Subject: Earth-Sheltered Houses

From: [email-masked] (JMarino222)
Date: 23 Jul 1995 15:41:41 -0400

I am interested in building an earth-sheltered home.  I have done a
considerable amount of reading on the subject (i.e., Malcolm Wells, John
Carmody and Raymond Sterling, Angus Macdonald, etc.), but would be
interested in comments and observations from individuals who have had
practical experience with these structures.

In particular, I would be interested in information on the following:

	--  The advisability of building a domed-structure (such as
offered by Performance Building Systems) as opposed to box-type designs.

	--  The reliability of waterproofing in earth-sheltered designs.

	--  The need for air conditioning in these structures.

	--  The cost of earth-sheltered housing relative to conventional
construction.

	--  The ability of contractors to handle this type of
construction.

Any comments would be appreciated.  Thanks.

---

From: [email-masked] (Kent Polk)
Date: 24 Jul 1995 22:38:59 GMT

> 	--  The reliability of waterproofing in earth-sheltered designs.

I am building a concrete-shell earth-sheltered house right now. Have
discussed this issue with 5 different people who have built such.
'waterproofing' is not only 'added' waterproofing materials (of
which current products do an excellent job), but also requires
thought concerning the construction process. I.e. you need to
provide as many 'backup' mechanisms as is reasonable to help
the situation.  

I'm using:
1) French drains
2) cutting form straps below the surface and patching
3) applying a water-based interior concrete sealer on ceiling,
   walls, floor and as the first coat on exterior cold joints.
4) trowel-grade exterior sealer with nylon webbing on exterior
   cold joints
5) Exterior rolled-on (as in paint roller) sealer
6) cap floors poured on top of 1/2" of sand on the footings
   which will be back-filled (on the outside). This is to
   provide water with a path - under the floor - if it does
   get through the footing/wall cold joint
7) 6 mil poly under the floors (see #6)
8) 6 mil poly on top of the exterior waterproofing
9) 4" layer of chat (limestone 'dust') against the exterior
   poly to prevent any rocks from cutting through the poly/
   waterproofing.
10) another 6 mil poly layer above the blueboard insulation
   just below the soil layer in the backfill

> 	--  The need for air conditioning in these structures.

Heat/cooling isn't the primary problem. Humidity is. A/C
units make pretty good dehumidifiers but may drop the temp.
too much.  I ahve been working with Carrier A/C Engineers
here in San Antonio in designing a unit which will primarily
dehumidify for actually less than the cost of a conventionally
sized unit. This requires the new variable-speed GE fan motors
running at a lower nominal speed than normal and an undersized
condensor with an oversized evaporator.  This covers the topic
waaay too fast, but our figures are showing a 1.5 ton condensor
unit to handle 2400 sq feet the way my house is being built.
(this is in San Antonio, TX, where it's 102 deg. outside right
now)   I also am controlling the sources of humidity, such as
bathrooms, etc, using ~100 ft long 4" PVC intake air tubes.
These act like small 'cool tubes' for the duration of the time
they are required to evacuate humidity from the isolated
bathrooms, etc.  I also have a similar arrangement for venting
the refrig/freezer.

> 	--  The cost of earth-sheltered housing relative to conventional

My construction is a bit more conventional than the balloon-form
monolithic domes, but is still a monolithic pour using a custom
dome form with conventional aluminum wall forms.  Cost, including
backfill, etc. appears to be about the same as conventional frame
construction.  Not that the shell is substantially more expensive,
but the interior is much less expensive.

> 	--  The ability of contractors to handle this type of

Not very many...  Took me months to find one - in a nearby city.
 
-- 
Kent Polk: Southwest Research Institute (will disavow any knowledge of me)
Internet : [email-masked]
(DoF #)  : Official DoF Squid Motto: "Ride Hard/Crash Gently"