Energy Conservation-Shallow Energy Retrofit

This post originally appeared on the Green Building Advisor website.

Several years ago, I performed a roof replacement for a customer, the customer wanted to change their older and failing asphalt shingled roof to a steel roof.  We stripped the old shingles and existing underlayment off, installed new synthetic underlayment and new steel over the 10/12 pitched roof.  I felt confident that this new roof would last many years.

The following year, the same customer asked if we would replace several windows in the upper level of his story and a half home.  The old windows were due for replacement, the single paned wood units appeared to be from the mid-1900’s.  Woodpeckers had pecked a hole nearly completely through one of the windows.  Several others were painted shut.  Again, a straight-forward job we had done dozens of times before.

The home with the roofing and window replacement that resulted in “attic rain”.

The spring after the window replacement, I received a call from the customer saying his roof was leaking.  He had water dripping in several areas in the upper level of the home.  A visit to his house did indeed show water damage, though it was not the result of a bulk water leak from the roof, but instead, air leaks from the interior had formed frost on the attic side of the roof sheathing, the home had never had this issue before.  I surmised that replacing the five upper-level windows had changed how this home handled air and moisture just enough to cause frost to form in the attic.  My first building science lesson about the unintentional effects of a shallow energy retrofit.

You’ve probably heard the term “Deep Energy Retrofit” (DER), the renovation of a home to reduce the structures energy usage.  Deep energy retrofits can make sense if a home is undergoing a renovation that also includes updating the exterior and interior finishes, and/or mechanical systems.  Usually, the cost for a dedicated DER is high, so performing a renovation just for energy cost savings does not make economic sense.  Many homeowners will instead choose only to update select problem areas, or areas having the greatest return on investment instead of going all in with a DER.  Let’s call this incomplete deep energy retrofit, a shallow energy retrofit.

Shallow Energy Retrofit (SER)-a limited renovation to an existing home with a focus on reducing energy usage. 

Of course, this is nothing new.  We have been performing “weatherization” duties to homes in my cold climate for decades.  The Department of Energy’s Weatherization Assistance Program (WAP) was started in 1976 with the goal of reducing energy consumption and improving the comfort, health and safety of many low-income households.  The scope of work for a WAP project is specified by a trained energy auditor, typically working for a local state agency.  The work is then performed by independent contractors or in-house teams trained in weatherization duties.  Decades of experience and the training of the workforce performing these duties has resulted in a successful weatherization program.  This program is designed for lower income households, but what about the millions of other homes that do not qualify?  Often, they rely on the advice of a contractor, or what they read on the internet for a scope of work to best fit the needs of their home.  I am performing more and more building investigations on homes that had work performed to reduce energy use and improve comfort without considering the effects these changes can have on how a home handles moisture.

Another example, I was asked to determine why there was some water dripping through the ceiling of a single level home that recently had closed cell spray foam installed on the unconditioned and vented attic floor.  Two inches of the CCSF was installed with an additional 12” of fiberglass insulation blown over the top in the attic space.  When I arrived at the home, I could not see out the windows.  Cold exterior temperatures and a high indoor relative humidity level had turned the windows into dehumidifiers, water was dripping down the glass.  The homeowner hired an insulating contractor to air seal and insulate the attic.  The contractor didn’t think to look in the crawlspace, which was not conditioned or air sealed, the crawlspace was connected to the living space.  The dirt floor was the source for the increased humidity inside the home.  Luckily, the issues were fairly easy and not overly expensive to resolve.

The dirt floor crawlspace that led to wintertime moisture issues.

One more example, this home was undergoing a renovation that was not completed before cold weather set in.  Incomplete air sealing changed the neutral pressure plane, moving it lower in the building assembly causing air to move through areas that previously did not have active air leaks.  The result was frost forming inside wall cavities.  When temperatures warm, this solid water becomes liquid water and funky looking icicles protruding out the wall were the result.  (By the way, this is my home.)

My home with the incomplete renovation.

My point to all this is shallow energy retrofits (or incomplete deep energy retrofits in the case of my home) can have unintended, and sometimes, unpredictable results.  With the high cost of new construction and the millions of older homes that could receive energy consumption upgrades, there are opportunities to improve our existing housing stock, but the work needs to be well thought out.  My friend, Peter Yost has a great saying, “you must manage energy and moisture with equal intensity.”  This needs to be the moto for Shallow Energy Retrofits.  In the coming months, I’ll be covering different topics relating to improving performance in existing homes, without performing a deep energy retrofit.  Stay tuned for more about the shallow energy retrofit.

One Reply to “Energy Conservation-Shallow Energy Retrofit”

  1. I’m glad to hear you are diving into SER end of the business. As a home owner and contractor it is difficult to know the energy impact of upgrades whether its windows, doors, insulation, etc. Plus, few people treat the home as an entire system that needs to be considered versus just slapping new windows or siding / insulation and then wondering why new problems have surfaced afterwards. Looking forward to it.

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