OPEN Scores on the Rise

A quick update on my March blog post about benchmarking the performance of our recently insulated apartment. We moved out at the end of June, but not before calculating one last OPEN score. Here’s the updated graph of our monthly scores and energy consumption:


As you can see, the cellulose insulation installed at the end of January led to improved OPEN scores through the spring, leveling out around 70—a nice jump from the 63 we averaged prior to the insulation work. Had we stayed in the apartment, our scores would have resumed their upward trajectory once we returned to heating season in the fall. Although we won’t be able to quantify the full impact of the cellulose due to the move, we know it was significant; our home is already operating more efficiently than 70% of homes in the U.S. I suspect our OPEN score would have plateaued around 75 if we had completed a full year in the apartment post-cellulose.

We used just 2,570 kWh and 629 therms of natural gas (used for heat and hot water) over the last 12 months of our occupancy, for a total cost of $1,424. The owner of the apartment is now using its efficiency as marketing for prospective tenants. The next occupants will save money and we (collectively) will avoid ~1 metric ton of CO2e emissions (roughly equivalent to driving a car 2,400 miles) each year for the life of the home.

Not bad for a few hundred dollars and a bit of coordination work.

OPENing Our Home

Our apartment in Cambridge Massachusetts is similar to many in the region—just under 1,000 ft2 of space in a three family home built in the early 20th century. It’s a wonderful building with charm and character, but literally no insulation. It’s been a cold and generally uncomfortable space during much of the winter. Fortunately for us, that changed this past January when we had cellulose insulation blown into the exterior walls through the Mass Save program. We had over $3,300 worth of insulation work done and paid just a fraction of the cost; if your state offers free or discounted energy audits and efficiency work, you should seriously consider it.

I’ve been tracking our energy consumption since we moved in just under 2 years ago, and calculating OPEN (operational energy) efficiency scores each month since our first year. Our average score has been a 63 (out of 100), which is above average but not great considering the steps we have taken to reduce our electricity use—killing vampire loads, using LED bulbs, shutting down our wireless router when not in use, etc. These steps certainly improved our score (and saved us money), but it’s just not possible to have an efficient home—even an apartment—in the northeast without insulation. Energy required for space heating dominates here; it accounts for approximately 68% of the energy used in our apartment, with 22% used for hot water and 12% for electricity (nationally these averages are 41.5%, 17.7% and 40.8% respectively).

My wife and I agree that the apartment feels more comfortable since the insulation was blown in, but I’ve been looking forward to seeing the impact the insulation work would have on our OPEN score. I want to be able to quantify the improvement rather than relying solely on our (likely biased) qualitative assessment. After receiving our first utility bills since the work was done and calculating a score, this is what we found:


After just a single winter month, our OPEN score jumped from an average of 63 to a 67! As you can see from the graph, our score over the last year (dark blue line) has been fairly consistent, bouncing between a low of 61 and a high of 64 prior to the insulation. It will be interesting to see how the score progresses over the next few months, but it’s already clear that there is a quantifiable improvement in our home’s energy performance. It’s gratifying to see that the money and time spent on the insulation work is having a definitive impact.

Calculate OPEN scores for your home here:

Author’s note: The OPEN score and energy consumption graph in this post was updated on March 29th 2017 to correct for a data entry error. Text referring to incorrect scores has been updated as well.