Phil Neve explains what Passivhaus Premium is and why he chose to target the standard for his own self build in Somerset. He also talks through his biggest project challenge, which was obtaining planning permission to build in open countryside.
Interview with Phil Neve
Phil Neve started his working life as a scientist and oceanographer. He always had a deep interest in alternative energy, and so eventually retrained as an energy consultant and Passivhaus Designer. He then spent 15 years working exclusively on low energy and Passivhaus buildings. Now retired, he is five years into his own Passivhaus Premium project, which has finally got planning permission under Paragraph 84 of the National Planning Policy Framework.
In the last podcast we talked about Passivhaus Plus with architect Heather Johnson. In this episode we’re looking at the Passivhaus Premium certification and how it differs from the other Passivhaus classifications. We’ll also explore some of the challenges that meant this project was on the drawing board for five years!
Renewable energy generation on a Passivhaus Premium project will produce a surplus
While Passivhaus Classic focuses just on the energy consumption of the building, Passivhaus Plus and Passivhaus Premium bring renewable energy generation into the certification process.
In addition to all the criteria for a Passivhaus Classic, a Passivhaus Plus project must generate as much energy as it uses over the course of a year.
Passivhaus Premium takes this even further, so that a surplus of energy is produced. Phil explains that this is calculated according to the floor area and the potential of the piece of land.
Typically a Passivhaus Premium project might produce two to four times the energy it uses. Whereas a Passivhaus Plus project will import energy from the grid in the winter, a Passivhaus Premium will rarely import energy. So the goal of this is to export a significant amount of energy to the grid. This also starts to affect the operational carbon calculations for the building, because you are producing zero carbon or very low carbon energy on top of what you need.
A Passivhaus Premium project will require permission to export to the grid
If you’re looking to export above five kilowatts to the grid, which will be a certainty on a Passivhaus Premium project, you will need approval from the District Network Operator. Another must is that you have a three-phase electricity supply.
Solar PV is often the most practical choice of renewable
Although any renewable can be used for a Passivhaus Premium project, as with Passivhaus Plus, generation tends to be with solar PV because it can be integrated seamlessly with the building and is generally much more accepted technology than wind turbines, etc. However, if the site has a natural resource to harness, for example being next to a watercourse, then obviously other methods of generation may be preferable.
Phil’s horticulture project
Getting consent to build in open countryside can be expensive and time-consuming
Phil’s self build journey began with a piece of land he owned for a horticultural project. He had absolutely no intention of building a house, but over time things changed. Unfortunately he knew that there was probably only one way to get planning permission to build on a site like this and that was to use the Paragraph 84 exception clause (previously referred to as Paragraph 80, Paragraph 55, etc.) of the National Planning Policy Framework. This allows exceptional one-off houses to be built, where quality is essential and the proposed dwelling significantly enhances the rural setting. However, it’s a lot of work, comes with numerous costs and is all at the self-builder’s risk until consent is granted.
A satellite view of Phil’s site
A Paragraph 84 permission often requires consultants
Whilst Phil felt he had an advantage with his background in construction and environmentally sound building, he was fully aware that he would still require a lot of help. He tells us that he has ended up employing around 10 consultants, sometimes two per topic, covering; architecture, planning, landscape design, ecology, highways and highway safety, and lighting! On top of that there was a design review process using an independent design panel, which was long-winded, complex and expensive. Phil knew all this was coming but it still came in at twice the budget he’d expected.
A Paragraph 84 consent requires deep pockets
One of Phil’s initial aims was to prove that exceptional house design under Paragraph 84 needn’t just be for mansions. Exceptional projects can be small scale and not break the bank. He admits he may have been a little naive about this but still believes he can bring the project in at a reasonable cost as a “sweat equity” self-builder.
Phil has an unshakable belief that we can create great buildings that are efficient, comfortable and healthy. We have the skills, knowledge and materials to do it, but we’re not doing it at volume. He feels that what most people are offered when buying a new house is rubbish and it needn’t be. So, he wanted to show that it could be done better and still be affordable.
‘Exceptional’ in this case is pushing the boundaries of what can be achieved
Phil wanted great performance from the building and to maximise energy generation, and so he targeted Passivhaus Premium. It also had to look good, be beautiful to at least some people, and be very low carbon, pushing the carbon budget down as far as possible. Beyond the house he wanted to improve the biodiversity and ecology of the whole site.
The size and design evolved over time
When Phil started the design process he was living on his own and looking at a two-bedroom house around about 120-140 square metres. As he now has a partner, the design has evolved into a more standard 3-4 bedroom family house of around 230 square metres.
In terms of Passivhaus design, he spent a lot time considering the form (or shape) of the building. The form factor can have a big impact on the ease of construction and the cost. A good form factor is two, with a poor form factor above four. Phil’s house comes in at 3. Early modelling of the building showed that it could achieve the Passivhaus standard, and that Passivhaus Premium was within reach with a PV array on the roof of the building. The overheating risk of the final design is zero.
“These ideas evolved into the concept of a wedge-shaped house with a single pitch roof facing south. A very simple design which works very well.”
A Passivhaus doesn’t have to be a boring box
Phil explains that to achieve an interesting shape for a Passivhaus there is some compromise on efficiency. However his design will create a fantastic south-facing roof for around 22 solar PV collectors, which will allow them to achieve the renewable generation targets. Internally there will be some sloping ceilings and slightly odd shapes, although Phil believes this adds to the aesthetic.
Minimising the overheating risk has been a priority
During the design process there is a balance to be achieved with solar gains. While these are beneficial to keep the house warm in the winter they need to be controlled to prevent overheating in the summer. For Phil’s project there are large windows on the ground floor of the south elevation, but these will be shaded from the summer sun with a 1-metre overhang. For the east facing bedroom windows, in addition to overhangs there will be some vertical shading. Phil also intends to grow plants up that side of the building to help shade those rooms. The building then becomes a place to grow things like hops and vines, producing food as well as providing shade.
Finding a collaborative architect was important to Phil
Phil chose friend and architect Mark Ellerby to work with him on the design as he wanted someone independent with good design ideas, who would also be receptive to his input. He says they’ve worked through challenges and ultimately produced a design that works and has satisfied the design review panel.
The Design Review Panel want to understand how you’ve arrived at the designs
When a panel of experts are reviewing your design it can feel subjective, because they decide if it is outstanding architecture and suitable for Paragraph 84 permission. So Phil explains that you have to show how you got to the final design – show your workings – and justify the decisions you’ve made.
Improving the ecology of the site has been a huge focus
How to improve the land for biodiversity has been a top consideration for Phil, so he asked his ecologist to show him everything he could do to increase biodiversity. He was also aware that they needed to convince people that they would actually put this into practice.
There are rules and regulations to meet as well as the requirement for biodiversity net gain calculations, which seem to conflict with what is needed for the bat populations. He has had to show that the bats won’t be disturbed by light coming from the house through light spill surveys including a 3D model of the house. This has been agreed by the county ecologist and is now with English Nature for their approval.
“To anybody embarking on a Paragraph 84 house, you have to look at everything in detail early, predict the problems and be ready to go out and spend the money to get the answers.”
For a Passivhaus Premium you must be able to export to the grid
Phil had originally thought about building off-grid, but to be certifiable as Passivhaus Premium you need to be able to export energy to the grid, otherwise you are potentially wasting the excess energy you produce. He now thinks you should only be off-grid for energy and water if you absolutely have to be. All the energy you export is contributing to a low carbon energy supply, and you can access energy yourself if needed.
Even before construction begins, Phil got a three-phase supply installed at a cost of £2000, and he will then have to run another 100 metres of cabling to the house.
PHPP calculates the primary energy target for the renewables
In addition to all the modelling that takes place in the Passive House Planning Package (PHPP) for a Passivhaus Classic project, for Passivhaus Premium there is an extra PHPP calculation for primary energy, which helps work out the renewable energy target. It calculates it in two different ways, so there’s some flexibility as to how much you need for different buildings. Phil’s target is 22 kilowatts. Just to illustrate how significant this is, the average maximum installation in the UK (without planning permission) would be about four kilowatts!
So there will be 100 square metres of solar PV, which will also be the roof covering. Phil will be using a small ground source heat pump in addition to the PV to provide all the heat and hot water they need. He may add batteries eventually, which with the right switching gear would provide a buffer against power loss from the grid.
A tried-and-tested build system will make life easy
Phil is very familiar with the PH15 system, having been part of the Passivhaus Homes team for over a decade.
Rather than reinventing the wheel with every new design, PH15 makes it easy to achieve Passivhaus performance. It is essentially as simple as you can make a timber structure. Structural I-beams provide the physical strength and form to the building, with a layer on the outside, which is insulation and a layer on the inside which is closing the cavity. This is the racking board, the airtightness and vapour permeability layer. This creates a box, which can then be filled with processed wood insulation. 85% of the structure is insulation, it’s structurally sound, made of natural materials and is airtight.
During the first couple of weeks of a build, all you’re doing is screwing things together. Phil describes it to clients as an Ikea flat pack house; it just comes on a truck instead of in a box! For Phil the other good thing about the PH15 system is that the internal floors are essentially hung on the inside from ledger beams. The roof is the same structure as the walls, essentially a portal frame structure, with the airtightness layer continuous on the inside of the building.
Reducing the embodied carbon of the building was part of the design process
Phil explains that for a typical dwelling there may be 40-50 tonnes of carbon within the concrete used in the groundworks and foundations, with another seven tonnes in the superstructure of a masonry house. Phil was keen to eliminate the use of concrete on his project.
One option was to use ground anchors, which are like metal screws that hold the building to the ground. The building then sits on holding plates, raised above ground with a ventilated cavity. This creates a suspended timber floor instead of a concrete slab. The approach is proving expensive and complex in terms of buildability.
A lot of people are now using a modification of a standard strip foundation, where you dig a trench, fill it with some concrete then build cavity blockwork, to allow you to pour a slab over insulation. Phil is looking at a compromise between the two, either by using low carbon cement or other materials instead of cement. Chem-free blocks and low carbon pozzolanic materials would reduce the carbon content of the concrete.
Another option combines limecrete with foam glass insulation instead of plastics. One challenge is that with these products the costs go up and the performance comes down a bit.
Building on a slope can mean a lot of excavation
Phil is building on a slight slope and made the decision early on to excavate soil to create a flat site for the house. This was to drop the house into the landscape for shelter as well as the visual aesthetics. Phil says he might make a different decision if he was looking at it today as it means moving a lot of earth around, although the soil will be used on site as part of the landscaping work and to help retain water on site.
The land sits between a wooded ridge above to the north and lower lying agricultural lands below to the south. The soil is fairly free draining and he’s aiming to reconfigure the landscape with a series of swales and two ponds to gather water before it penetrates down the site.
Prices have shot up across the board since Covid
Phil started the project with a working budget for the building of between £1800 – £2,000 per square metre, but prices have gone up massively since COVID. He’s now looking at over £2,500 per square metre and needs to keep it below the £3,000 mark. He is also planning to do some of the work himself to reduce the costs. Phil will be project managing the build with a small team, commissioning items from local people where possible, and avoiding bigger contractors who sub-contract things out and are therefore more expensive. He admits it’s still an unknown, until he’s got detailed costings and is actually building. He’s keeping the landscaping as a separate budget and one or two of the higher cost items, such as the 100 metre electric mains supply, that other people might not encounter. He aims to have transparent costings that can help inform others.
A slightly longer build programme aims to take the pressure off
Phil is setting the build programme to around 18 months, rather than a year, so that there is not too much pressure on everyone. He’s in good health, has always been active, and thinks if you have the right project that’s moving forward the time will fly by. He’s also aware that building projects often go through a hiatus somewhere in the middle, when you wonder why the hell you started and whether you’ll ever get to the end. He’s seen that in other projects, so is prepared for it and knows you just have to get on with it.
Planning has been the biggest challenge
Phil has a lot of sympathy for planning departments and can see that they are massively under-resourced but the result is that the system doesn’t work, especially for individuals. The big developers can throw money at it, take everything to appeal and essentially sidestep the planning process on the basis of housing supply need.
“I’ve always said to my clients, if you’ve got planning and land, you’ve got 60% of the job done.”
Everything Phil has done so far to get planning approval has been at his own risk. He gives an example, of having to pay an archaeologist to produce a strategy for the build and to be on site whilst holes were being dug. That money would be wasted if he didn’t get planning permission. With approval comes 22 planning conditions, four of which need to be discharged before construction can even begin. If for any reason he couldn’t go ahead with the build after approval, at least he would have a site with planning permission, which would be worth considerably more than before.
It is all about risk prior to planning approval, so he’s had to be very patient and have deepish pockets to pay for it all!
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Transcript
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Exemplar Sustainable Buildings Awards
The winners of the Exemplar Sustainable Buildings Awards have been announced.
This was a one-off event to celebrate the 20th anniversary of the Sustainable Development Foundation. It brought together two alliance partners, the Alliance for Sustainable Building Products and the Passivhaus Trust so all of the entrants had to prove performance and demonstrate careful choice of materials and products.
There were some wonderful projects, and it’s definitely worth taking the time to dig into the details and watch the videos.
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