Concentration of CO2 in the Atmosphere

Low Hanging Fruit – Stop the Heat Loss

– Where to Start


A Blower Door Tests Air Leakage. Photos courtesy of Mark Boudreau.

What is an energy audit, why is it important and why it’s the starting point for any upgrades you make?

Your house loses heat in a way similar to how your body does. Here is the analogy, explained..

The thick sweater you wear under your shell or windbreaker  is insulation. In the nerdy building science world we call it the “thermal boundary.” It traps heat near your body. Your house’s thermal boundary is the insulation that you have in your walls and in your attic. Sometimes this is fiberglass, cellulose, foam, newspapers in older houses or mineral wool. Houses can have many different types of insulation in their walls depending on when they were built. Some homes have no insulation at all.

Testing a Heating System’s safety and efficiency.

Testing a Heating System’s safety and efficiency.

On your body, your windbreaker is the air barrier. It stops the wind from robbing the heat your body worked so hard to produce. We also call this “air- sealing” or “air leakage.” Imagine your windbreaker is full of holes. It will feel drafty and uncomfortable especially where the holes are. The air barrier in your house stops the heat from passing through the thermal boundary and escaping to the outside. The windbreaker (air-sealing) in your house can be made of many materials. Sheetrock, plastic, paper, as well as some very green and high tech air barriers that allow water vapor to pass through but very little air to escape. When we do audits we regularly find MANY holes in the air barrier in a home. This holds true for historic 200 year old homes as well as brand new homes.

What the Audit Does

The energy audit identifies how well the house’s “sweater” is working and how many holes the house’s  windbreaker has in it. It also evaluates the efficiency of your heating and cooling systems, electrical efficiencies, indoor air quality, ventilation as well as moisture and mold issues.

The audit locates the areas that need improvement and gives you a way forward toward a better performing and less costly “winter coat.”

The audit is the starting point for making any informed decisions regarding home performance and energy efficiency. The audit takes a holistic approach to looking at your houses efficiency. It is the point at which we collect all the related data the house has to offer and synthesize it into a format that helps us identify the ways that the various pieces of the house are working together or are creating problems for the house and you. With it we can develop a complete and comprehensive picture of how it can be improved. We can predict how adding something or taking something away will have a ripple effect through the whole system of your house.

Air-sealing in the attic.

Air-sealing in the attic.

We look at every assembly of the house from the basement to the attic. We look at windows, obscure assemblies and things called “thermal bypasses” that you might not expect would be sources of heat loss. These are areas such as house connections with chimneys, porches and garages. Based on this list of observations we come up with recommendations on improvements.

The audit starts with a site visit that lasts for up to six hours and is completed after another several hours of energy modeling and report-writing in the office. It also includes infrared imaging on the house which will help us pinpoint specific areas of the house where heat loss and air leakage is happening. At our company we provide a very detailed report  discussing how the house is currently operating, what measures could be undertaken and how much they would likely cost. Most Building Performance Institute-certified auditors provide these reports.

Foam Insulation above and Cellulose insulation below.

Foam Insulation above and Cellulose insulation below.

After the audit you will have the information you need to take the next step with heating systems, insulation and any other items that might be on your audit report. The audit should include some energy modeling that shows you how each change you make will have an impact on the performance of your house as well as predict cost savings from that measure. In essence we can show which improvements are going to be the “lowest hanging fruit” in terms of maximizing the return on your investment. The modeling is a key component in helping you focus your resources on the biggest impacts in improving the efficiency of your home.

Some states have special incentive programs which pay you incentives for making energy improvements. In Vermont, Efficiency Vermont administers many of these programs via partner contractors who are specially certified and vetted to perform these audits. Check with your state to see what yours has to offer in terms of financial incentives.

Audits generally cost between $200 and $500 depending on the auditor and the thoroughness of their examination. Some auditors offer the audit for free if you hire them for your work. Those generally have a cost structure that factors the cost of their time to do the audit in their quotation for their weatherization work.

A key point. Don’t skip the energy audit. You can add insulation to your house but not fix the leaks and actually end up causing problems. You can seal all the leaks and also end up causing problems with how the house is ventilated. Consult with a qualified professional before you decide to take on do-it-yourself work. It is easy work and it is also easy to get off track. Some measures if not done properly can lead to mold and rot issues that wouldn’t have been present prior to the work. Start with an audit and understand how the various pieces work together in the ecosystem that is your home.

Mark Boudreau is Co-owner of Lewis Creek Company, a full-service design-build company consisting of both trades-women and men located in North Ferrisburgh, VT. They create homes that integrate a holistic approach to new building and renovating weaving together people, homes, the environment, beauty, economy, and performance.



1 Blower door Test  1290: A  Blower Door Tests Air Leakage.

2 Reading test results  1057:  Testing a Heating System’s safety and efficiency.

3 Air-sealing in the attic

4227:  Foam Insulation above and Cellulose insulation below.


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