To start, let’s ask ourselves why ventilation and outside air requirements exist in the first place – what’s the problem they’re trying to solve, and how does outside air accomplish that?
The problem: Poor indoor air quality due to contaminants in the space.
These contaminants may include odours and chemicals, and these may be introduced into the space from a variety of ways, including off-gassing from the products and materials within the space.
This problem is common to both the IAQP and VRP methods, and what they each aim to solve. Where they differ, is the approach that they use to manage these contaminants to improve the indoor air quality.
The solution:
VRP: introduce enough outside air to adequately dilute the contaminants. Prescriptive based approach
IAQP: look at both the rate of production, and rate of removal of contaminants (eg by an air cleaning device) when determining how much outside air must be used. Performance based approach
The advantages:
VRP: simple, prescriptive based approach that is easy to follow and that most people are familiar with
IAQP: may allow you to reduce outside air requirements by up to 80%, while still meeting code. ie, potentially substantial cost and energy savings on heating and cooling loads and their associated equipment
The disadvantages:
VRP: a missed opportunity on potential cost and energy savings. Not necessarily knowing whether the approach worked, or what the resulting IAQ is of the space once occupied
IAQP: more complicated process which involves determining expected level of contaminants, determining rate of removal, and testing IAQ of finished space to confirm that required IAQ is achieved
Why now? What’s changed recently that has been encouraging designers to start following the IAQP approach?:
ASHRAE 62.1: in the latest update, ASHRAE has given more guidance on how to determine the expected level of contaminants in the space. This greatly simplifies the process and reduces the liability that would have previously fallen on the engineer’s judgement.
Manufacturers: more and more manufacturers are starting to offer products that aim to take advantage of the IAQP method, and reduce outside air requirements for a job – in most cases meaning a substantial savings in energy and cost savings, both upfront (reduced equipment capacities required) and ongoing (reduced operating loads).
IAQP calculators: these are starting to be offered, both by ASHRAE as well as equipment suppliers, and in many cases make the calculations involved in the IAQP method as simple as looking up tabulated values like with the VRP method.
Interested in how the IAQP method paired with an air cleaning device may help you or your client to reduce energy consumption and associated operating costs? Feel free to reach out to your local O’Dell salesperson and they’ll be happy to explain which types of jobs can benefit most from the IAQP approach as well as run a preliminary IAQP outside air reduction analysis.
