Passive Annual Heat Storage

Hi guys,  my first post...  glad to be aboard.  I am just wondering if anybody here is familiar with the PAHS system coined by the Rocky Mountain Research Centers John Hait and whether it could be incorporated in the Wofati design for even further efficiency.  The web-site can be found at: www.earthshelters.com 

I bought the book and have read it several times.

I tried to work some of those ideas into the wofati design. 

Apparently, there is at least one PAHS house here in missoula.  I wonder where it is and if I could get a tour of it!

Check out: www.thenaturalhouse.com  He simply puts a rigid insulation 'skirt' around the whole structure.  With the help of french drains and plastic to keep everything nice and dry, you are essentially using the soil under your house as a giant thermal mass!  Brilliant!

Hellow Strangeloop. 


We are actually building one that we hope will be done by fall of this year.

Here's the link to our thread if your interested.

http://countryplans.com/smf/index.php?topic=5690.0

If you have any questions I try to answer
peace
jeff

strangeloop wrote:
Check out: www.thenaturalhouse.com  He simply puts a rigid insulation 'skirt' around the whole structure.  With the help of french drains and plastic to keep everything nice and dry, you are essentially using the soil under your house as a giant thermal mass!  Brilliant!

I tried to follow the link, but it went to ... something else.

AArrrgghhh, sorry about that  -  www.thenaturalhome.com  NOT 'house'  He calls them Zero Energy High Thermal Mass Homes,  so googling that will also get you there, but the link should work now.

Speedfunk-  Thanks for the link - I will definitely be following your progress  - I'm sure I will have a few questions also, but for now I want to ask you if you are familiar with the HTM concept - again found at; The Natural Home web-site?  It is a very similar concept to yours ie: dry-stacked blocks, earth-bearmed, passive-solar design.  With a few added features that you may want to consider, ie: round-wood roof system, interior planterbeds, and earth-tubes.

Speedfunk...  One more link you might find worhtwile reviewing is www.zeroenergydesign.com  Especially checkout how he does his roofs with rigid insulation with reflective material on the underside of the roof.

Yeah - that seems like the PAHS stuff.  The house looks earthship-esque.

Strangeloop:  Thanks for the 2 links.  The zero energy one I have not seen before so that's cool.  The natural home website I found maybe 3 or 4 years ago when looking into dry stack and was a very important site for me personally b/c it shows it could be done to heat your whole house on solar .   Although my location is more challenging with a lot of cloud cover during the year.   However this site was a huge help and I applaud him for giving so many drawings .  I also give him a great of credit for his design and implementation!!    It takes people to go out on a limb and push conventional thinking.

There were 3 main influences that I've since come to knowledge of but this house was a great launching off point.  Paul mentioned earthship, no doubt about that one.  The angled glass in the front and the floor plan are both heavily influenced from mike reynolds designs.  The 2nd is PAHS by john hait, his envelope design (mostly) along with the earthtubes.  Rob Roy was the 3rd I believe where the use of drystack as a DIY building system and footer and rear wall designs.   The whole design of his house is a real gift to anyone with codes to contend with.  The house can be easily built in the strictest of code area.  Even the Dry stack could be done away with and use full concrete.  This is important b/c if the world is to change is design strategies we need shelters that use what we have now and is excepted in strict code areas.  He also does consulting I'm sure he be worth the added cost for anyone who needs / wants some help.

There's a few things in the design I don't understand.

* His use of insulation (rigid) on the rear and side walls in addition to the horizontal umbrella/cape/skirting that goes out 20'. This is interesting b/c in design where you are trying to store energy and moderate your internal temp when the sun heats up the house in the summer you want a direct path of dense mass between your home and the surrounding earth.  I believe he was just a bit nervous about a full Passive Annual Heat Storage type house and compromised by adding 2"'s of blue board insulation along rear wall vertically.  I mentioned have to shade in the summer b/c of overheating.  I'd be interested to find out if he removed the rear wall vertical  insulation (would be way to expensive to break insulation cape/skirting/umbrella ,what ever u call it ), would he have less overheating issues?



* The second thing is the requirement of a floor plan to have interior high mass walls.  He makes sound as if they are needed to act as a fins of a radiator, increasing the surface area of the underlying mass.  I'm not sure how much difference it makes but he feels that it makes a lot of difference.   

The earthship and all solar design have one similar issue.  They all try to collect the heat in the living space!  I eventually came to the conclusion that this is a bad idea.  There are Tons of solar houses that have to shed summer sun, heck even I HTM.  Houses with out enough thermal mass and highly insulated is the worse.  So if heat is so valuable we need to use every bit.  When you live in the solar collector there's only so much solar energy you can bear to be in however if you move the solar collectors  out of the house wow neat things start to happen.  Instead of 80 degree's being the max temp the collector can go to, the temps can now approach the temp of a solar oven (200-300 degree's f)  This changes things substantially.  The challenging solar environment ( rainy, cloudy) I live in has led me to this conclusion, others in more moderate area's can probably work with other designs to accomplish their goal

The solar collectors most likely built from single pane glass sheets.  They are pictured in front and to the sides of our house. FYI



This option allows use of other types on energy sources to be used.  For instance if the temps are not what I need it to me, i can turn these external solar collectors into a compost pit to harvest that energy given off during anaerobic decomposition of organic matter ( leaves , twigs, compost, grass).  So instead of just depending on the sun there is a wide variety of natures matter that can be used   flex fuel for the home which means more independence.  This also gives me the advantage to shut the collectors in times of no sun or dead winter where I could lose more then I gain.  Shutting off your main source of light to your house is doable but it some cases a pain.

I hope I'm not beating a dead horse but moving the solar collector from your house also offers much more freedom in floor plans.  I personally (and wife) do not really like the interior layout of earth ship type houses.  No light from rear , the hallway in the front disconnected rooms.  We prefer a much more open house environment that can circulate fresh air to all parts of the house.   I've noticed in Reynolds latest designs he is dividing the front walk way/solar collector from the rear part of the house so I think he's even come to terms with the challenging of overheating the collector.  As you can imagine i bet this makes the house even a bit darker.

sorry for the book..it's just i'm pretty into coming up with better designs.  The passive exterior collector is even my own idea  

Jeff in NY 

speedfunk wrote:
* His use of insulation (rigid) on the rear and side walls. This is interesting b/c in design where you are trying to store energy and moderate your internal temp when the sun heats up the house in the summer you want a direct path of mass between your home and the surrounding earth.  I believe he was just a bit nervous about a full Passive Annual Heat Storage type house and compromised by adding 2"'s of blue board insulation along rear wall vertically.  I mentioned have to shade in the summer b/c of overheating.  I'd be interested to find out if he removed the rear wall vertical  insulation (would be way to expensive to break insulation cape/skirting/umbrella ,what ever u call it ), would he have less overheating issues?

It is pretty well documented that earth is not a good insulator. Especially wet earth. PAHS seems to get around it by not using the earth as an insulator, but as an extended storage mechanism. PAHS only works by keeping that earth dry and insulated on top. If you don't have a large area you can disturb and cover with insulation and plastic, PAHS won't work as well.

Emory Lovins home http://rmi.org/rmi/Amory's+Private+Residence is also a high thermal mass earth bermed home. The media at the link discusses how he avoids the overheating issue. Mostly strategic thermal mass and operable windows.

* The second thing is the requirement of a floor plan to have interior high mass walls.  He makes sound as if they are needed to act as a fins of a radiator, increasing the surface area of the underlying mass.  I'm not sure how much difference it makes but he feels that it makes a lot of difference.   

In his lecture http://sic.conversationsnetwork.org/shows/detail3265.html Emory also mentions using conductive walls to transmit absorbed heat into rooms away from the direct gain rooms. I don't see that being the case in Bruce's HTM design, as he doesn't have any living spaces behind the direct gain rooms. That said concrete is a decent conductor of heat. The direct gain heat is going to sit at the top of the rooms. It seems that the high thermal mass walls would enable some conduction of that heat down.
Also important in his design is the use of those internal walls to hold up the roof beams. If you skip the HTM walls, you'll need to move to Post and Beam as Wells and Oehler do.

Emory also mentions using extra mass in rooms to act as a flywheel to carry through colder times.

They all try to collect the heat in the living space!  I eventually came to the conclusion that this is a bad idea.  There are Tons of solar houses that have to shed summer sun, heck even I HTM.  Houses with out enough thermal mass and highly insulated is the worse.  So if heat is so valuable we need to use every bit.  When you live in the solar collector there's only so much solar energy you can bear to be in however if you move the solar collectors  out of the house wow neat things start to happen. 

I tend to agree, although I have no practical experience mind you. I've become a fan of using AGS and active solar thermal collectors. I'd be happy to get some direct gain, but I'd prefer to have great daylighting (no overheating and no high glare) and let the heat gain be done via water and solar driven pumps.

This option allows use of other types on energy sources to be used.  For instance if the temps are not what I need it to me, i can turn these external solar collectors into a compost pit to harvest that energy given off during anaerobic decomposition of organic matter ( leaves , twigs, compost, grass).  So instead of just depending on the sun there is a wide variety of natures matter that can be used   flex fuel for the home which means more independence.  This also gives me the advantage to shut the collectors in times of no sun or dead winter where I could lose more then I gain.  Shutting off your main source of light to your house is doable but it some cases a pain.

If air is your collection mechanism, I'd be cautious of mixing in a compost. Use the compost, but heat water with it and pipe it into a floor bed.

I hope I'm not beating a dead horse but moving the solar collector from your house also offers much more freedom in floor plans.  I personally (and wife) do not really like the interior layout of earth ship type houses.  No light from rear , the hallway in the front disconnected rooms.  We prefer a much more open house environment that can circulate fresh air to all parts of the house.   I've noticed in Reynolds latest designs he is dividing the front walk way/solar collector from the rear part of the house so I think he's even come to terms with the challenging of overheating the collector.  As you can imagine i bet this makes the house even a bit darker.

I think many authors, Mike Oehler, Malcolm Wells, and Rob Roy would agree with you on the light from many directions point. I know I do. If you are looking for natural circulation of air. Look into using a solar chimney to draw air out of the house without use of fans. David Wright's book has a nice discussion about natural air movement.

Jim

paul wheaton wrote:
I bought the book and have read it several times.

I tried to work some of those ideas into the wofati design. 

Apparently, there is at least one PAHS house here in missoula.  I wonder where it is and if I could get a tour of it!

That would rock Paul.  I'm allready impressed with the kick ass video's you've gotten so far.

Silver wrote:
It is pretty well documented that earth is not a good insulator. Especially wet earth. PAHS seems to get around it by not using the earth as an insulator, but as an extended storage mechanism. PAHS only works by keeping that earth dry and insulated on top. If you don't have a large area you can disturb and cover with insulation and plastic, PAHS won't work as well.

Yeah it's just a cheap thermal energy battery below your house, I love the simplicity of it.  Very true about the needed space for PAHS.  The earth around your home will vary in density but has air in it which slows down the transfer of heat.  You could probably experiment though.  The university of Minnesota ( as cited in john hait pahs) did a test of the same amount of rigid foam ran strait down the basement wall (or just wall) vs running it straight outward and running it horizontally out from the house was more efficient.  It's then pitched slightly b/c you want to drain water of course.

Emory Lovins home http://rmi.org/rmi/Amory's+Private+Residence is also a high thermal mass earth bermed home. The media at the link discusses how he avoids the overheating issue. Mostly strategic thermal mass and operable windows.

Also important in his design is the use of those internal walls to hold up the roof beams. If you skip the HTM walls, you'll need to move to Post and Beam as Wells and Oehler do.

Thanks for more good links to check out, this thread has some great reading thanks all.  All though he uses very HIGH TECH type devices.  1/2 million for his house...wow.. i'm trying to keep ours under 50g.  Certainly Lovins has done alot in helping advance smart ways of being efficient.

Good point about the interior walls being load bearing.  We elected to use post and beam all though I've seen others use trusses also

. I've become a fan of using AGS and active solar thermal collectors. I'd be happy to get some direct gain, but I'd prefer to have great daylighting (no overheating and no high glare) and let the heat gain be done via water and solar driven pumps.

The one thing you have to give John Hait is his attempt to have the house run it's self.  It looks cool to have all these pumps and gadgets to run things but it costs more money, will require more maintenance, and have a higher chance of failure, also takes up more space.  All though solar driven pumps are a smart use of the sun.

The external collectors I refer to will have absolutely no mechanical items in them.  The one thing that I'm thinking of (will do really just need to figure out details of design) is run pvc or some time of rigid 4" tubing between the collectors and around the house.  I believe this to be necessary to increase the surface area of the insulated solar collectors.  Rather then just the earth in direct contact with the sun I could increase this to the surface area of all the pipe run in the ground!

So the heat collectors heat up, the hot air goes down into the tubes which are set under the insulation umbrella/cape/skirting.  After a year or so I will have to analyse how things are working.  If I feel that I need to moderate the heat collectors temp I can add water in some containers, so that the suns energy would be stored in the water and released at a slower pace allowing the earth to be able to absorb it during the night. 

If air is your collection mechanism, I'd be cautious of mixing in a compost. Use the compost, but heat water with it and pipe it into a floor bed.
I think many authors, Mike Oehler, Malcolm Wells, and Rob Roy would agree with you on the light from many directions point. I know I do. If you are looking for natural circulation of air. Look into using a solar chimney to draw air out of the house without use of fans. David Wright's book has a nice discussion about natural air movement.

The insulated boxes do not actually vent anywhere , they are self contained.  The above solar collectors with the poly tubing and compost would be used to pre-heat water for showers etc (just trying to figure out how to get a warm MORNING shower with no sun all night).  Air going into the house will be done through separate earth tubes.  So there would be no risk of making your self sick. 

Jeff

I saw your blog. It was enjoyable to read. You are way ahead of me.

I thought reflective barrier insulation needed an air gap. You are talking about putting it in the ground Do I have the wrong information?

Where did you learn to do drystack block? The only thing I've found so far is a youtube video advertisng a book/dvd

Silver:  The insulation I'm pretty sure I'm using is called tekfoil.  It's a bubble's of air sandwiched in between two tough layers of Plastic?  So it's both a water barrier and a thermal barrier.  There is stuff that has a radient barrier (foil faced) meant to be exposed to reflect.  This material I'm going to use is the same stuff the use under poured concrete slabs.

I learned most of it from stacking lego's as a kid.  Seriously it's not that deep.  Very DIY friendly vs mortaring each joint.  We then filled the bond beam and every 4 or 5 vertical cores with rebar and concrete. 

Jim Argeropoulos wrote:
I thought reflective barrier insulation needed an air gap...

radiant barrier will heat up so in roof/walls it is recommended to have an air gap but, I don't think it's required.

Reflective insulation only works because at least one side is facing air. If it is in contact with any material, it will conduct heat and radiative resistance will not be a factor.

Glenn Herbert wrote:Reflective insulation only works because at least one side is facing air. If it is in contact with any material, it will conduct heat and radiative resistance will not be a factor.

It also depends on the material.
Some radiant barrier materials don't heat up and therefore would not need an air gap. At least according to http://www.zeroenergydesign.com/.
I also don't think it is correct to call it reflective insulation. it is a radiant barrier, it blocks radiant heat, it does not necessarily insulate.

Radiant heat transfer happens through air or vacuum, not through solid or liquid materials. So any radiant barrier needs air; it could be incorporated in the inner surfaces of bubble-type material. A radiant barrier is generally reflective to some degree, though the two properties are not identical.

That website looks like it was built around 1979 , but it does have this to say about radiant barriers:
"It IS very important that radiant barriers have at least a 3/4 inch air gap on one side of them (or conductive insulation like Dacron, etc.), to also block conductive heat flow. ...

If dust settles on top of a radiant barrier, it becomes much less effective. Its ability to reflect radiation drops, and its emissivity increases in a negative way that increases undesirable heat flow."

The quote mentions an important factor in radiant insulation, that if it is not vertical (or hermetically sealed), the radiant surface needs to be facing down, or else dust will over time settle on the surface and reduce the insulation value.