Gimme Shelter Construction Workshop

Gimme Shelter Construction gave a very good workshop at the MREA Energy Fair that describes their construction techniques.  Their scheme emphasizes the use of sustainable materials, durability, cost effectiveness, and very good energy efficiency. 

 

The material below consists of a scan of the workshop handout, and some notes that I took.

 

More material can be found at their website ( www.GimmeShelterOnline.com ).
 

Scan of the Workshop Handout:

Presented by: Mark Klein and Jim McKnight

Thanks to Mark and Jim for allowing the use of their workshop material here!

High Performance Construction Specifications

 

 

 

 

 

Foundation:

Exterior 4" drain tile in gravel bed covered with filter cloth at footing level. Interior radon barrier consisting of a
4" flexible pipe grid in gravel bed below slab, vented through a sump or through roof to outside. 2" minimum rigid
insulation under slab, vapor barrier run continuously to connect with wall vapor barrier, caulked and taped at
seams and sump penetrations. Interior basement walls are 2x4 walls set away from exterior walls. Entire 7"
cavity is then filled with sprayed cellulose or blown-in insulation at R-28. Tu-tuff Vapor barrier is continuously
sealed to under slab VB and joist VB. All mechanical penetrations through exterior are taped with 3M sealing
tape or caulked with Tremco Acoustical Sealant.

 

 

Framing:

Floor joists are set back 51/2" on 2x10 treated plates. A 2' flange of VB is laid on plates before joists are set, assuring a continuous VB connection to basement and sidewall VB. Deck is then glued & nailed down
with 1 x1 0 shiplap pine boards; VB is temporarily stapled to deck and 2x6 exterior sidewalls are dropped onto treated plates. This "band cavity" can then be filled with sprayed cellulose or  blown-in fiberglass insulation and sealed as part of the wall insulation and VB package, assuring a higher R-value and a tighter perimeter than in
conventional framing. All penetrations through the band joist are caulked and taped.

 

 

Exterior Walls:

2x6 walls with horizontal strapping create a 7" wall cavity filled with sprayed cellulose or blown-in fiberglass insulation at R-28. Vapor barrier is sealed to band flange and ceiling VB by tape or caulk assuring a continuous seal. Airtight electrical boxes are caulked and taped to VB. 1x10 pine shiplap boards are used as exterior sheathing and as base for exterior treatments. Alternative exterior is to place the strapping on the outside of the wall and use vertical pine or cedar in a single layer as both sheathing and siding (either in a board & batten or vertical T&G application). Double masonry walls, straw bale construction and cobb (clay/straw) construction are
other sidewall choices.

 

 

Roof System:

Truss or rafter framing incorporates a 12" miniumum energy heel which allows for the full amount of insulation at perimeter. Blown cellulose at a minimum of 15" for R-60 ceiling insulation. Continuous VB tied to wall VB, all penetrations sealed with caulk and tape. IC airtight ceiling cans sealed to VB when set, prior to insulation (observe code clearances). Galvanized standing-seam metal roof recommended for long term performance.

 

Windows & Doors:

Low-E, argon-filled, triple pane glazing with "warm edge" technology; good U-ratings. Insulated steel or fiberglass exterior is most maintenance-free. Casements & awnings most energy-efficient over time. Swinging exterior doors in general are most efficient over time than sliders.


Exterior Surfaces:

Cement-based stucco; cement siding; natural or stained vertical white pine boards (board & batten); natural or stained cedar fastened with stainless steel nails, galvanized metal; steel lap siding; stone, or brick.
 

Interior Surfaces:

Walls - thincoat plaster finish surface (one or two-step) for higher durability and greater thermal mass; wood paneling; masonry. Floors - tile, concrete, soil cement, or stone for mass and durability. Native hardwoods, cork, or bamboo for wood flooring.


Recommended Systems:

Air-to-air heat exchanger, exhaust only fans with makeup air (controlled ventilation) or breathable walls systems; in-floor radiant heating using high-efficiency (98%) pulse boilers; direct-vent high efficiency water heaters; masonry heaters; fresh air intake for combustible appliances and wood burning masonry heaters; efficient lighting and appliances; renewable electrical systems; central vacuums.

 

 

RESOURCES


Periodicals

Fine Homebuilding - Taunton Press, www.taunton.com .800-477-8727: construction, design Journal
of Light Construction - www.jlconline.com • 800-375-5981: construction, design Home Energy -
www.homeenergy.org • 510-524-5405: construction
Homepower - www.homepower.com .800-707-6585: alternative energy
Solar Today - www.solartoday.org: building analysis, solar
Environmental Building News - www.buildinggreen.com .800-861-0954: analysis, construction
 

Books

A Pattern Language, Christopher Alexander, et aI., Oxford Univ Press: design
Canadian Home Builder Manual- www.buildermanual.com .613-230-3060: construction techniques Patterns
of the Home, Jacobson, et.al., Taunton Press: design
The Solar House: Passive Heating and Cooling, Daniel D. Chiras, Chelsea Green Publishing: design The
Natural House: A Complete Guide to Healthy, Energy-efficient, Environmental Homes,
Daniel D. Chiras, Chelsea Green Publishing: design, green building
The Not So Big House, Sarah Susanka, Taunton Press: design
 

Websites

Midwest Renewable Energy Association - www.the-mrea.org .715-592-6595 Green
Built Home - www.greenbuilthome.org: builders, information
Green Building Alliance - www.wgba.org: builders, information
Wisconsin Focus on Energy - www.focusonenergy.com: information, builders, grants
Wisconsin Focus on Energy - Home Performance -www.focusonenergy.com/page.jsp?pageld=25:
performance testing, consultants, information for existing homes
Energy Center of Wisconsin - www.ecw.org: information
American Solar Energy Society (ASES) - www.ases.org: information
Renew Wisconsin - www.renewwisconsin.org: information
Shelter Supply - www.sheltersupply.com • 800-762-8399: vapor barrier supplies
Masonry Heater Association of North America - www.mha-net.org .802-728-5896: masonry heaters, masons North
American Wetland Engineering - www.nawe-pa.org
Gimme Shelter Construction, Inc. - www.gimmeshelteronline.com: builders, technical specs, masonry heaters

 

 

My Notes From the Workshop:

 

Overall:

They reminded us that the construction technique they use was developed for the Wisconsin climate.  It will likely work well in similar climates, but will not be appropriate for some climates.

 

In designing and building homes, they emphasize:

1) Energy efficient construction

2) Durability -- they aim for a home that will last a 100 years

3) Sustainability in the selection of building materials

4) Achieving the three items above with a minimal cost increase over conventional construction.

Construction details are very important -- doing the details carefully makes a large difference in the finished homes energy efficiency and durability.

 

They have changed from sprayed fiberglass insulation to sprayed cellulose insulation, and feel that this provides better performance, and is more sustainable.  They try to arrange the framing so that all of the insulation can be sprayed at one time to reduce labor costs.  When asked about spray in place foam insulation, they expressed some reservation about shrinkage cracks forming in the insulation over time, and reducing its infiltration resistance.

 

They emphasized time and again the importance of of good sealing.  Their houses are blower door tested, and achieve a 0.1 ACH rating due to careful attention to sealing.  They recommended the Energy Star checklist on sealing a good guide.

 

Foundation:

In the area they build in, about half of the homes will test above the recommended limit for Radon.  So, they put in provisions for controlling Radon in all their homes.  The provisions consist of a 4 inch layer of gravel with a grid of 4 inch perforated drain pipe installed under the slab.  The drain pipe connects to a sump, which can be sealed and exhausted to the outside at roof level to control Radon.  A Radon fan can be used in the vent system if required.  The provisions for controlling Radon cost about $500.

 

They use R10 rigid foam insulation under the slab.  Note that the foam insulation wraps up the edge of the slab to prevent thermal short circuit from the slab out through the footings.  Careful installation and sealing of the vapor barrier is important for moisture and Radon control.

 

They insulate the foundation (basement) walls inside by including 2X4 framing inside the basement walls with

sprayed cellulose insulation.  In their view, this is more cost effective than insulating the outside of the concrete wall with rigid foam, because  most home owners will want finished walls in the basement anyway.

 

Walls:

Two keys to good  wall construction are:

1) have a water barrier (such as Tyvek) that prevents any liquid water (rain) from getting into the wall structure.  This barrier must be carefully detailed to do this job well.  This outer water barrier does allow water vapor to exit the wall, so that any water that does get in the wall cavity can dry out -- i.e. the wall "breathes" to the outside.

2) have a very carefully detailed vapor barrier installed near the inside surface of the wall (inside of the insulation).  All the seams and penetrations must be sealed and taped to prevent interior water vapor from entering the wall cavity, and to reduce heat loss due to air infiltration.  It would be hard to overstate how much emphasis they put on carefully detailing of the vapor barrier.

 

The walls system has some unique features.

The walls are framed with 2X6's on 24 inch centers.  Then, 2 by lumber is installed perpendicular to the 2X6 wall studs on the inside surface of the studs -- i.e. the wall is strapped horizontally with 2 by lumber.  This strapping might be at about 2 ft(?) spacing.  This provides a wall cavity with a depth of 5.5 + 1.5 = 7 inches for insulation.  It also minimizes thermal bridging that would result if the studs were simply made from 2X8's.   This is somewhat similar to the Mooney Wall, and has the same thermal bridging benefits.  You can get an idea how important this elimination of thermal bridging is by using the Whole Wall Calculator

 

The 2X6 wall studs are extended all the way down to an extra wide sill plate that rests on the top of the foundation walls.  The first floor rim joist then rests against the inside surface of the 2X6 wall studs -- see the diagram in the workshop handout.   This allows much better insulation and infiltration control in the rim joist area than does the conventional technique of framing up from the top surface of the rim joist.  Seems like a good idea. 

 

They emphasized the importance of getting a continuous and well sealed vapor barrier in the areas around the first and 2nd floors rim joist area.  They discussed some details for doing this that I did not get down. 

They use shiplap for the sheathing.  This is intended to be a more sustainable sheathing solution than OSB.

 

Sealing around windows and electrical outlets is very important.

 

Roof

The roof uses heeled trusses to provide good attic insulation depth right to the edges.

 

They emphasized the importance of good sealing of vapor barrier penetrations -- particularly "can" lights, which should be "air tight" and rated for direct insulation contact.

 

 

Some Home Power Articles written by the Gimme Shelter Crew:

Gimme Shelter: Solar Hydronic Space Heating, Klein, McKnight, Reser and Shantz

Home Power Magazine, issue 49, Oct/Nov 1995

 

Gimme Shelter, Klein, McKnight, Reser and Shantz

Home Power Magazine, issue 46, April/May 1995

 

You can download these (for a small fee) on the www.HomePower.com website by searching the achieves for the issue number.

Gary

7/1/2006