[Greenbuilding] Unifoam vs Plastispan

Wed Oct 4 05:46:32 CDT 2017

the Passive House Planning Package (PHPP) has a function to evaluate "Heat
Losses Via The Ground." The variables include all manner of local climate
data, average ground surface temp. and water table depth, as well as the
thermal conductivity and heat capacity of the soil, and the depth of your
assemblies.

The thermal conductivity value is a significant factor. For example, the
program's embedded default values for solid rock range from R-0.02 to
R-0.07, whereas dry sand ranges between R-0.6 to R-1.0.

This is still playing in a fairly narrow range, given (as Norbert says) the
delta is pretty small. I did a "what if" on a passive house project which
was based on 9" of high density foam under the slab, (in order to hit the
magic 4.75 KBtu/SF/year space heat demand), changing it to 2 inches of
foam. It saved something like $14 per year in natural gas.

Nevertheless, in modeling projects in mixed humid climates, I find that it
is much easier to reduce heating loads than cooling loads--because latent
loads are not very response to insulation.

This leads me to the assumption that it might be best to sacrifice a little
heat loss through the slab in winter, to gain the heat sink effect in
summer.

-aa

Alan Abrams, CPBD, AIBD
*Associate Designer Helicon Works Architects
<http://www.heliconworksarchitects.com/>*
*Certified Professional Building Designer, American Institute of Building
Design <http://aibd.org/> *

*President, National Council of Building Designer Certification
<http://ncbdc.com/>*
cell     202-437-8583
alan at abramsdesignbuild.com

On Wed, Oct 4, 2017 at 12:42 AM, Lynelle Hamilton <lynelle at lahamilton.com>
wrote:

> Thanks, John.
>
> Frost protected shakkow foundation, yes. but not t a purchased "system"
> for cost and delivery time issues. Am planning to construct my own, Soil is
> a mixture of sand and sandy loam. Land around me is damp, although the
> previous cottage had a crawl space that was dry.  Those are the concerns
> with regard to insulation. Because the perimeter (and a centre "channel"
> that is to support an interior load bearing  wall have to be 30psi, I will
> glue a 25 psi skirt around the perimeter, with additional width at each
> corner.
>
> Lynelle
>
> On 2017-10-03 11:00 PM, John Salmen wrote:
>
> Depends on perimeter depth. Are you doing a frost protected foundation? Or
> are the footings below freezing and fully wrapped? consideration on the
> perimeter and bridging. I’ve typically gone R20 on slab but R30 on
> perimeter.
>
>
>
> *From:* Greenbuilding [mailto:greenbuilding-bounces@
> lists.bioenergylists.org <greenbuilding-bounces at lists.bioenergylists.org>]
> *On Behalf Of *Lynelle Hamilton
> *Sent:* Tuesday, October 3, 2017 7:50 PM
> *To:* greenbuilding at lists.bioenergylists.org
> *Subject:* Re: [Greenbuilding] Unifoam vs Plastispan
>
>
>
> Norbert, is the 50F true when the slab is shallow (e.g. essentially on
> packed earth that is 16" below grade?
>
> Lynelle
>
>
>
> On 2017-10-03 7:19 PM, Norbert Senf wrote:
>
> Way high. If you do a payback analysis for the last R-10 it is close to
> infinite. Ground temperature around here is 50F, so your maximum
> differential is maybe 20 degrees ............... N
>
>
>
> On Tue, Oct 3, 2017 at 7:11 PM, Gennaro Brooks-Church - Eco Brooklyn <
> info at ecobrooklyn.com> wrote:
>
> R-35 under slab is high or low?
>
>
> Thanks!
>
> Gennaro
>
>
>
> On Tue, Oct 3, 2017 at 6:59 PM, John Straube <jfstraube at gmail.com> wrote:
>
> I am not sure what is special about your slab, but standard XPS (25 psi
> max) has been used for decades.  Hence, EPS with more than 25 psi seems odd
> anywhere except where a concentrated load occurs.  Remember, 25 psi is 3500
> psf, which is more than most soils can take. But to answer part of the
> question I have use PlastiFab EPS of wide range of strengths successfully
> for a long time, and have no experience with Uniform.
> Of course insulating with R-35 under slab seems very odd… the result of
> bizarre interior conditions or bizarre calculation methods?
>
> > On Oct 3, 2017, at 6:24 PM, Lynelle Hamilton <lynelle at lahamilton.com>
> wrote:
> >
> > I am insulating under a floating pad. The engineer has specified 25psi
> under the slab and 30 psi on outer edges.   I've been looking at two
> products: Unifoam 25/30 and Plastifab 25/30. Aiming for R35 under the
> slab.  Price differential is significant (Unifoam is nearly $3000 more) for
> the house.
> >
> > Has anyone had experience with either product? From the specs, Unifoam
> appears to absorb less water and has less deflection, but both are within
> the ASTM spec for the issue.
> >
> > Many thanks for any insights!
> >
> > Lynelle Hamilton
> >
>
> >       Virus-free. www.avast.com
> > _______________________________________________
> > 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
> > http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.
> bioenergylists.org
>
>
> _______________________________________________
> 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
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.
> bioenergylists.org
>
>
>
>
> _______________________________________________
> 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
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.
> bioenergylists.org
>
>
>
>
> --
>
> Norbert Senf
> Masonry Stove Builders
> 25 Brouse Road, RR 5
> Shawville Québec J0X 2Y0
> 819.647.5092
> www.heatkit.com
>
>
>
>
> _______________________________________________
>
> 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
>
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org
>
>
>
>
>
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
> Virus-free. www.avast.com
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
>
>
>
> _______________________________________________
> Greenbuilding mailing list
> to Send a Message to the list, use the email addressGreenbuilding at bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web pagehttp://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org
>
>
>
> _______________________________________________
> 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
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.
> bioenergylists.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20171004/81df98c2/attachment.html>