Hi,

I have a 50-year-old backsplit that has a large uninsulated crawlspace
under the living room and kitchen. The crawlspace has a concrete floor
and is about 4' high. It connects with the heated part of the basement
via a short door. It's not directly heated by a duct, but the
temperature never gets anywhere near zero.

In winters (which are pretty long in Ontario), the living room and
kitchen get very cold; the floor is extremely cold. My plan is to
insulate between the joists in order to keep the heat where it is
needed. I plan on running a duct into the crawlspace to keep pipes from
freezing.

My question is ... do I need a plastic vapour barrier? I thought so,
but a Government of Canada website on the topic says no. To quote:

"If the floor above the crawl space is already covered with an
impermeable material (e.g., linoleum or plywood), you already have a
vapour barrier where you want it. The solid materials of the floor can
serve as the air barrier, but be sure to locate and seal any air
leaks."

This is good news for me, because I don't know how I could lay strips
of barrier in the bays between the joists and make an airtight seal.
It's way easier just to stuff batts betwen the joists. But is this is a
mistake? If it matters, I'm using Roxul insulation -- unfaced and not
affected by moisture.

Thanks for any insights anyone may have.

Tom

A vapor barrier wont help, a cheaper way to keep pipes from freezing
would be to use electric pipe tape with a thermostat and insulate the
pipes well.

Thomas Nickerson wrote:
Hi,

I have a 50-year-old backsplit that has a large uninsulated crawlspace
under the living room and kitchen. The crawlspace has a concrete floor
and is about 4' high. It connects with the heated part of the basement
via a short door. It's not directly heated by a duct, but the
temperature never gets anywhere near zero.

In winters (which are pretty long in Ontario), the living room and
kitchen get very cold; the floor is extremely cold. My plan is to
insulate between the joists in order to keep the heat where it is
needed. I plan on running a duct into the crawlspace to keep pipes from
freezing.

My question is ... do I need a plastic vapour barrier? I thought so,
but a Government of Canada website on the topic says no. To quote:

"If the floor above the crawl space is already covered with an
impermeable material (e.g., linoleum or plywood), you already have a
vapour barrier where you want it. The solid materials of the floor can
serve as the air barrier, but be sure to locate and seal any air
leaks."

This is good news for me, because I don't know how I could lay strips
of barrier in the bays between the joists and make an airtight seal.
It's way easier just to stuff batts betwen the joists. But is this is a
mistake? If it matters, I'm using Roxul insulation -- unfaced and not
affected by moisture.

Thanks for any insights anyone may have.

Tom

You might get better results sealing & insulating the outer walls of
the crawl space and allowing conditioned air into the crawl space.
TB

wrote:
...


You might get better results sealing & insulating the outer walls of
the crawl space and allowing conditioned air into the crawl space.
TB

I agree.

--
Joseph Meehan

Dia duit

in this case, the only worry is moisture from condenation, and
freezing, the vapor barrier might actualy make that worse, if you could
insulate below the pipesyou could save a lot of trouble, even if you
had to box them in.

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Thomas Nickerson wrote:
Hi,

I have a 50-year-old backsplit that has a large uninsulated crawlspace
under the living room and kitchen. The crawlspace has a concrete floor
and is about 4' high. It connects with the heated part of the basement
via a short door. It's not directly heated by a duct, but the
temperature never gets anywhere near zero.

In winters (which are pretty long in Ontario), the living room and
kitchen get very cold; the floor is extremely cold. My plan is to
insulate between the joists in order to keep the heat where it is
needed. I plan on running a duct into the crawlspace to keep pipes from
freezing.

My question is ... do I need a plastic vapour barrier? I thought so,
but a Government of Canada website on the topic says no. To quote:

"If the floor above the crawl space is already covered with an
impermeable material (e.g., linoleum or plywood), you already have a
vapour barrier where you want it. The solid materials of the floor can
serve as the air barrier, but be sure to locate and seal any air
leaks."

This is good news for me, because I don't know how I could lay strips
of barrier in the bays between the joists and make an airtight seal.
It's way easier just to stuff batts betwen the joists. But is this is a
mistake? If it matters, I'm using Roxul insulation -- unfaced and not
affected by moisture.

Thanks for any insights anyone may have.

Tom

This is probably a stupid question, but do you mean the outside of the
outside walls, or the inside (ie in the crawlspace)?

Thanks


TN

Joseph Meehan wrote:
wrote:
..


You might get better results sealing & insulating the outer walls of
the crawl space and allowing conditioned air into the crawl space.
TB

I agree.

--
Joseph Meehan

Dia duit

m Ransley wrote:
A vapor barrier wont help, a cheaper way to keep pipes from freezing
would be to use electric pipe tape with a thermostat and insulate the
pipes well.

Why do you mention 'freezing pipes'. The OP says that 'It never gets
anywhere near zero'. His worry is the cold floor and heat loss down
through it to a basically unheated space.

Since it's Ontario, Canada. (most of the world uses metric now) that's
most likely 'Zero' Celsius/Centigrade. In other words it "Never gets
anywhere near 32 F".

Thomas Nickerson wrote:
This is probably a stupid question, but do you mean the outside of the
outside walls, or the inside (ie in the crawlspace)?


He is talking about the inside of the outside walls, the 4' concrete
walls. If the walls are not studded, then you can insulate the floor
but without a vapor barrier.