Energy Audits

What is an Energy Audit or Home Performance Evaluation (HPE)?

Blower-Door-InstructA Home Performance Evaluation (Energy Audit) can be thought of as an approach of looking at the systems within a home (the building envelope, the heating/cooling system, and the occupants and their respective behaviors), assessing both the relations of these systems with each other and the possible effects of these relations on both the building and the occupants. What is called a "systems" or a "whole house" approach.

Having a HPE is important because unlike in the old days when construction methods were basic, building materials simple and heating fuel affordable, today's homes involve advanced concepts and materials that don't function the way the older concepts and materials did. Without the proper understanding of these interrelations, unexpected outcomes/complications can be expected. These outcomes are almost never positive. From mold, to combustion appliances not working properly (i.e. back drafting, incomplete combustion), to ice dams and roof rot, to indoor air quality issues, all these outcomes lead to the same things: higher energy bills and a decrease in both building durability and occupant comfort and safety.

How is Home Performance Assessed?

Home Performance is assessed by having a Home Performance Evaluation conducted. The evaluation involves a certified Evaluator/Analyst coming to the home and looking at the home not as a series of unrelated parts (e.g., attic, windows, furnace), but as an integrated system with each parts' success/failure being dependant on the others. Visual inspection combined with cutting-edge diagnostic testing is the backbone of this process. Airflow in and out of the building is the primary driving force for the overwhelming majority of building performance flaws and issues. This metric is measured & quantified with a Blower Door test. Air is pulled out of the building with a large fan, creating an air pressure difference across the building envelope between the inside and outside. Houses that have uncontrolled or excessive air leakage have higher energy bills, decreased durability and tend to be less healthy and comfortable to live in.

What Went Wrong?

In the past, houses were "built to breathe". There was no attention to air leakage in and out of the building nor was there an awareness of the benefits of having a thermally resistant structure. Heating sources were extremely affordable (coal, wood and eventually heating oil) and the excessive amounts of natural air exchange kept indoor air clean and dry. But as construction methods evolved and heating fuels became both expensive and geo-politically sensitive, the need for tighter, warmer buildings has become paramount. Not just tighter and warmer, but also ventilated properly.

The Need for Change

For the past 60-70 years, the typical home building process has gone something like this:

  • The Architect/Designer designs the basic shape and layout of the home, and is finished.
  • The site work/foundation is done by a construction company, and then they're finished.
  • The house is erected by the framer, possibly finished by the same contractor, and then they're finished.
  • The electrician connects the service panel and wires the house, then is finished.
  • Insulation is installed by an insulation contractor, using age-old trade practices, with no attention to the importance of air sealing, and then they're finished.
  • The painter/siding company comes and "shines it all up", then the house is done!?!?


Where Does this Lead Us?

The end product is not a designed system of compatible assemblies, but a bunch of systems thrown together. No forethought into the potential impact(s) that these systems have on the durability of the home, the occupants' health & safety or on the respective systems themselves is ever contemplated.

Here is a typical scenario; the furnace or boiler is back-drafting, spilling flue gas (carbon monoxide) into the living space effecting the health, safety & comfort of the occupants. Who's to blame? Is it the builders' fault for building such a tight house? Is it the electricians' fault for installing venting appliances like bath fans and range hoods? Is it the mason's fault for building a chimney, which mandates that a naturally drafted combustion appliance be installed to handle the heating of the dwelling?

If you asked each tradesman, they would attest to strict adherence to their trade standards. Chances are, they did do their jobs as specified, but the major problem here is that their "trade standards" never account for the possible negative outcomes that arise from the interrelation of these systems.

Here is another common scenario; an older home that was built "loose" (high air exchange) has been retrofitted with insulation. Throughout the past, this was looked on as a positive thing, keeping you warm and lowering energy bills. There was never any attention paid to the potential negative aspects of insulation, namely its' ability to create condensing surfaces within the enclosed cavities of the building envelope. The insulation raises the surface temperature of the heated side of the envelope but lowers the surface temperature of the exterior surfaces inside the envelope (inside surface of the sheathing, mainly). If moisture gets into this cavity it commonly condenses on the cold surfaces, causing rot and mold. The points of air leakage into/out of the dwelling need to be located, measured and analyzed and plugged. Only then can the installed insulation perform without increasing the risk of mold and rot.

What Now?

If you want the home to work properly as a system, then a SYSTEMS APPROACH needs to be taken. A Home Performance Evaluation / Energy Audit should be scheduled and conducted. Performance issues will be discovered along with prescriptive measures and solutions to remedy these deficiencies.

There is no other way. Contact Build Green Maine today!