Solar PV | Marsh Flatts Farm Self Build Diary

The original plan was to get everything ready for Passivhaus certification (including the air tightness) and then get an Energy Performance Certificate (EPC) which reflected that. The delay to achieving a Passivhaus level of air tightness has meant a delay to the EPC.

A few weeks ago it became clear that it would be best to get an “interim” EPC which reflected the current energy performance and then get a revised EPC once all the issues have been ironed out, and that interim EPC was issued today.

The interim EPC is near the top end of Band B, with a score of 88 (Band B is 81 – 91 and Band A is 92 or greater). The good news is that:

It’s now possible to commission the Solar Panels, which were installed months ago but are not currently operational
- The procedure for applying for the current scheme of Feed-In Tariff payments requires that an EPC – dated before the commissioning of the Solar PV installation – shows that the property performs at Band D or better (without any Solar PV installed) to prevent people getting FIT payments for properties that have serious energy efficiency shortcomings
- May is typically the peak month for Solar PV generation, and that’s just around the corner
The Ecology Building Society reserve their maximum mortgage interest discount for properties that have obtained Passivhaus certification but they do offer more limited discounts for achieving EPC Band A or B

One of the recommendations from the interim EPC (which was required to exclude the Solar PV installation) is to install a Solar PV system, with the indication that a 2.5 kWp solar array will bump up the EPC score to 92 (i.e. just enough for Band A). The solar array is actually rated for 5.4 kWp so once commissioned that should place the property firmly in Band A territory.

Week 50, Day 1:

A bit more second-fix plumbing, installing the WC and the flush plate for the concealed cistern in the Master Bedroom En-Suite and some other work on the plumbing systems
More second-fix electrical, including commissioning the ImmerSun Solar PV diverter which is connected to the immersion heater
- This monitors the amount of on-site generation (Solar PV power) being exported to the Grid and runs the immersion heater on something equivalent to a dimmer switch in order to use as much self-generated power as possible even if not generating the full 3kW required to run the immersion at full power
- This is expected to meet most, if not all, of the hot-water demand in the summer months, instead of running the heat pump
- Similar devices are available from other manufacturers but I chose the ImmerSun because it seemed to be the most mature solution on the market and has the best remote control and monitoring integration, uploading data to The Cloud at http://www.myimmersun.co.uk/
- Unfortunately, just after I’d bought the ImmerSun unit and its optional remote monitoring add-on, the company who manufactures the units (and runs the websites) went into administration so I was kicking myself for not going for an Open Source solution such as the one from the Open Energy Monitor Project and wondering whether the radio communications between the main unit and the monitoring add-on might use a standard protocol I could pick-up with an RFXCOM transceiver
- Fortunately the company has now been rescued and the websites are back up and running