Ground Source Review: Silver Spray
Rory Jenkins runs his Web Site Agency from Perranporth in North Cornwall. He’d often walk his dog up on the cliffs at Droskyn Point, where he’d pass a little old cottage with a spectacular view out across the beach. When he saw that the property was up for sale, he managed to buy it.
He wanted to create an eco-inspired, highly insulated, energy efficient home with sedum grass roofs and locally sourced timber cladding.
The existing bungalow had had its day. You could put your hand through the cracks in the walls and some of the sub floor was completely rotten.
I had never done a self-build project before, but the plot was in such an amazing location, I decided to go for it! It took a couple of years to arrange finance and finalise the plans, but I was granted planning permission without too much hassle.
The majority of Cornwall is off the gas grid, so Rory had to look into alternative heating options. He didn’t want to be at the mercy of fluctuating oil prices. He was also wary of using air source heat pumps, as he knew that they are particularly vulnerable to corrosion from the salty air, which would be an issue living so close to the sea.
Rory decided that ground source heat pumps presented the best solution. Kensa Heat Pumps was recommended to him by a friend whose role as a Project Administrator for a local construction firm meant that he knew of many successful ground source installations they had undertaken.
I liked the fact that Kensa were a local company and they obviously know what they are doing, because you only hear good things about them!
As the ground source heat pump would need to provide 100% of the property’s space heating needs, and an abundant supply of hot water for multiple bathrooms plus an outdoor hot tub, Kensa specified a 15kW Twin Hybrid. This model has two compressors and boasts a large heat capacity, with the ability to efficiently deliver hot water to 60°C. Rory also decided to install Solar PV on the rear roof to generate electricity.
He approached a number of local architects with a brief to create a modern domestic property, featuring an office space with separate access, plus a self-contained flat which Rory could either rent out or incorporate into the main house if he wished. He chose to work with Robert Atkinson who owns ra-studio.org in nearby Porthtowan.
Robert was the only one to provide initial ideas that proved he had understood the brief and would make the most of the site. Robert did an amazing job of a design the brings in lots of natural light from the rear, while maximising the north facing sea views.
The site is relatively narrow and gently slopes downward towards to sea. There wasn’t enough exposed land area available for slinkies, so Rory opted to have three boreholes drilled at a depth of around 100m each to extract the low grade heat from the ground.
The drilling all went smoothly and was completed within a day. I was surprised at how manoeuvrable the equipment was – it got up and down steps relatively easily! The process was however quite dusty. So despite most of the dust being contained and sprayed down, I did organise a clean of the neighbour’s windows!
The ground source heat pump is housed along with the buffer tank, thermal stores and other white goods in a downstairs utility room. Rory is able to monitor the temperature of individual rooms with a sophisticated heating control system that automatically regulates temperature.
Because of its exposed location, Rory was keen to make the new house as thermally efficient as possible. The windows are triple-glazed, and the building has thick walls filled with sheep’s wool insulation. Rory has opted for underfloor heating throughout the property which works well with the ground source heat pump, as it is a low flow temperature device. The house also has an MVHR system and was built to be “air-tight” with an air permeability test result of 3.62m3.h-1.m-2 @50Pa.
I’m very pleased with the ground source solution from Kensa. We’ve lived in the house through one of the coldest winters we’ve had for years and have been perfectly warm. We just don’t think about it. The house is warm and the system comes on when it needs to. My young children are used to crawling around on a warm heated floor, which is a luxury we are grateful for and lucky to have.