Hilltop passivhaus progress


As the house became increasingly weathertight, with good progress being made on the roof, the attention turned to the inside, with the underfloor heating pipes laid ready to accept the floor screed.

Its a common misconception that Passivhaus certified buildings don't need heating- and while it is dramatically reduced compared to even a 'well insulated' Building Regulations house, a small heating load is required to cover the very small head losses- in this case, it is in the region of 2kW- for the whole house- the equivalent of a very small electric heater, or a standard kettle!

In this image you can also see the metal-web floor joists used in the first floor construction, while very efficient, and utilising less material, they also allow for pipes, wires, ducts and drainage to be run with great ease! This is particularly important in a Passivhaus project, as the design includes a mechanical ventilation system (known as a MVHR) which distributes and extracts air to and from a central location. This means that excess heat can be recovered from the extracted air (recovered from hot and humid kitchens and bathrooms) before the air is sent outside.  This ductwork is generally 4-5 inches in diameter (100-125mm) so the open joists give much more design flexibility in laying out the system.

The rapid speed of erection of the timber frame allowed the internal fitout to progress quicker than a masonry construciton- once the 'first fix' plumbing and wiring was in place the house was plasterboarded out- below you can see the double height entrance arrival space taking shape! Top lit with quintuple (5 panes!) glazed Velux windows for extra-good thermal performance!

The bedrooms too have feature oak trusses (fashionably protected with the yellow tape!) which accentuate the 'up-in-the-eaves' character of the upper floor.

High quality natural materials- in this instance natural slate have been taken through the interior- to unite the house with it's rural setting. Large format slates (900mm) were chosen to further increase the sense of space and openness.

A truly defining characteristic of Hilltop is the external stone cladding- Natural Purbeck Stone quarried 15 miles away near Swanage. Designed to give the appearance of a dry stone wall- all the mortar is carefully recessed providing a rich texture and depth to the elevations.

The previously defined projecting 'fins' on the gable ends becoming even more prominent due to the thickness of stone returns.

Here you can see the further insulation added to the outside of the timber frame - an additional 140mm of woodfibre insulation, manufactured by Pavatex.
This ensures the entire building is wrapped insulation, from top to bottom! This ensures there are no 'thermal bridges' ie. paths for heat to escape though structural elements which have to connect both the inside and outside faces of the timber frame.

Preparations also began for the groundworks and drainage- Adrian, ECA's Architectural Assistant helpfully providing some scale for the size of the storage tank for the drainage from the stables! (the rural site has no mains drainage!)