizes the ducts. (It doesn’t push air.) It pulls air out and pulls the seals tighter to the ceiling/walls.
- The duct blaster brings the system’s ducts to 25 pascals of pressure before getting a reading.
- It measures how much air it’s able to pull out of the system. The only air the fan can pull out is through the leaks in the ductwork because, remember, all the vents are sealed.
HOW THE RESULTS WORK
Since the air flowing into the duct blaster’s reader can only be from leaks in the system’s ductwork, that number is divided by the total Cubic Feet per Minute (CFM) determined by the size of the system. There are 400 CFM per ton. So, a three-ton system would provide 1,200 Cubic Feet per Minute (CFM.)
On the house Andy tested, he pulled 177 CFM of air leaks out of the duct system. 177 CFM leakage is divided by 1,200 total CFM, the percentage of lost air in this house is 14.75%.
HOW TO EVALUATE THE RESULTS
The goal is to have an air leak rating of 10% or lower; but not every duct system can be brought below 10%. For example, older homes have a higher percentage of lost energy due to the outdated/inefficient construction. The investment to reduce the loss below 10% is often not cost effective because the return on investment is too low to justify the spend on construction to open walls, etc. only to save a few dollars on a monthly energy bill.
FACTS TO CONSIDER
- The average duct leak is 27%.
- Duct board has several places where it can leak and is more prone to leaks than flexible duct, which only has two opportunities to leak: at the two connection points. Duct board is harder to seal up because it has several seams.
- When you have excessive duct leakage, not only are you losing valuable conditioned air to the attic but this also causes your home to have a negative pressure. A negative pressure in a home causes unconditioned air to infiltrate your home from around doors, walls and windows. A tight duct system is key to help ensure a comfortable and energy efficient home.
- When engineers design systems, they allow for 500-600 of built SqFt per ton. So, a 1,500 SqFt house will require a 3-ton system. However, newer building materials can allow for a lower ton system because new construction is so much more efficient and is sealed tighter.
Remember, energy audits are required by the City of Austin whenever a house is sold and it’s the seller’s responsibility to provide the results to the buyer. It’s very simple; the results tell how much air is being lost in the ductwork. A responsible, ethical expert will help you with recommendations that will provide the highest return on investment when weatherizing your home. Don’t spend $15k to save $15/mo on your energy bill! Big thanks to Andy Pell with Earth Energy Audits. Call Andy at (512) 466-7679 to schedule your energy audit today.