In 2007 the domestic sector was responsible for 27% of all energy consumed by final users in the UK, yet only 1.5% of this energy was met by renewables. The utilisation of renewable energy systems such as active solar water heating with Phase Change Material (PCM) thermal storage, offers vast potential for reducing energy use and CO2 emissions in the domestic energy sector in the UK. Previous research indicated that the incorporation of PCMs in underfloor heating had the potential to make energy savings, but their use in combination with renewable energy had not been explored in the UK. Consequently this was identified as a gap in the current knowledge that the current research would fill. A shortage was also identified in real life performance data on PCM space heating system performance in the UK. The current work successfully addresses this shortfall in data and in doing so provides a significant contribution to knowledge in the area of using solar thermal storage for space heating of residential buildings. An in depth literature review was undertaken as part of the research programme, which identified the key shortcomings in existing PCM based thermal storage systems for space heating. An underfloor space heating system for residential buildings was therefore developed that addresses the weaknesses of the existing systems highlighted in the literature review. The system stores solar thermal energy during the day and then uses this to provide space heating in the evening, thus addressing the problem of matching solar availability to demand. An experimental approach was adopted for the study as numerous researchers (Kauranen et al., 1991, Hasnian, 1998, Kenisarin and Mahkamov, 2007), have demonstrated the unreliability of manufacturer's published thermophysical properties of PCM. Therefore, this research chose to adopt an experimental model approach instead of a mathematical modelling approach. A model consisting of a full size solar collector 4m2 in area and a PCM filled underfloor heating panel was constructed in the laboratory. A methodology was developed to measure the performance of the key modules which allowed the performance of the system to be evaluated. The experimental data indicated that it was possible to use a low flow rate of 2.52 litres per minute, without a detrimental effect on the performance of the PCM panel. The use of a low flow rate minimises parasitic losses and produces significant energy savings in comparison to the use of higher flow rates. The experimental results indicated that the system was able to provide adequate thermal comfort with a maximum floor heat emission of 158 W/m using a flow rate temperature of 50°C. Comparisons of the annual space heating energy of the developed integrated system versus a wet central heating system in the UK revealed a significant reduction of energy use and associated CO2 emissions by as much as 52%.