A semi-detached Edwardian house with loft rooms and basement in Eltham, South London is undergoing extension and refurbishment to EnerPHit standard.

The house had been extended at the rear, and the loft converted to a poor standard. Air leakage testing demonstrated that the loft was the main cause of air leakage and thermal bridging. The extensions were badly laid out and suffered from poor detailing and thermal bridging. The air leakage test result was 13ACH.

It was decided to demolish and rebuild the extensions as a unified open plan family space, and dismantle the dormer window and loft rooms completely, to enable a fresh start at second floor level.

The original loft conversion had failures with the continuity of insulation between the first floor ceilings, ashler walls, skeilings and loft ceilings, and left gaping holes for draughts, tarpaulins had been used instead of vapour control layers. By dismantling the roof under the cover of a temporary scaffold roof we could detail the loft rooms correctly and reform the insulation build-ups using natural breathable materials. The whole roof structure is now a warm roof.

The new extension uses simple solid construction. External wall insulation is used throughout the new and existing walls apart from the front elevation where the original soft red bricks and details are retained, this elevation is insulated internally with breathable materials and lime plaster.

Existing floors are insulated between and below the joists. Two variations of triple glazed windows are used along with a PH certified entrance door. MVHR is installed covering the whole house, heating is provided by a heat pump.

Air tightness was detailed very carefully, the preliminary air test result of 1.59ACH gave us confidence to continue with the works.

The property will be open to the public for the Passivhaus Trust Open Days on Sunday, 9 November 13.00 – 14.30. To book your place click here