Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
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Glossary of Terms


A zone is controlled by a thermostat with or without a humidistat.

The thermostat can control a damper, zone valve, circulator or fan; or it could in the case of a single zone also control a furnace or boiler.

The zone controller is not the operating controller for the heating and cooling plant. It only focuses on the space conditions. It may be integrated as a feed back or feed forward device into a more sophisticated building management control system.

For radiant floor systems, a loop is only a zone when that loop has its own actuator and thermostat. Multiple loops does not equal multiple zones unless one or more of the loops are controlled by a separate thermostat.

For example a single thermostat controlling flow to a 10 loop manifold is a single zone regardless of the 10 loops.



Zoning: How to divide a building into zones
Copyright (c) 2012 Robert Bean, R.E.T., P.L.(Eng.), Editor, All Rights Reserved

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Zoning a building for HVAC control is much of an art as it is a science. Certainly when we treat buildings as a simple single zone we ignore the dynamics of both external and internal loading. Assigning the control of the building volume to a single thermostat (with or without humidistat) which are at best poor occupant ambassadors to the HVAC system creates indoor environmental problems as frequently witnessed through occupant complaints.

Proper zoning can address some of the dynamics, however there must be reason when dividing a building into multiple zones since the end result is a more costly and complicated system.

Below are the criteria we use when evaluating buildings for indoor environmental quality including the control over temperature, moisture and pressure. This is not an exhaustive list but covers off the major items which should be considered.

Room use: rooms or spaces should be separated out or consolidated based on functions such as;

  • grooming

  • socializing

  • entertaining

  • resting

  • working (also type of work)

  • office types and office support (printing/publishing rooms)

  • meeting rooms (consider also flexible spaces /partitions)

  • exercising

  • storage

  • preservation (library, paintings, instruments, heirlooms)

  • personal spaces (music rooms, kraft/hobby rooms etc.)

  • rooms used for short or long term healthcare

  • percentage of time occupied versus unoccupied

  • basements (sub set for walk outs)

  • garages

  • home theatre

  • wine storage

  • cold storage

Proximity to similar spaces (see room use): rooms and spaces should be separated out or consolidated based on similar functions typically;

  • bedrooms

  • bathrooms/powder rooms

  • kitchen/dining/nook

  • family/living rooms

  • Dens/home office/library

Potential magnitude for sound and contaminant transmission; heat loss, heat gains;  and moisture gains: rooms should be separated out or consolidated based on;

  • solar exposures (based on orientation)

  • wind exposures (dominant orientation)

  • rain exposures (dominant orientation)

  • window to wall ratios

  • choices in external and internal shading

  • lighting

  • equipment (includes appliances and IT and A/V)

  • indoor pools, spas and steam rooms

  • transmission potential of external or internal sources of noise

  • transmission potential of external or internal sources of contaminants

Surface treatments: rooms should be separated out or consolidated based on;

  • chemical properties of finishes for VOC emission evaluations

  • optical properties, emissivity and absorptivity especially for radiant heating and cooling systems

  • thermal properties, conductivities especially for radiant heating and cooling systems

Orientation to north: rooms should be separated out or consolidated based on;

  • similar solar loading

  • choice in internal or external shading devices

  • presence of natural shading

Architectural layout: rooms should be separated out or consolidated based on;

  • geometry such as height and shape

  • changes in planes (L shape versus rectangular etc.)

  • changes in floor elevation

  • plans for expansion or potentials for repurposing of rooms and spaces

Impact from extraordinary items: contributions to moisture, sound and contaminates transmission; and internal heat gains; these include;

  • home theatre equipment

  • fireplaces

  • lighting

  • entertainment rooms

  • hobby, shops and exercise rooms

  • A/V and IT equipment

  • pets

  • medical equipment

A lot of the above is filtered out when budgets have been established for the enclosure, interior finishes and choices in HVAC systems. In general, the higher the performance of the enclosure, the more homogenous the spaces, the greater the use of low voc materials the less zones are required and the simpler the hvac system will become.


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