Just as the Indoor Air Quality Conference has transitioned to be the Indoor Air Quality and Energy Conference, energy efficiency and indoor air quality have become very intertwined when planning both new buildings and the retrofitting of existing buildings. This is for good reason. When you tighten a building’s envelope and potentially reduce air exchanges to achieve energy efficiency, there is definitely a possibility of negatively impacting the IAQ and health of that building. There are plenty of cases where this has happened.
Having worked with many, many projects that have been focused on energy efficiency as their primary goal, I have seen both good and poor outcomes with respect to IAQ. Many times, there is a plan in place to achieve both very high energy efficiency, and good IAQ. And yet the end result falls short, and usually at the expense of IAQ and health of the building and its occupants. And in many cases, this is the result of good old fashioned value engineering.
I actually don’t understand the phrase “value engineering”. Because in most cases where I have seen this performed, value has been significantly compromised. When it comes to buildings, there is generally a disconnect between the architects/engineers who design the project, and the builders/contractors who build it. And then there are the developers/owners that manage the budget, who are often not well informed about the impact that the compromises that are made during the value engineering process will have on both energy efficiency and IAQ.
In most cases today, the cost savings have been found in the ventilation system budget. Because ventilation in not well understood both from an energy perspective, and from an IAQ perspective, it is ventilation that gets “value engineered” to reduce costs. A couple of examples:
Case 1: Residential. A retrofit residential project includes installation of a Heat Recovery
Ventilation system. But the installer decides in the field to continue to use the bath fans for
bathroom exhaust ventilation, to reduce the cost of ducting from the bathrooms. He installs a single return in the hallway/living area. As a result, the bath fans exhaust a significant amount of energy in the winter time, and depressurize the home when running, and imbalance the HRV.
Result: Significant loss of energy both from exhausting warm air in winter, and in significant
reduction of efficiency of the HRV when imbalanced. Additionally, the risk of mold in exterior walls due to drawing warm, moist air in during summer months while running the bath fans is increased.
Case 2: Commercial/Multi-family. A developer chooses to build a highly energy efficient
low income housing apartment building. Budget is critical, and during the design process a
significant value engineering process is undertaken. As a result, the ventilation system utilizing multiple rooftop Energy Recovery Ventilators is re-designed to provide a single
supply point to each apartment. In the one bedroom apartments, it is in the bedroom,
which is good design. But in the two and three bedroom apartments, it is in the hallway/
living room. This was done, apparently, to reduce costs. But as a result, the bedrooms have
compromised ventilation. Based on multiple studies, with the bedroom doors open air changes are minimal. With the bedroom doors closed, air changes are almost non-existent.
Result: IAQ and health for bedroom occupants in the two and three bedroom apartments is
compromised. As a result of poor ventilation, occupants open windows for air, also seriously compromising energy efficiency. And of more significant concern, without proper ventilation the bedroom exterior walls are exposed to moisture penetration in winter, and the possibility of condensation within the wall assemblies, and resultant mold growth.
These are just a couple of examples of the unintended consequences of value engineering in buildings. I am confident that many of our readers could add to these examples, with some not-so-significant impacts, and with some catastrophic results. I would recommend that teams involved with developing buildings and/or retrofitting buildings explore the potential unintended consequences when undertaking value engineering exercises. And when it comes to HVAC, be very careful with regards to the V component. Ventilation is historically undervalued, and not fully understood, but in the built environments of today it is becoming the most important piece in delivering healthy, comfortable and energy efficient buildings.