Old Timberyard gets new lease of life
Passivhaus designer & Architect Richard Dudzicki of RDA Architects has practised what he preaches by creating an EnerPHit-certified home for himself and his family in London.
Originally a Vistorian workshop, converted into offices formerly used by RDA Architects, the building is located in a tight urban spot surrounded by other buildings, which meant that demolition was not an option. The 4/5 bedroom family home stakes a claim as the UK's first Passivhaus conversion of a commercial building to a family house. The building has been stripped back and retrofitted to meet EnerPHit; the Passivhaus retrofit standard and supplemented with an additional basement, front extension and new barrel-vaulted roof.
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We had outgrown our existing two bedroom house. My teenage kids were keen to save energy and had heard a lot from me about Passivhaus and encouraged me to practise what I preach
Richard Dudzicki, Director RDA Architects
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Design
The many challenges of improving the efficiency and airtightness of an existing building were tackled by creating a 'building within the building'. The existing building was lined with a steel frame, an additional floor was added on the roof and the partially existing basement was dug out to create some more room at the lower levels, primarily for ventilation and heating services.
Window installation
To improve airtightness and minimize thermal bridging around the window frames the existing windows were removed and the window frames were moved to the inside of the building and located within the 120mm internal insulation space . A specialist window installation system (Iso-Top Winframer 'Type 1'), designed to minimize thermal bridging, was used with airtightness paint applied around the edge, linking the lime parge coat to the ISO top system. Airtightness tape was also used around the windows.
Barrel roof
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A barrel roof incorporating the extra floor was added to the existing building. the beams were made out of structural grade plywood which was laminated and glued. The roof structure was then covered with ribs, similar to an aircraft wing, staggered and filled with wood fibre insulation, lined with plywood skins to create a diaphragm.
Internally the barrel vault was lined with the plywood was painted and sprayed airtightness paint and airtightness tapes were around the roof structure, the window frames, and the junctions. Upstands were made for the skylight windows which were insulated to minimize thermal bridging.
Airtightness
The preliminary test was undertaken before the windows were installed (lining the window openings with a DPM membrane) to see whether the wbuilding was close to the target of below 1 n50 p/h air change. The first air test at this stage came at around 2 n50 p/h, The second test was after window installation and came in at 0.98 n50 p/h, demonstrating that the window installation had been undertaken very carefully.
Challenges
Daylighting & preventing overheating
The orientation of the building meant that the main aspect of the building faces towards the south west, with the rear/north eastern side not accessing as much daylight. This meant incorporating shutters in the south west elevations to prevent solar gain and overheating. The existing industrial window openings were maintained. The team had to look at ways of bringing the light all the way through the building using skylights. The lighting strategy had to be carefully modelled and tested in PHPP (Passivhaus Planning Package).
Minimising thermal bridging around the steel frame
It was important that the steel frame was separated from the existing walls or floor slab to prevent any cold bridging. The space behind the steel frame and existing brickwork was approximately 20mm wide.
- To separate any thermal bridging between the internal steel frame and the existing external brick walls Farrat plates (structural thermal breaks) were used.
- The steel frame structure had to be braced with bolts going into resin anchors in the wall and the Farrat plates were placed around the bolts and structure, separating the steelwork from the walls.
- Fiberglass coverings were also created in some areas within the basement, by pouring resin over the top of the pads and over the Farrat plates to help isolate them and prevent the steelwork from being subjected to damp.
- Aerogel was used behind the steel frame to ensure that the steel frame was isolated from the existing brickwork.
Structural issues
The existing building brickwork was in poor condition in places. The original London stock brick walls were repaired and stitched were necessary. Some of the walls were leaning into the building more than the structural engineer liked and so certain sections of the first floor top walls were re-built.
Internal wall insulation
It was important to be aware of interstitial condensation risk when undertaking internal wall insulation (IWI) measures. The IWI strategy at the Old Timberyard used materials designed to manage moisture risk and comprised:
- Parge coat: e-cork lime render
- 120mm of wood fibre insulation
- E-cork lime render
- Graphenstone paint.
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Floor Insulated concrete U value: 0.2 W/m2K
Wall Wood fibrre insulation U-value: 0.15 W/m2K
Roof Plywood barrel roof U-value: 0.120 W/m2K |
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Predicted energy performance
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24 kWh/m2.yr |
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11 W/m2 |
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107 kWh/m2.yr |
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0.8 ach @ 50Pa |
Key team
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Discover more Passivhaus self-build schemes here. Did you know that you can visit one in-person to get a first-hand experience during the Passivhaus Open Days. The next event takes place in June 2023.
Further information
Passivhaus Open Days 2022: Winter Edition
14th November 2022
Get involved with the UK Passivhaus community
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