Sustainability


Compact building form


Draught-free construction with continuous air barrier


Thermal bridge-free construction


Summer shading


Operable windows


Optimum winter


solar gains


Triple-glazed PH-standard fenestration


How Passivhaus technology works


need to put the heating on doesn’t even occur. The shell of the building also needs to be air tight so that the warm internal air doesn’t all escape, although this doesn’t mean you can’t open the windows. Of course, rooms still have to be ventilated, but the Passivhaus solution is to do this in an energy efficient way to ensure clean, healthy air is delivered silently and continuously to all the rooms, whatever the weather.


Climate change


Whatever the weather, winter or summer, care homes must protect their residents, visitors and staff from excessive temperature fluctuations; being too hot can also be a problem. Climate change is expected to result in hotter, drier summers, with more intense, longer heat waves that are likely to have serious health implications for elderly people.


A study by the Joseph Rowntree Foundation entitled ‘Care Provision Fit for a Future Climate’ reports that there is not enough recognition given to the health risks from excessive heat in the care sector.3


However, it identifies a


number of strategies for addressing overheating, such as improving awareness, better heating plant management and the implementation of training for extreme events. Of particular significance to architects are the report’s key recommendations for the design of care facilities to address


climate change impacts such as location, orientation and other physical measures to avoid future overheating problems. This is where Passivhaus technology offers obvious solutions for the care home sector, in addition to significant cost savings on heating during the winter. Passivhaus design is about creating stable and comfortable internal temperatures all year round with the minimum of energy input. Insulation works just as well to keep heat out as it does to keep it in – think of your highly insulated fridge freezer. The problem tends to be that the heat gains that supplement your conventional heating system in winter continue to add unwanted heat in the summer. The extra warmth from the use of appliances and lighting, cooking or hot water storage therefore have to be limited in summer to avoid excessive internal temperature rises.


However, most significantly, beneficial passive solar gains during the winter then present an overheating risk during the summer months. For this reason, the Passivhaus standard places a limit on excessive internal temperatures of 25 ˚C that should only be exceeded for a small percentage of hours during the year, according to its modelling design software.


In order to remain below this temperature cap, designers need to carefully consider shading and ventilation strategies that will combine to keep a building interior cool during a


March 2020 • www.thecarehomeenvironment.com


heatwave. Passivhaus buildings eschew large extents of east and west-facing glazing in favour of windows orientated to the south where the higher mid-day sun angles, which allows devices such as overhangs, brise-soleil, louvres, shutters and awnings to avoid direct warming of the interior.


Windows that open are essential in a Passivhaus, especially where they can be left open securely overnight, perhaps with fixed external decorative guarding, which allows cooler night air to replace warmer internal air escaping via high level clerestory windows or roof lights. Passivhaus with heat recovery ventilation and air tight building fabric offers distinct advantages over conventional accommodation; for example, where external temperatures are high during the day, the interior air at 21˚C can be used to cool down the fresh but warm incoming air. During late summer evenings, when external temperatures drop lower than internal ones, a summer by-pass can be engaged so that the cooler incoming air directly lowers the temperature of the interior air and the building.


Other considerations include better insulation and planning of the hot water distribution network to avoid long hot corridors, perhaps using shorter horizontal runs with more vertical stacks. The use of reflective facing materials can help and for courtyards and large flat roofs, planted green areas will absorb


31 Supply air Extract air


Exhaust air Intake air


Whole house mechanical ventilation with heat recovery


Supply air Extract air


Super insulation via a continuous thermal envelope


Night purge ventilation in summer


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