passive solar home

ammiannAugust 22, 2013

Has anyone in this group had a passive solar home built? If so, I am open for advice on design and construction.

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good job considering this option. There are a few of us who have solar tempered homes or semi passive. However you would benefit best from a passive solar designer or architect that is also very knowledgable on shell design for the home too. After you collect the heat, you need to be able to store and retain it.

Passive solar takes a lot to achieve and there are some areas where your design is dictated on what is required to be passive. Many people confuse the two and assume "passive solar" means just having good windows but do not understand the ratios of glass to mass to area involved. However solar tempering may be a better option. It bascailly uses the sun's heat to warm spaces during the day, but does not store it and release it over night. These types are typically cheaper to build, still perform decent, but do not feature quite the heat collection. However if you do a super insulated shell, solar tempering will still work quite well.

Post up your location (zone), size of assumed home and some other info and we might be able to help you at. In the mean time, read read read. Do a lot of searching and research on the topic and design so you can not only understand the process, but also the importance of some of the features.

    Bookmark   August 22, 2013 at 12:28PM
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Thank you for your reply. I have been researching for a year and find making a decision very difficult with all the information out there. The house will be near Raleigh, NC, and hopefully I can keep it around 1500 sq. ft. Maybe sun tempered is the route I should go rather than passive solar. I have read the good and bad about polystyrene vs. polyurethane SIPs vs. using 2x4 framing with continuous R10 insulation board. It is hard to know what is best. I talked with a local architect but I didn't connect with him and was told by a family member to consider a design build company instead, but I haven't located one in this area who does passive solar. Right now I am considering purchasing a passive solar plan and having it altered to suit my needs. I was hoping to build something that wouldn't require ductwork if possible.

    Bookmark   August 22, 2013 at 12:57PM
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Hi amimian, Congrats on the good research so far. The amount of info can be overwhelming but research and work in the front end always pays off. I would like to echo lzearc in that the importance of the building envelope (air-sealing and continuous insulation) is just as important if not more important than the passive solar aspect of the design.

Passive solar design can provide 40-90% of your heating for free, abundant daylighting and offers passive survivability during power outages. There are no moving parts or maintenance needs other than occasional window cleaning. Its possible to do this for zero extra upfront costs.

Iam amazed that people dont take advantage of this simple strategy more often and its usually a matter of not having the perfect building site. However, even imperfect lots and sites could have much higher performing designs by knowing the basic fundamentals of passive solar design and sun tempering.

I recommend reading Cost-effective Passive Solar Design over on the Green Building Advisor website. That site provides a fairly unbiased view of many things that will go into building a healthy, energy efficient home and recommend as much reading there as you have time for. Of course GW has some great info in this area as well but I think the content has drastically improved in the past year or two compared to some of the older threads.

Best practice passive solar design is a much easier proposition than the best ways to build a cost effective building envelope. It will really depend on the designer and builder experience and preferences but the main thing is to shoot for the 2012 IECC prescriptive minimums. Hiring an independent energy rater or consultant might be a good fit and have builder recommendations or working with the one you have to create a well built home. Its good to see people coming to GW interested in the bigger picture.

    Bookmark   August 22, 2013 at 2:20PM
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Brian, I highly respect your knowledge on passive solar and have read the Green Building article you referenced above. Will check out the 2012 IECC Prescriptive minimums today. If anyone else contemplating passive solar is reading this, they would do well to read the article about your Springtime cottage.

I am dertermined to build this way; just want to do it as well as possible.

    Bookmark   August 22, 2013 at 3:00PM
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We'll be building a home about 4-5 hours west of you in the foothills of NC and it will be designed for passive solar heating AND the all important (for our area) passive cooling. Lot selection will be your first hurdle as you want to make sure that you can orient the home on as much of an east-west axis as possible. Deciduous trees, extended overhangs and glazing selections will all be very important in addition to other things. Just keep in mind that the sun is higher in the sky during the summer than it is during the winter and design accordingly.

For instance, we will have clerestory windows that will receive winter sun, but will be shaded from the summer sun by a 24" overhang in concert with nearby trees. These will also be operable windows that will give us the heat chimney or stack effect to be able to exhaust the warm air up and out while drawing cooler air from windows on the north facing rear of the house. Those windows will be casements that should allow us to "dial in" based on wind direction.

I'm glad you started the topic and I hope to learn a lot more while we are still in the design phase ourselves. As Brian_Knight said, it's amazing that more people don't take these things into consideration when they have the opportunity to design their new house. Truthfully, as a society I think we are more in tune with countertops and range hoods than we are with that giant, glowing, gaseous orb in the sky.

    Bookmark   August 22, 2013 at 3:06PM
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I think my east facing 1+ acre lot is nearly perfect There are woods on the south and west to the east and north. It slopes slightly to the south and is part of an old hay field. Are you using an architect or altering an existing design? I would love to know more about your passive cooling, whether you are building over a crawl space or a slab, whether using SIPs or not, flooring....anything that might help me. Thank you.

    Bookmark   August 22, 2013 at 3:28PM
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amminann, We're just using a draftsman to draw up our design. The long axis of our house is almost perfectly east/west, which puts our front facade within a few degrees of true south. So we will be minimizing west facing windows and all south/east/west windows will have enough overhang to shade most of the window on June 21 and fully expose them on December 21, which is not perfect but gets you pretty close.

The house will have a full walk out basement and will most likely be ICF (insulated concrete forms). The only solar thermal storage that we might try to incorporate would be along the inside of the north wall, that would receive winter sunlight. We might do some stonework or something similar to try to retain a little heat for the overnight hours, but nothing major.

The south and west woods should really help you assuming they are mostly deciduous. Most of what I've learned I gathered from various web resources and a couple of books. "The Solar House: Passive Heating & Cooling" by Chiras is a great resource. And this article written by none other than a previous poster on this thread is a great primer:

Here is a link that might be useful: Passive Solar Design from GBA

    Bookmark   August 22, 2013 at 3:54PM
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SIPs or ICF makes for a great solar design starting point. Of course you can build it out of more traditional stick framing, but the ease of tightness with these 2 products are a great place to start.

    Bookmark   August 22, 2013 at 4:38PM
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Thank you for all the info. Why did you select the ICFs over other building forms/techniques? Would I need a draftsperson who is familiar with passive solar? Are you using backup heating/cooling of any type? I prefer having a ductless house if possible.

The woods are mostly deciduous and if I site the house as planned, it will be closer to the west trees than the the south. My lot slopes slightly to the south so I need to investigate the feasibility of a walk out basement.

    Bookmark   August 22, 2013 at 4:43PM
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If you have a south facing lot, that would be great to gain solar heating to the main level and a basement level.

I too used ICF for my home. For me its the air tightness, the realatively higher continuous r value of the forms I used (r28 average), no hot or cold spots in the wall, stregth, sound, and 1 continuous product from footing to roof line with no breaks in the sealed, insulated shell at the floor line.

Hiring or bring in someone who is very familiar with your goals would be well worth the investment for you. There are drafters out there that know about it obviously, but having someone vested in the design principals can only benefit you. You have some fairly unique goals (passive design, unique home shape/design to fit the site, high performance shell, and ductless heating/cooling) and your designer/drawing should share those. In your climate, you can easily do a ductless house using highly efficient mini splits, however layout of them will be critical and super insulating your shell will be a must.

    Bookmark   August 22, 2013 at 5:01PM
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Re: SIPs
I have read they are more expensive to build with, especially the polyurethane and there is some controversy over those vs. the polystyrene. After I had made up my mind to go with polyurethane, someone told me this, so now I am more perplexed than ever.
"prefer the EPS (polystyrene) because houses need to breathe in our mixed-humid climate and the EPS is vapor permeable while the closed cell polyurethane insulations are not. Lack of permeability in walls that have vapor drive from one direction in the summer and another in the winter can lead to all kinds of condensation problems. not worried so much about health implications of the EPS because it is completely encapsulated within the walls.

    Bookmark   August 22, 2013 at 5:13PM
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did a EPS SIPs dealer tell you that? ;)
never heard of that before, ever.
Condensation occures when you have a condensing plane (say the OSB) that is either cold or hot on either side with moisture going through it. The very nature of SIPs basically eliminates that, meaning the thickness and air tightness of the panel keeps either exterior osb or interior osb at the same realative temp as its surrounding air temp (interior or exterior).
With iso panels though, you will have vapor drive to the interior, or rather no vapor drive to the exterior due to the low perm of iso. Because of this, you need mechanical ventilation (ERV or whole home dehumidification) typically in high performance homes.

    Bookmark   August 22, 2013 at 6:07PM
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Moisture is always a concern and tight homes are arguably more susceptible to poor construction details.

Top 3 moisture concerns when building a home:

1. Bulk water from leaks in flashing, water barriers and plumbing.

2. Air leaks. Air can carry a lot of water in the form of humidity and will condense on cold surfaces. This can be indoor air going out or oudoor air coming in.

3. Uncontrolled spot or source moisture; Inadequate bath fans and vent hoods.

Vapor permeance of materials did not make my unofficial list as its rarely a problem and simply untrue with the SIPS. Now below grade walls should be impermeable but we are talking about above grade I think. Dr. Joe says beware of moisture reservoir cladding like masonry and fiber cement siding. Its not a problem with the right details.

As to the cost-effectiveness of SIPS, its all in the details. I think that both foams can be competitive to conventional framing with the proper design, planning and execution. ORNL seems to agree although not everyone sees the benefits.

In our area, pre-cast concrete panels reign supreme over ICFs in almost every category. I also tend to think a traditional poured wall or CMU wall can be made as efficient as ICFs for cheaper. There is something to be said about lzearcs ability to achive a continuous R28. How thick does that end up? I think the masonry based systems are harder to make airtight than the wood based systems too. I consider most SIPS a wood based system and carpenters take to them really well. Metal SIPS not so much but they have other advantages.

PHD, 2' sounds a little too deep for proper overhang sizing..

This post was edited by Brian_Knight on Thu, Aug 22, 13 at 20:46

    Bookmark   August 22, 2013 at 8:39PM
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We are in Chatham county, so not that far from you. Our house is made from pre-cast concrete. While our house is not passive solar (it is a Passive House, which is different), it is east/west oriented. We are also in the woods with a south facing slope, so we have a walk out basement.

We used a local architect, but I know there is a least one design build firm in Chatham county that does passive solar.

I have posted these pictures before to show the shading on the equinoxes.

South side, summer equinox

East side, summer equinox

South side, winter equinox

    Bookmark   August 22, 2013 at 10:59PM
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Izerarc, it was an architect who told me that about the SIPs panels. Don't Energy Star houses require mechanical ventilation? dekeoboe, thank you for the photos and information. I contacted one design build firm near you through their website but did not get a reply. My location may be out of their range. Brian, thank you again for your detailed information.

    Bookmark   August 23, 2013 at 5:50AM
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I have read some about the passive house(passivhaus). With a very tight construction, good fresh air delivery and high performance windows, don't currently built Energy Star houses perform like passive houses? It is confusing.

    Bookmark   August 23, 2013 at 6:03AM
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Passivhaus homes run circles around Energy Star. An Energy star home can not even come close, can not even touch a Canadian R-2000 for that matter. Past ES requirements have been a joke in the high performance home scene, not to mention the laughable requirements in IECC. Luckily 2012 is increasing them some. ES simply requires meeting IECC with a few additional minor requirements. Different tiers of ES are better, and ES 3.0 is better yet. That being said, my home is an ES 3.0 home, but only because it was a low hanging fruit for rebates. Most homes in this arena will perform 20-50% better than ES requirements, mine inparticular is approximately 30%, and I would assume something along the lines you would construct would be in that area as well.

Passivhaus is, for lack of better terms, an insane standard to build the home. It has very few requirements, however to achieve those requirements one has to have an super performing home.
The basic requirements are air leakage no more than .6 @ 50 pac. Canadian R-2000 is 1.5, and ES 3.0 is 3. Huge difference.
It has heating and cooling max loads of 4755 btu per sqft/ per year. Cooling is 1.39 kWh. Total power usage is 120 kWh per sqft per year.
It does not place requirements on r values, insulations types and construction methods, however it makes recommendations, such as max u of .14 on glazing. However in order to hit the numbers above, typical PH will be r40-60 walls, r100 roofs, and r30-40 below slabs. Many use solar panels to meet the power demands.

While I fully support high performance homes, I think PH is abit over the top, but support a growing trend established at Green Building Advisor called "Pretty Good House".

These are standards placed that hit somewhere between ES 3.0 and PH that are much more obtainable for high performance construction. Super insulation (r40 walls, r60 roof, r20 subslab), air leakage at 2 @ 50 pac, and some other more design and functional related things such as universal design and "green" material selection. It sort of pulls concepts from LEED, PH, and general design common sense.

    Bookmark   August 23, 2013 at 8:51AM
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The differences between Energy Star ES and PassiveHause PH is a great question and contributes to much confusion. Both are third party certifications that will go a long way to contributing to a well-built home. While I agree past versions of ES were a joke, the new version 3 (minimum) aint too bad.

I agree that PH usually outperforms ES. However, ES and the accompanied HERS rating allows more flexibility and can ultimately outperform PH. The main difference as I see it is that PH focuses on the building envelope and ES is more holistic and allows solar panels and mechanical systems to contribute to its performance rating.

There are great arguments for both sides. When you increase airtightness and insulation to a certain point, cost effectiveness can drop. Many point that PH goes too far, mainly in the R value recommendations needed under slab. Its arguably more cost effective to use solar panels to offset energy use rather than spending so much on insulation.

PH points out that mechanical systems have short lifespans and will eventually need to be changed. The building envelope is the longest lasting feature of a home and the hardest to correct and improve once built. Building envelopes usually have zero maintenance and is the biggest variable when evaluating a comfortable, durable and energy efficient home.

Those interested should familiarize themselves with the HERS rating which is an energy use point system with 0 representing a Net-zero home and 100 representing a code built home. PassiveHaus (without solar panels) will generally be about a 10 which is pretty amazing because most ES homes will need a lot of solar panels to get there.

The bare minimum Energy star V3 should get a HERS of about 65. Usually ES homes use more solar panels to get a better HERS rating. I think that the most cost effective level of insulation and air sealing is in between this typical ES bare minimum and PH requirements. Where will depend on many variables. Cost effectiveness is often in the eye of the beholder. Raters, builders and designers will have different views which may be based on experience or perception.

Both certifications rely on modeling software and it seems like those that have worked with both may prefer the PH when it comes to the building envelope but the software associated with HERS can be used to evaluate more criteria. Its important to note that in this world of high performance building, individual results (occupant behavior) will vary and can throw off the modeling in a big way (as can poor data entry). Its best to take the literal HERS numbers and PH spreadsheets with a few grains of salt and be aware of the daily habits which can influence performance.

I tend to favor HERS and net-zero homes because I see solar panels as a big benefit to society and communities as a whole. Photovoltaic arrays PV (solar panels) contribute energy to the grid during peak demand hours which reduces the demand to build new power plants and helps lower surrounding home's energy and environmental footprints and lowers the chance of power outages due to peak demand.

I do think that PH can be done cost effectively and could result in the smallest possible PV system to achieve net-zero energy and beyond.

    Bookmark   August 23, 2013 at 10:53AM
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Thanks for all that info...a lot to digest. Another question. I think I want to build over a crawl space rather than on a slab. Any opinions or advice on that?

    Bookmark   August 24, 2013 at 8:48AM
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Why would you want to build a cave below your home?

    Bookmark   August 24, 2013 at 9:22AM
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Why would you want to build a cave below your home?

    Bookmark   August 24, 2013 at 9:56AM
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ammiann ... In North Carolina, you should also be concerned about the summers.

Make sure the design has some good ventilation features: some way to take advantage of days when you want to cool the house and it's nice outside. High windows (clerestory or 2nd floor) and low windows you can open to get air flowing up and out do a good job.

You will need some sort of active ventilation because energy efficient means tightly sealed and stale air. Those heat-transfer ventilators that bring in outside air and exhaust inside air.

And for NC, maybe a dehumidifier.

There's a fine line between building an energy-efficient house and building one that's ridiculously expensive just to get a few % more in savings.

The "pretty good house" ideal, if followed everywhere, would do more than having only those who can afford the PassivHause style builds.

    Bookmark   August 24, 2013 at 9:57AM
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Why would you want to build a cave below your home?

    Bookmark   August 24, 2013 at 10:01AM
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Annie Deighnaugh

Interesting discussion. I always said our house was passive solar, but I realize now it is is solar tempered. We built into a southern facing slope so the main floor has 3 windows on the north side and south side and finished basement (underground on the north side) has lots of windows. We gain about 4 degrees in temp on a sunny winter day. The lower level is not heated or cooled and maintains a temp of between 63 and 78 degrees year round.

I was in a solar house that was designed a long time ago and it was pretty awful...they had this huge glass room (impossible to clean the glass) and rooms open to it around the was way too hot and uncomfortable yet it became the main focus of the house. So I decided I didn't want to live "in a furnace".

We also went with geothermal heating/cooling and 5 kw active solar panels to support the geothermal unit. We went with closed cell insulation.

Front, north facing facade (upstairs dormers are just unconditioned attic space):

South side with walk out "terrace level":

We also did things like locate the deck in the south east corner where it captures the morning light and is protected from the prevailing NW winds so we get many months use out of it.

    Bookmark   August 24, 2013 at 10:28AM
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Ok, Brian, I get your point. So slab is your suggestion? Annie, it looks like you took a lot of things into consideration. Did you utilize flooring for your solar gain?

    Bookmark   August 24, 2013 at 12:44PM
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Annie Deighnaugh

ammiann, no we didn't use the flooring...only the southern facing slope and the amount of glass on the south side...which also worked well from the inside as, being a "basement level" but not wanting it to feel like a basement, the greater window to wall ratio helps a does the 9' finished ceiling height on the lower level. For example, my exercise room does not feel like a basement.

Note the tray ceiling...the near side of the ceiling is actually where the heating duct is, but rather than have a bump that everyone sees as a heat duct, architect turned the ceiling into a tray which camouflages it beautifully. Further, having all the duct work in conditioned space is more energy efficient.

The guest room is also in the "basement".

    Bookmark   August 24, 2013 at 2:37PM
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Annie, I like how you handled your basement. Does anyone have an opinion on ENERGY STAR certified ductless heating and cooling systems? The architect I talked with this week is not familiar with them, suggested radiant floor heat, and said that the one time she used SIPs it caused a condensation problem that affected the woodwork. I don't think I will be comfortable with her.

    Bookmark   August 24, 2013 at 9:20PM
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Annie Deighnaugh

We did spend some time working with a fellow from a green design architectural firm who was a materials expert. He was not a fan of SIPS panels...I can't quite remember why, but I remember part of it was what they did during a fire....

We looked into radiant floor heat, but had concerns with how that would limit floor finishes. We definitely wanted luxury vinyl plank flooring and had concerns that the heat would dry out the glue. We didn't think it made sense to put down in the bedrooms where we knew we wanted carpeting for the softness. We were also in another house that had radiant heat in the floor under "hardwood" which may be fine with the hardwood of yesteryear, but today's "hardwood" is often not dried enough, thick enough or whatever and it tends to shrink and cup. With the added heat under the floor, it wasn't pretty. We have electric radiant under our bathroom tile which is a real pleasure in the winter though. But we definitely didn't want the hardness of tile or stone flooring throughout the house.

We did have to drag our architect and builder "kicking and screaming" into going the builder asking us where the compressor was going for the a/c! But eventually they came around and took our house as a learning experience...but it meant I had to do a lot of the learning and research to get what I wanted.

It is essential to get a fresh air exchange system in a tight and green house to keep the air fresh and to deal with any excess moisture. Code requires bathrooms to be vented anyway, so our system exhausts air from the bathrooms and replaces it with fresh air through the plenum so it spreads throughout the house. It can change the air in the house in as little as 3 hrs. I don't run it when it's very cold outside though as I don't want the unit to freeze...I wait til it's above freezing in the winter.

    Bookmark   August 24, 2013 at 11:45PM
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Does anyone have an opinion on ENERGY STAR certified ductless heating and cooling systems? They are widely used in Europe, especially for retrofitting housing that has no ductwork. It would be a definite advantage if the use of the rooms is erratic - each unit has its own t-stat.

Also, raising or lowering temp in the rooms would not screw up the air balance like it does in a forced-air system.

Those, and some sort of in-floor heat under the bathroom tiles, would probably be all you need.

No ducts - less sound transmission between rooms, quieter house

I don't know how the cost compares to the standard installations, because we reused the existing ducts for my new HVAC. However, the contractor does quite a lot of the ductless because he retrofits old adobes.

said that the one time she used SIPs it caused a condensation problem that affected the woodwork ... you have to pay very careful attention to sealing the home and using good air exchange and dehumidification practices with SIPs, AAC, or CFCs ... you can't assume there will be air infiltration to cover your lack of venting.

    Bookmark   August 25, 2013 at 9:03AM
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Thanks to everyone for answering my questions/concerns. Time to move forward and make some decisions. I know that things won't be perfect, but nothing is in life.

    Bookmark   August 25, 2013 at 9:50AM
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ductless systems in tight homes:
while ductless systems, such as mini splits, can work great in a tight, super insulated home, you still need to control air exchanges. Many homes like this still install a small ducted (4" or 6" hard piped) duct system connected to the ERV or HRV. The ductwork is obviously much smaller and can be run through 2x6 walls if going with the 4" version.

my question for you is, what is the strong focus on SIPs for?

    Bookmark   August 26, 2013 at 8:57AM
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I just want to make sure I get the best constructed house that I can for the $$ invested.

    Bookmark   August 26, 2013 at 9:15AM
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I think you could probably get a similar performing structure for less cost than SIPs without the issues SIPs can have. This, of course, depends on pricing in your area for SIPs compared to high efficient construction.

Other types to consider would be:
2x6 framing, ZIP sheathing, 2" exterior foam, blown fiberglass/cellulose, and air tight drywall. R30ish wall (less with framing factor)

Super insulation would be double stud walls, ZIP sheathing (air tight exterior), blown fiberglass/cellulose, air tight drywall. R40+ wall.

Both of the above options should be cheaper than SIPs and come without the possible issues.

ICF wall would most likely cost more than SIPs and the above methods, but might be worth considering in your climate.

    Bookmark   August 26, 2013 at 11:27AM
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Wow, I'm very excited I found this thread. I'm working on building a passive solar home. As of right now, we're still in the design stages but we look forward to getting started quite soon. I would love some opinions on our extreme building methods though! Initially, my wife and I had planned on building a Simple Survival Earthship, which is more or less a bare-bones solar home. But we recently came across some information that should accomplish the same thing, yet be way cheaper and quicker. I would love to hear what this group of experts think!

The concept is a machine-compacted home. The Earthship design used tires as a form to hold dirt, which you would pack tight with a sledgehammer. The end result is a 3-foot thick thermal mass wall. This requires a good deal of tires, time, and chiropractic treatments. Instead, we would use a bullldozer to accomplish the same ends, in a much faster timeline. The walls will be similar to a pond/dam wall. Heavily compacted clay walls, track-rolled with a 3+ ton machine. Instead of months and months of pounding dirt into tires, it can be accomplished in an afternoon. After the walls have been compacted, the backhoe uses it's bucket to cut a straight vertical wall out of the compacted clay. The end result is a 5 foot thick compacted wall. On the interior and exterior of the wall, we would then plaster with a breathable plaster. This should eliminate any moisture issues. The floor of the structure will be a stained concrete. Also, the house will be aligned on an East/West access, facing south, with an attached solar greenhouse. The house's interior will be bisected lengthwise by some form of brick wall. The north side of the house will be devoted to the "cool" rooms (bedroom, bathroom, laundry) whereas the southern rooms will be devoted to the "hot" rooms (kitchen, living room, lounge). Adjacent to the home is going to be a heavily shaded, mulched, misted area which will act as our shade house. This shade house will provide cool air which we plan to draw into the home through cooling tubes (buried three feet down, running roughly sixty feet long, sloping downward into the home). The roof will be composed of metal (still deciding the details) which will be used to collect rainwater, stored in cisterns located amongst the shadehouse. All greywater will be recycled and divided between the greenhouse and the shadehouse plants. Half of the greenhouse will be devoted to relatively hardy tropical plants (bananas, etc.) and the other half will be used to house aquaponics systems. We plan to generate our electricity via solar panels.

Question Time! The home itself is going to be bermed into a hill. Should I be concerned about below-ground water flows? Or should my compacted earth wall be sufficient? I haven't decided upon the materials of the central wall running the length of the home yet. It will most likely be a structural wall which will assist in holding up the roof. Should I go with cheap, concrete blocks filled with cement, and then cover with a brick veneer? Any other suggestions for a cheap, yet effect thermal mass wall? Any other ideas of how to get an effective, yet nice (pretty, non-crappy) wall. We plan on centralizing all of the plumbing along the west wall, located near the cistern set-up. To bring the plumbing to the outside and to transfer the cool air in, we've decided upon burying pipes into our compacted earth wall. Can anyone foresee any issues with that setup? We hope to move water in and out of the home via gravity. Any estimated costs on such a structure? We figure the actual earthworks will be no more expensive then say $3,000. After that's done we'll need to build the central wall and stick a roof on. From there the plaster will follow. The house will be roughly 1200 Square Feet, with enough overhang to shield the house from the summer sun. It will more or less be my experimental starter home. Any idea of a cost estimate to stick a roof on this thing? After the main structure is built, we will invest in the attached greenhouse followed by the shadehouse.

I would love to hear everyone's opinions on such a structure. Has anyone heard of such a home being constructed? In theory it should work no different then an Earthship or passive solar home. Yet there is virtually no material out there using this kind of technique. I'm trying my best to foresee any possible traumas. If all goes well what we'll have is a "relatively" cheap, fireproof, tornado proof, self-sufficient, off-grid home. Although the initial investments will be huge, the long view of the houses expenses will be way minor compared to normal home upkeep costs.

    Bookmark   September 3, 2013 at 8:19PM
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Hi there ALbound, love your enthusiasm. I dont want to discourage any innovation that could lead to better ways of doing things but happy to share my thoughts. You may get a warmer reception at permies, a permaculture site.

The riskiest proposal is your earthbermed wall. AL is home to some fine quality, hard packing red clay but you need some type of impermeable water barrier or you will likely experience some serious moisture issues. The same goes for earth tubes (mold tubes) and greenhouse integration.

If you are planning on using PV, then why not stick with with more modern, scientifically proven methods where folks are routinely achieving homes that all but eliminate the main source of our dwelling's environmental footprints. Thermal mass is not nearly as important as air sealing and insulation levels. As hard as it is for natural focused builders to admit, air sealing and insulation is probably the best thing one can do for the environment (and comfort, energy costs and perhaps durability). The excessive humidity of AL, and that created in air tight homes, is already challenging enough without bringing a greenhouse into the mix.

Building a passive solar home that meets the 2012 IECC is probably the most affordable and proven platform to add a cost-effective amount of PV to and achieve a net-zero energy home. The ASHRAE 62.2 ventilation requirements in that important building code will also give you the best chances of having healthy indoor air quality.

    Bookmark   September 4, 2013 at 12:01AM
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It sounds like you are just interested in a well designed
cost effective house and not necessarily very passive.

Here is a good source of info:

As with everything, the more you research and learn yourself the better off you are.

I would spend money on better products before spending it on ratings. The best rating is always proven low energy costs.

The strategy is fairly simple:
tight -minimize leaks

continues boundary layer -uniform insulation to the recommended level for your area

simple - minimize surface area in relation to interior volume

windows -minimize heat gain in warm weather, use deciduous trees, design them for your actual use. -I have many clients that almost never open their windows and so cross ventilation effectiveness would not be an actual factor for them.

My personal experience here in Texas is that the temperature is either cool enough to open windows or it is not and there are very few days where more effective ventilation would make the difference.

High efficiency HVAC with straight duct runs which are within the insulated boundary layer.

Short runs to the hot water heater.

Many of the modern ranch style houses built in the 60's and 70's where actually pretty good.


    Bookmark   September 4, 2013 at 11:27AM
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Well, it is now 7 months later and I have just talked with a design/build architect. In our conversation, she said I would need either a loft and/or sunroom. She also warned me about how hard concrete floors are on joints. Brian Knight, your Springtime home doesn't utilize a loft or sunroom, but works well from what I have read. Any comments? Chris Stewart, everything you spelled out above makes sense, so maybe with my small house, sun tempered would make more sense. The architect is going to present me a proposal based on reworking a passive plan she has already built. After I see that I should be able to make a decision about moving forward with her, but I would like answers to the loft/sunroom issue. Thanks everyone!

    Bookmark   April 12, 2014 at 11:19AM
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Annie Deighnaugh

If you haven't been, I would go to a place that has a sun room...they are terribly uncomfortable and can be very expensive to heat and cool. (They had one at MIL's nursing home that no one ever used.) As I said earlier, they are essentially a "furnace" for the home and so the room itself is only a comfortable place to be a few days of the year. Further you have to deal with the heat loss through the glass once the sun goes down which means motorized shades or some such. So fundamentally you are devoting sq footage to space that is largely unusable, and needs to be managed on a daily basis depending on how much sunshine you have and when the sun goes down.

When we looked into passive solar design, we decided it would have to be a concrete room on the south side of the house with angled glass on top which we would then use to circulate air into to heat it and which could be shut off easily at night, but it was never going to be living space.

We ended up deciding we wanted to keep the space living and beneficial too. We are happy with our 4 degree gain on sunny winter days from our solar tempered design. And, while we can, we don't heat or cool the lower level as it maintains temps between 60 and 78 all year round. Works for us.

    Bookmark   April 14, 2014 at 9:44AM
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