Indoor Environmental Quality

In order to deliver superior Indoor Environmental Quality (IEQ), the designer must consider methods for introducing proper amounts of outdoor air into the space for the purposes of dilution (IAQ), while controlling the temperature and humidity levels within the space and delivering that conditioned air to the space without producing high levels of acoustic disturbance.

Indoor Air Quality (IAQ)

Recommended Ventilation Air GraphAs a brand offering Dedicated Outdoor Air Solutions®, there are two parts to supporting the IAQ goals of any HVAC project. The first aspect is directly related to the equipment being supplied; ensure that it complies with all the usual codes and standards by including proper levels of filtration, proper design of the intake and discharge openings to prevent the possibility of re-entrainment or short-circuiting, and to eliminate potential for microbial growth on or within the unit itself.

To that end, all of Venmar CES’s semi-custom and applied equipment includes:

  • Thermally broken no-through-metal exterior panels, doors, center partition, roof and base structure to maximize heat transfer and minimize the possibility of condensation on interior or exterior surfaces
  • Double wall construction to eliminate the potential for fiber erosion in the supply airstream
  • IAQ sloped drain pans and materials to help prevent microbial growth and provide easily cleanable surfaces (smooth interior finish) along with easy access for regular cleaning and maintenance
  • Minimum MERV 8 on the supply and return airstreams with easy upgrades to provide MERV 14 (or much higher upstream and downstream filtration depending on the equipment used)

Optionally, equipment can be selected with direct drive fans to eliminate belts (and further reduce the possibility of fiber erosion), or in some cases a washdown cabinet can be selected for more extreme applications.

The second aspect of meeting IAQ as a manufacturer is designing equipment that can deliver the proper levels of IAQ to the space in the most energy efficient manner possible. Certain unit configurations and building designs can do this more effectively than others, but in general, including some form of exhaust air energy recovery typically allows for the most economical method of introducing outdoor air by reducing the capacity of the post conditioning equipment required to treat air for the space.

Temperature and Humidity Control and Acoustics

Additionally, air-to-air energy recovery takes a large percentage of the load off of the mechanical equipment, and in the case of enthalpy energy, the recovery device follows the sensible heat ratio to allow the air conditioning equipment to be significantly downsized and to operate more efficiently and effectively.

Energy recovery in-and-of itself does not ensure precision temperature and humidity control, but there are a number of standard and optional features that can be included at the time of equipment selection to provide superior performance in this regard. Using a DOAS configuration is an option which provides the ability to decouple the outdoor air loads from the internal sensible loads of the space and has repeatedly proved to be not only an easy way to control temperature and humidity, but also one of the most economical (and sound sensitive) methods as well.

Outside of the overall configuration though, chilled water and hot water coils have historically provided very good capacity modulation; if an electric heater is used (either as a preheater or for post conditioning) the inclusion of an SCR is strongly recommended.

Venmar CES equipment also includes a number of additional features to ensure superior temperature and humidity control along with inherently quiet operation. If a unit is configured with gas heat, it is important to size it for the actual capacity (do not oversize) and ensure that you have an adequate turn-down ratio.

Integrated packaged systems, either WSHP/GSHP or air cooled condensing units, all typically have quiet fan (air cooled) and compressor combinations and can be selected with Variable Refrigerant Control (VRC)® for Dx capacity modulation (either on the lead compressor so that it acts much like an SCR or on each circuit). This provides 10–100% modulation ability eliminating hot gas bypass which is extremely inefficient but also provides superior part-load performance.

FANWALL TECHNOLOGY® also provides an extremely efficient method of air movement. It significantly improves the heat transfer performance of all of the major components, but allows superior abilities with respect to air management, and has an extremely quiet acoustic signature.

External Links

AEE
ASHRAE
DOE
IAQ Design Guide

CaGBC
USGBC