HVAC DISTRIBUTION and DELIVERY SYSTEMS (Part 2) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 1 Contextual Reminder All-air systems Single zone Terminal reheat Multi-zone Dual-duct VAV Combinations (such a dual-duct VAV; or VAV with reheat) Air-water systems All-water systems Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 2 1
Air-Water Systems Both air and water are distributed to zones for climate control purposes usually with the explicit intention of reducing the overall size of distribution components Several types of air-water systems are available to address various contexts; the more common ones are presented in this slide set Air-water is a mixed system choice Much smaller ductwork sizes than with an all-air system Retains potential for good IAQ control There is often a volumetric intrusion of HVAC equipment into spaces (for heat exchange between water and room air) Little potential for smoke control (as part of fire protection) Some current design trends overlap this category of systems Dedicated outdoor air systems (DOAS) Chilled beams (radiant cooling) Opinion: Air systems with water-based reheat are conceptually not air-water systems because the size of supply air ductwork is not reduced by shifting loads to the water side of system. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 3 An Air-Water VAV System? (opinion: NO just hot water reheat with all-air ductwork) no reduction in duct size due to water Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 4 2
Air-Water Systems We ll look at the following air-water systems: Air-water induction Rarely seen today, but historic and worth understanding Air-water fan-coil A very common system; lots of terminal options Air-water employing some radiant element Not common, but interesting (especially with respect to thermal comfort) Hydronic* radiant floors (using hot water) are often used in several building types An emerging trend in European commercial buildings is use of an air-water chilled beam (radiant cooling) system *hydronic, in HVAC, refers to water-based distribution Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 5 Air-Water Induction room air supply air induction unit air nozzle A fairly complex air-water system Constant-volume central air flow (conditioned OA) Numerous zones of control (one per induction unit) Fairly high cost (need induction units, fans, pumps ) Can heat and cool different zones simultaneously Not common (a high-end and outdated system) Air supply is normally no more than the quantity required for IAQ Induction device is located in occupied space (but has no fan) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 6 coolingheating coil (water) air from AHU 3
Air-Water Induction Units (Cabinets) www.rittling.com/ www.jfwhite.com as installed under renovation Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 7 Air-Water Fan-Coil fan coil unit (see next slide) A moderately complex system Constant-volume central airflow Numerous zones of control are possible (one per fan-coil unit) Fairly low cost (common equipment with good price competition) Can heat and cool simultaneously (if using a 3- or 4-pipe distribution) A mechanical device (the fcu) is installed in the occupied space Several varieties of units (wall, ceiling, ) are readily available Air supply from AHU is normally just the quantity required for IAQ Fan coil unit is located and serviced in occupied space Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 8 4
Fan-Coil Unit (the delivery device) 2-pipe: one supply and one return not flexible (system cannot heat and cool simultaneously) 3-pipe: two supply and one return flexible, but energy wasteful 4-pipe: two supply and two return expensive, but flexible and energy conserving required at each fcu within each zone Architectural Graphic Standards, 10th Ed. Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 9 Example: Fan-Coil System probably a retrofit; university classroom water handles most of room load via fcu supply air for IAQ condensate drain, downhill by gravity Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 10 5
Examples: Fan-Coil Units (reminder: outdoor air is provided independently of fcu device) supply return fcu in soffit, above doorway below window (MRT control) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 11 Air-Water Radiant Floor radiant floor Conceptually, a fairly simple system Separate constant-volume airflow (minimum OA to address IAQ) Multiple zones of control are possible (the floor can be zoned) Higher-end cost (for radiant element installation) Can heat or cool (but NOT simultaneously) with cooling being problematic (due to condensation potential) Not common (but with a good reputation for comfort) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 12 6
All-Water Systems Only water is distributed to zones for climate control (no air is circulated from a central location) Many delivery options (devices) are available to fit various contexts (these include: fan coil, radiator, radiant floor, baseboard, unit heater, convector, ) We ll look at: All-water fan-coil All-water radiant floor There is often a volumetric intrusion of delivery equipment into the occupied space Previously a very common system choice, but lack of positive IAQ control is a serious concern today No ductwork is the main design attraction There is no potential for smoke control (for fire protection) unless a separate system is installed Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 13 All-Water Fan-Coil www.esmagazine.com/ A very simple system Single speed or multi-speed fans can be used Numerous zones of control are possible (one per fcu) Low cost system Can heat and cool simultaneously if using 3- or 4-pipe distribution Previously very common in many building types IAQ control is a serious concern requires guaranteed passive or unit-based ventilation (which can be done, with care) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 14 7
Design Issues All-Water fcu system www.esmagazine.com/ Aesthetics (louvers in wall; look like window air-conditioning units) Air cleanliness (cheap filter, rarely changed) Energy (fairly rough control of outdoor air flow rate; no opportunity for air-to-air heat exchanger) Coil freezing (if damper sticks open in winter) No OA when unit is off (such as at night; pollutants can build up) Noise (there is only a thin piece of sheet metal between outdoor environment and the occupied space; fan is in the room) (the wall would be insulated) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 15 All-Water Radiant Floor www.greenbuildingadvisor.com A fairly simple system Multiple zones of control are possible by zoning the tubing layout Higher end cost (installation of tubes is expensive) Typically used as a heating only system (condensation on floor would be very dangerous; and if there is no condensation then there is no latent cooling and RH is not controlled) IAQ control a serious concern requires guaranteed passive ventilation Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 16 8
SHIFTING THE FOCUS A BIT TO ENERGY EFFICIENT AND INNOVATIVE SYSTEMS AND COMPONENTS Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 17 not really a trending system, but an interesting concept LOOPED HEAT PUMPS seldom required In a building with balanced zone loadings (heat losses nearly equal to heat gains; such as a building in a cold climate with a large interior zone) boiler and cooling tower operation can be minimized The water piping can act as a transfer loop to move heat around a building from where it is a problem to where it is a resource With near-room-temperature water as a source, the heat pumps can operate with high COPs saving more energy Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 18 9
Looped Heat Pumps return air used only as needed to maintain water loop conditions refrigeration supply air Uses water-source heat pumps (vapor compression refrigeration) An interesting local / central system Intriguing energy synergies are possible via interconnections of units Numerous zones of control are possible (one per heat pump) Moderate cost Can heat and cool different zones simultaneously Not common Noise is a concern (vapor compression equipment is near spaces) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 19 not really a new idea, just good fundamental design HEAT EXCHANGERS provides for sensible heat exchange; usually by passing intake and exhaust air streams next to each other separated by a metal divider plate reduces the amount of energy required to heat/cool outdoor air for ventilation Architectural Graphic Standards, 10 th Ed., Wiley in smaller buildings this device may be called an HRV (heat recovery ventilator) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 20 10
HEAT EXCHANGERS provides for sensible and latent heat exchange; by passing intake and exhaust air streams through a chemically treated rotating (wheel) heat exchanger reduces the amount of energy required to heat/cool outdoor air for ventilation Architectural Graphic Standards, 10 th Ed., Wiley in smaller buildings this device may be called an ERV (energy recovery ventilator) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 21 GROUND SOURCE HEAT PUMPS (the outdoor coil is below ground a more hospitable environment for both dumping and extracting heat) ground versus air temperature at 2 PM (think about 2 AM) 21 February 2006; 2:00 PM; 39 deg F outdoor air temperature http://www.whrc.org/building/education/sysdet2.asp Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 22 11
GROUND SOURCE HEAT PUMPS heating or cooling? heating or cooling? heating or cooling? what s going on with the temperature patterns: WAHP #1 versus the other WAHPs and WWHPs? WAHP = water-to-air heat pump; WWHP = water-to-water heat pump Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 23 UFAD: UNDERFLOOR AIR DISTRIBUTION suggested benefits as described emerging system in North America www.architechweb.com/.../5131/default.aspx Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 24 12
UFAD: UNDERFLOOR AIR DISTRIBUTION consider what happens aesthetically to the ceiling plane news.cision.com tateinc.com Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 25 CHILLED BEAMS suggested benefits as described emerging system in North America these claims need to be rationally evaluated; latent cooling is a serious issue www.treehugger.com/.../11/chilled_beams_f.php Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 26 13
CHILLED BEAMS www.mccoysales.com consider what happens to the ceiling plane www.dadanco.com.au Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 27 emerging system in North America DOAS: DEDICATED OUTDOOR AIR SYSTEM suggested benefits are consistent ventilation that is independent of control for thermal comfort options OA system www.reliant.com/en_us/page/generic/public/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 28 14
DOAS EXAMPLES buildingscience.com/ one approach: central OA system with local thermal comfort system another approach: central OA system with central thermal comfort system (see slide 12) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 29 Reflections on HVAC Systems If thermal comfort was the only concern, any of the many systems presented could do the job BUT IAQ is a serious concern, leaving all-water systems rather suspect (unless passive ventilation is well-designed) If energy was not an issue, then the all-air terminal reheat system might be used whenever there was space for ductwork BUT energy is a concern, leading to the common use of VAV systems As a designer, consider the tradeoff between more ductwork in building infrastructure spaces (all-air) and the need for a heat exchange device within the occupied spaces (air-water) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 30 15
consider the aesthetic potential of HVAC distribution elements www.williamleggio.biz/ someone is paying for the stuff, whether hidden or seen www.tellthetruthtravel.com/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 31 www.flickr.com/photos/hoknetwork/ netzerocourt.com design for the future, not for the past Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 32 16