Solar Thermal Case Study 1
4 Bed Detached Bungalow (210m²) - Retrofit
Location: Dublin
Year built: 2001
Panel Area Installed: 6 m²
Panel Type: Flat Plate
Mounting: Integrated with Roofing System
Storage Tank Volume: 300lt
The solar thermal water heating panels were installed recently as a retrofit. As recommended by the installer, the flat plate collectors were integrated into the roof system. This involved stripping back the roofing slates. The photos show the extent to which the slates were stripped back and the installed collectors. Access was by scaffold to the eave level and from there by roofing ladder. Once the panel was installed, the roofing tiles were laid back to the bottom edge of the collector. The appropriate flashing and attachments, consistent with the collector design and roofing slates, were then installed. Finally the remainder of the roofing slates were reinstated.
Key Point: It is crucial that the contractors carrying out the roofing work understand how the flashing details work and complete the work in the proper sequence. Failure to do this may allow wind to undermine the flashing, causing it to be damaged.
A 300lt glass-enamelled storage tank was installed. The tank design is of high quality and allows better stratification of the water in the cylinder. This preserves a cold layer in the tank so that, even when the temperature coming from the collector is not very high, that heat is still transferred to the cylinder nonetheless. Insulation to a high standard was also supplied.
Together with the 300lt tank, 6m2 of panel is expected to supply about 60% of the hot water annually for four occupants. The percentage yield is dependant on the appropriate controls being used and the user being mindful of how the hot water is generated, when deciding when and how much hot water to use.
The selection of the storage tank is crucial to the overall efficiency and effectiveness of the system in converting sun-light to hot water. The tank fitted in this case has three coils: The bottom connected to the solar collector system; an intermediate for future connection to a wood stove; the top-most connected to the oil fired central heating, for supplementary heating.
All piping was rated for 150ºC and 6Barg Pressure, and insulated using Class 0 Armaflex® material. Typically 25mm piping is used. For reasons of safety and operability, a small diaphragm tank, relief valves and anti-scald valves were also installed.
Flat panel installations can be expected to last up to 30 years or more. Typical installation costs for similar installations is of the order of €3,000 to €5,000, however to this may vary considerably depending on the situation.
Points to Watch – Roofing
The following needs to be checked with the installer prior to work being undertaken and preferably before an order is placed:
Identify the roof type and pitch and determine that the roof is actually suitable for the roofing system employed (this is particularly important on dormer houses) and that the flashing details are appropriate for the roof system and pitch.
Check if asbestos tiles are used, this may require the use of a specialist.
What is the current state of the roof: Is there a water resistant membrane? Is there any damage to the roof from mould, wood worm or water ingress?
If you are intending on selling the house in the near to medium term, it is worth considering having the installation certified, this may add several hundred Euro to the cost but will ease the passage of a sale.
Check that the tiles or slates can be replaced, as inevitably there will be breakages and that you will be happy with the appearance of the roof after the works are complete.
During the Work:
The bottom or toe flashing is normally installed first. This is followed by a toe seal at the base of the panel and then the panel itself. A holding frame may be installed prior to the panel. The panel should be leak tested prior to continuing with the completion of the flashing and the re-instatement of the tiles or slates. The side and top flashing are installed with seals placed underneath. Ensure that any gutters in the flashing allow water to flow out onto the top of the tiles/ slates. Finally the roof tiles/ slates are reinstated back to the ridge of the roof.
System designed and installed by
in partnership with Solar Energy North East 041 9823605