Good stock - Stylish Stockport retrofit achieves radical energy savings

Energy bills £28 per month for gas
Building: Deep retrofit & extension
of 1960s brick house into 150 m2 near-passive home
Location: Stockport, Greater Manchester
Standard: AECB Standard

Two architects relocating from London with a young family took on the challenge of converting a derelict 1961 suburban house in Stockport, Greater Manchester into a passive house.

Russel and Anna Hayden were excited about imposing their modern vision on what was then an ordinary property with brick and block cavity walls, in the hope of creating a replicable example that could be copied up and down the length of the country.

The house they created has bright and spacious modern interiors that belie its relatively ordinary facade. And although the couple narrowly missed achieving the Enerphit standard for passive retrofits, their house performs superbly well and meets the slightly less demanding AECB Standard.

“It was disappointing not to achieve passive house as I’m a great supporter of the thoroughness of the process, but we only just missed it. We achieved 1.18 air changes instead of the target of 1.0 and it doesn’t change the fact that the house is comfortable and pleasant to live in,” says Russel, who self-managed the project from his parents-in- law’s house across the road. “We also love the timeless Scandi simple look, and we’ve reused lots of things from the original house. We turned the rails on the stairs into door handles, and we sandblasted the cedar cladding from the dining room and put it in the hall.”

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The thermal performance of the retrofitted property has also easily surpassed that of the couple’s previous house in London – in both winter and summer. Two years ago, when temperatures rose into the mid thirties outside, the inside of their new house was no more than 25 or 26 degrees. “The roof light at the top of the stairs makes a huge difference as it creates a stack effect, so we only need one or two windows open downstairs to keep it cool,” Russel says.

“Even when it’s less than five degrees outside, the one radiator downstairs is enough, and it barely comes on. Upstairs, the radiators are never needed.”

The clean indoor air has improved the sleep of Anna, who had bouts of insomnia in London. “It was noticeable as soon as we switched on the MVHR and felt the trickle of cool, filtered air that we both enjoyed deeper sleeps and vivid dreams. I’ve read scientific research suggesting the effect is caused by lower CO2 levels,” Russel says.

1 The derelict 1961 suburban house was bought in a sealed bid in March 2016; 2 & 3 fl oor to wall junction, with 150 mm Dow Styrofoam and damp proof course at underside of external wall insulation; 4 airtightness detailing around windows, with windows to sit within the external insulation layer; 5 roof to wall junction, showing Rockwool insulation meeting the external insulation, and airtightness taping; 6 close-up of the 280 mm Graphite EPS external wall insulation, bonded to existing brickwork with min 10 mm continuous adhesive to form airtight layer; 7 & 8 airtightness detailing and insulation to Lindab ductwork, for the mechanical ventilation with heat recovery system; 9 Tescon Vana breather membrane lapped out under the roof with tiles, with external insulation being installed.

Without dust, he adds, there are no spiders and even their dog’s hairs don’t settle and are easily sucked into the vacuum cleaner. Meanwhile, the triple glazing makes it so soundproof that the couple barely notice planes going overhead, and even slept right through a police car chase that ended in the garden of their next-door neighbour.

The Haydens bought the derelict property for £310,000 in a sealed bid back in March 2016. It was in the popular Heatons area of Stockport, in Greater Manchester, which Russel says, “ticked a lot of millennial boxes”. “It’s green and leafy, with a good sense of community, but it’s a bit more suburban than nearby Didsbury. It was also opposite Anna’s parents’ house and they kindly allowed us to move in there while we got everything sorted,” he says.

The couple hired a local builder who began ripping out the insides in April 2016. After he had demolished all the internal walls and stripped out all the fittings, it left an empty shell. In the summer of 2016, the family left London, where Russel had worked for Nicholas Hare Architects, and Anna for Stanton Williams. They moved into the house of Anna’s parents, with their two children, Dexter, now eight, and Zoey, now five.

To make the project affordable, Russel project-managed the retrofit from over the road. Meanwhile, Anna took a job as project director for the special exhibitions gallery at Manchester’s Science and Industry Museum, and the couple rented out their London property. The cost of converting the house came in at £170,000, but it would have been far more without Russel’s DIY skills.

To make the project affordable, Russel project-managed it from over the road.

He had acquired a theoretical knowledge of techniques from the AECB CarbonLite Passivhaus Designer course and had shown a keen interest in sustainable design at his practice in London.

“I procured all the materials and agreed with the builder what to do each day. I did all the taping as the sequencing is so critical and later on I did all the finishing off. The local builder was a fantastic help, spending many evenings on YouTube researching passive house techniques. That was a real bonus for us as it’s hard to describe accurately what’s required when builders haven’t done passive houses before. It’s one of the biggest challenges in the industry,” he says.

Russel developed the design closely with environmental consultancy Enhabit, who provided passive house design services, airtightness testing, the MVHR system and the windows, and who have subsequently merged with fellow passive house specialist suppliers Green Building Store. “Russel didn’t need as much guidance as most of our clients because he was already knowledgeable,” says Akta Raja, director of Enhabit.

“But one course doesn’t teach everything you need to know about the building physics of passive houses and getting all the detailing right. We helped Russel to build the PHPP model.”

Even with the help of Enhabit and a design plan in place before they moved to Stockport, the practicalities of self-managing the project were far from straightforward.

“I didn’t realise at the time just how passive house workmanship has to be a level above what the average builder is used to achieving. The course gave a flavour of how to do taping, for example, but it’s not the same as working on a whole house. You can have drawn every detail before you arrive on site, but lots of things crop up unexpectedly,” says Russel.

1 & 2 Construction of the new roof with 325 mm deep OSB ribs creating cavities for the installation of new Rockwool insulation; 3 insulation and airtightness work around the opening for a new triple-glazed Fakro rooflight; 4 construction of the new timber-frame extension with 150mm studs waiting for insulation; 5 Insula structural thermal break under steel column; 6 Lindab spiral galvanised ducting for the Paul MVHR system.

Russel spent a lot of time over the Christmas period of 2016 laying industrial parquet flooring throughout the house while it was still empty, spending late nights sanding and re-sanding. “The floor is a key element as it provides a sense of unity throughout the house. The spaces all meld into one, which is lovely,” he says. As soon as he had finished installing the floor, the family moved into their new property in February 2017. Although it felt quite cold during that winter, the installation of 280 mm of thick expanded polystyrene to the exterior transformed the feel.

The house has not been significantly altered structurally, which helped to keep costs down. The couple removed both kitchen walls and a chimney breast in order to create a large, open-plan space downstairs, with living room, dining area and kitchen. Upstairs they rebuilt partition walls in order to create three better-proportioned bedrooms, a bathroom and an en-suite.

Part of the large garage was converted into a shower room and utility space as part of a new timber-framed studio extension downstairs, which doubles up as an extra bedroom for guests. The extension is clad with cedar square-edge boards that Russel collected from a sawmill in Hereford and then air-dried naturally in the back garden. The same boards were used to clad the replaced tumbledown porch.

On the roof, the old 1960s tiles were stripped off. New Larsen-truss type beams were fixed to the side of the existing rafters to make up the depth for almost 400 mm mineral wool insulation, before installing the new concrete tiles. On the ground floor, Russel and Anna opted to keep the existing slab and apply the insulation and screed on top, then the oak parquet flooring, which reduced some of the head space.

To gain back some head space, they left the plasterboard off the ceiling joists, which also provided a more rustic feel. “It raised a few eyebrows, but we like it as it’s gnarly and a bit rough,” Russel says. “We also had to jet-blast the joists and underside of the floorboards [above ground floor] and paint them with intumescent paint to satisfy fire regulations.”

Having not quite reached the Enerphit target for airtightness, Russel spent a day looking for small holes. But he soon realised that fixing the issues would require unpicking a lot of the structural work and cost a fortune. The primary air barrier for the original walls was the layer of continuous 10 mm thick adhesive that joined the external insulation to the brickwork (for the new extension walls it was 18 mm SMARTPLY OSB 3 board taped at junctions).

“Our weak point was where the garage and the extension joined onto the rectangle of the house. There were quite a few areas where we didn’t have the parge coat. Next time, I would pay more attention to the continuity of the outer later, especially where you have the roof [of the extension] coming into the cavity wall,” he says. “Once the air gets in there, there’s nothing you can do. When we dry lined the interiors, we could also have made them even more airtight as a second line of defence in case the outer one wasn’t working perfectly.”

Enhabit’s Akta Raja sees the project as a great success. “It’s tricky when you’ve never done it before and you’re project managing, to achieve passive house, especially with an existing building. But it’s a great way of setting a target and there’s no reason to feel a failure if you don’t quite reach it. The energy consumption is still 90 per cent better than it would have been otherwise and all that carbon annually will be saved for the rest of a lifetime. Russel and Anna have created a genuinely brilliant house which is comfortable to live in and has great indoor air quality,” she says.

Passive house workmanship has to be a level above what the average builder is used to.

She believes the AECB Standard is an excellent alternative to passive house. The AECB, of which the Passivhaus Trust is a subsidiary – was instrumental in bringing the passive house standard to the UK. Based on the same methodology but recognising that meeting the passive house standard can prove too challenging in some situations, the AECB Standard specifi es good low energy performance via a fabric-first approach, utilising the passive house methodology and design software, PHPP.

“Not only is it easier to meet, but members of the AECB are able to self-certify, which saves them the extra costs of passive house accreditation,” she says. “The project was a good learning experience and [Russel] has brought his deeper understanding of energy performance to his new work.”

The AECB told Passive House Plus it is now poised, however, to allow only certified passive house designers and other suitably qualifi ed individuals to self-certify projects to improve on quality assurance. Others will be able to hire qualified individuals for certification.

Russel Hayden now works as an architect out of the house’s studio extension. The project was a good learning experience and he has brought his deeper understanding of energy performance to his new work.

“Typically, I’ve been designing kitchen-diner extensions on the back of leaky Victorian semis. Clients like the juxtaposition of contemporary designs with the older house. I’ve also been involved in retrofitting older houses to make them more energy efficient. To date, I’ve not been commissioned to do a passive house, but I have the understanding now and I’d jump at the chance,” he says.

Image gallery

• Ground floor prop presentation Ground floor prop presentation
• First floor prop presentation First floor prop presentation
• Eaves details Eaves details
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• First existing First existing
• Ground existing Ground existing
• Floor to wall junction Floor to wall junction
• Window detail Window detail
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