There are quite a few things we’re excited about with Dianthus, the landscape, the ash tree, location and of course building a passivhaus. One of the biggest issues with building a passivhaus at the moment is the “Green Premium” you pay. Bill Gates describes it in his new book, How to Avoid a Climate Disaster. I highly recommend everyone reads the book.

The Green Premium is the additional cost of choosing a clean technology over one that emits a greater amount of greenhouse gases. For example, today we spend approximately £1500 per annum on heating oil where we’re living at the moment nor is Dianthus on any mains other than water, electricity, cable and telephone. The green premium here is the extra amount of money this roof is costing us vs. A standard roof slate without PV.

The heating oil is delivered in a tanker twice or sometimes three times a year. We’re not on the mains for a gas connection in the village we live in at the moment. We also spend approximately £1300 on electricity per annum. Granted our Electricity is from Octupus Energy which is supposedly 100% renewables. However, our Heating Oil is fossil fuel. So, when it came to Dianthus, we were prepared to pay a green premium to move away from fossil fuel energy. The upside for us now given we don’t plan to move again is that our energy generation will be close to positive with the option of exporting back to the grid using the Smart Export Guarantee Scheme which the Solar PV Slates qualifies for and the Ground Source Heat Pump qualifies for Renewable Heating Incentive Grant.

When we started thinking about our brief for Dianthus, we wanted to be able to convince others to go the on journey as well by the choices we’ve made. The reality is some of these things are still expensive and we hope the government will assist to make more people aware of how easy it is to make the right choice. This hopefully, should encourage people to make sustainable choices.

Ben at Max Fordham advised us early on when we were looking at PV slates options to consider GB Sol, they’re a Welsh company that manufacture PV Slates.

What are Photo Voltaic Slates?
PV Slates are small PV modules that are designed to look like normal roof tiles or slates. When the main barrier to investing in solar is appearance or perhaps you live in a conservation area like we do, PV Slates can be the perfect solution. People also refer to them as solar shingles or rackless solar systems, as they don’t have the mounting frames in traditional rooftop installations.

It’s unlikely you can integrate PV slates into existing roofing. They’re generally suited to new builds like Dianthus or renovations. The Dianthus roof is a mix of PV slates and natural slates You’d struggle to tell the difference. They look the same but don’t generate electricity. These cover unfavourable parts of the roof, like north-facing or shaded surfaces, or to scale the size of the PV system to the electricity demand of the property. In our case, the layout looks like the diagram below.

The main advantage is aesthetics, which is particularly important in conservation or protected areas like Houghton. We did look at Tesla Tiles but they’ve been vague about when it will be available in the UK never mind throughout the US. So we discounted them.

We settled on GB Sol and some of the key features we liked include the following;

They have a Natural blue-grey slate effect, Each module replaces 3 regular slates. They’re surrounded by normal slates to fill in gaps and where slates have to be cut. The PV Slates have a 10 year product and power warranty. 35W output per module. They are lighter than standard slates so no roof strengthening is needed. The minimum pitch of 22°, though over 30° is better. We’re about 45°.

In terms of complementing slates, we went for the Siga 37. It’s their “blue grey” slate in the same Commercial range as the 54X we originally looked at. The blue greys appear to be the lightest grey they have,

Here are the photos I took earlier today. The guys are still installing them. It will take them a few days before they finish.

I also recorded a short video chatting to James Brealey the GB Sol PV slates installer, his brother and Malcolm Yates from Bootley Roofing. Enjoy! We’re very pleased with it.

Some key stats as follows:-