'We wanted something warm, and cheap to run' - Couple's EnerPHit home, the passive house retrofit standard
Homeowner Paul Tully says that he and his wife Deirdre spent 10 years trying to figure out what to do about their house.
"It was cold and draughty and very expensive to heat. And we didn't have enough space; we needed more bathrooms. So we watched Grand Designs and all of the building shows on TV, we went to all of these building and energy exhibitions, and we also went to see a couple of passive houses being built. We realised then that that was what we wanted. Something cheap to run, and warm."
Planning authorities scuppered an early plan to demolish and start again, leading the Tullys ultimately toward a decision to do a retrofit of their bungalow that would bring it to passive house standards.
Stephen Young, of Young Design Build, was contracted to design the house. Young is a veteran of passive building, but this was his first EnerPHit project - EnerPHit being the passive house retrofit standard. It's not quite as exacting as the standards for new builds - the air-tightness threshold is a little lower, as is the space heat demand - but the reality is that refurbishing an old house to achieve even these targets can be considerably more challenging than starting on a greenfield site.
Moreover, the design brief extended well beyond achieving passive thresholds, Stephen Young explains. "Paul wanted to increase the area of the house, he wanted to make it more open, he wanted the bedrooms to be enlarged, and en suites added to all of them. Because we were going to undertake a huge amount of work, it made sense to remove the roof and go for a storey-and-a-half."
The house was stripped back to its bare bones. The roof was demolished, along with all of the internal walls, to leave just the foundation and the external walls.
The existing cavity walls had been pumped with a fibre insulation in earlier years, so it was decided to leave the cavity untouched. To beef up the spec, external wall insulation was added, while the windows were moved forward into the insulation zone in order to avoid thermal bridges.
Removing the bungalow feel from the house was central to the whole design process. With the internal walls gone, the team could completely revamp the internal layout, creating a modern, open-plan design.
"We changed the orientation of the windows," Young explains. "Instead of the long, horizontal windows, we broke out openings and used vertical windows in the west elevation. In the south, we went with floor-to-ceiling window heads. That changed the dynamic of that whole facade."
Improving air-tightness was vital - both to deliver a comfortable temperature and to ensure that the building hit the EnerPHit standard. This was largely achieved through a wet plaster finish internally. "No top of the range additives or systems," says Young, "we didn't use any of the air tight plasters or anything like that."
That said, the process of achieving such a high standard of air-tightness did require careful detailing and scheduling, with everything worked out ahead of time on paper. Planning, Young emphasises, was central to the success of the project.
If you've got great air-tightness, then you also need great ventilation. A Paul Novus MHRV system was installed in a soundproof closet adjacent to the master bedroom. Tully says there are no noise issues with the technology. In fact, one of the big advantages of the passive standard building envelope is noise reduction.
"We live on the N2," Tully says, "which is a very, very busy road. You get lorries going up and down the road from five in the morning. Now, with the triple-glazed windows, you can't hear them. It's only a gentle sound in the background."
He goes on to say that in delivering the project, there were two major difficulties. "Planning and money. They were the hardest. The actual construction of the building went very, very smoothly."
They have now been in the house coming on two years. "It's been brilliant," says Tully, "warm, spacious, comfortable... and we hardly ever need to put on the heating."