Download Vacuum-insulated prefabricated elements in construction

Vacuum-insulated prefabricated
elements in construction
Fig. 1
䊳 Complete insulation of a building with VIP
elements is possible
䊳 The passive house standard is achievable
with 4 cm thick VIP
䊳 After the first year of operation all VIP
elements are intact
䊳 No condensation problems identified
How sensitive vacuum insulation panels (VIP) stand up to general
construction and building operations is tested in demonstration buildings.
E
nergy-optimised buildings usually require a thick thermal insulation. With passive houses insulation thicknesses of 30 cm and
more are not uncommon. If the external dimensions of a building are predetermined, e.g. by existing neighbouring houses or
building lines, high energy-oriented quality is achieved at the cost of
the internal surface area. Conversely, until now it has been difficult
to achieve high-grade thermal protection if only limited space is available or thick insulation layers are unwanted. This can affect the
retroactive insulation of an individual terraced house facade, but also
“classic” thermal bridges such as shutter boxes, window reveals and
balconies.
In such cases insulation with vacuum insulation panels (VIP) can be
a solution. The panels can achieve a much greater insulation effect
with the same thickness as conventional materials. Thus slim
structures are possible, even for well insulated buildings or building
sections. VIPs are made up of a porous, pressure-resilient core, sealed
in a diffusion tight high-barrier plastic film in a vacuum chamber. The
technology used for the manufacture of cooling and refrigerating
units has now been developed – also in the framework of research
projects – for application in construction. To avoid relativising the
good insulating effect in the centre of the panel, the thermal bridges
at the edge of the panels and other connection points first had to be
minimised. Furthermore, it was necessary to develop vapour diffusion
tight joints for the elements as well as VIP connections for floor,
facade and roof. Also necessary were practicable solutions as to how
the highly sensitive insulation material should arrive at the place of
installation in undamaged condition and how it should provide faultfree service over many years.
Following the first field tests with VIP insulation on individual building elements, demonstration buildings should now provide more
detailed information for planning and building with VIP. The Federal
Ministry of Economics and Technology (BMWi) is therefore sponsoring the planning, optimisation and monitoring of a passive house
completely insulated with VIP prefabricated elements. The building
was constructed in 2005 and since then continuous measurements
have been taken. The following presents the experiences with the VIP
elements, mainly independent of the elaborate building services
equipment.
䊳
VIP elements
Fig. 3 Glass fibre anchor for connecting
prefabricated elements
Fig. 2 Selected building elements of the demonstration building
Element / U-value
Structure (from outside to inside)
Foundation slab
U=0.06 W/m2K
100 mm foundation course
10 mm sealing
50 mm VIP insulation elements
250 mm reinforced concrete slab
Floor structure
Wall type 330
(ground floor walls)
U=0.11 W/m2K
60 mm precast concrete outer shell
49 mm (possible) in-situ concrete layer
51 mm VIP insulation element
70 mm precast concrete inner shell
Wall type 270
U=0.12 W/m2K
(upper floor walls)
55 mm wood facade
70 mm face concrete shell
50 mm VIP insulation element
150 mm concrete inner shell
15 mm plaster surface
Wall type 150/1
U=0.12 W/m2K
(upper floor walls)
33 mm Kerto wooden panel
51 mm VIP insulation element
94 mm cross layer wood
15 mm plasterboard
Flat roof
U=0.12 W/m2K
8 mm protective matting
2 mm roof sealing
50 mm wood material panel
51 mm VIP insulation element
incl. vapour barrier
96 mm wood element
30 mm surface heating system
15 mm plasterboard
The vacuum in the panels, which is the basis
of the good thermal insulation, is secured
by high-barrier film. If this is damaged the
insulation effect is considerably reduced.
The aim of this research project was therefore the development of prefabricated
elements with irreversibly built-in core insulation of VIP, designed to protect the panels.
䊳
Foundation
slab
Walltype 330
Walltype 270
Walltype 150/1
Flat roof
The building elements delivered from the
factory, with integrated VIP, already include
all static-constructive apertures, as well as
those required for installation.
A complete assembly kit of wood and concrete VIP prefabricated elements suitable
for use in passive houses with corresponding
connection details was developed in advance.
The demonstration building
Fig. 4 Building summary
Location
Neumarkt in der Oberpfalz
Construction period
07/2004 – 12/2004
Net floor area
294 m2
Area with energy
requirement
280 m2
Mean U-value
0,15 W/m2 K
Heating requirement 15 kWh/m2 p.a.
VIP integration
exterior wall in wood construction
exterior wall in concrete con
struction
■ ground contact, pressurized
exterior wall in concrete
construction
■ foundation slab
■ flat roof in wood construction
■ gable roof in wood construction
■
■
The three floor single-family house should
be exclusively insulated with VIP and have
as many different installation situations for
the insulation panels as possible. Therefore
the outer building elements are partly installed as solid construction (cellar walls,
parts of the exterior walls, ceilings) and
partly as lightweight wood construction
(other exterior walls, roof). They are prefabricated and delivered to the building site
with built-in VIP. The roof also has two
installation variants: On the west side it is
flat and has a gable roof on the east side. A
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BINE projektinfo 09/07
sloping building site was intentionally
selected to subject the VIP elements in the
cellar area to high demands in terms of static,
joint tightness and moisture protection. For
this reason a combination of VIP with double concrete walls of water-impermeable
quality has been developed.
The elaborate technical fittings combine
two rain water cisterns embedded in the
slope, a water/water-heat pump, evacuated
tube collectors, a stratified buffer storage
tank as well as an electric backup heat exchanger. Surface heating systems are mounted
The layers of the concrete elements are
joined at certain points, under tension and
pressure, by a glass fibre anchor so the VIPs
contact each other jointlessly on all sides
and heat loss through the wall is minimised.
The wood elements are screwed through
specified and appropriately prepared penetration points. The static building elements
with VIP core insulation in passive house
standard reach, at total thicknesses of 150
mm, U-values between 0.06 W/m2K and
0.12 W/m2K. The static properties of wall
or roof elements are tested by means of
detailed component tests. The VIP prefabricated elements can support very high slope
loads or imposed building loads. Long-term
tests for VIP beneath the foundation slab, at
a pressure load of 300 kN/m2 over 50
years, show projected deformations from
3.5 to 5 mm.
Planning and building with
VIP prefabricated elements
VIP insulation should be planned in close cooperation with the manufacturer. Either the planning grid is aligned to the panel sizes or the
elements are made to measure. However it is
expedient to plan with large format VIP in order
to optimise the insulation properties with uninterrupted surfaces that are as great as possible in
ratio to the edge seal – the “weak point” of VIP.
This also shortens installation times and thus
lowers labour costs.
The prefabricated building elements are joined,
as usual, with compriband or butyl sealant on
the construction site. The demonstration building proves that damage-free insulation is possible. For this reason, the installation of VIP
elements does not necessarily have to be reversible. The further processing of VIP prefabricated elements requires consultation and, if necessary, training and instruction of the relevant
personnel. The installation can then be carried
out be any specialist company.
to the ceiling for heat distribution; these are
also used for cooling in summer in combination with a heat exchanger in the cisterns.
An important feature of the passive house
was a ventilation system with heat recovery,
used exclusively for air intake and extraction.
A photovoltaic system should deliver as
much power as the technical installations
consume.
䊳
Optimisation of details
At the beginning of the project the energyoriented influences of different construction
variants and connection details were tested
with the help of the passive house planning
package (PHPP) and thermal bridge simulation programmes. These were, for example,
the influence of the thickness of the VIP
material, the arrangement and the spacing
of the vacuum insulation elements in the
concrete or wooden elements and the thermal
bridges.
The calculations showed: Changing the
dimensions of the vacuum insulation panels
from 30 mm to 40 mm reduces the heat energy requirement by approx. 4 kWh/m2 p.a.
The heat energy requirement increases by
approx. 1.8 kWh/m2 p.a. for 30 mm thick
VIP panels and approx. 1.4 kWh/m2 p.a.
Fig. 5:
Corner solution with uninterrupted
VIP insulation level
Fig. 6 Foundation slab / wall connection
for 40 mm per centimetre distance between
the individual insulation panels. The use of
glazing with a high g-value (0.6 instead of
0.48) reduces the heat energy requirement
by 3.5 kWh/m2 p.a. A better heat recovery
level of the ventilation system (0.85 instead
of 0.8) lowers the heat energy requirement
by 0.8 kWh/m2 p.a. By adjusting the different parameters, the final planning achieved
the limit value of 15 kWh/m2 p.a. for the heat
energy requirement of a passive house.
In order to keep thermal bridges to a minimum, and thereby their influence on the
heat energy requirement of passive houses,
several details were optimised in the house
design in the course of the planning process.
Particular attention was paid to the joints of
the prefabricated elements, which with a
total length of approx. 700 m could have a
major influence on the thermal insulation
behaviour of the building. The VIP aluminium vapour barrier causes a significant reduction in the formation of thermal
bridges, particularly at joints with thermal
bridges. Die aluminium facing should therefore be interrupted at the joints (fig. 5).
Initially, the connection between the wall
and the foundation slab proved to be critical:
The solid connection of the outer concrete
shell with the foundation slab allows heat
flow from the inside of the wall into the air.
However, appropriate application of perimeter insulation reduces these influences
considerably (fig. 6). The air-exposed building elements were less problematic in
terms of thermal bridges. Overall the influence of thermal bridges on the heat energy requirement amounted to approx. 25%
after optimisation.
Fig. 7
䊳
Measurement results
The building was continually documented
via 150 measuring points. The monitoring
of the building proves that the main aims
have been achieved:
Thermal imaging shows that none of the VIP
elements installed above ground were damaged during the construction process (fig. 7).
Moreover, the weak points in the sealing of
the film could be identified; these have since
been remedied. A blower door test showed
a very good air tightness characteristic value
of n50 = 0.33 h-1 (incl. all window and door
joints). In order to also control the longterm behaviour of the multi-stage airtight
connection concept, a new air tightness test
is planned after 3 to 4 years operation.
The heat energy requirement of 20.4
kWh/m2 p.a., daily temperature adjusted,
(measured: 19.4 kWh/m2 p.a.) is still above
the calculated value of 15 kWh/m2 p.a. It
can be assumed, however, that the vacuum
insulation elements will prove their calculated properties so that the desired insulation
effect is achieved.
In the joints of the VIP (measured on the
joints of the technical room – ground contact
wall) the dew point was never fallen short
of during the measurement period. Thus
there is no danger of condensation at these
connection points. The minimal change in
the value of the material moisture sensor in
a prefabricated element proves that no
moisture penetrates through the vapour
barrier at this point. Evaluation of temperature sensors, fitted in the living room area
on both sides of a VIP element in the vicinity
of the roof, also show that there is no risk
of condensation at any time of the year.
The primary energy requirement of the
building (excluding household current) is
Thermal imaging: the vacuum
insulation panels in the external
wall show uniformly good
insulation properties
65.4 kWh/m2 p.a. The proportion of auxiliary energy for pumps and control amounts
to approx. 21%. This requirement can be
significantly reduced with improved coordination of the operation of the building
services equipment. The control parameters
were appropriately adjusted in spring 2007.
BINE projektinfo 09/07
3
䊳
Outlook
PROJECT ORGANISATION
The vacuum insulation of buildings enables slim structures with good thermal insulation.
The panels have now been developed to a stage where they can be used both for new buildings and for refurbishment: in floors, roofs and walls, as thermal insulation connection systems, in ventilated facades or as core insulation or small surface panels, e.g. for
the insulation of shutter boxes or roof dormers. Building regulations approval for VIP as
a building element, including the complete static loading calculation for roof and wall
elements, has been applied for and is expected to be granted in the near future. The required preliminary and general tests have been completed.
One research project is currently investigating the suitability of vacuum insulation panels
for interior insulation. Both the high insulation effect of VIP and its diffusion tightness
would seem to imply suitability. However, the effects on the humidity content of the main
walls have to be tested.
In order for VIP insulation to be accepted, planners and builders have to be convinced of
both the soundness of the vacuum envelope in the processing of the VIP on the building
site and of its lasting quality. The demonstration building in Neumarkt can increase confidence in the new material. It proves that insulation with vacuum insulation panels is
possible in the most diverse installation situations and is also practicable by means of integration in prefabricated elements. To date, no damage to the elements has been identified. According to measurements, the installed panels and structures fulfil all expectations
as regards diffusion tightness and freedom from condensation. However, due to the
special characteristics of the material, an exact analysis of the connection details is
indispensable.
In addition, a VIP quality association involving many manufacturers is being initiated,
to define, control and document the necessary quality criteria, processing guidelines and
test specifications in cooperation with testing institutes.
In another research project, experiences of competed construction projects with VIP technology (refurbishment and new building) should be evaluated and workable concepts
should be developed for the integration of vacuum insulation panels in building envelopes.
■ Project Funding
Federal Ministry of Economics
and Technology (BMWi)
D-11019 Berlin
Project Management Organisation Jülich
Research Centre Jülich
Markus Kratz
D-52425 Jülich
■ Project Number
0327321D
IMPRINT
■ ISSN
0937 – 8367
■ Publisher
FIZ Karlsruhe
D-76344 Eggenstein-Leopoldshafen
■ Reprint
Reproduction of this text is permitted provided
the source is quoted and a complimentary copy
is provided to the publisher; reproduction of
the images contained in this newsletter requires
the prior approval of the copyright owner.
■ Editor
Dorothee Gintars
BINE Information
Service Energy Expertise
BINE provides information on energy
efficient technologies and renewable
energy:
Using a combination of free brochures,
the BINE web site (www.bine.info) and
a newsletter, BINE shows how innovative
research ideas hold up in practice
(in German).
• Demonstration building
Im Voggenthal 21
D-92318 Neumarkt i. d. Oberpfalz
Manufacture / Contractor
• Variotec
Christof Stölzel
Weißmarterstr. 3-5
D-92318 Neumarkt i. d. Oberpfalz
Architecture
• Forstner Architektur
Martin Forstner
Weinbergstr. 24
D-92318 Neumarkt i. d. Oberpfalz
Monitoring
• Fraunhofer-Institut
für Solare Energiesysteme ISE
Jan Wienold
Heidenhofstr. 2
D-79110 Freiburg
4
BINE projektinfo 09/07
ADDITIONAL INFORMATION
On the topic of VIP available from
BINE Information Service:
• Projekt-Info 08/06
„Gebäude sanieren – Gemeindezentrum”
• Projekt-Info 08/04
„Vakuum-Isolation in Fassadenelementen”
• Projekt-Info 04/01
„Vakuumdämmung”
Internet
• www.vip-bau.de
• www.enob.info
Images
• Figs. 1, 2, 4, 5, 6: Variotec, Neumarkt
• Fig. 7: Fraunhofer ISE, Freiburg
FIZ Karlsruhe, Büro Bonn
Kaiserstraße 185 – 197
53113 Bonn
Service
• Additional information in German such as
addresses and internet links are available
from BINE Information Service, or online
at www.bine.info (Service/InfoPlus).
Tel.: 0228 92379-0
Fax: 0228 92379-29
[email protected]
www.bine.info
KERSTIN CONRADI · Mediengestaltung, Hennef
PROJECT ADDRESSES
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