New construction

I am a beginner when it comes to High Thermal Mass and passive energy building in general. I am in the design stage of a 600 sq ft home in southern Arizona and I have been reading www.thenaturalhome.com. I am very confused. It says not to use any cover of the interior block walls because it will interfere with the HTM but it is okay to use any standard flooring over the cement slab which will not interfere with HTM. I am worried about building an oven for a house since cooling will be a greater issue than heating. I am also concerned with my choice of roofing which is a product called Ondura. It is made from 60% recycled asphalt and has a lifetime warranty. I used it on my current home and love the stuff. My concern is that I want to use rainwater collection and though I have called the company and been advised that it is used in this way, I am not convinced that it is safe for converting (through filtration) to potable water. My home will have a rear wall facing south that will be an enclosed patio which I want to be my doggy den. I will use an ample overhang of 6 ft to shade the glass at that end of the home if that is not too much, and that 30 ft side of the house will be open floor plan leading to the front door at the other end. The front door will be within a small atrium with an outer door. My hope is that I can create a funnel effect to help with cooling. Please teach me.

This page looks at a study that shows that asphalt roofing was actually a fine choice for rainwater harvesting.

As far as cooling the house, consider putting in a cold air pipe.



From the page: "The cool air pipe needs to be buried at least 1 meter, and should be 15-20 meters long. The pipe should be laid at an angle that slopes away from the dwelling to allow for the condensation that develops to drain away from the house. The Outlets of the pipe should be covered with screen to keep animals out."

I've seen these installed in earthships and do great job of supplying 55º-65ºF air even in the hottest of climates.

Wow! Thank you. The cooling tube is so simple!

Kat Green : With a deep overhang the noon summer sun will be too high in the sky to shine into and heat up your house by striking the internal Thermal mass.

depending on how you site your house on your lot you may be able to get direct sunlight into your house Ether in the morning or evening when it is low on
the horizon, and should enjoy lots of solar gain during the winter months when the sun is low on the horizon all day !

The use if a Black or Solar chimney will create its own draft, venting hot air out through its top and pulling in cooler air via the cold air pipe ! It really can be
that simple!

At your location a simple water catchment system that diverts the 1st few gallons away from your catchment tanks until the roof has been washed of is a good
idea , after filtering, direct sunlight can raise water Temps above150 degrees F, at hat temp water sterilization is accomplished by the suns UV rays !

Good luck, For the good of the crafts ! Big AL

Thank you for your advice Allen.

Should the water be stored in black poly tanks to reach that temp? Or do I need to run it through a smaller tank first? How large is the diameter of the cooling pipe and what type of material. PVC, black pipe, galvanized or ? I was planning on a solar chimney but I have not heard of a black chimney.

Do you think that I could go with a 4" slab over rock on the floor and just sealing up the walls or should the walls be cement? I have the steel frame from a 20x30 carport that I thought I could use for the skeleton of the house. The damaged metal has already been reused elsewhere. I thought about using the Ondura as siding horizontally at least partially with the lower couple of feet in cement and mortar . It would be fairly easy to make air tight. I would also insulate an apron around the house with rock, straw, and black plastic. Do you think that would be enough or should I use dry stack cement block filled and plastered? Next question would be what insulation and how much for walls (none I guess with the cement walls) and the ceiling? Weight of materials is a consideration as most of the project will be DIY by me alone. So, the Ondura would be easier on me. I have had previous experience with stick building a guest house and some outbuildings and many small renovation projects but I am feeling my years. I love building but this will probably be the "final frontier." But those who cant build can still design!

Oh! One more (for the moment). If I use the steel frame from my old garage/carport, is it legal (i.e. Universal Code is all that is required for electric and septic) to surface mount with those covers if I use cement blocks for the walls? Or can romex be run through the hollow steel? Keep in mind that this is a high lightning storm area but it will be well grounded with rebar from the foundation running through the steel and bolted on.

Thank you ahead. It is so reassuring to have someone to advise me.

Kat Geen : I will only try to help with a few more pieces of the puzzle. I like the Idea of re-useing the frame from a carport! But, thinking on it,
it only had to be designed to withstand wind loading !

When ever possible you should catch and store (and filter) as much of your water as close to the roof line as possible, this lets gravity work for you
with a very low structure the distance from your tank to your sink is not going to be much and you will be working with a very slow flow, small
volume, this will actually help your sanitizing your water, think of a clear plastic tank painted black only on the side facing inside the house catching
sun most of the day filled once or twice a day, you read a thermometer then at 150*F you start a simple timer, as soon as your timer 'Dings'
then you can have instant hot water exactly like you had a tankless water heater mounted right there at your wash station/prep sink !

Outside of that portion of your water that you have immediate control over like in your instant drain down system, I would try to keep my water as
cool as possible we don't want to create a perfect medium for growing nasty bacteria!

Non potable water ,like for watering your garden or washing clothes, can be stored in separate containers than the stream of water you hope to keep
potable!

Solar chimney / black chimney are two different names for the same thing. I was going to warn you than as you go further north this system has
problems but not at your location !

I believe you have a requirement in your location for above grade slabs, once you get past the dilemma of trying to be green and use concrete it
comes down to the parts you feel comfortable with !

I am not going to attempt to speak on what is or is not code in your area except that much of what a code enforcement officer looks for is the use
of Correct terminology on the application ! Good Luck Big AL !

I wont have a problem with wind and the carport because I bought the heavy duty version with 2 1/2 inch steel square tubing. The only problem was when it was reinstalled after moving it by some irresponsible hired men and that was due to not using enuf screws or reusing the same holes. So, now all of the original holes make a sieve out of the metal and it partially blew off and twisted. I lived in a high wind area then.

The rain is mostly during the monsoon season and it may be as much as 12 inches in one month, so, water will have to be collected in a large container in a hurry but it could be white and near the house with a black side. It will just take longer to sanitize so it sounds like that would still work in theory. Considering that, I think I had better have a separate water heater. For the water heating, I have a crazy idea of burying copper pipe in a compost pile and running it to an enclosed 55 gallon metal drum to keep it warming. I might not need anything more than the sun but it would be interesting to try. Someone else has probably tried it. I could then answer someone asking why I have a horse when I don't ride. I can say that she is the water heater as well as the weedeater! The reality is that I have broken enuf bones and had enuf stitches to understand the horse's opinion on the matter of riding and my horse and I are now on the same page.

In my county of Cochise, Arizona I can use the owner builder opt-out with the building dept. and then only have to comply with septic and electric. That will be my choice.

My thought at the moment is to have a foundation using a trench filled with rock and rebar with a reduced amount of dry cement mixed in and water added, then two feet of cinderblock with the rebar extending up to the top, then the steel frame bolted onto the top course of the cinderblock using hooks that catch the top horizontal rebar and are threaded on the other end that will go through the steel frame and be secured with nuts at the top. The cinderblock will be dry stacked and filled with cement in the rebar spaces and sand in the other spaces and covered with surface bonding cement. In the surface cement, I will set some random brick facing that I have had in storage for years to give it an old world look. Above the cinderblock, I will add quilted foil covered with osb. This will leave an air gap provided by the steel frame on the inside which can be covered with drywall to create the inside walls. On the outside, I will stack rice hull filled earthbags against the osb using barbed wire as needed and supported by the cinderblock and then side it with Ondura. Ondura is 4x6.5 sheets that are corrugated. I will run these horizontally and try to make them look like skinny logs with paint perhaps. To the steel rafters on the roof, I will have to add height to allow room for the earthbag insulation there. I can think of only wood unless someone has another idea. Ondura roofing on top, earthbags, supported by osb which will be attatched to the steel rafters with self-drilling screws and then quilted foil, air gap and finally the ceiling. For the ceiling, I hope that I can use some recycled corrugated metal for a rustic look. For the floor, I am thinking a 4 inch layer of small rock (peagravel?) and then a 4 inch cement slab that will be finished with a plastic "make your own pavers" tool pressed into the partially set cement and cement stain to color. The floor will be on grade and supported by the first course of cinderblock foundation.

All the gaps in the corrugated ends of the Ondura will be filled with expanding foam and the corners will be covered with trim which could be plastic composite wood material. All windows will be double glazed using recycled windows and a sliding door that I have collected. I have also collected a deep soapstone sink for the kitchen and recycled kitchen cabinets, Spanish accent tiles and an second hand replica antique electric range. Perhaps a zinc facing for a countertop with a couple layers of osb underneath.

I know that it is not all green but I will come as close as possible. criticism and suggestions are gratefully accepted!

Kat you've got some interesting ideas going and dont want to hold back your innovative and creative process but youve got many areas of concern. It sounds like your project will not be very energy efficient and that your OSB could be at risk of rotting. Are those wall details from your book? Have you sought out the help of any local design professionals? There is plenty of room for collaboration and you could end up with some very reasonable design assistance if you look in the right places.

Just did a quick scan of the website you mentioned. Lots of good info but lots of questionable stuff too. There seems to be a noticeable slant towards products for sale.

Brian, Can you suggest a fix for the osb? It is enclosed within the wall system and not exposed to air or moisture. What book? I cant afford a design pro. Since I am using earthbags, dbl windows, adding thermal mass with the floor, I will be using a cold air pipe, and solar gain from southern exposed glass, where am I falling short on energy efficiency? Please explain.

Full disclosure, Iam a "conventional" builder and not very familiar with your climate, planned details or building site. Energy efficiency is a big world of many options and systems. In terms of new construction, there is no better use of resources than creating the building envelope. It has the biggest impact on heating and cooling, will be relatively permanent and expensive or troublesome to improve once built.

Most evaluate building envelopes on how airtight they are (ACH50 as measured by a blower door), insulation and fenestration. The only detail you mention that effects these "big 3" is the passive solar aspects which falls into the fenestration category. As al pointed out, big overhangs and passive solar generally dont go well together. There are many excellent threads here on passive solar design. Its one of the cheapest and easiest things you can do to help with heating for new construction.

More important than passive solar, is how airtight your home will be. The OSB could be a good part of the system with taped seams but "foil bubble wrap" is almost a scam product with few good uses in most building envelope. OSB between masonry and this vapor barrier will not allow it to dry despite it not really being exposed to air or moisture. Indoor humidity could condense on it in cold weather.

Thermal mass TM concrete floors are my favorite form of TM as they can make a beautiful, durable floor and its a common construction detail. I dont think there is much benefit to adding TM outside of a concrete floor. There are many building envelope details more important for performance like how much thermal bridging is in your walls, roof and transitions.

The rice hull bags could work especially for your DIY aspects but I dont think they have that great R per inch and they will not stop air movement. You would also need to pay attention to how they wrap the transitions to reduce thermal bridging.

The cold air pipe is probably better called an earth tube. Plenty of threads here on those too. Iam generally not a fan because humid air will condense on the inner walls surfaces and collect dust and pollen which leads to nasty stuff. This happens much more than a typical home's ducts because they are colder being in contact with the ground and a home's ducts has conditioned air flowing through them. The fact that site compared the two is amazing. Earth tubes might be a good fit in your climate and situation just dont ignore the cleaning precautions which I think are a much bigger pain than that website makes it out to be.

Your compost water idea is a good one! I think you will be better off using it is a pre-heater for a heat pump water heater though. I recently completed my compost water heater but its 6' in diameter which I kind of think is a minimum without having to rebuild it every month. Hoping for 6 months of good heat but looking like 4ish at this point. The 100 degree water is already in the low 90s after 1.5 months.

Reading back on my hastily written stuff makes me want to add that thermal mass walls could be fine in your climate but certainly would go with conservative windows sqft oriented to south, and as airtight as possible roof with very high levels of mostly unbroken insulation maybe R50ish minimum? I wonder how many inches of rice hulls that is? Big overhangs are great other than blocking south windows or getting light through other intended windows. I also like to make the distinction that the fresh air considerations of earthtubes and HRV/ERVs hurt energy consumption but are needed for health reasons. How efficient the fresh air system is another bigger energy consideration than extra TM IMO

Hi Brian, The climate at the location VERY rarely goes below freezing in the winter and reaches over 100 for about 15 days of the summer. One month is humid. There is sunshine for over 300 days a year. So, I am more concerned about building an oven than an icebox if I have to choose. I love and believe in insulation and if I remember correctly when I researched fillers for earthbags that the rice hulls sounded good but I will check again. The Ondura product will allow me to achieve a nearly air tight envelope as long as I am diligent in sealing the bottom where it will join the cinderblock and the top where it will join the Ondura roof material and corners and windows and doors of course. I am aware that the earthtubes will need cleaning but they are cheap and easily disconnected if they don't work out. Since there is so much sun, I will need overhangs of at least 2 ft (if my calculations are right) even on the south and still be able to take advantage of the low hanging sun in the winter but that is easily adjusted if need be. Maybe I can eliminate the osb and use stucco wire as a support for the earthbags. I have 2 full rolls of it in my stash that would be enough so it will save some $ too. I guess you advise that I leave out the foil but I wonder if we are talking about the same thing (quilted or non-quilted, comes on 4 ft wide rolls about 100 ft long). The manufacturer claims and R-value of 25 for this application.

Thank you very much for the guidance.

Rice Hull information http://blog.greenhomebuilding.com/2004/12/amazing-rice-hulls.htm

Kat,
You are attempting to mix modalities. Earth bag construction a la Nadir Khalili is a great way to build naturally in hot dry climates such as yours. These are never square. You are attempting a square metal-framed basically post and beam construction that lends itself to infill type insulation. You can still use rice hulls if that is your wish, but you will want to incorporate them into a matrix like cob or attempt to dense pack them into a framed and sheathed wall, but I think in that scenario you would probably be better off with shredded newspaper, blue jeans, rugs etc. I remodeled a cafe in Tucson, so I know the place a bit. It seems like you are surrounded by volcanic activity that has left a variety of prime building materials free for the taking. The owner of the cafe let me stay with him in his beautiful little adobe while I worked for him. Temps were over 100 at 9am, but his little place was still quite comfortable all day long. My point is, insulation is not nearly as important as thermal inertia in a desert climate.

http://earthbagbuilding.files.wordpress.com/2012/01/rice-hull-wall-section.jpg
Very interesting.

Hi Kat,

I like the "concept" I see in the elevation cross section view shared in your previous post. It has some structural and building challenges that indication that this has not been built yet and is only in a "conceptional phase." I love many of these idea, as I have shared, yet 90% conservatively are just that: "conceptional" and have not be scrutinized by PE and/or Professional Builders to vet the possible short and long term issues.

I would, as a word of encouragement, state that I think you can use the RH the way you plan...whether it is cost effective or the best choice, I can not tell unless a side by side vetting is conducted to determine if this is the most viable for your location or the most cost effective in the long term.

As for the R factor, I find many of these web sites are very "liberal" when conducting cross lateral comparatives in their statistics..R3 may be possible...yet like Brian I would have to see the testing moralities used. I suspect that it is more like 1.8 to 2.5 tops in a real world average.

I do believe a hybrid of timber framing, mass wall, and rice haul would create a wonderful home in your region.

Good Luck

j