‘Under the Sun’, Birmingham
the front of the house on its opening day, late 2009
Bringing existing houses up to a high standard of energy efficiency is a much greater challenge than with new ones. This particular example of eco renovation is outstanding because of the way it will achieve a net zero carbon rating while at the same time reaching CSH level 6. Not only that, it has been enlarged from the original two up, two down layout to provide extra rooms including an attractive new second floor studio with a roof which supports a large solar array of both PV and thermal panels. The house will benefit from a a number of green features -
- Extremely high insulation levels to all the external surfaces - approximately 200mm of insulation - mainly a special high grade of expanded polystyrene (Neopor) and also Warmcell and mineral fibre. Triple glazing to the windows.
- A very high level of air tightness using pro clima Solitex membrane.
- Over 5 kW (peak) of PV generation which should soon be attracting a good feed-in tariff.
- A 48 tube array of evacuated solar thermal collectors feeding into an 850 litre Solus CL water accumulator tank.
- A Lenius wood pellet stove also feeding into this accumulator.
- Heat reclamation from the ventilation system, similar to the Passivhaus model.
- Glazing is carefully positioned to get daylight down into the centre of the house and window openings have generous reveals so that the maximum of light, view and solar gain is achieved.
Materials
Materials have been chosen carefully to be low embodied energy and or reused/reclaimed -
- Many of the new walls are of unfired clay blocks to reduce embodied energy
- Recycled newspaper insulation
- reused maple flooring
- sweet chestnut exterior cladding to the top floor
view from the garden at the rear. Notice the very deep window reveals
The design work has been carried out by the owner, John Christophers of Associated Architects. The building was originally a fairly normal early Victorian house with brick walls and slate roof. It has now been imaginatively extended to the rear and upwards to the attic room which has good sound insulation from the rest of the house and fine views over the city. There is a new, gently curved stair well and interesting shuttered openings which interconnect rooms. Occasionally glass flooring has been used to further help natural light penetrate into the house.
300mm insulation between unfired clay blockwork and external bricks
Avoiding cold bridging
What is really interesting is the degree of care taken to remove cold bridging and to create air tightness. As some of the insulation has had to go on the insides of walls and some on the exterior it has meant isolating sections of structure from each other by cutting out slices and then inserting the insulation. TeploTies have been used as wall ties because of there low thermal conductivity. Windows generally have plywood liners. The breathing air tight membrane (Solitex) has likewise had to weave around parts of the structure in many places. This is especially true where the new extensions meet the old building.
A novel way of preventing cold bridging by existing brick cross walls which go down into the ground has been developed. The walls are largely cut away at ground floor level and supported on reinforced concrete beams so that insulation can be inserted and the degree of bridging is greatly reduced. (see below)
bricks removed and replaced by insulation
There are plans to create a double storey hight sun space to the rear of the house which should extend the pleasure of garden enjoyment further into the spring and autumn and create an extra skin of insulation in the winter. More information at Under the Sun
