In April 2010 the Fenix Group produced a report titled "ECOFILM Ceiling Heating in Low Energy Houses". The purpose of this report was to demonstrate that satisfactory thermal gradient comfort curves can be achieved for large area low power radiant ceiling heating systems installed in low heat loss properties.

The test area used for this report was a well insulated modern building and the test results clearly illustrated that satisfactory thermal gradient profiles can be achieved for power dissipations between 80 and 140W/m² (active heating element area).

The purpose of this followup report is to further demonstrate that for power dissipations in the range 40-100W/m² installed in low energy houses (20-30kWh/m²A) identical floor to ceiling thermal gradients are achieved for each power dissipation.

To carry out these new tests a purpose built low heat loss test room was constructed within an unheated storage bay. The floor, wall and ceiling were insulated to a high level replicating insulation levels found in modern low energy buildings. Standard ECOFILM heating elements were used as the heat source and by reducing the supply voltage power dissipations as low as 40W/m² were achieved and the various surface temperatures and vertical floor to ceiling incremental temperatures were recorded for comparison.

Fig. 1 - Floor 220x45mm wood joists, 120mm Kingspan 22mm chipboard, 6mm Depron insulation 15mm engineered flooring U-value: 0.18W/m²K	Fig. 2 - Wall 195x45mm wood joists, 170mm Kingspan TW55 12.7mm plasterboard(internal side) 12mm OSB board(external side) U-value: 0.18W/m²K
Fig. 3 - Ceiling 220x45mm wood joists, 12.7mm plasterboard ECOFILM heating element(500/600 Type C) 200mm fibreglass insulation, 22mm chipboard on top U-value: 0.19W/m²K	Fig. 4 - Window 1700x990mm UPVC double glazed U-value: 1.79W/m²K

Fig. 5 - Air Thermocouples

A total of 24 individually connected heating elements were installed within the ceiling. The heated area of each element was 0.495m² giving a total heated area of 11.88m². The elements had a rated surface power of 150W/m² at 230V and by reducing the supply voltage using a variable transformer power dissipations of 40, 60 ,80 and 100W/m² (heated area) were achieved. K-type thermocouples connected to an HP 34970A data logger were attached to the surface of the heating element, plasterboard surface and also inserted within a series of matt black plastic spheres which were attached to the test frame shown in Figure 5 at 200mm centres. These thermocouples were used to measure the vertical temperature profile within the test room for each power dissipation.

The heating system was controlled by a standard Aube TH232 digital electronic room thermostat operating in air sensing mode. The output relay from the thermostat was used to switch an external contactor connected to the variable transformer and heating load. One pole of the contactor was connected to one of the data logger inputs and this was used to record the ON/OFF switching of the heating system.

Fig. 6 - Data Logging

Fig. 7 - opposite shows a typical thermal image of the heated ceiling under test

Figures 8-11 below show the respective temperature/time charts for each power dissipation. These charts clearly illustrate that although the time taken to reach the thermostat 21°C set-point is shortest for the highest power dissipation, the actual individual temperatures recorded for each are almost identical. The chart in Figure 12 shows the floor to ceiling recorded temperature profile for each power dissipation at time =70 hours. This chart clearly shows that for low heat loss installations the temperature profile once equilibrium has been achieved is the same for all power dissipations between 40 and 100W/m².

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Fig. 12

The above charts show conclusively that low surface power heating film provides ideal comfort conditions when installed in low energy houses and the respective vertical floor to ceiling thermal gradient is identical to those of higher dissipations.
In addition these charts also illustrate that in low energy houses, low power ECOFILM can achieve mean ambient air temperatures of 21°C with a maximum steady state element surface temperature of only 25°C making ECOFILM radiant ceiling heating systems the ideal heat source for low energy buildings.

May 2011