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Deviheat™ System Design Tips |
 The term 'heating the house' is a little misleading. An electric floorheating system is designed to warm the occupants, not the house. When designing a heating system we need to know something about the way a body reaches and maintains a desirable level of comfort. Body heat loss should not occur more quickly than body heat generation. The human body feels comfortable when the balance between heat being generated within and the rate at which it is being lost is perfectly maintained. This will enable our body to maintain it's normal temperature of around 37ºC.
Heat will move from areas of high temperature to areas of low temperatures to decrease the imbalance in temperature. Thus, if our environment is dramatically cooler than our body temperature our rate of heat loss will become too high. Then, of course, we will feel cold and uncomfortable.
The heating load is defined as the amount of energy required to maintain a comfortable room temperature in comparison to the outside temperature. That is, how much heat is required to replace the heat being lost from the environment. By replacing the heat being lost from the environment we are able to slow down our bodily heat loss, making us feel more comfortable. Thus, when designing a good floorheating system it is important to determine the correct heat load to ensure maximum heating efficiency with minimum installation and running costs.
Over sizing or under sizing the heating load can lead to inefficient operation.
Oversized equipment results in wasted capital cost and higher running costs.
Undersized equipment means the system runs continuously at maximum output without achieving the desired comfort level.
Consideration should be given to:
- The desired inside temperature
- The heat losses of walls, ceiling, windows, floor etc.
The heat losses of the walls, ceiling, windows, floor etc contribute to the heat loss of the environment. This is directly related to what is called the "U" value, or Thermal Conductivity, of a material, such as glass, concrete, timber etc. This is the ability of a material to allow the passage of heat through it and is defined as measurements in W/m2K or W/mK. 1W/mK is the heat flow that occurs across a cube 1m2 in cross section and 1m in thickness when there is a 1ºC between the two faces.
The actual calculation of heat flow through any structure, such as a wall or ceiling, is done by adding the combined effect of the resistance of all materials used in its construction, then adding a figure for the surface resistances to arrive at a total. The reciprocal of resistance, i.e. conductance, is then used to determine heat flow.
For example, if a ceiling has a U value of 2.5W/m2K and there is a 10ºC difference between the inside and outside temperatures, then the heat flow rate out through this ceiling will be 2.5 x 10 = 25W per square meter. To work out the heat loss through this ceiling, we need to work out the number of square meters of ceiling and multiply this by 25 to arrive at the total ceiling heat loss in watts. |
The Heat Load can then be related to various heaters or heating systems available.
When building a house, heating decisions are best made at the planning stage rather than later when further constraints exist. Consideration should be given to the following:
- The position of the house on the block
- The direction the house faces
- The building materials used
- The insulation proposed
- The type of floor coverings
- And other items which may affect the thermal properties of the home
We at DEVI offer over 25 years experience in the design, supply and installation of radiant heating systems for Australian conditions. For further information on the best heating solution for your installation or an obligation free system design and quote please contact DEVI or your local representative. |
