How an Energy Audit, Some Caulk and Insulation (Total Cost $1175) is Saving Me $1000... Per Year.


This is the story of how an $1175 investment in improving the energy efficiency of my home is saving me about $1000 per year in energy costs, and has made my home much warmer and more comfortable in the process.

Last May I had a home energy audit conducted by Flemming Lund of Infrared Diagnostics in Sudbury, MA. The results weren't entirely surprising; I didn't expect my aging suburban home to be completely leak-free and perfectly insulated. Nonetheless, the energy audit was extremely useful in pointing out several actionable, high-ROI steps that I could take to increase the energy efficiency of my home.

Next step, equally important: I got down to it. I installed blown in cellulose insulation in areas where it was deficient, air sealed cracks and gaps, replaced old weather stripping, and then had a follow up energy audit to assess what kind of progress I had made. The pictures below are from the two audits, and show just how much of a difference the work I had done made -- you can almost feel the increased warmth and comfort of the house where blue spots turned to red on the infrared images. 

Although Flemming calibrated the infrared camera to account for temperature differences between the two audits, It's worth noting that the outside temperature during the first audit was 50 degrees Fahrenheit and 38 degrees Fahrenheit during the second audit.

The following photos will take you through the steps that I took to improve the air sealing and insulation of our house.  Blown in insulation was all installed by hired contractors, as was much of the air sealing work.  However, many of the most significant improvements were made by myself -- looking back over the initial audit report, I simply retraced the steps on a cold day, found air leaks by hand (literally) and sealed them with a caulking gun. We'll start there. 

Air Sealing:

Here are just a few examples of where I did air sealing work:

Aside from the very cool infrared images of improved insulation (posted below), perhaps the most valuable information gained from my follow-up audit was that these simple air sealing measures reduced my home's air infiltration from 0.87 NACH (natural air changes per hour) during the heating season to 0.42 NACH, and I have continued to make improvements since the second audit.

My air sealing work and the benefits it reaped confirmed my long-held belief that air sealing should be step one in improving a home's energy efficiency.  It's cheaper and easier than an insulation upgrade, and helps to ensure that insulation will remain effective (if air is permitted to move through insulation, it loses r-value).  It also goes to show that simply hiring a contractor to get the job done may not be the right course -- in my case, I think as much of the benefit came from simple things I did as from what the insulator did. 


Still, once air sealing is done, improving insulation makes sense and can add to the benefit by helping your house retain heat.  I'll let the following images speak for themselves:

Although insulation isn't necessarily the first step you need to take, we notice that there are no longer cold spots on the walls that create uncomfortable areas in the house.  As a result of our upgraded insulation, in addition to our air sealing work, the house is more comfortable, takes less time in the morning to heat up when the programmable thermostat kicks in, and our utility bills are much, much lower.

Lessons Learned:

Having taken these steps, we've also come to realize that there is no silver bullet: improving the energy efficiency of our house is an ongoing process -- there is still much to be done. The follow-up audit showed that there was still much room for improvement, and we have since taken steps in that direction. Some examples of where we initially fell short:

Although the follow-up audit pointed out some problems that I missed during the upgrade, as well as some new ones that were overlooked during the first audit, it was also helpful in confirming that much progress had been made.

So what's the payback time for these improvements?

I will note that my gas utility, National Grid, had a program that paid a rebate of 75% of the cost of the air sealing and insulation, which made something of a difference.

That said, the numbers are staggering:

The cost of the audit was $400, the follow-up would have been $200.  The cost of the insulation after rebate was $475.  Materials for sealing (caulk, foam, insulation board) was about $100.  I can also deduct some of the materials cost in my federal tax return (maybe worth $50 or so).
So for a total cost calculation: I paid $168/month x12 before (2016 per year), and pay $89/month x 12 now (1068/year) for heat and hot water and stove (neither of the latter have changed), which means I will save almost $1,000 per year as a direct result of these improvements... every year.  It looks like this job had a one year payback.
I am comfortable, using less energy and spending a lot less (even if using the house more!).  That's exciting!

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Paying attention and taking action is good. Not sure about the math! Disaggregate DHW/Cooking. Need a year's data.

Jamie -- yes, you're right about some of the math methodology here, perhaps, and a year will tell the true tale. But I think these numbers are going to turn out to be about right.

I have been working on a spreadsheet that backs out the non-heating gas uses (based on summer usage patterns), and 2) is based on therms, as reported by my gas company, 3) normalizes based on heating degree days for the period reported (check out the ever-so-cool, and 4) normalizes for number of billing days.

Kind of complicated, but it gets worse, of course since, for example, I am now working out of the house most days (and occasionally turn up the heat), maybe programmed our thermostat differently, as well as other variable factors.

But actually heating degree days may not be granular enough, and I am not really sure -- should I use the 65 degree default...

So anyway, knowing what I do know, and using a reasonable amount of common sense, I now have three monthly bills, and the numbers are coming in at about 45% reduction in therms used, so it seems to be tracking pretty closely to what the gas company has figured out about my usage patterns. Over the rest of the heating season we'll get a clearer picture.

But I can say with certainty: we're far, far more comfortable. Our main concern now is how to justify the fact that my wife and I both have iPhones, and they cost more than we pay to heat and light the house! Hmm, time to buy some stock in Apple...


I prefer proof to claims - too much wishful thinking going on out there. I like that comfort is as an important "payoff" and would prefer to see that as the lead - at least until you have data that supports the model (the inaccuracy of modeling needs to be better understood).

Thanks for sharing your experience.

This is a great personal story! Thanks so much for sharing.

What a great example of documenting an energy efficiency effort! I think stories like this can take some of the trepidation out of just going ahead and doing the energy audit, the caulking, and maybe even the insulation... The audit visuals are really effective! Thanks for sharing!

Jamie, yes a lot of wishful thinking and overblown claims are out there -- they can confuse and undermine solid data. I prefer proof to claims, as well. But I would also like to share what we have learned and observed.

I completely agree with the idea that comfort is an important payoff. In fact, honestly the major payoff for me (personally) is that I believe our house now emits far less CO2 for heating than it would have last year. But for most of us, cost is a factor.

My results are just one data point, but while they may not be proof, they are fact: I will spend about $948 less for heat, hot water, cooking this year than last -- the gas company has already done their "level-billing" projection for the year, and other than the adjustment that they do in August every year, it's pretty much a done deal (in the 12 years I have lived in the house the adjustment has always been in my favor, in other words, they over-bill). How relevant that is to you is your call. Even after a year, no amount of data or fancy modeling could "prove" my claims, as I intend to keep improving the efficiency of my house in every way that I can.

My point is that whatever the motivation, our experience taught me many things about what matters in this kind of process, and this seemed worth sharing ... now.

In talking with neighbors, I have come to see that people hear "weatherization" or "home efficiency" and don't really have a clue where to start. They replace a lightbulb with a CFL, or hire an insulator who does a lousy job (like the one I hired the first time, before I knew anything about energy audits). They feel like the job is done. But then see no results. It's frustrating, and this is a much more significant issue, in my view.

My neighbors have good intent, but poor information. A site like Energy Circle is working to educate people through real-life experience, and yes, evangelize home energy conservation without going over the top.

Perhaps the lead on this story should have been a little less dramatic. The goal here is to help people understand what the process is like, learn that it doesn't have to be incredibly costly, and make some important points about people's misperceptions about insulation versus making the house tight.

But it doesn't take a lot of math or models to see that this kind of effort is remarkably cheap, and it appears, based on the numbers we have so far, to be remarkably effective.

As I noted before, I do have a model in place that backs up my preliminary numbers, and actually, the gas company has some very sophisticated modeling that they use to do level-billing projections. My claims are not wishful thinking, at least not for my house and this year's gas bill.

Sorry to run on. I'll talk to the editors here and see if we can tone down the title a bit :-)

Thanks Michelle! (And djthiede).

I was really lucky to have Flemming Lund do our energy audit. Frankly, I probably would not have ponied up for the normal 1/2 price re-audit, but for me, this was really where I became convinced of a few things: 1) what we did had an impact, 2) we would have done many useless things without the original audit, and 3) even after doing a lot of work and sealing and caulking and the like, he found a few spots that I had just forgotten to do, or done poorly -- $1 of caulk and foam around my dining room window could end up being as important as some of the other things we did that cost far more.

Anyway, get at least one audit from a pro like Flemming, and then start sealing all the gaps. It's kind of fun, actually.


Thank you for the outstanding post. Consumers and homeowners all want the same thing, and that is to save energy and lower their utility bills. However, they are skeptical about spending the money and are always asking what are the concrete savings to implementing a weatherization plan. This is one of the best post detailing an actual energy saving project as it rolled out. Thanks again.

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