Civil Engineering Reference
In-Depth Information
Windows have insulated frames and triple glazing. Doors are highly insulated. To
sum up, the parts of the envelope are usually identified as walls, roof, ground and
windows and doors with a thermal bridge-free design. Triple glazing also provides
efficient acoustic insulation—an added value in noisy urban environments.
There also needs to be a continuous airtight layer around the volume of the
whole building. A precise design is necessary to support this requirement. One
control procedure performed at the design stage is to be able to draw a line with a
pen on a building plan, and to follow the air tightness layer and come back to the
starting point without leaving the paper. Glazing is a part of this air tightness layer.
Special attention is paid to reducing penetration through the air tightness layer.
Good sealing materials (membranes and tapes) are used in the connections. Crit-
ical connections are where different elements meet—like roof-wall, wall-floor,
building boards, penetration of ventilation ducts, electrical cables or plumbing
through the envelope, windows and door openings. When the air tightness layer is
installed, a pressure test must be executed to check the air tightness value.
When such a high level of air tightness is achieved, ventilation is secured in a
controlled manner. Good indoor climate requires a minimum flow of air to remove
excess moisture and pollutants and to provide fresh air. Expelled air takes heat with
it, creating heat losses. To limit these heat losses through ventilation, a balanced
ventilation system with highly efficient heat recovery is usually recommended. The
general PHPP recommendation for ventilation is 30 m
3
/h per person, a level that
refers to the requirements of the German standard DIN 1946 part 6 (Feist
2007
).
Filtration of incoming air removes particles and pollen, offering an added value. It
is recommended to use low-emitting materials to limit the need for ventilation.
Ventilation is always designed so that there is no noise annoyance from it.
The requirements of the Passivhaus standard apply to any building; however, it
has been recognised that upgrading to that level of energy efficiency is not always
feasible. Recently, ''EnerPHit—Quality-Approved Modernisation with Passive
House Components'' was introduced by the PHI to allow a certification for the
retrofit to the Passivhaus standard where the heat demand has to be lower than
25 kWh/(m
2
.y). Otherwise, according to EnerPHit, the same characteristics have
to be addressed, with a focus on the same design principles based on the use of
Passivhaus elements. The designer is confronted with particular challenges,
including limiting existing thermal bridges, securing air tightness and imple-
menting balanced ventilation. For example, existing buildings usually have large
thermal bridges that can be inaccessible (such as the building's foundations).
Ventilation systems may require new space for the ductwork and technical room.
In addition, existing structural elements might need to be perforated. Attention is
also drawn towards other energy uses in a building, such as domestic hot water
(DHW) and electricity for light and amenities. Therefore, daylight use is optimised
for both comfort and energy, and presence controls and light controls can be
implemented. Heritage buildings, though, present additional constraints.
The Passivhaus Institute offers certification of building elements or compo-
nents. The process of certification for a building is simplified by the use of certified
elements and certified designers (PHi
2011
).
