Passivhaus Retrofit and EnerPHit Standards
Passivhaus standards, where buildings are constructed with high levels of insulation and low levels of heat loss, are not just used for new build projects; these standards can also be applied when refurbishing buildings or retro fitting buildings to create similar levels of energy savings using the EnerPHit standard.
However achieving the Passivhaus standards in older buildings is not always a realistic goal. Instead the EnerPHit Standard for refurbishments can be used. This modified version allows for slightly more generous standards which are more realistic to achieve in refurbishments.
- Specific heat demand of ≤ 25 kW.h/m2/yr;
- Primary energy demand of ≤ 120 kW.h/m2/yr;
- Roof, wall and floor U–values of ≤ 0.15 W/m2.K;
- Windows and doors (including frame and glazing) U–values of ≤ 0.8 W/m2.K;
- Thermal bridging psi values to be less than 0.01 W/m2.K;
- Whole house mechanical ventilation with heat recovery (MVHR) that is ≥ 75% efficient and exhibits a specific fan power of ≤ 0.45 W.h/m3; and air–leakage of ≤ 1.0 ach at 50 Pa.
The EnerPHit standard places great emphasis on airtightness and thermal bridging, to improve the efficiency of the building fabric. Mechanical Ventilation with Heat Recovery (MVHR) is also used to ensure a steady supply of fresh air within buildings renovated to this standard, because of the low level of air–leakage that is required.
Retrofitting a building to Passivhaus standards can be affected by the location of the property and its surroundings. For example on Lena Gardens, shown in the picture above, a Passivhaus refit which was in a conservation area of London, the limitations due to being in that conservation area and the fact it was a terraced property meant that all of the insulation had to be placed on the interior of the building. Relatively thin layers of insulation were used to achieve the very high levels of thermal performance needed without impinging on the floorspace excessively.
Full details about how this property was retrofitted to the Passivhaus standard can be found on our website.
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