General Process

We were gifted a huge resource of design review by Building Science Corporation, through the National Grid DER pilot program. Their advice was very valuable as we navigated this new construction style. And we sought input from other NESEA members, notably Paul Eldrenkamp and Marc Rosenbaum. We worked closely with builders during design to choose buildable approaches to this retrofit. And we worked with manufacturers to find new applications for interesting new products (see envelope description).

Design for Adaptability:

We did not need three baths for our unit, but in discussions with realtors, we found that would be the preferred arrangement for any future residents. It also allows for the unit to be inhabited by more unrelated people, for example as a student rental.

Software Tools

Software Tools:

National Grid pilot program spreadsheet, which asks pertinent questions about energy efficiency that are often hard to find in manufacturer's literature. A good high standard for specifications.

General modeling information:

Lessons Learned

Outcome of project goals:

The initial building team did not meet the air sealing goals for the project, and indeed was not actively testing for them. The site super was religious about carrying a foam gun around to get each penetration, but the initial air barrier layer was poorly installed and not corrected when it was called out. As framers are asked to do new jobs in this high performance building method, it may be useful to tie their contract to the air barrier goals to ensure each responsible party is on board with the goals.
We borrowed blower doors and did our own testing, and one weekend dropped 500cfm just by caulking some of the framing. (Thanks to Byggmeister for the loan of the door and smoke machine!) And we did a lot more air sealing on the interior, which was expensive, time-consuming, and aesthetically challenging. Ultimately, with the new team, we exceeded our goal by a healthy margin, which was a very exciting reward for all that extra work!


The Thermatru doors gave an overall unit rating that met our program requirements, but in order to get this rating, they needed to be "impact rated" which includes more metal framing in the door. Significant thermal bridges result. We have not changed out the doors, but next time we do any work on the house they will be on the list, as the condensation around the windows is considerable. While PHPP is a daunting level of design investment in a project, we all need to learn to think like a Passive House designer at least on a macro level to catch these egregious discrepancies.