Windows and the Fingerprint of Continuous Layers

Written by Jon Davies
Technical Sales Support and Education Manager, Pro Clima New Zealand

Building envelopes are often missing three out of four key elements. In this article I'll describe an overall theme of connectedness and describe how we can connect windows more effectively.

The four key layers are:

Continuous structure
Continuous insulation
Continuous weathertightness
Continuous air control

Fig 1. Fingerprint

The basic expectation of a building includes it being able to stand up unassisted, therefore we can confidently say that (new) buildings have a continuous structure — a combination of framing, maybe a floor slab, all connected together.

What we cannot say for certain is that the other three critical layers exist in continuity.

Insulation

In our experience, insulation is rarely connected at a number of junctions, including floor to wall, ceiling to wall and window to wall.

Weathertightness

Weathertightness layers such as a flexible wall and roof underlay (as the last line of defence) are rarely connected at floor to wall, wall to roof, window to wall or underfloor junctions.

Air Control Layers

Traditionally plasterboard has been used as an air control layer which might be ok if we didn't poke holes in it to run power points, light switches, data points, extract pipes, plumbing gas and drainage pipes, not to mention windows and doors. The connection is missing for this critical 'draught stopping' element at these junctions: floor to wall, ceiling to wall, window and door seals (unit) and flooring to flooring.

Window and Door Performance

So what to do? Let's pick on one area that is 'low hanging fruit' for the performance of our buildings in general — windows and doors.

Structural connection is relatively easy: Fix it to the building.
Insulation should line up: The position (depth) within the wall makes the biggest difference. Aside from the fact windows are ten times weaker in thermal performance than the wall they sit in, the IGU should run in the same plane as the wall insulation and this gives lots of scope for positioning. The 'highest performance' window will still perform poorly if it is hung outside the building/insulation line. Bring windows inside.
Weathertightness layer should connect at the outside: we can't keep relying on a temporary product 'system' like PEF rod and foam to provide adequate weathertightness performance. I encourage you to pick up a pencil and draw where the weathertightness layer actually goes in a standard detail — it may surprise you to see how many corners you'll end up making as your line wriggles all the way in to the PEF rod and out again till you get the glass (see fig. 2 with red pencil line below). Compare this with the Altus 'Smartfit' window and its weathertightness connection which is in a straight line with the wall underlay. We offer multiple solutions for connecting weathertightness at the outside for all types of windows.
The 'air control' layer (airtightness) can be connected to the inside in a very similar fashion to the external side and the additional benefit is the ability to insulate further between those two layers.

Fig 2. Red pencil

Outcome

What is the gain? Improve the performance of windows for H1, E2, E3 and B2 performance requirements.

What is the loss? Condensation. Drafts. Mould. Fear of water ingress if we bring windows inside the line of the building envelope.

Written by Jon Davies
Technical Sales Support and Education Manager, Pro Clima New Zealand

Intelligent Airtightness Membrane (INTELLO PLUS)

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The pro clima airtightness system prevents uncontrolled air infiltration or leakage through the building envelope, and assists the drying capacity of the building through its unique moisture control properties.

Suitable for all construction and where there is risk of interstitial condensation
The protection of insulation from air movement
Preventing uncontrollable air flow though the building envelope
An optional continuous cavity for electrical and plumbing services can be created on the inside face of the external wall by fixing battens horizontally over the INTELLO membrane before installing the wall lining
The main advantage of a service cavity is to shift the plumbing and wiring out of the insulation layer
A service cavity also reduces the penetrations through the airtightness membrane allowing easy and fast installation of services
This also eliminates pressure points on inner lining (eg. plasterboard) from insulation expansion

The NZBC requires only that airtightness be considered, not measured. INTELLO directly assists with meeting the following requirements:

Clause E3.1 INTERNAL MOISTURE: Buildings must safeguard people against illness, injury, or loss of amenity that could result from the accumulation of internal moisture
Clause E3.2 INTERNAL MOISTURE: Buildings must avoid the likelihood of fungal growth or the accumulation of contaminants on linings and other building elements
Clause E2 EXTERNAL MOISTURE: Concealed spaces and cavities in buildings must be constructed in a way that prevents external moisture being accumulated or transferred and causing condensation, fungal growth, or degradation of building elements
Clause E2 EXTERNAL MOISTURE: Building elements must make due allowance for the following: (a) the consequences of failure, (c) variation in the properties of materials and in the characteristics of the site
Clause E2 EXTERNAL MOISTURE: Interior linings with all joints stopped require barriers to airflow
Clause H1 : ENERGY EFFICIENCY: The building must be constructed to limit uncontrollable airflow
Clause H1 : ENERGY EFFICIENCY: Account must be taken of physical conditions likely to affect energy performance of buildings; (c) Airtightness of the building envelope.
Clause B2 : DURABILITY: Performance B2.3.1(a), not less than 50 years, B2.3.1(b), 15 years and B2.3.2

BRANZ Appraised

Roof Underlay (SOLITEX MENTO 3000)

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SOLITEX MENTO 3000 roof underlay is a three-layer roof underlay designed to be used with most typical roof cladding systems. While providing temporary weather protection it can remain exposed for up to 90 days.

SOLITEX MENTO 3000 has been appraised for use as a self-supporting roof underlay on buildings within the following scope:

the scope of limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1 with regards to building height and floor plan area; and,
with masonry tile roof cladding; and,
with metal tile and profiles metal roof cladding; and,
suited to NZS 3604 Wind Zones up to, and including Extra High.

In the opinion of BRANZ, SOLITEX MENTO 3000, if used, designed, installed and maintained in accordance with the statements and conditions of the BRANZ Appraisal, will meet, or contribute to meeting the following provisions of the NZBC:

Clause B2 DURABILITY: Performance B2.3.1(a), not less than 50 years, B2.3.1(b), 15 years and B2.3.2 SOLITEX MENTO 3000 meets these requirements. See Paragraphs 9.1 and 9.2 of the BRANZ Appraisal.
Clause F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1 SOLITEX MENTO 3000 meets this requirement and will not present a health hazard to people.
Clause E2 EXTERNAL MOISTURE: Performance E2.3.2 When used as part of the cladding system, SOLITEX MENTO 3000 will contribute to meeting this requirement. See Paragraphs 12.1 and 12.2 of the BRANZ Appraisal.

BRANZ Appraised

Wall Underlay (SOLITEX EXTASANA)

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SOLITEX EXTASANA is a synthetic flexible wall underlay designed for New Zealand conditions, produced in Germany, and exceeds all of the testing standards of E2/AS1 Table 23.

Has been assessed for use as a flexible wall underlay on timber framed buildings within the following scope:

the scope limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1; and,
with absorbent wall claddings directly fixed to framing; and,
with non-metallic, non-absorbent wall claddings directly fixed to frame; and,
with absorbent and non-absorbent wall claddings installed over an 18 mm minimum drained cavity; and,
with masonry veneer in accordance with NZBC Acceptable Solution E2/AS1; and,
situated in NZS 3604:2011 Wind Zones up to, and including ‘Very High’.

Has been assessed for use as a flexible wall underlay on steel framed buildings within the following scope:

the scope limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1 with regards to building height and floor plan area; and,
with absorbent and non-absorbent wall claddings installed over an 18 mm minimum drained cavity; and,
with masonry veneer in accordance with NZBC Acceptable Solution E2/AS1; and,
situated in NZS 3604:2011 Wind Zones up to, and including ‘Very High’.

Has been assessed for use as a flexible wall underlay over rigid wall underlays on timber and steel framed buildings within the following scope:

the scope limitations of NZBC Acceptable Solution E2/AS1 (August 2011), Paragraph 1.1 with regards to building height and floor plan area; and,
with absorbent and non-absorbent wall claddings installed over an 18 mm minimum drained cavity; and,
with masonry veneer in accordance with NZBC Acceptable Solution E2/AS1; and,
situated in NZS 3604:2011 Wind Zones up to and including ‘Extra High’

If used, designed, installed and maintained in accordance with the statements and conditions of the Installation Guide and the Codemark Certificate, will meet, or contribute to meeting the following provisions of the NZBC:

Clause B2 DURABILITY: Performance B2.3.1(a), not less than 50 years, B2.3.1(b), 15 years and B2.3.2. meets these requirements.
Clause E2 EXTERNAL MOISTURE: Performance E2.3.2. When used as part of the cladding system, will contribute to meeting this requirement.
Clause F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1. Meets this requirement and will not present a health hazard to people.

BRANZ Appraised

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