Guide to understanding the
ECAD Report Form
Because Austin's ECAD Report is a little confusing for the average homeowner, we've put together this guide for understanding the report.
AFUE: AFUE (annual fuel utilization efficiency) is the most widely used measure of a furnace's heating efficiency. It measures the amount of heat actually delivered to your house compared to the amount of fuel that you must supply to the furnace. AFUE for natural gas furnaces can range from 60-96%.
BTU: BTU stand for British Thermal Unit, and is used to describe the heat value (energy content) of fuels, and also to describe the power of heating and cooling systems.
CFM: CFM stands for cubic feet per minute (CFPM or CFM), which is unit of measurement of the flow of air.
CFM Leakage %: Leaky ducting is quantified as a CFM Leakage %. This is the measured duct leakage rate of CFM leaking out of the ducting. Duct leakage up to 10% is considered acceptable, and anything above this is considered leaky and a comprehensive duct sealing will be recommended.
Comprehensive Duct Sealing: A comprehensive duct sealing includes sealing all air distribution ducting connections with a product called mastic. This material is like a thick grey latex paint that hardens when dry.
EER: Energy Efficiency Ratio, or the EER, is an efficiency ratio similar to the more commonly used SEER rating. EER is the measure of air conditioner efficiency at maximum air conditioning load. It is measured by the ratio of BTU per hour of cooling or heating load, to watts of electrical power input. The higher the EER number, the more efficient the air conditioner.
HVAC Delta T: The temperature difference between the air at the return grill and a supply grill is called the delta T. A low delta T (temperature difference) can indicate a problem with the cooling equipment. Manufacturer minimum delta T can vary, however low can be defined as less than 10⁰ - 12⁰ degrees Fahrenheit.
Low-E Glass: Low-E refers to window glass that has low emissivity. Emissivity refers to the ability of a material's surface to emit or reflect radiant energy. Low-E glass is energy efficient because it has the ability of reflecting solar heat away from the surface of the window.
Plumbing Penetration: One of the common places in a house that leaks air is at areas where plumbing piping passes through an exterior wall. These areas can easily be sealed with expansion foam or caulk.
Radiant Barrier: A radiant barrier (or reflective barrier) inhibits heat transfer by thermal radiation. Radiant barriers are installed in attics to help reduce the amount of heat gain in the space, which in effect can reduce the amount of heat that transfers into the attic. Installations in attic spaces generally consist of reflective foil that is on the underside of the decking. There are other radiant barrier products, such as radiant paint coatings and loose foil.
R-Value: R-value stands for resistance value. The r-value of a material such as insulation determines how well the material works to resist heat. The thermal boundary of a house is determined by location of insulation and the r-value of the insulation so as to create a barrier between the conditioned space (inside the house) and unconditioned space outside or in an attic.
System Tons or Tonnage: The cooling capacity of the cooling equipment is measured in tons. A ton historically referred to the cooling capacity of a ton of ice.
Thermal Bypass: A thermal bypass is an area where heat transfer may occur from an unconditioned space to a conditioned area. This is commonly found in an attic space where there is an empty wall or second story floor cavity that may serve as a chase for drain vents, CO vent pipes or HVAC lines or ducts.