![radiant heat tubing radiant heat tubing](https://s3.amazonaws.com/finehomebuilding.s3.tauntoncloud.com/app/uploads/2020/12/01111301/floor-700x438.jpg)
The curves in Figure 2 show the predicted surface temperature profiles for the model of Figure 1. Each time the model is run it determines the temperature at hundreds of points within a small region of the slab including points spaced 1/2-in.apart along the floor surface. Several versions of this model are used to simulate tubing at different depths in the slab. (R-5) polystyrene insulation and covered by 3/8-in.
![radiant heat tubing radiant heat tubing](https://www.pmmag.com/ext/resources/PM/2017/Oct-2017/PM1017_ElecRadiant_WarmlyYours4.jpg)
One of the models I constructed is shown in Figure 1.
#Radiant heat tubing software
The calculations this software does in a couple seconds would take years to complete by hand. FEA software allows one to build a model of the situation you want to test, run it and then see what the temperature would be at any point you’re interested in. To get a handle on the tube depth issue I turned to a specialized technique called finite element analysis (or FEA for short). Is the change in performance worth a few well-chosen words with a disinterested mason? How much is performance affected by tubing depth? This can be a real problem in buildings with significant internal heat gains from sunlight or other sources, especially when those gains follow a cold night in which significant heat was added to the slab.Ĭonsidering these issues it seems obvious that placing tubing higher in the slab will improve its performance. A fully charged slab can hold several hours-worth of heat that will continue to flow into the space as long as the air temperature and/or interior surface temperatures are cooler than the floor surface. It also lengthens the cool-down time after heat input is interrupted by system controls. This lengthens the time it takes to warm the floor surface to normal temperatures following a call for heat. When the tubing ends up near the bottom of the slab more of the slab’s thermal mass is above the level where heat is being added. Thermal losses are obviously greater in the latter case. This is true with or without underslab insulation. The closer the tubing is to the bottom of the slab the greater the underside heat losses should be. The higher the thermal resistance, the higher the water temperature required to maintain a given rate of heat transfer.
![radiant heat tubing radiant heat tubing](https://www.choretime.com/uploads/photos/800/Chore_Time_Radiant_Tube_Heater_JET25_RR_R.jpg)
The deeper the tubing is the greater the thermal resistance between it and the slab surface.