Is this the end of south-facing glazing?

Guest post by fellow blogger Mark Brinkley

Open any book on house design written in the past 30 years, and it will almost certainly make the point that a well designed house will face south. Orientation, they call it. It means that there will be large areas of glazing on the south side, where the sun is to be found, and that the dayrooms — kitchen and lounge — will be situated on the south side to take advantage of this. Not only does this instinctively feel right, especially in the wintertime, but you also get a significant flow of solar heat coming into the house on sunny winter’s days.

But the move towards zero-carbon homes may be about to rip up this long established nostrum. The next generation of homes are going to be so well-insulated and are going to require so little heating that direct sunlight risks upsetting the balance. The wintertime passive solar heat is simply not needed to fulfil the space heating demand, and instead the summer sunshine risks overheating the house.

The prime example of this new trend is the Kingspan Lighthouse, a prototype zero carbon house built for demonstration purposes at the BRE’s Offsite 07 exhibition in June last year. It was the first house to reach the coveted top level 6 of the Code for Sustainable Homes, which if all goes to plan, will become the benchmark for all new homes by 2016. As you might expect, it’s as much a test bed as it is a house and it is full of cutting-edge green technologies. It has a roof full of solar panels (both thermal and photovoltaic), a biomass boiler, grey water and rainwater recycling, two ventilation systems (one mechanical and one passive) and a mirrored light tower.

But perhaps the most intriguing feature of all is the tiny slit window over the kitchen sink. It’s there to provide daylight, and a view, for the person working at the sink — something required by another section in the Code — and it’s the only opening on the south elevation of the house. I asked the project architect, Martin Rose of Sheppard Robson about it: “We’ve designed it this way because we reckon that summer cooling is more of an issue than winter warmth. In fact, we’ve gone beyond the demands made by the Code for Sustainable Homes, which don’t include any requirements for summer comfort. We have taken the long term view that this is a problem which will increase in significance as the climate changes.”

As you might expect in a house like this, the glazing itself is incredibly energy efficient. The windows, by the Norwegian firm Nordan, are triple-glazed and the frames are themselves insulated: the stated U value is just 0.7 (as compared with 1.8 currently permitted under our building regulations). At this level of insulation, the windows actually work to stop heat getting in through them and you would anticipate that they would help stop the house overheating in summer. Even so, the architects still reckon that the main glazing areas are best located to the east and the west.

Expect to see more Lighthouses in the near future. Kingspan, the acquisitive Irish insulation manufacturer behind the project, have recently purchased Potton Homes, our leading selfbuild package home supplier, and Potton are currently working with the architects, Sheppard Robson, to produce a catalogue of different house types aimed at the selfbuilder. Potton have already received many expressions of interest from selfbuilders and they anticipate that over the coming years their entire product range will move across to the ultra-modern Lighthouse range.

However, whether Potton’s customers will be entirely happy with an almost total absence of south-facing glazing remains to be seen. I suspect that they may have to build a few show houses first and get people to view them first hand, or even stay in them to become convinced that this is indeed the way forward.

Mark Brinkley writes at House 2.0

Comments

[Nick Devlin]

Summer overheating risk is a major issue in lightweight houses, such as the lighthouse. There's no mass and so all summertime cooling has to be achieved through ventilation rates. These houses therefore are unlikley to ever be cooler than external temperatures during the summer without mechanical cooling of some kind.

Minimising solar gain from the south during the summer is not that difficult, whereas protecting from mid to late afternoon sun from the west is both more critical and problematic as the sun is lower and air temperatures peaking.

Interestingly, this means that the masterplanning for such low mass houses is almost as restrictive as passive solar design with its south facing mantra.

I am not bad-mouthing this approach in any way, just a little concerned as to what happens when a developer squeezes 'one-more' dwelling onto that last bit of the plot which is south facing?

[Andy Brunt]

Interesting. The debate on thermal massing isnt over though and there is still a lot of merit in traditional forms of build, done properly. One valid approach is to have south facing ' solar conservatory' type structures which can be isolated from the main living space when necessary and used as a buffer zone, allowing the heating/cooling effect to be used in a positive way whilst maintaining the benefits of large south-facing glazed aspect. There is room for both MMC and traditional build techniques in my view, given the wide range of site conditions, user preferences and functional priorities