Radiant Floor Heating and Cooling

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Contents

What is It?


A Radiant Floor Heating and Cooling System is used to heat and cool the Green Garage building. PEX (cross-linked polyethylene) tubing will be placed below the finished floor material, in zones sized to meet the heating and cooling demands of the zone. A current ASHRAE study showed that these radiant floors can be used for cooling if they are kept no cooler than 68F. (Lower temperatures can create moisture issues in the floor.)

A Radiant Floor Heating and Cooling System can include:

  • PEX tubing. PEX comes in various diameters, with larger diameter tubing being placed at wider spacing than smaller diameter tubing.
  • With a new concrete slab, tubing is typically poured in the concrete.
  • Tubing in a floor joist system can either be applied under the sub floor between joists or over the joists in grooves of the sub floor system. With joists, a heat emission plate is typically used as well to disperse the heat over an area of the floor.
  • Also known as: Radiant heating, Solar radiant heating, Hydronic radiant heating

Why is it Important?


A Radiant Floor Heating and Cooling System is important to a building's sustainability because it:

  • Reduces energy operating costs because it is a more efficient method for heating spaces with high ceilings.
  • Adds to the comfort of the occupants by providing a more even heat.
  • Is an excellent application for the use of solar panels, used for heating the fluid circulating in the radiant floor tubing.

When to Use It?


It is appropriate to use a Radiant Floor Heating and Cooling System when:

  • The building envelope has already been improved to reduce the heating and cooling demand. In the case of super insulated buildings, radiant flooring may not produce much value for their cost, unless the building has high ceilings. See resource below.
  • It is particularly efficient in situations where there is a high ceiling, as radiant floor heating puts the heat where the people are... heating approximately up to 7' above the floor surface.
  • You have professionals available with the experience to properly install the system.
  • Sufficient space is available for solar panel installation. Radiant floor heat is a great way to utilize free energy from the sun.

Green Garage Use of Radiant Heating and Cooling


Sustainability Goals

The sustainability goals for the Radiant Floor Heating and Cooling system are:

  • Integrate the radiant floor heating with the solar panels and mass thermal storage to maximize the use of the sun's energy.
  • Meet the Green Garage heating and cooling loads per Energy-10 modeling results.
  • Our heating and cooling energy usage would be only 10% of an equivalent commercial building (per ASHRAE data.)
  • Connect the building and the occupants to natural systems.
  • Ensure a healthy indoor environment.
  • Allow components of the system to be bypassed when they don't contribute to these goals.
  • The system should be simple to maintain, adapt and control, and should position the Green Garage for a net-Zero energy future.

Strategy and Conceptual Design

Radiant Floors

The radiant floor system will be used to heat and cool the Green Garage building. PEX (cross-linked polyethylene) tubing will be placed in the sand base of the floor, in zones sized to meet the heating and cooling demands of the zone. A current ASHRAE study showed that these radiant floors can be used for cooling if they are kept no cooler than 68F. (Lower temperatures can create moisture issues in the floor.)

  • Overall Floor Designs
    • Historic
      • Existing concrete floor
      • Vapor barrier or sealer.
      • Leveling course of slag/sand on top of the existing concrete floor.
      • Two layers of 1" XPS with seams staggered. (2" total thickness)
      • PEX tubing will be placed between the sheets in the bottom layer of foam, to serve as a heat dump to help cool the mass thermal storage in the summer. This will be done only in the center of the building where the floor temperature is nearly constant, at least 10' away from the exterior walls.
      • Reflective radiant barrier (could be foil on the XPS foam boards or roll product).
      • 1.5" wood sleepers
      • PEX_Al_PEX tubing for heating/cooling loops.
      • Solid core flush wood doors for flooring. (Click here to see doors used in this application in Oregon).
  • Annex
    • The annex portion of the Green Garage is intended for use as work shop/studio. For comfort, temperatures in a workshop area are typically kept lower than those in an office environment. This, coupled with the probable need of moving (heavy) materials on some type of lift lead to the decision to keep the existing concrete floor as the finish surface.
      • Cut out 2' of concrete floor at the outside wall. Install 2" (horizontal) rigid insulation. At exterior wall, bring insulation through concrete, to finish floor elevation. This provides a thermal break to the outside block wall.
      • Place PEX tubing in area of removed concrete, and pour into new concrete.
      • Construct new wall system at exterior perimeter.
      • Use moisture resistant drywall for bottom 4', with radiant barrier on inside.
      • Install PEX tubing horizontally on inside of lower wall, with horizontal firring. Use fiberboard or plywood on inside as wall finish.


  • Fluid temperatures in floor tubing:
    • 90F maximum in the winter...higher tempeatures may harm the floor material.
    • 68F lowest temperature for summer cooling. The coolant temperature in the radiant system should not go below 68F. This eliminates any risk of condensation and the human comfort is good (i.e. no cold feet). See ASHRAE article cited below.

Integration and Controls Design Requirements

Overview

Integrating the radiant floor heating and cooling system requires significant design effort. Some of the controls will be manual and some will be automated. The key integration and control areas are:

  • The supply-demand mixing valve for the radiant floors will control the temperature of the fluid in the radiant floor tubing (PEX).
  • Integration with heat exchanger measuring the delta T of the radiant water entering and leaving the heat exchanger.
  • There are four zones in the radiant floor system:
    • Historic - Front
    • Historic - Center
    • Historic - Back
    • Annex
  • Zones are thermostatically controlled and designed to keep the flow rates of the water within acceptable boundaries.
  • Zones can heat and cool. One, two, three or four zones can heat at one time. One, two, three or four zones can cool at one time.
    • The heat exchanger can provide heating or cooling, but not both within a season.
    • If cooling is needed in the heating season the geothermal heat pump does it directly, by-passing the heat exchanger.


Default Settings

The default setting is no heating/cooling supplied to the floor zones. This results in the following default settings for the pumps and valves:

  • Pumps
    • Off - Pumps 2,3,4,5,6,7
    • On - None
  • Valves
    • Manually Adjusted Balance Valves
      • Fixed Open Position - Valves 3, 9
      • Closed - None
    • Manual Valves
      • Open - Valves 8, 10, 11, 13 - 16, 21 - 24
      • Closed - None
    • Motorized Valves
      • Open - 6 (adj to last temp)
      • Closed - V-19 and V-25 standing state closed
Heating (Winter) Modes
Geo-Solar Hybrid Heating and Cooling - Shown in Heating Mode (01/22/10)
Geo-Solar Hybrid Heating and Cooling - Shown in Heating Mode (01/22/10)
  • Occupied - Closed
    • During heating mode, radiant floor supply water 3-way mixing valve V-6 blends hot water from the mass thermal storage tank via the heat exchanger with the return water from the radiant floor distribution system to maintain heating hot water supply temperature T-8 setpoint (90 deg F, adj).
    • Pump P-3 operates to supply the mixed hot water to the primary loop manifold.
    • The primary loop manifold supplies water to the various spaces zoned with individual thermostats.
    • When a zone thermostat calls for heating, the pump for that zone (P4, P5, P6, or P7) is activated until the zone thermostat setpoint is reached (heating 68F adj) at which point the pump would be deactivated. Only the pump for the zone calling for heat is activated, all other zones remain off unless they are also calling for heat.
    • Zone pumps P4, P5, P6, and P7 run independent from each other. Any number can be activated at the same time. If any zone pump is activated, pump P-3 must be activated and valve V-6 must be modulating the temperature.
  • Occupied - Open
    • During heating modes, if Occupied - Open hours are designated, radiant floor heating and cooling system is deactivated and locked out from operation.
  • Unoccupied
    • Same as Occupied - Closed hours heating mode. Setback is 0F(adj).
  • Emergency
    • Tank-based Emergency
      • Entering the Emergency Mode
        • Step 1: Manually close valve V-26. Ensure motorized valves V-19 and V-25 are deactivated and in default closed position.
        • Step 2: Manually open valves V-17 and V-18.
        • Step 3: Manually switch Altherma to Emergency Mode:
          • allowing it's heating operation to be initiated by the input from a zone thermostat.
          • blocking any calls from the domestic hot water tank for heat from the heat pump.
      • During Emergency Mode
        • Altherma pump P-8 is activated by thermostat in the front of the historic building. When the front zone calls for heat, pump P-8 and all zone pumps P4, P5, P6, and P7 are activated until the heating setpoint is reached (68F, adj.)
        • Altherma pump P-8 and pumps P4, P5, P6, and P7 are deactivated when the heating setpoint is reached (68F, adj.)
        •  ????confirm current design will work???? Mixing valve V-6 blends hot water from the Altherma with the return water from the radiant floor distribution system to maintain heating hot water supply temperature T-8 setpoint (90 deg F, adj).
        • Domestic hot water will get all it's heat from the electric heating strip contained within the unit itself...the Altherma heat pump will not respond to calls for heat from the domestic hot water.
      • Exiting Emergency Mode
        • Step 1: Manually off Emergency Mode for the Altherma decoupling it from the zone thermostat and allowing calls for heat from the domestic hot water tank to be responded to by the heat pump.
        • Step 2: Manually close valves V-17 and V-18.
        • Step 3: Manually open valve V-26. Ensure motorized valves V-19 and V-25 are operational (???) and in default closed position.
    • Zone or Loop-based Emergency (e.g. leak)
      • Entering the Emergency Mode
        • Step 1: Manually switch off power to the pump related to the affected zone/loop. Example: manually switch off power to pump P-4 for zone 1.
        • Step 2: Manually close the valves on both sides of the pump in the affected zone. Example: manually close valves V-21 and V-13 for zone 1.
      • During Emergency Mode
        • All other operations occur as indicated in normal operations.
      • Exiting Emergency Mode
        • Step 1: Manually open the valves on both sides of the pump in the affected zone. Example: manually open valves V-21 and V-13 for zone 1.
        • Step 2: Manually switch on power to the pump related to the affected zone/loop. Example: manually switch on power to pump P-4 for zone 1.




Cooling (Summer) Modes
Geo-Solar Hybrid Heating and Cooling - Shown in Heating Mode (01/22/10)
Geo-Solar Hybrid Heating and Cooling - Shown in Heating Mode (01/22/10)
  • Occupied - Closed
    • During cooling mode, radiant floor supply water 3-way mixing valve V-6 blends cold water from the mass thermal storage tank via the heat exchanger with the return water from the radiant floor distribution system to maintain heating hot water supply temperature T-8 setpoint (68 deg F, adj).
    • Pump P-3 operates to supply the mixed cold water to the primary loop manifold.
    • The primary loop manifold supplies water to the various spaces zoned with individual thermostats.
    • When a zone thermostat calls for cooling, the pump for that zone (P4, P5, P6, or P7) is activated until the zone thermostat setpoint is reached (cooling 76F adj) at which point the pump would be deactivated. Only the pump for the zone calling for cooling is activated, all other zones remain off unless they are also calling for cooling.
    • Zone pumps P4, P5, P6, and P7 run independent from each other. Any number can be activated at the same time. If any zone pump is activated, pump P-3 must be activated and valve V-6 must be modulating the temperature.
  • Occupied - Open
    • During Occupied - Open hours, radiant floor cooling system is deactivated and locked out from operation.
  • Unoccupied
    • Same as Occupied - Closed hours cooling mode.
  • Emergency
    • Same as heating mode above.



Shoulder (Spring - Fall) Modes
Geo-Solar Hybrid Heating and Cooling - Shown in Heating Mode (01/22/10)
Geo-Solar Hybrid Heating and Cooling - Shown in Heating Mode (01/22/10)
  • Occupied - Closed
    • In the Spring Shoulder Mode the radiant floor system will automatically respond as it normally does in the Occupied - Closed for the Heating Mode.
    • In the Fall Shoulder Mode the radiant floor system will automatically respond as it normally does in the Occupied - Closed for the Cooling Mode.
    • Refer to details in the heating and cooling modes listed above.
  • Occupied - Open
    • During Occupied - Open hours, radiant floor heating and cooling system is deactivated and locked out from operation.
  • Unoccupied
    • Operation during Unoccupied hours is the same as during Occupied - Closed hours for the mode of operation, heating or cooling, selected by the building operator.
  • Emergency
    • Operation during Emergency conditions is the same as during Emergency mode of operation related to mode of operation, heating or cooling, selected by the building operator.



Controls - Open Design Points
  1. Condensation in space is often in hidden places that cannot be seen by casual observation. Consider using space temperature and humidity readings to determine when dewpoint may be an issue rather than just observation or use contact temperature sensors?


Supporting Science / Experience

The detailed thermal calculations are shown in pages included here. We thank Laurie Catey for her great contributions to our understanding of the science behind radiant floors.

Proposed Materials / Suppliers

  • Radiantec A number of good installation manuals are available here, including a towel

warming rack!

Development Story

The Radiant Floor Heating and Cooling System - Development Story page contains many images and videos documenting the process used at the Green Garage to design, build and operate our Hybrid Ventilation System.

Related Internal Links

Resources


  • Radiant Floor guide... great guide...diagrams
  • Radiant Design Software from Viega
  • Radiant over Existing concrete Design Guides
  • Building Science Report on Concrete basements...also good for walls.
  • Over existing concrete forum reply
  • Gypcrete over existing concrete is an accepted and common practice. Any "cementious" material designed for the purpose will do. If you have a walk-out or suffer from high ground water, then one inch of closed cell polystyrene would be in order if you live above the Mason/Dickson line. Each manufacturer will tell you how deep to pour but 1.5" is typical with a 1/2" cover over the tube.
  • Here's a great article showing that it may be overkill to use radiant floors in super-insulated buildings when the energy demands are already low. Environmental Building News The author states that the exception is in super insulated buildings with high ceilings.

To Do's

  • Laurie's data for floors
  • Resources
  • Short Video
  • Upload images onto Development Story page
  • Image for top of page - comes from Kevin


Peggy edited this page :)

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