The first certified passivhaus in Cumbria

In 2010 Cheryl Hitchcock and Dudley Thompson were living and working in a large Victorian end of terrace house in Kendal. Cheryl and Dudley are technical authors trading as Education and Training Solutions. However, working from home meant keeping a large old house warm all day every day and, despite all attempts to improve the energy efficiency (roof insulation, double glazing, door and window seals) the annual energy consumption was 44,000 kWh. So when they decided it was time to do less work, they wanted to downsize and find a house that was much more energy efficient.

Kendal house – Annual energy use

Gas: 41,000 kWh – 7.8 tonnes CO2

Electricity: 3,000 kWh – 1.3 tonnes CO2

Total CO2 – 8.1 tonnes.

Discovering passivhaus

We were happy living in Kendal so we first explored smaller properties in the town. However, it proved very difficult to find anything with a decent energy rating and, having become accustomed to Victorian build quality, we found the attention to detail in new builds very disappointing.

Then we read an article about Lancaster Cohousing, an intentional community of 40 properties to be built to passivhaus standard on the banks of the River Lune in the village of Halton, about 4 miles outside Lancaster. After visiting the site, attending a couple of planning meetings and talking to the directors we applied to join the group. We were accepted in October 2010.

For the next year or so, we were kept busy with monthly planning meetings and other work commitments as the project moved into the build phase. We learnt a bit about passivhaus and met the architect for the project, Andrew Yeats of Ecoarc. In early 2012 our circumstances changed and we decided to leave the project. However, by then, we had decided that we wanted to build our own passivhaus. Andrew agreed to be our architect. All we needed was a plot.

the first certified passivhaus in Cumbria
ecological architecture project
passivhaus plot in Cumbria

The plot

We had seriously underestimated the difficulty of finding a plot. Any land that became available in Kendal went to developers. The occasional plot appeared in nearby villages but they were generally unsuitable and commanded Lake District prices.

Having just about given up, we went to look at an eco-house for sale in a small village just south of Penrith. The house wasn’t right for us, but the trip led to a couple of breakthroughs. First, we discovered the village of Crosby Ravensworth a few miles further south in the Lyvennet valley. Second, we made contact with Trevor Lowis of Eden Insulation who had built the eco-house. He was to play a major part in our project.

Crosby Ravensworth is a pretty village with a strong community spirit. Many of the nearby villages had lost their pub, but when the Butchers Arms in Crosby faced closure, a group of locals formed a co-operative and organised a share issue so that they could buy it and run it as a community pub. Similarly, when a stoneworks in the heart of the village ceased trading and the site seemed likely to be bought by a developer, a group formed a Community Land Trust (CLT) and purchased the land. The aim was to build 12 affordable houses, some for rent, others for shared ownership and to finance this through the sale of eight self-build plots. Both the affordable homes and the self build plots were originally restricted to those living in the parish but around the time we were looking, the catchment for the plots was extended to all of Cumbria and we were eligible. We found a south-facing plot that we thought would be suitable for a passivhaus and paid our reservation fee in August 2012.

Planning

Having been surprised by the difficulty of finding a plot we were about to be astonished by the apparently arbitrary nature of the planning process.

To gain overall planning permission the CLT had commissioned an architect to submit a design for each plot. Our plot had been granted planning consent for a bungalow with a detached garage. We didn’t want a bungalow or a garage so had to submit a new design to planning. However, because the CLT structural engineer considered the plot to have been made unstable by the action of stone saw cooling water, the footprint of the bungalow had been stabilised with rock piles. The result was that we were constrained to an external footprint of 10m x 9m, larger than we would have chosen.

In Lancaster Cohousing, we would have had a two-storey house with a floor area of 80m2. We believed we could manage at this size but we would also have had separate offices nearby with additional storage. In Crosby, with offices in the house and no external storage, we were budgeting for around 120m2 of floor area.

Through autumn 2012, we had a series of meetings with Andrew to develop the design. We identified the furniture we wanted to keep (almost all of our traditional Victorian furniture went to auction) and the activities we would like to make space for (some work, painting, woodwork).

To keep the treated floor area down, Andrew developed a design similar to many found in the borders with bedrooms in a warm roof and dormer style windows. We liked the design a lot. It was submitted to planning in December 2012.

south elevation - first application
north elevation - first application

In January 2013 the Parish Council unanimously agreed the plans. In February, tight against the deadline, the planner rejected them without being specific about his objections.

Andrew completed a significant re-design including a reduced roof overhang, removal of wood cladding and removal of gable windows. Lucy, Andrew’s partner, presented this design at a meeting with the planner in early March. These plans were also rejected. The planner finally indicated that he would be happier with a more traditional two-storey design and that more stonework should be added.

In response, Andrew developed a two-storey design which included a new stone porch over the front door to the north, symmetrical full length windows on the two floors to the south and a stone sitting wall on the north and west boundaries.

south elevation - final application
north elevation - first application

Lucy took the plans to a meeting with the planner in late March. The parish council approved the design in April but we didn’t receive our final Notice of Decision from the planner until the middle of June 2013.

This meant it had taken 26 weeks from our initial submission for our plans to be approved.

We instructed our solicitor to purchase the plot. This was completed in late August 2013 but we had to wait until we had sold our house in Kendal before proceeding with detailed construction drawings and starting on site.

However, we were able to make progress with decisions about the build and heating strategy.

Masonry or timber frame

The 40 passive houses at Lancaster co-housing were built successfully using a masonry construction so it was tempting to go down this route.

However, Andrew had other clients, Tim and Sarah, who were building to passivhaus standards using a timber frame construction. We were able to visit their site as the frame was being assembled. We liked the idea of a frame being made in factory conditions with the insulation and airtight membranes in place before delivery to the site.

We engaged a firm of quantity surveyors to make two estimates of the building cost, one based on masonry construction and the other based on timber frame. The masonry construction was less expensive but not to the extent that it dictated the decision.

We had already talked to a local frame manufacturer, Trevor Lowis from Eden Insulation based in Appleby, about 5 miles from our site. Eden Insulation had completed two energy efficient frames utilising a ‘fabric first’ approach on the site at Crosby Ravensworth but neither home had attempted to achieve the passivhaus airtightness standard. However, Trevor was confident that the standard could be achieved and he was happy to take on the role of airtightness champion for the build.

The decision was made. Stoneworks Garth would be a timber frame construction from Eden Insulation.

Heating and ventilation strategy

We appointed Alan Clarke of Elemental Solutions to help with the heating and ventilation design and to carry out our PHPP analysis.

Stoneworks Garth is not on mains gas so heating strategy was something we were concerned about. The decision came down to a choice between LPG and an air source heat pump (ASHP). The initial costs were lower for the former while running costs are lower for the heat pump.

The predicted Coefficient of Performance (CPO) for the heat pump was at a level where the CO2/kWh for the two strategies were about the same. This would move in favour of the heat pump if, in the future, CO2/kWh for the UK grid improved. LPG also had the disadvantage of requiring regular deliveries of cylinders, estimated at 6 per year.

The south-facing roof was ideal for solar capture and we considered incorporating both solar PV and solar thermal. However, working with Alan, we decided that the simplest strategy was to install only solar PV. With the output from the PV feeding the heat pump, this was predicted to provide us with free domestic hot water (DHW) for 6 months of the year.

We decided to use a Viessmann 3kW air source heat pump with 4kW of Romag integrated solar tiles on the roof.

Firewood is readily available locally so we decided to also install a Morso S11 wood-burning stove. As well as looking cheerful, this would provide a backup in the event of power cuts. Although the S11 is not marketed as a passivhaus stove it has a suitable low output (2-4kW), the option of an external air supply and Alan had experience of using them successfully in previous projects.

A Paul Novus 300 mechanical ventilation and heat recovery unit (MVHR) was selected for the ventilation.

Detailed design

Despite much talk in the press about an overheating housing market, it took until April 2014 to finalise the sale of our home in Kendal. We moved into a rented cottage in Crosby Ravensworth and Ecoarc started work on the construction drawings.

Ground Floor Plan

The ground floor comprises:

  • entrance hall and library
  • workshop
  • shower room
  • utility room containing MVHR and ASHP
  • open plan kitchen, dining room and living area

First Floor Plan

The first floor comprises:

  • main bedroom
  • guest bedroom
  • sitting room
  • studio / office
  • bathroom

On the ground floor sliding glass doors open on to the garden. A brise soleil provides summer shading. On the first floor, full-length windows open to Juliet balconies. North facing windows are relatively small, in keeping with traditional Cumbrian design.

High insulation levels were achieved with:

  • Timber frame comprising 300mm deep Masonite I-beam panels with 40mm thick Gutex woodfibre insulation on exterior face filled with Warmcel.
  • 250mm Isoquick insulation beneath the floor slab and 150mm Isoquick edge modules to avoid thermal bridging.
  • 600mm layer of Warmcell in the loft space.

The external walls were 100mm recycled blockwork finished in K-Rend with colour banding around the windows and doors.

The airtightness was achieved with:

  • 12mm Durelis Vapour Blockboard on the internal face of the timber frame taped to the floor slab with Proclima tape,
  • Pro Clima DA vapour control layer on the ceiling taped to the Durelis Blockboard with Uni Tape,
  • Suitable grommets and Pro Clima tape sealing all service penetrations.
ground floor plan
first floor plan
passive house floor plan

Project management and budgeting

We did not have the skills to play any part in the hands-on building of Stoneworks Garth. However, we had worked in project teams for the last 30 years so felt we could play a part in project management.

Our aim was to use local contractors and suppliers as far as possible. We were also happy to take recommendations rather than spend lots of time seeking competitive quotations.

The key appointment was a main contractor for the build. Trevor at Eden Insulation recommended Alan Brockbank, B&H Construction. Alan is based near Appleby and had worked with Trevor before so was familiar with timber frame construction.

We met Alan on site. He had no experience of passivhaus but was interested in the challenge and he agreed to act as our main contractor and site manager.

Our informal agreement was that we would be responsible for ordering the main specialist components (eg Isoquick slab, Internorm windows, heat pump, MVHR etc). Alan would arrange other building supplies (eg concrete, masonry etc) and recommend and schedule sub-contractors.

We also took responsibility for organising the utilities, water, electricity and phone connections.

Once the build was started, as well as our regular visits to the site, we had monthly meetings which Andrew attended. These meetings were formal, starting on site so that Andrew could assess progress and pick up on any issues then going on to a round table meeting with agenda, minutes and action plans.

As mentioned previously, we had engaged a firm of quantity surveyors to provide an estimate for the cost of the build. This meant that we had a framework for the expected cost of each stage of the build against which we could compare Alan’s estimates.

Alan provided an initial overall estimate of the cost and then a very detailed estimate at the start of each stage. We were clear that these were not expected to be fixed price contracts. If issues arose on-site that affected the cost then these were discussed at site meetings.

In practice, the strategy worked very well. The only significant increase in actual cost compared with the QS estimate was at the foundation stage where the structural engineers insisted on a much greater depth of concrete and reinforcement than we expected.

Fortunately, all other stages came in cheaper than QS estimate, probably due to the lower overheads of a main contractor who was a sole trader rather than a larger company.

The build

Work eventually started on site at the end of August 2014. Around 0.8m of spoil had to be removed across the site to achieve the correct level before the foundations could be excavated.

The first stage was a general fill of concrete into the strip foundations. Next came a second fill of concrete reinforced with steel mesh. The earth between the strips was removed and the space filled with gravel. A 250mm Isoquick raft was laid on the gravel to provide insulation. A radon barrier and another steel mesh were added before the final pour of concrete for the floor slab.

October was quiet because we were in a queue for the timber frame. This was being manufactured in Eden Insulation’s factory in Appleby from Masonite I beam panels as follows:

  • 300 Masonite I beam wall stud sheathed externally with 40mm Gutex Multitherm and Fronta Humida membrane.
  • Racked internally with Spano Durelis Vapour Barrier board with 50mm service cavity. All board joints taped with Tescon No 1 in the factory.
  • All panels injected with cellulose fibre to over 60Kg/m3.

Ecological Building Systems, based in Carlisle provided all the tapes and membranes for the project.

ecological building systems
passive house design architects
eco house design
passive house diagram

In early November, the frame was erected and made watertight over two days. We had glorious weather on the first day and driving Cumbrian rain on the second.

The house has four ground floor and four first floor panels. The four metal web joist floor cassettes were supported on an internal bearer to help with airtightness. The roof trusses were placed on the first day and sheathed and protected with a membrane on the second day. The ceiling to the underside of the trusses was formed using 9mm OSB with a taped Pro clima DB + membrane.

The majority of the airtightness taping to the walls was completed in the factory leaving only the corners and joint between ground and first floor panels to tape later.

By early December, the windows were in, the slates were on, the blockwork was up and the solar PV panels had been fitted on the roof.

passivhaus first floor panels
passivhaus second floor panels
passivhaus solar panels

We were ready for our first airtightness test. This was conducted by Paul Jennings of Aldus. Current building regulations require less than 10 air changes per hour. Passivhaus certification requires less than 0.6ACH – and we achieved 0.34 ACH so everyone was delighted.

Through the winter, the team made good progress internally. By early January the first fix plumbing and electrics were almost complete, including the ducting that connects the mechanical ventilation and heat recovery (MVHR) unit to air valves in most of the rooms. By February, the internal walls were plastered and drying out and work was starting on the bathroom.

Apart from the heat pump and the stove, all the services had been fitted through the walls and sealed so we were ready for our second airtightness test. We achieved 0.21 ACH, a significant improvement on the first test.

In March, the external walls were rendered, including the banding around the windows, so the scaffolding could be taken down.

Internally, the flooring was laid upstairs and the kitchen was almost complete. LB Joinery in Kendal built and fitted the open plan oak staircase.

In April, the brise soleil was erected. It was originally designed to have posts only at the front with brackets supporting the weight at the wall. However, once the main beam had been fabricated we all agreed that additional posts at the wall would be advisable.

Internally, the woodburning stove was fitted and the airtightness improved with some technical guidance from Morso.

We were into the final stages now. In early May, the MVHR (which was installed by Richard, our electrician), was set up by the Green Building Store, the heat pump was installed and the final airtightness test provided an average result of 0.30 ACH, easily within passivhaus standard. WARM completed their analysis and we were awarded certification in August.

open plan oak staircase
passive house building exterior
passive house build

Moving in

We moved into our new home in mid-May 2015. We had a difficult start. Six weeks after moving in the seal on the internal water meter failed (the utilities contractor fitted the wrong washer) flooding the ground floor to a depth of three inches. Although we managed to continue living in the house for most of the time, the floor, internal doors and kitchen units all had to be replaced. We finally moved in properly at the end of November.

Fortunately, the timber frame was undamaged and, with some re-taping, we achieved a similar airtightness result to before the flood.

Energy use

15 Stoneworks – Annual energy use

Electricity: 3,000 kWh (estimated from 10 months use)

Total CO2 – 1.3 tonnes.

 

The house has performed well and we are very comfortable although the winter of 2015 – 2016 was not severe in terms of low temperatures. (We escaped the terrible floods caused by storm Desmond. Sadly, others nearby were less fortunate.)

So far, from the beginning of June 2015 through to the end of March 2016 (10 months) we have drawn 2,600kWh of electricity from the grid. This would suggest an annual figure of around 3,100 kWh. However, since this period includes three weeks when we had fans and dehumidifiers running for around 14 hours a day, we expect our annual use going forward to be lower than this.

The low figure is partly due to our direct use of energy from the solar PV which we have tried to maximise by using appliances such as the dishwasher and washing machine during the day. Coincidentally, the total generated during this period has been almost exactly the same as the amount drawn from the grid.

However, at the moment we don’t have data regarding the proportion of house demand being met by the solar PV. To improve our understanding we have recently installed an Emonpi which enables us to monitor house demand and the proportion of energy provided from the grid and solar PV. In future we hope to extend the monitoring to include internal and external temperatures and heat pump performance.

In conclusion

We have enjoyed building our passivhaus. Our policy of using local suppliers and contractors and relying on recommendation rather than trying to make decisions based on multiple quotes worked well. Maybe we were lucky but the resulting team made it seem very easy and our early anxiety soon disappeared. Our house is warm and comfortable. Our bills are much lower and we have reduced our home related CO2 emissions by almost 80% (from around 8.1 tonnes to 1.3 tonnes).

Would we do it again? We struggled with the planning process and the flood was very discouraging but we probably would – so long as we could have the same team.

Links

Ecoarc – www.ecoarc.co.uk

Eden Insulation – www.edeninsulation.co.uk

WARM – www.peterwarm.co.uk

Butchers Arms Community pub – www.thebutchersarmscrosbyravensworth.co.uk

Lyvennet Community Trust – www.lyvennetcommunitytrust.org

Emonpi – www.openenergymonitor.org

Lancaster Cohousing – www.lancastercohousing.org.uk

completed passive house exterior
exposed oak staircase and wood burning stove
photovoltaic panels