好色先生TV

Something like this happened to developer Kim Slowe when his recently completed office fell foul of the Duchy of Cornwall's strict design guidelines. Two columns at the front of the building were too small. "I had to knock them down and rebuild them," he says ruefully.

However, the experience hasn't stopped Slowe from developing in Poundbury, which lies on the outskirts of Dorchester in Dorset. Far from it 鈥� his company Cornhill Estates has just completed a terrace of five three-storey homes. Slowe says he appreciates the Duchy's traditional approach to design and its fastidious attention to detail. "There's an element of complexity at Poundbury that makes building there challenging and exciting. If it wasn't complex, Poundbury wouldn't be the place it is," says Slowe.

Although Slowe's homes look as though they were built in the late 18th century, they are made with modern building systems. Slowe wanted to prove that he could build financially viable, energy-efficient homes within the architectural constraints of Poundbury. This meant that he had to find low-cost and innovative building systems that did not compromise the Georgian appearance of the building. And central to Slowe's sustainable goal was the specification of the masonry. As well as providing a high level of thermal insulation the blockwork system had to interface with the other building components cheaply and efficiently.

The three-storey terrace of five homes is being built as part of the second phase of Poundbury. This extension to Dorchester is an attempt by the Prince of Wales to engineer a traditional urban community where the pedestrian takes precedence over the car. 好色先生TVs have to be built in the local Dorset vernacular to a high density and private and social housing has to be built alongside factories and shops to create an integrated urban mix.

Architect Stephen Mattick has based the four-bedroom homes' appearance on the Georgian town houses typically found in London and Bath. He was careful to adhere to the Duchy of Cornwall estate building code, which offers extensive guidance on what building materials should be used for walls, lintels and non-masonry items such as roofs, windows and doors (see "By royal decree: Poundbury design guidance", right). The detailed designs were carried out by architect John Matthews, who ensured that all the homes complied with 好色先生TV Regulations.

For the homes' structural walls, Slowe specified Thermalite's thin joint masonry system. He considered using a timber-frame system, but decided that the greater thermal mass of two skins of aircrete blocks would mean that the homes would be less prone to overheating. (See "Grand designs: The wall specification", overleaf).

Thin joint mortar was selected because it offered a better thermal performance than conventional mortar. "With thin joint there's far more insulated block and less of the mortar, which has poorer insulation properties," says Chris Kirby, general technical manager at Thermalite. The amount of mortar in the wall has been reduced from 7% mortar to less than 1% according to Kirby, which means a U-values of 0.24 W/m²K and 0.20 W/m²K can be achieved for the ground floor walls and other walls respectively.

The use of thin joint mortar did throw up design challenges for contractor KDJ Slade. The reduced depth of mortar meant that Celotex insulation sheets had to be cut before being inserted into the cavity. Each 450 mm sheet was meant to be the same depth as two courses of blockwork, but because of the thin mortar, the actual depth of the aircrete was only 432 mm. This meant that 18 mm of Celotex had to be shaved off each sheet. KDJ site manager Paul Studley says that 432 mm depth Celotex sheets would be specified next time.

The thin amount of mortar also had repercussions for the installation of the wall-hung floor joists. As the hangers are thicker than the thin joint mortar, KDJ had to rasp a groove 2-3 mm deep in the aircrete blocks to allow the hangers to fit flush with the top edge.

One of the biggest specification challenges for Kim Slowe was choosing an appropriate render for the facades. Walls constructed from aircrete blocks are softer and are more likely to move than if they were built with dense blockwork. This means the render may crack because it will move at a slower rate than the aircrete. Slowe shopped around, looking at a number of solutions before opting for a system from Alsecco that offered a 10-year anti-crack guarantee.

The Alsecco Flexewall render system has a similar compressive strength to aircrete, which means it is flexible enough to absorb the thermal movements of the blockwork. A glass-fibre mesh is applied on top of a layer of render, which is sprayed onto the outer leaf of blockwork. A second layer of render is sprayed over the mesh and then rubbed down when it has gone partly off to achieve a dimpled finish.

As well as constructing thermally efficient walls, Slowe was keen to specify high levels of acoustic insulation between homes. To achieve this, he insisted that the blockwork was wet-rendered before it was drylined with plasterboard on dabs. Slowe says that the cost of the extra wet-rendering was negligible: only 拢700 for all five homes. This separating wall construction method features in the House Builders Federation Robust Standard Detail programme 鈥� a set of design details to comply with the latest edition of Part E, the acoustic regulations. If the government accepts the principle of these RSDs, housebuilders will be able to use them from 1 January 2004.

Slowe also insisted on filling the homes with as many sustainable features as possible. They include greywater recycling, heat recovery and solar water heating systems. The energy-saving devices, in conjunction with the thermally-efficient aircrete walls, meant that Slowe only needed to specify a cheap, simple boiler that requires minimal maintenance.

One area where the developer was able to specify a sustainable product without affecting the homes' appearance was in the loft. Rather than selecting mineral wool for the loft insulation, Slowe specified sheep's wool from Ochre. The UK distributor Joulesave says that although natural wool is more expensive than mineral wool, it is easier to fit and has a lifespan twice as long as synthetic alternatives (see "Raising the baa: The sheep's wool insulation", page 6).

The selection of sheep's wool is typical of Kim Slowe's unconventional approach to housebuilding. As a latecomer to the industry 鈥� he was a Captain of a Navy Frigate until five years ago 鈥� Slowe operates with an outsider's perspective. His direct involvement in the specification process shows how keen he was to prove that sustainable and innovative systems can be used in masonry-built homes. Mainstream housebuilders, he says, are too conservative to try something similar.

His approach makes commercial sense too. He knows many housebuyers are put off by wacky-looking homes that wear their sustainable hearts on their sleeves. As he proudly remarks, his energy-efficient homes "don't look as though they've come from outer space". A sentiment that will no doubt please the firmly grounded Prince of Wales, Duke of Cornwall and King Charles III-to-be.