[Greenbuilding] insulating beneath an existing floor.

Thu Jul 30 12:22:38 CDT 2015

>From your description, it sounds maybe like:
- spray foam underneath
- spray plaster or some kind of insect and vermin proof coating over the
foam. Rustoleum Vertical Restore looks interesting.
- vent the crawlspace

Norbert

On Thu, Jul 30, 2015 at 12:59 PM, Sacie Lambertson <
sacie.lambertson at gmail.com> wrote:

> Thanks for the so-far responses to my query (John and Bob).  To clarify
> the problem:
>
> The house is sitting on top of the stone wall foundation so there is a
> space between the floor and the ground.  Presume (because the house won't
> be gutted for a year or more) the yellow pine floor rests on joists.  There
> is no access to the space underneath, short of tearing up the floor.  This
> seems to me entirely unnecessary given those boards have been there for
> over 130 years.
>
> I mentioned the old limestone wall only because I think placing insulation
> against the wall as might be normally recommended, is not a good idea given
> the potential for the limestone to deteriorate when it is thus enclosed.
> We have a good friend who is a master stonemason whose opinion I will ask
> about this problem.  Also will ask him to check out the existing wall which
> will need repointing IMO.  Have no idea what material has been used to
> point up until now.  Will check on this again.
>
> I'm thinking someone will have to crawl through some access point into the
> crawlspace of the floor and with good light insulate the floor from
> underneath, presumably a spray foam.  I think this is what you are
> suggesting Bob.  Further, your assessment of the situation is sound me
> thinks.  Wonder if putting vents in the wall would assure an air flow?
> Necessary?  There are none now.  The limestone wall around the main house
> is in very good shape.
>
> Assume without knowing, the floor joists are fairly deep given the rooms'
> dimensions (@14' x 14'-a bit over 1000 sq ft total).   So if only the
> joists were enclosed in foam, the space beneath would be left as is--ie
> open dirt surrounded by limestone walls.
>
> The lot is flat flat.  There is no indication of water damage around the
> perimeter except in the back where the lot actually slopes toward the house
> and where the foundation to the  addition is failing (added about 100 years
> ago on top of a similar limestone wall).
>
> The addition and wall will be demolished.  There is a small rudimentary
> basement under the addition.  A proper small basement will be built under a
> new addition and a good french drain will be placed in the yard behind it
> (the slope can not be changed).
>
> Further responses valued.  Sacie
>
> On Thu, Jul 30, 2015 at 9:05 AM, home-nrg <home-nrg at dnaco.net> wrote:
>
>> Sacie,
>>
>> Without more info on your earlier experience, and in view of
>> how limestone is subject to erosion by water contact as well
>> as the freeze/thaw cycle, protecting the foundation would
>> seem to be essentially isolating it from moisture in any
>> form.
>> The airflow of an exposed, unsealed foundation traditionally
>> provided this.
>>
>> The measures for reducing structural heat loss is likely to
>> change the conditions which drove that airflow
>> (ventilation).
>>
>> Presumably the "floor" inside the foundation is ground (soil
>> or gravel) without a moisture barrier seal. This leaves that
>> soil as a moisture source in most parts of the country.
>>
>> What sort of provision have you made for perimeter drainage?
>>
>> From what you describe, I'd suggest you consider treating
>> the floor as a sixth exterior wall, with suitable insulation
>> and air sealing.
>>
>> An alternative to a compulsively complete, fully sealed
>> over-soil moisture barrier would be a dedicated fan to
>> pressurize the enclosed (crawl) space, to provide the force
>> for air flow through the foundation.
>>
>>  (Find something more durable than construction-standard
>> 6-mil plastic. Clients have had good luck with 10-12mil
>> commercial membrane.)
>>
>> Just my speculation, without seeing the site or having more
>> information (and not having to fund the work).
>>
>> Bob Klahn
>>
>> ----- Original Message Follows -----
>> From: Sacie Lambertson <sacie.lambertson at gmail.com>
>> Subject: [Greenbuilding] insulating beneath an existing
>> floor.
>> Date: Wed, 29 Jul 2015 22:58:45 -0500
>>
>> > What is the best way to insulate the floors of an old
>> > house that sits on a 30 inch limestone foundation wall?
>> > The wall, solid since 1883, needs to continue to
>> > 'breathe'.  Limestone such as is used for the foundation
>> > is similar to that used in old barns; the stone will last
>> > a very long time as long as it does not have dirt behind
>> > it, ie as long as it is free standing.  We've had personal
>> > experience with this when we used old barn foundation
>> > stone to build rock walls behind which is dirt.  They
>> > began to deteriorate relatively fast.
>> >
>> > Most of the interior of the old house will be nearly
>> > gutted, leaving only the the exterior siding, which is
>> > also original amazingly enough, as is essentially the
>> > interior.  The old yellow pine floors will be retained but
>> > must be insulated underneath.
>> >
>> > The house will be reconstructed with double passiv haus
>> > type walls.
>> >
>> > Thanks for your advice,  Sacie
>> >
>> >
>> > _______________________________________________
>> > 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20150730/68432c41/attachment.html>