Scope of use
The INTELLO Humidity Variable
Intelligent Airtightness System has been appraised for use as a vapour control
layer and air barrier on buildings within the following scope:
- constructed
with timber framing in accordance with NZS 3604, or to a specific engineering
design; or
·
- constructed
with steel framing in accordance with NASH Standard Part Two, or to a specific
engineering design; and
·
- used on
walls and ceilings which incorporate fibrous thermal insulation.
The use of the INTELLO Humidity
Variable Intelligent Airtightness System in buildings with high moisture loads
such as swimming pools, commercial laundries and kitchens or with non-vented
membrane roof coverings has not been assessed and is therefore outside the
scope of this Appraisal. Contact Pro Clima (NZ) Ltd for use of the INTELLO
Humidity Variable Intelligent Airtightness System in these building types.
Design requirements
Design Information
General
1. INTELLO membranes function as an
air barrier to limit air infiltration between the indoor and outside
environments. Controlling air leakage contributes to improving the thermal
efficiency of a building, as it reduces the heat lost from uncontrolled air
flows, particularly for fibrous insulation as the R-value is reduced due to air
infiltration. Controlling air leakage can also reduce the chance of
interstitial condensation, because it can help prevent moist air reaching any surfaces
that may be colder than the dew point of the moist air. Whilst limiting
uncontrolled air infiltration is desirable from an energy and building
durability standpoint, it is important that adequate ventilation levels are
provided for indoor air quality.
2. INTELLO membranes can function as
a vapour control layer to lessen diffusion between the indoor and outside
environments. If it is desired to lessen the rate of diffusion through the
building envelope, INTELLO membranes can be used because they have a higher
vapour resistance under normal operating conditions than the materials
typically used in walls and roofs. Under typical winter conditions, this has
the effect of lowering the vapour pressure (and consequently the relative
humidity) at the locations outboard of the membrane. The general rule of thumb
is to have the highest vapour resistance in the wall on the warm side of the
insulation in winter.
3. INTELLO membranes are not what
has been traditionally referred to as a ‘vapour barrier’. Under normal
operating conditions they have a moderate vapour resistance. This means that
they can reduce the rate of diffusion through the wall, not eliminate it. In
the event that there is liquid water in the wall, the vapour resistance of the
membrane is such that water vapour can diffuse through it i.e. the wall can
still dry to the inside, in much the same way as ‘typical’ New Zealand walls.
4. The vapour diffusion resistance
for the product varies depending on the relative humidity (RH) from 1.25 MN s/g
to 125 MN s/g. INTELLO has a specific moisture profile (vapour resistance
versus relative humidity). At an RH of 70%, the vapour resistance is 10 MN s/g
and at an RH of 60% the vapour resistance is 7.5 MN s/g. During ‘winter’
conditions the vapour resistance increases preventing water vapour from moving
from the building interior to the exterior. In ‘summer’ conditions the vapour
resistance decreases, allowing vapour to flow from the building structure to
the building interior.
5. INTELLO and INTELLO PLUS
membranes are not vapour barriers. The product is fitted to the inside-face of
the building envelope on the warm side of the thermal insulation.
6. The designer must consider the
intended and future occupancy of the building and provide adequate ventilation
mechanisms (e.g. openable windows and doors, mechanical ventilation systems),
appropriate to the expected moisture loading and occupancy.
WUFI®
Software
7. WUFI® is computer software
developed by the Fraunhofer Institute for Building Physics that allows modelling
of heat and moisture flows through building elements. The software may be used
to model buildings that are to incorporate the INTELLO Humidity Variable
Intelligent Airtightness System. The WUFI® properties for the INTELLO membrane
are contained within WUFI® software. Modelling must be undertaken by a
competent and appropriately qualified person, using relevant parameters
appropriate to New Zealand conditions, for the intended building site.
Blower
Door Tests
8. The quality of airtightness is
determined by the freedom from air leakage in the building envelope. To verify
the airtightness of the complete building, Blower Door testing should be
completed prior to installation of internal linings in accordance with the
Technical Literature and AS/NZS 9972 or EN 13829. Typical airtightness targets
are < n50=3 air changes per hour (ACH) or < 1.5 ACH for buildings with a
balanced heat recovery ventilation system. Remedial work may be required to
seal air leakage paths in the building prior to installation of the internal
linings, to achieve the desired airtightness target.
Ceilings
9. Timber ceiling battens are fixed
conventionally to the underside of the ceiling rafters over the INTELLO
membrane. Steel ceiling battens are also fixed directly to the underside of the
ceiling rafters without using the clips/hangers that are typically part of
these ceiling systems. Installation should then follow the lining supplier’s
instructions.
Walls
10. INTELLO membranes can be fitted directly over
the wall framing or over battens used to form a cavity. This cavity can be used
for small services such as water supply pipework.
Mid-Floors
11. Where the INTELLO Humidity
Variable Intelligent Airtightness System is used in multi-level construction,
the airtightness must be detailed to be continuous. Refer to the Technical
Literature for detailing options.
Maintenance requirements
Provided the internal lining is
maintained in accordance with the lining manufacturer’s instructions and the
lining remains sound, the INTELLO Humidity Variable Intelligent Airtightness
System is expected to have a serviceable life equal to that of the internal
lining.
