REFURBISHMENT CASE STUDY SOCIAL HOUSING
The success of the retrofit will rely heavily on the occupants’ comfort and satisfaction levels, combined with how well they engage with the new technologies and conserve energy at home
insulation, whilst being highly transparent to light and solar radiation. It is available commercially as translucent granules encapsulated within glass or multi-wall polycarbonate sheets, or as particles embedded within opaque insulation boards and blankets. The material can be applied to a building in a variety of ways. Linked to the property’s MVHR, extracted air from the kitchen and bathrooms is fed into the solar collector cavity, where it is heated by incoming solar radiation. This heat is then used to provide additional energy indirectly to heat the incoming fresh air supply to the property’s living room and bedrooms. Automatic flow and bypass controls maintain comfortable living conditions all year round. Some promising monitored results have
already been observed for this system, indicating that it will play an important role in heating the property during cold-sunny conditions. During a seven-day controlled test in October 2011, the solar collector outlet reached 45C on a cold sunny day, pre- heating the supply air in the mechanical ventilation system to 30C, enabling the house to maintain comfortable living conditions at 21-22C, without additional heating. A custom-built ‘aerogel door’ developed
Specification: Thamesmead refurbishment
Walls: 300 mm of Permarock EPS insulation to achieve U-value of 0.1 W/sq m.K. Yellow render with aluminium fins
Roof: New roof with airtight membrane, services core and PIR 300mm insulation for U-value of 0.1 W/sq m.K
Windows: Passivhaus-certified Nordan N-tech triple glazing with U-value of 0.8 W/sq m.K and solar G-value of 0.5
Doors: Passivhaus-certified front door. Plant door custom built by Proctor Group with U-value of 0.65 W/sq m.K
Ground floor: U-value of 0.15 W/sq m.K throughout. Spacetherm aerogel insulation used in zone with 80mm space available
Air tightness: Pro Clima airtight tapes, sealants and sleeves used throughout. Target: 0.6 cu m/sq m/hr @50 Pa. Best on-site : 3.5 cu m/ sq m/hr @50 Pa
Ventilation: Nuaire MRXBOX95B-WH1 unit with summer bypass. Extract air for heat recovery boosted by aerogel solar collector
Heating: Warm air supplied by MVHR. System boiler with small-zoned radiators for peak winter conditions
Hot water: 500 litre cylinder fed by electric immersion and boiler. A 3 sq m vacuum tube collector meets 42% of load
Electricity generation: Ten PV panels generate 2.30 kW peak. Array is ballasted using aluminium frame to avoid piercing insulation.
Lights and appliances: Low energy fittings and light bulbs with A-rated appliances specified throughout property
Predicted CO2 emissions Baseline: 111 kg CO2/sq m/year Post retrofit: 14 kg CO2/sq m/year Predicted saving: 87%
40 CIBSE Journal June 2012
by Proctor Group was also integrated into this retrofit. The double leaf plant room door incorporates a 30 mm-thick opaque aerogel blanket, capable of achieving a central U-value as low as 0.39 W/sq m.K, or 0.65 W/sq m.K including the frames. In a separate application, 80 mm of aerogel was also applied to the ground-floor slab in a zone where the floor-to-ceiling height was limited.
Evaluation Onsite work at the property finished in March this year, and a large family is expected to move in over the next one to two months. Since last August, and for another 18 months, a package of wireless monitoring equipment is being used to capture important information such as the internal temperature and CO2 levels within the house, power consumption of the MVHR, energy generation of the PV panels and solar water heater, as well as the total consumption of gas, electricity and water. A roof-mounted solar radiation sensor, combined with temperature and humidity sensors inside the aerogel solar collector cavity and MVHR ductwork, provide a unique insight into this system’s performance. Ultimately, the success of the retrofit will
rely heavily on the occupants’ comfort and satisfaction levels, combined with how well they engage with new technologies and conserve energy at home. Interviews will be held to facilitate this process. Nevertheless, through this deep retrofit, the expected value of the property will have increased greatly, particularly due the extended living space, new kitchen-diner and additional two bedrooms. There is scope to retrofit millions
of buildings to make deep cuts in CO2 emissions. However, effective implementation is no small task. Solutions must account for the variety in age, size, quality, composition, function, asset value and social value across the existing building stock, as well as the different needs, expectations and budgets of homes owners and occupiers. Understanding which solutions are cost effective and deliver real savings in-use is imperative. CJ
l MARK DOWSON is a research engineer within Buro Happold’s sustainability and physics team, London.
mark.dowson@
burohappold.com A full scientific paper on the aerogel solar collector’s performance can be found at
http://dx.doi.org/10.1016/j.enbuild.2012.02.007
www.cibsejournal.com
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