Grand Designs: The Street – Paul & Blanka’s self-build project

In 2015 we were approached by a client who had undertaken a pioneering project – to build his family’s first house out of hempcrete – himself….  Novice self-builder, Paul Troop and his wife Blanka, had designed the home for themselves and their two young sons and chosen a plot on the innovative Gravenhill site at Bicester – a site that is fast becoming a blueprint for future self-build programmes across the country.


Such a ground-breaking experiment as this is likely to attract attention and Kevin McCloud, having recently visited the self-build mecca of Almere in the Netherlands, galvanised the team at Grand Designs to follow the individual house builders on their journeys over 5 years and create Grand Designs – The Street.


Paul and Blanka wanted to build a high-performing eco home made out of hempcrete and were looking for the most sustainable solutions to complement their design. Their plan was to create a thermally efficient and airtight Eco-home, which would result in them needing a sympathetic ventilation solution to ensure the building was healthy.


Once Paul contacted us we asked him to send through his plans so we could review them. We were then able to specify a suitable system – a roof-mounted Passive Ventilation with Heat Recovery (PVHR) system that could provide enough fresh air to maintain a healthy and efficient indoor environment without using fans.  With heat recovery fitted as standard to all models the system sat well with the design brief of a low-energy house.

When asked what led Paul towards a natural rather than mechanical ventilation solution, he said that “The philosophy of our build was to find natural solutions to manage the behaviour of the house using natural forces and principles rather than technology where possible, avoiding reliance on pumps, fans, electricity etc. For example we wanted to use the roof overhangs with the angle of the sun to warm the house in the winter and shade it in the summer (when the sun is higher) and we wanted the hot water from the fire to naturally rise to the heat store as it is more buoyant that cool water (so we put the heat store in the roof). Much of the technology relies on natural forces (like the position of the sun at different times of the year, the siphoning effect of warm water, gravity to collect rainwater).”

“We were aiming for a very airtight house, which requires ventilation (and ideally heat recovery). It occurred to me that it would be possible to do this with natural forces, for example stale air is warmer, so it would naturally float up to the roof, where we could put a heat exchanger to transfer the heat to the incoming fresh air. As the transfer would never be 100% efficient, the warmed incoming air would still be heavier, so would naturally move to the ground floor of the house, setting up a circulation. I then started looking around to see if anybody had previously tried this.”

So, how did you find Ventive? “With great difficulty! I had never heard of Ventive and did not find the system by searching on the internet. In the end I posted on an online green building forum and somebody there suggested the name. I was really pleased to find that a British company had worked out how to do this.”

As with any building project there are always some issues, but the main challenge, according to Paul was “routing the vents from each room to the heat exchanger, as buoyant flow needs a continuous upward slope. Our house is deliberately quite compact, so it was fairly straightforward to sort out the routes. However, there were still a couple of rooms which were pretty challenging. Ventive were really helpful in suggesting solutions.”

How would you describe your experience working with Ventive? “The selection process was easy, there is nobody that does anything like them.  We wanted a warm, well-ventilated, efficient house that used minimal energy that just worked.  The Ventive system does this perfectly.  In addition to this, Ventive have been amazing – when any issues have arisen, they solved them quickly, and have been very generous in letting us have spare parts if needed.”

So what is the air quality actually like in a house with a Ventive system?  “The air quality is great. One thing that is amazing is how dry the house is!  People talk about the terrible damp and cold in the UK, but it turns out that that is just in poorly ventilated houses (most of the houses that we’ve ever lived in). It is really, really comfortable, even with minimal heating.”

When asked if he would recommend Ventive to others, Paul stated:Without any hesitation. Particularly if you’re doing a new build, you have the scaffolding access to put the heat exchanger on the roof and can plan the flow routes at the design stage.”


To see the story unfold, watch the series on Channel 4 from 4th April 2019.

If you have a self-build project you would like to discuss please contact us.


Useful Links

Grand Designs: The Street – Interview with Kevin McCloud

Grand Designs: The Street – Paul & Blanka