Anyone seen/done a double envelope style log home?

[Reb]

I was wondering if any of the LHBANA members have done (or seen) a double envelope style log home. (The passive solar type, with a roof that has a row of windows in the center of it, where the two sides meet at different angles.)

[honestdragon]

I have never heard of that! I also am very intrigued. I hope someone with knowledge about it answers cause I'll be back to check this out. This is what I found though:

http://www.wapa.gov/es/pubs/esb/2000/00Dec/dmea.htm (no pictures though :cry: )

http://enertia.com/archred.htm

Anyone have any ideas on how a butt and pass style can be adapted to take advantage of this type of construction?

Thanks.

[Reb]

What a surprise! Reading that article, I discovered that the inventor of that style of construction lives in Wake Forest, which is about 30 minutes from our place!

I may have to look him up and ask him some questions...

[honestdragon]

Reb...by all means PLEASE find out all you can. That is AWESOME!

Thanks.

[Hillbilly]

Does this butt & pass log home have a roof design like the one your interested in?

http://www.sites.onlinemac.com/alderwood/page4.html

http://pg.photos.yahoo.com/ph/papabare2/album?.dir=1eb6&.src=ph&store=&prodid=&.done=http%3a//pg.photos.yahoo.com/ph/papabare2/my_photos

[The Biss]

I have talked to the owner of the company on occasion and I too have wondered about making a double walled passive solar log house. Enertia originally began as a log cabin company in the early 1970s.

Sometime in the mid 1970s, they build their first passive solar home off Purnell Rd here in Wake Forest. I took my 8 year old out there a few weeks ago to show her how the double wall envelope style of house works.

For those of you in the Raleigh area interested in seeing their prototype house for real, here is a Google map to the house (http://maps.google.com/maps?f=q&hl=en&q=36.007451,-78.52778&om=1).

[Jordan Laube]

Hello All -
I have also considered building butt-and-pass with the Enertia (double envelope) concept...Have been awaiting updates / pictures but no movement on the subject and thought I would pull the subject back into everyone's radar.

For those of you who are not very farmilliar with the concept - I have copy / pasted a quick summary from their web site (below). I hope that someone has some experience with this type of heat regulation - it seems to make sense to me and am interested in learning more from someone who has an unbiased opinion.
J-
-------------------------------------------
In the Enertia® Building System, solid Energy-Engineered(tm) wood walls replace siding, framing, insulation, and paneling. An air flow and access channel, or Envelope, runs around the building, just inside the walls - creating a miniature biosphere. Here solar heated air circulates, pumping and boosting geothermal energy from beneath the house, storing it in the massive wood walls. Thermal inertia causes the house to "float" between the cycles of night and day, and even between the seasons.

Many aspects of the Enertia® House are unusual and innovative - but backed up by science, common-sense, and prototype homes across America. In fact, each aspect listed below increases the energy efficiency of the building. The effect is Synergistic - equal to more than the sum of the parts. The Enertia® House can make more energy than it uses!

SOLID WOOD
In 1981 the National Institute of Standards and Technology constructed six test buildings in Gaithersburg, Maryland and tested them for energy efficiency. Much to their surprise, Building 5, with walls made of solid wood, was the most energy efficient. This was attributed to "thermal inertia," a phenomenon where the solid wood walls stored energy during the day, and released it during the night. Actually the energy efficiency of solid wood is well known in the Scandinavian countries where it is the prevalent method of building. (Its long life is well known too. When interviewed during the 1994 Winter Olympics, a Lillehammer couple casually remarked that their solid wood home had been built in 1406!)

THERMAL INERTIA
There is no logical reason to use a drop of fuel, or a watt of energy, to heat or cool any home or building attached to the Earth. Just below the surface, within reach of the average basement, is an infinite reservoir of heat that never drops below 50 degrees F. The night-day cycle is more than ample to raise that temperature into the comfort zone, with a simple shift in Time. The use of daytime heat at night, and nighttime cool by day, is made possible by Thermal Inertia, and the engineered Lag-in-Time is a property of the thickness and Specific Heat of the solid wood walls.

HEAT PUMP HOUSE
The task of extracting useful heat from the geothermal reserve or outside air is usually relegated to the electric Heat Pump. They have been tacked onto homes by the millions - encouraged, even financed, by the electric utilities. You have seen them - noisy, power-hungry, CFC-filled, life-support machines - hanging off the side of an obviously troubled building.
Our solution, in the Enertia® Building System, is to make the house itself a heat pump, using the natural energy of rising solar-heated air to extract and enhance the pool of geothermal energy just beneath the building's floor. Simple, foolproof, no CFC's, no electric bill (see "Heat Pump House," Popular Science, June 1992, p.42).

Winter day and night

THE ENVELOPE
Just how does a house, or office, or any ground-based structure get turned into a natural energy machine? The secret is an air path, or "Envelope" just inside the structure's solid wood skin. It is a heat path on a sunny Winter day, a continuously recharging convection loop. A heat source, and extra insulation for a cold Winter night. A miniature biosphere, oxygenated by Sunspace plants. A fresh air-to-air exchanger with walls that breathe. A buffer zone to noise, wind, and outside pollution.
It is a ventilation path on the hot Summer day and on the cooler Summer night, when it is open to the atmosphere. It is the dehumidification system when its permeable outer wall is hit by the sun. And always, an access channel to otherwise unreachable parts of the house when it comes time to update, add new wires, cables, pipes, or technology.


"FLOATING"
The Enertia® House works because the walls have the ability to gain, hold, and release heat. They do double-duty as structure and storage. Their thermal mass and thermal lag leads to "Floating," where stored daytime energy cancels out night-time need. Floating can last for days, keeping the house comfortable during periods of little or no sun. Massive houses experience seasonal "Float" as well, and can coast a month or longer when lightweight houses need artificial heating or cooling. Enertia® Houses float right through heat waves and arctic blasts that would endanger occupants of other buildings. ("Floating," Abstract: A Field study of the Effect of Wall Mass on the Heating and Cooling loads of Residential Buildings, Doug Burch, et. al. National Institute of Standards and Technology, 1982)

DELTA T
All architects and engineers work with the Heat Loss Equation. Heat loss equals the temperature difference (Delta T) divided by resistance (the familiar R factor). All modern attempts at energy efficiency have focused on the "R" factor - i.e. more and more insulation into a thicker wall. But reducing Delta T has the same effect - why not look at that? While insulation is necessary to increase "R" factor, Delta T can be reduced by natural means. The Envelope presents an entirely different Delta T to the living space than it would see if the house were single walled. Because of it, the living space never "sees" conditions colder than the geothermal temperature under the house! As the sunshine raises the Envelope temperature in the closed Wintertime loop, Delta T goes to Zero, and "R Value" is meaningless. At this point the Enertia® house is in equilibrium and Heat Loss = 0.

RADIANT HEATING
The ultimate in heating and cooling, radiant walls and floors are inherent in the Enertia® Building System. When your feet are warm, you feel warm all over. It is efficient, dust free, even heat - more healthy and invigorating because the air you breathe is cooler. On the coldest Winter day, the Envelope keeps the North wall warm and you can lean up against it. Try that in a conventional house.

Summer Day and Night

RADIANT COOLING
The same thermal mass that acts as a heat source in winter becomes a heat sink in summer, again enabling an energy-shift- in-time. The envelope is opened to the outside for summer cooling - basement windows for intake, rooftop windows for exhaust. Natural ventilation carries off internal heat captured by the massive walls during the day. The permeable walls allow humidity to migrate towards the outer surface where it is evaporated by the sun. Because of the envelope, the house is wrapped by the cool in-ground climate. (The House that Needs No Fuel, Architectural Designs, August, 1988, p.6)

[grannyk]

Just wondering if any of you have tried to build a home like this?
If so, how has that worked out for you?

[Jordan Laube]

Thought I would bring this thread to the top and see if anybody has any opinions / thoughts. I am very intrigued with the Double-Envelope construction, does anybody know how B&P log construction would translate and if anybody has actually tried it.

The following website describes the science behind the idea (http://www.enertia.com/Science/HowItWorks/tabid/68/Default.aspx)....Look forward to any / all input...
J-

[Klapton]

I'm sure it would work with log construction. You'd just have to build the house, then build the second, BIGGER house outside of it. I'm sure someone is going to do that.

[shawnis]

I remember seeing the model for this in the atrium at the Patent Office a few months ago. It was very cool and impressed everybody who looked at it, but yes, I do believe it would jack up material costs. But, hey, aren't logs supposed to be the cheap part?

Anyway, here's the patent. Looks like it's expired so this is now public domain. Use freely.

http://www.google.com/patents?id=sqQzAAAAEBAJ&dq=sykes+envelope

The claim in that patent mentions "salt-impregnated wood." What does this do?

Click the "Citations" links on that page to get the related patents. They're also expired by now so you can use them with no worries.

Patents and patent publications are a good area to look for information. I suggest you meander through them. It's also very educational!

[kahle]

I worked on a solar envelope house in Standwood, Washington many years ago. It was not done with logs but ordinary framing. They took advantage of having a south facing slope. They buried ground tubes out of the back (north) side of the house for summer cooling and had water barrel storage in the basement. Personally, I think this is a very interesting house design for temperate areas. And it seems take full advantage of passive heating and cooling options. But I don't think it is the best solar design for a log structure. The envelope house (EH) is all about R-values because the inner house is trying to maintain a moderate temperature while the envelop surrounding the house cycles through extreme temperatures. The biggest drawback of the EH is that you have to build two houses. With logs, you can build a much simpler structure that takes advantage of the thermal mass of the logs and you will get almost as much passive solar as you will with the EH for a lot less money and work. Just follow these simple rules. Minimize northern windows. Maximize southern exposure windows. Design your roof line to shade the south side during the summer and maximize sunshine on the windows and log walls in the winter. Extra insulation on the roof (not just code). Use heavy insulated curtains that you can close at night. Deciduous trees (those that loose their leaves in winter) south of your house, coniferous trees north of your house.

[dmencer]

Commercially available kits can be found at

Conestoga Log Cabins and Homes
Lincoln Ave
Lebanon, PA 17046
1.800.914.4606
http://www.conestogaloghome.com/index.asp
http://www.conestogaloghome.com/system_difference.html

[Yuhjn]

Commercially available kits can be found at

Conestoga Log Cabins and Homes



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