John: How many times have you heard that a
building needs to 'breathe'? But what does
'breathability' actually mean?
John: Okay, this is gonna get really confusing.
John: Joseph what is the definition of
'breathability'?
Joseph: Well, 'breathability' and 'breathe' is a very
confusing term because the everyday use of
the term is meaning how we inhale and
exhale of air. In the material science
term 'breathability' is about how well a
material can allow moisture and water
vapour to permeate through, in order to
maintain a balance of vapour, or a
moisture level, on both side of the
material. John: So Andy, on this product you've
got "Let your building breathe" what does
that mean for the wall cavity in
relation to air tightness?
Andy: To a certain extent we are guilty of using a
bit of marketing which really confuses
on the building science side of things.
John: Yep
Andy: So people need to breathe it's a
physical action of breathing inhaling
and exhaling just like you said. We're
wrapping up a building here with an
airtight material. John:Right! Andy: There's no air
movement moving side to side of this
material. John: Yeah Andy: But what it does is that
allows vapour to pass through this
material so you're not getting
condensation forming on the inside of
that material by allowing vapour to
pass through. Perhaps we need to change
the logo. John: So this keeps your wall
cavity dry and then also allows your
insulation to work as it's been designed.
Andy: So you've got, you've got essentially a
water control layer so during
construction and for the life of the
building this is a water control here, to
stop liquid water from getting into the
building. The other side of water is that
when water is a gas and reaches dew
point it turns into into water and you
don't want that to happen within your
insulation. You don't want to have that
happen on the structural side of your
building wrap, so you need to get that vapour
to pass through slowly into the
into the cavity where it can drain away
safely. John: Right. So Andy this product is fantastic
for keeping water out of the wall system.
How do other products compare to this
product? Andy: So there are a lot of different
technologies about providing
breathability within within textiles.
John: Mm-hmm. Andy: Now this works because there's a
micro porous film there, which based on
vapour pressure difference, allows vapour
to pass through very small pores within
the material. It still maintains under
normal circumstances a very good air
tight layer. The other technologies, which
we also use our air permeable membranes
which have a certain degree of water
hold-out but they transport that vapour
through them, through air movement. So you
can have excellent levels of vapour
permeability, but there is some sacrifice
in terms both air tightness and water
tightness. John: So Andy, what criteria
does the Enviroseal Proctorwrap product
cover for building performance? Andy: Okay.
Andy: Something we talked about earlier about the
building envelope and materials acting
as control layers. We look at what
control layer functions the membrane can
offer. John: Yeah. Andy: So primarily you've got your
temporary and your long-term water
control there, to stop water getting in.
John: Yeah Andy: But also, because of the nature of
the product, it also provides an air
control layer. Your buying an airtight
material, you're not having air movement
through the wrap, provided it's
adequately taped and formed a complete
air barrier. The other function it does
is it ensures by being vapor permeable
allows the vapour to escape through the
membrane safely without causing damage
within the structure and within the
insulation. Joseph: So in a nutshell, the
Enviroseal Proctorwrap is a multi-function
product, not a single function product.
John: So to finish with this, modern-day
building products and airtight
construction can be 'breathable' which
means it can diffuse moisture trapped in
the wall construction without moving air
through. Watch our follow up video on
building performance where we go over
the super exciting concepts of control
layers for maintaining a healthy and
higher performing building.