AlumiPex Radiant Tubing
A. Tube Layouts for Radiant Heating
1.Radiant Floor Heatng
a.Hot water flowing in the radiant tubing under the finished flooring heats the flooring and the heat emission plates. The heat emission plates help spread the heat evenly across the flooring.
b.Heat must pass through the flooring and the coverings on the floor (low pile carpeting and thermal pads, for example). See Figure 1.
•The more the flooring and coverings act as insulators, the higher the tube water temperature has to be to cause the floor surface to heat up.
•Heavy carpeting and pads resist heat transfer and are not recommended for use in radiant floor heating.
c.Heat will also try to move downward.
•In suspended floor applications, heat will try to pass to the space underneath. So insulation is needed under the floor to prevent this heat movement.
Figure 1 - Heat flow from tube through slab
Carpet
Pad
Subfloor
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Sleepers |
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Subfloor
InsulationJoist
3.Radiant Floor Heating Design
a. The heating system designer must determine:
2.Heat Output from Radiant Floors
a.The floor surface is usually heated to a maximum temperature of about 85 oF - the surface temperature of human skin.
•Higher floor temperatures in occupied areas could be uncomfortable.
•Floor surface temperatures up to 92 oF are often used around the outside perimeter of rooms and in other areas where foot contact is limited.
b.The heat given off by the floor depends on the difference between the room temperature and the floor temperature - the larger the difference in temperature, the greater the heat.
•With the floor at 85 oF and room temperature at 70 oF, each square foot of the heated floor will give off about 30 Btu’s per hour.
c.The spacing of tubes affects how much heat can be moved through the floor.
•Closer spacing increases the heat per square foot of floor.
•This is why tubes are often spaced closer together along outside walls with high heat losses - like next to large windows or patio doors.
•The heat loss for each room.
•Square feet of room floor surface available for floor heating.
•The water temperature in the tubing and spacing between tubes - to match the heat given off by the floor to the heat lost from the room.
4.Tube Layout Patterns
a.The routing of the tubing in the room affects room comfort and effectiveness of the floor heating system.
b.Figure 2 shows typical tube layouts for above floor installations.
•Where possible, the hottest water is usually routed along the outside walls.
•Tube routing in above floor installations is limited by the practicality of variations in sleeper layouts. Sleepers are the boards used to separate the tubing and support the flooring.
c.Where the outside wall loss is particularly high, such as caused by patio doors, the tubing will sometimes be spaced closer together for a few feet out from the wall as shown in Figure 2.
b.Pay close attention to the key information given in these illustrations, such as:
• flow direction
• minimum bend diameters
• spacing to walls
• heat emission plates
• passage under walls
• use of closer spacing
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