[Greenbuilding] Which insulation? How to install?
Stuart Fix
sfix at renubuildings.com
Mon May 28 11:53:11 CDT 2012
I would suggest that the ideal crawlspace design is no different than a
proper wall or roof design. In a 7500 HDD climate, it should have poly on
the warm side, be well insulated, and be very air tight. The underside of
the crawlspace ceiling should be airtight, but vapor open. Just like a
wall or roof, your floor must minimize heat transfer, bulk air movement,
and vapor diffusion from inside to outside.
Humidity within the crawlspace should be controlled via poly on the ground
and proper ventilation (either passive screens or active fan/humidistat).
The crawlspace walls are there to stop animals and excessive wind washing.
The site must be properly graded if you have any hope of a dry crawlspace.
If this approach is followed properly, you can use any insulation type
within the floor assembly. However, if you case cannot achieve the best
practice design, you'll be best served using materials that are mold/rot
resistant (ie, Mineral Wool & plywood vs cellulose & OSB). But I would
rely on proper design, not proper materials, to ensure a long lasting
crawlspace ceiling.
Cheers,
Stuart Fix, P.Eng., LEED® AP
PHI Certified Passive House Designer
MASc. Building Science
Mechanical Engineer
ReNü Building Science Inc.
52 Airport Road | Edmonton, Alberta | T5G 0W7| C. 780.554.8192
| sfix at renubuildings.com
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Today's Topics:
1. Re: Which insulation? How to install? (Eli Talking)
2. Re: Which insulation? How to install? (Eli Talking)
----------------------------------------------------------------------
Message: 1
Date: Sun, 27 May 2012 15:05:21 -0400
From: "Eli Talking" <elitalking at rockbridge.net>
To: "Green Building" <greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] Which insulation? How to install?
Message-ID: <EA361B380F8C4EF5B8B465728C4594B9 at NewCentury>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
I do not have the answer. I do have a similar situation. I am designing
a renovation of an old farm house that has a crawl space with a rough
ground surface that tapers from 5' to a few inches. Basically, the grade
of crawlspace follows the original grade of the hill. I have accepted the
need to excavate to at least 18 inches. However, we are using mini-split
heat pumps to deliver heat directly to rooms, therefore do not need crawl
space for air ducts or mechanical equipment. I was planning on the
addition being built over grade slab, but one day my contractor client got
so enthusiastic with her excavator that she assumed a crawlspace and
excavated accordingly. It will be a crawlspace. We are using closed cell
foam for walls and below roof deck. We do have the budget to install what
will work best. I want to insulate above the crawlspace along the floor
plane.
We could insulate between joist with closed cell foam. However, this
leaves the bottom of the joist exposed to potentially high humidity.
However, with the tight insulation, the bottom surface temperature would
be closer to the ambient, even in the summer, reducing the vulnerability
to condensation on surface during active cooling.
We could install a rigid insulation board thick enough to achieve vapor
tightness along the bottom of the joist. This would also eliminate
thermal bridges. Sealing the seams would become the critical execution
issue. By installing the thermal barrier below the floor joist, the joist
cavity could be available for wires and plumbing without all the sealing
issues. 3" iso foam could provide R21+- continuous which is a vapor
barrier that begins at both the top and bottom surface. The crawl space
is pretty open ventilated to the outside. Warm air entering the shaded
area would only be cooler because the ground in the crawlspace is not
being heated by the sun.
Additional lower cost fiberglass batts could be installed to increase R
value. For durability and to provide fire retardant barrier, I would
bottom off with 7/16 osb (low cost).
I hope our list experts comment on my hunch that a floor or below thermal
barrier that was tight on both exterior and interior side such that there
is no flow through it above an ambient ventilated crawl space would keep
the surface temperature above dew point to avoid the consequences of
condensation.
Eli
-----Original Message-----
From: Corwyn
Sent: Sunday, May 13, 2012 1:38 PM
To: Greenbuilding
Subject: [Greenbuilding] Which insulation? How to install?
Greetings,
What insulation would people recommend for a short crawl space? This is
in a cold climate 7500 HDD, and the house is sitting on posts about 1'
above the ground (a few inches at some points). There is a insulated
skirt around the perimeter with 2" of foam board insulation. There is
incomplete vapor barrier on the ground. Acknowledging that some digging
may need to be done, but budget concerns make serious work unaffordable.
The budget is very small. Is air entrained concrete a workable option?
Any thoughts?
Thank You Kindly,
Corwyn
--
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.greenfret.com/
topher at greenfret.com
(207) 882-7652
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------------------------------
Message: 2
Date: Sun, 27 May 2012 15:45:41 -0400
From: "Eli Talking" <elitalking at rockbridge.net>
To: "Green Building" <greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] Which insulation? How to install?
Message-ID: <A3A16EA3E59843AA936C6DB0E83F1A71 at NewCentury>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
I do not have the answer. I do have a similar situation. I am designing
a
renovation of an old farm house that has a crawl space with a rough ground
surface that tapers from 5' to a few inches. Basically, the grade of
crawlspace follows the original grade of the hill. I have accepted the
need
to
excavate to at least 18 inches. However, we are using mini-split heat
pumps
to deliver heat directly to rooms, therefore do not need crawl space for
air
ducts or mechanical equipment. I was planning on the addition being built
over grade slab, but one day my contractor client got so enthusiastic with
her excavator that she assumed a crawlspace and excavated accordingly. It
will be a crawlspace. We are using closed cell foam for walls and below
roof deck. We do have the budget to install what will work best. I want
to
insulate above the crawlspace along the floor plane.
We could insulate between joist with closed
cell foam. However, this leaves the bottom of the joist exposed to
potentially high humidity. However, with the tight insulation, the bottom
surface temperature would be closer to the ambient, even in the summer,
reducing the vulnerability to condensation on surface during active
cooling.
We could install a rigid insulation board thick enough to achieve
vapor tightness along the bottom of the joist. This would also eliminate
thermal bridges. Sealing the seams would become the critical execution
issue. By installing the thermal barrier below the floor joist, the joist
cavity could be available for wires and plumbing without all the sealing
issues. 3" iso foam could provide R21+- continuous which is a vapor
barrier
that begins at both the top and bottom surface. The crawl space is pretty
open ventilated to the outside. Warm air entering the shaded area would
only be cooler because the ground in the crawlspace is not being heated by
the sun.
Additional lower cost fiberglass batts could be installed to increase R
value. For durability and to provide fire retardant barrier, I would
bottom
off with 7/16 osb (low cost).
I hope our list experts comment on my hunch that a floor or below thermal
barrier that was tight on both exterior and interior side such that there
is
no flow through it above an ambient ventilated crawl space would keep the
surface temperature above dew point to avoid the consequences of
condensation.
Eli
-----Original Message-----
From: Corwyn
Sent: Sunday, May 13, 2012 1:38 PM
To: Greenbuilding
Subject: [Greenbuilding] Which insulation? How to install?
Greetings,
What insulation would people recommend for a short crawl space? This is
in a cold climate 7500 HDD, and the house is sitting on posts about 1'
above the ground (a few inches at some points). There is a insulated
skirt around the perimeter with 2" of foam board insulation. There is
incomplete vapor barrier on the ground. Acknowledging that some digging
may need to be done, but budget concerns make serious work unaffordable.
The budget is very small. Is air entrained concrete a workable option?
Any thoughts?
Thank You Kindly,
Corwyn
--
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.greenfret.com/
topher at greenfret.com
(207) 882-7652
_______________________________________________
Greenbuilding mailing list
to Send a Message to the list, use the email address
Greenbuilding at bioenergylists.org
to UNSUBSCRIBE or Change your List Settings use the web page
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------------------------------
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End of Greenbuilding Digest, Vol 21, Issue 12
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