IEQ Investigations – The 4 P’s
IEQ Investigations – The 4 P’s
Indoor Environmental Quality (IEQ) is critical for occupant comfort, productivity, and well-being. An IEQ investigation should be performed proactively in order to avoid occupant complaints and decreased productivity, and to minimize long-term damage to building materials. Too often, IEQ investigations are made reactively – in response to occupant complaints or known building problems. In such cases, there is often distrust or dissatisfaction of occupants or tenants, and perceived or real ill-health effects are already being reported.
The old adage, “an ounce of prevention is worth a pound of cure,” rings true with regard to IEQ inspections. Being proactive is always best, and often saves building owners and managers many times the cost of the inspection service.
Many Indoor Environmental Professionals (IEPs) utilize a simple method of assessment that categorizes relevant elements into the “4 Ps.” These variables are present in almost every building, and a good IEP will want to understand each element in order to develop and test their hypothesis. Should a problem exist, targeting at least one of the P’s should begin to address the issue. Knowing how to analyze each P and identify the easiest control method is the art of an IEQ investigation.
Here are the 4 P’s:
IEQ Investigation – People
Comfort, productivity and occupant health don’t really matter in an unoccupied building. But in an occupied building it’s important to understand the People. Young, old, sick, or immune-compromised in the building changes how an Indoor Environmental Professional (IEP) will consider the building and potential IEQ problems. If someone suffers from asthma or allergies indoors, or if symptoms have already been reported, it’s critical the IEP collects sufficient information during an interview phase in order to grasp what is happening to People indoors, and to put up the red flag if there are known sensitive occupants or serious symptoms being reported.
Symptoms such as headaches, dizziness, nausea, sinus congestions, coughing, or itchy throat or eyes are clues not to be missed by the astute IEP. Sometimes sufficient information can be gathered directly from occupants or the Human Resources department, and other times it’s best to work directly with medical personal familiar with occupant health complaints. All medical issues revealed to an IEP should be kept confidential unless ordered otherwise through subpoena.
IEQ Investigation – Pressure
Airflow is created by pressure differentials, and airflow is usually the Pathway (3rd P) by which Pollutants (4th P) are distributed throughout a building. Pressure is a fundamental element in understand IEQ. The nature of physics dictates that there is a constant push for pressure equilibrium, and air always flows from higher relative pressure to lower relative pressure. Outside wind, fans, temperature differentials (“stack effect”), and elevators may influence pressures in a building. The stack effect essentially defines how warm air is more buoyant and rises naturally. This is how a chimney works, and also how buildings frequently become positively pressurized at higher levels (or in attic) and negatively pressurized at lower levels (or in crawlspace/basement.) Depending on temperatures inside and outside the building, and how mechanical ventilation affects the space, pressure conditions can swing dramatically.
I’ve heard that the stack effect was so strong when they built the Empire State building… that the doors couldn’t be opened from the street. I’ve been told that is when they developed the rotating door system is still used today in many skyscrapers… although mechanical ventilation now helps offset the dramatic pressure differentials created by stack effect in very tall buildings.
The most common force affecting indoor pressure is the HVAC system. Mechanical air movement via fans creates positive and negative pressure areas within any building. When contaminated spaces (wall cavities, crawlspaces, ceiling plenums, duct work) become positively pressurized relative to occupied areas, there is a natural tendency of air flow from high (contaminated) to low (occupied), and problems may arrise.
IEQ Investigation – Pathways
Air and contaminants will flow through any crack or opening in order to try and achieve pressure equilibrium. Windows, doors, cracks under doors, HVAC ducts, cracks in walls or floors, electric or plumbing chases, etc., all become pathways for contaminants (4th P) to enter an occupied space.
If you’ve ever been around during a blower door test you’d know that air takes amazingly complicated paths through wall assemblies. There is almost always air humming from around can-lights, outlet covers, switches, cabinets, and plumbing penetrations. Given the right Pressure scenarios, all these viable Pathways may introduce Pollutants into an occupied space.
IEQ Investigation – Pollutants
Pollutants exist in outdoor and indoor air. External Pollutants may include pollen from grasses and trees, mold spores, soil gases (e.g., radon), exhaust emissions from lawn care or nearby traffic, or VOCs from wet-applied finishes applied to outside walls or roofs. Internal Pollutants may include a myriad of chemicals and biological agents. Asbestos and fine particulates (e.g., mold spores) may be drawn into an occupied space from a wall cavity if Pressure conditions cooperate and there are Pathways.
Consider the 4 P’s next time you don’t feel good indoors or suspect an IEQ problem. If all four elements are present you know you’ve got a problem, and the solution lies somewhere in eliminating at least one of these variables from the equation. Take away the Pollutants, eliminate Pressures or Pathways, and the IEQ problem can be solved.
Who is Healthy Building Science?
Environmental Testing Services at HBS
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