We are now able to test wall system U-value on-site. The test method is based on ISO 9869-1, with some improvements for Singapore’s environmental conditions.
The measurement instrument setup is illustrated below:
The following 3 quantities are measured:
- Indoor side wall surface temperature (by a temperature sensor)
- Outdoor side wall surface temperature (by a temperature sensor)
- Heat flux through the wall (by a heat flux sensor)
The instruments need to be deployed on-site for a few days. The thermal resistance (R-value) of the wall system is calculated from the averaged results. The thermal transmittance (U-value) of the wall system is calculated from the R-value and the surface film resistances defined in the BCA ETTV code.
For better measurement accuracy, a surface electric heater of the size 0.5 m x 0.5 m is attached to the indoor side of the wall system to increase the indoor/outdoor temperature difference across the wall system.