SUSTAINABLE BUILDING
PASSIVHAUS DESIGN
Green Building Store’s Chayley Collis looks Airtightness: Air
at the growing popularity of the Passivhaus
leakage through
unsealed joints must be less
approach to low carbon building
than 0.6 air changes per
hour @50 Pa (for
assivhaus is a performance- ventilation and heat recovery systems, houses,
P
based set of design criteria for Passivhaus design can create healthy and generally
very low energy buildings, which comfortable buildings that require minimal equivalent to
can help create buildings which heating. an air permeability
use around 90% less energy A building designed to the Passivhaus of less than
than standard UK buildings. Developed in standard typically does not need a 1m
3
/m
2
/h
Germany at the beginning of the 1990s traditional heating system or air @50 Pa).
by Professor Wolfgang Feist with Professor conditioning to be comfortable to live in, Ventilation: over 80%
Bo Adamson from Lund University, thanks to the use of a mechanical heat recovery from
Sweden, Passivhaus design is based on ventilation and heat recovery system. ventilation exhaust air, using
well researched and proven building Except for very cold days, often the only an air-to-air heat exchanger
physics. heating required for Passivhaus buildings Total energy demand for space
Passivhaus design aims to minimise derives from incidental gains from heating and cooling = less than
the need for space heating and cooling occupants’ (and pets’!) body heat and 15 kWh/m
2
/yr treated floor area
and is based on the principle that cooking/ showering activities. Total primary energy use for all
reducing heating loss to a minimum is the appliances, domestic hot water and
most robust – and cost-effective – way of KEY FEATURES OF PASSIVHAUS space heating and cooling = less
achieving a low carbon building. Instead BUILDINGS: than 120 kWh/m
2
/yr
of complicated design and expensive bolt- Super insulation: Exterior
on renewables, Passivhaus design focuses insulation of a Passivhaus building PROVEN EFFECTIVENESS
on: maximising the use of super to achieve a U value of less than Over 10,000 houses, schools, offices
insulation; stringent airtightness; and 0.15 W/m
2
K and factories have been constructed to
paying meticulous attention to the removal Windows: Energy efficient glazing the Passivhaus standard in Europe,
of thermal bridges. By combining this with and frames should have U-values USA and many other parts of the world,
passive solar gain and mechanical not exceeding 0.80 W/m
2
K with the first houses completed as long
Case study: Denby Dale Passivhaus
The Denby Dale Passivhaus project in TECHNICAL DATA levels of airtightness (0.6 ac/h@50pa).
West Yorkshire will be one of the first Roof U value = 0.099 The Denby Dale Passivhaus’ design and
certified Passivhaus homes in the UK and Wall U value = 0.102 construction pays particular attention to
is expected to be the first to be built in the Floor U value = 0.125 junctions, which are always difficult for
British vernacular style, using a cavity wall Window U value = 0.8 airtightness because of the differential
construction. The house will require Airtightness ac/h@50pa = 0.6 movement between different materials.
minimal heating and will use 90% less Space heating kWh/m
2
/yr = 14.0 The airtightness barrier between the roof
energy for space heating than the UK and wall junction will use traditional two
average (15 kWh/m
2
/annum, as opposed MINIMISING THERMAL BRIDGING coat wet plaster, combined with a variety
to 150 kWh/m
2
/annum). Built to a tight Understanding and modelling thermal of other innovative airtightness measures,
budget of £140K, the 118m
2
three-bed bridging is becoming absolutely critical to including use of airtightness membranes
detached house aims to be an exemplar accurately predicting the heat loss of a and tapes.
of how Passivhaus construction can be building. The Denby Dale Passivhaus uses
achieved inexpensively by a small, skilled a combination of details to minimise CODE FOR SUSTAINABLE HOMES
construction team. The project is being led thermal bridging. Measures include use of Research just published on the current
and managed by Green Building 300mm insulation in the cavity going right Denby Dale Passivhaus project in West
Company (Green Building Store’s down to the strip foundation, so that any Yorkshire has illustrated some serious
construction division). heat lost from the concrete floor slab will flaws in the energy calculations used for
Project Leader Bill Butcher is writing a have a longer thermal transfer path. Code for Sustainable Homes (CSH). The
regular blog (the Passivhaus diaries) as the Lightweight aerated block is also used academic report, undertaken by Jim
build progresses over the next few months, below ground level, which does not Parker, CSH Assessor and consultant at 1st
highlighting along the way the special transfer heat as readily as standard Base Projects, includes an energy CSH
challenges – and pitfalls – of Passivhaus concrete block. assessment of the Denby Dale Passivhaus
construction in a UK context house and has concluded that “a
(www.greenbuildingstore.co.uk). MAXIMISING AIRTIGHTNESS Passivhaus dwelling’s energy savings are
Passivhaus buildings require very high not realistically represented by its Code for
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SUSTAINABLE FM | NOVEMBER/DECEMBER 2009
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