This is a deep retrofit project we currently have underway. This project is a single room in a 120 year old brick villa. The room was desperately in need of refurbishment. So rather than just tarting the space up the decision was made to pull the room back to it bones and do it right.

The Floorboards were removed, the existing chimney was demolished and rotten floor joists replaced. A high quality breathable building wrap was laid between the floor joists, and the spaces between were insulated with fibreglass batts. The floor was then made airtight by placing a layer of Proclima Intello airtightness membrane over the top of the joists.

Due to the historic exterior of the building the decision was made to insulate the inside of the brick walls. New timber framed walls were constructed on the inside of the existing brick walls. The cavities between the framing were then insulated.

Adding insulation to the inside of masonry walls can be a very dangerous thing to do as condensation is almost guaranteed to form on the inside of the cold masonry wall behind the insulation when the room is heated and the outside temperature is low. This creates a perfect habitat for mould and rot.

In order to avoid this problem we modelled up our solution in a programme called WUFI which can predict how different wall constructions will perform overtime. We developed a solution which included an intelligent airtightness layer behind the plasterboard to prevent warm moist air from reaching the cold masonry surface. We also used absorbent dense packed cellulose insulation which would be able to absorb any condensation if it did form and allow it to dry back into the room. We also added a through-wall balanced ventilation system with heat recovery which is able to provide a constant supply of fresh preheat air to the room and prevent the buildup of moisture within the room. Finally the room was tested using our blower door to ensure that room achieved our airtightness target.