Welcome

Hello, this is where I post content that I want to share. Most of it is simple information about programming problems I've run into. Hopefully there will be more posts about the house that I'm building on the land that we're buying with a new cooperative we're starting in Bloomington Indiana!

What species of wood should be used for bond beams, lintels, gringo blocks, etc. when building a CEB wall, if I don’t want to treat the wood with chemicals?

It appears no to matter much, but around here (Bloomington, Indiana) the most common rot resistant woods are Black Locust, White Oak and Cedar. I might just wind up using poplar because it is easy to source and cheap. Especially for the wood parts that aren't in direct contact with the CEBs. Not sure if black Locust everywhere that touches the CEBs is overkill ...

Tip seems to think that poplar should be fine, especially if it is coated with pine tar in places it touches the CEBs.

Acceptable Gap Size in Concrete Forms

We had some gaps between boards that were 1/8" that were not a problem, but I would not go much bigger than that. The aggregate is what determines how big an acceptable gap might be. The aggregate we used was typical for a footer, and some of the bigger pieces were maybe an inch in one dimension.

Thermal Bridging in a CEB Dual Wall with Cavity Insulation and Buttresses

Wall systems made of two CEB walls with cavity insulation lead to unusual (to other wall systems) thermal bridging problems.

Say you have two walls made of 4" wide block forming a 12" insulation cavity. CEBs have r-value of 0.25 while insulation have an r-value of 2.7. The total r-value is roughly 34.4 which is great:

0.25*4" + 2.7*12" + 0.25*4" => 34.4

Suppose that every 4 blocks, you place a block lengthwise to add some micro-buttresses which give extra strength to the wall. According to the typical linear r-value method, you would do a weighted average of the two different situations:

12" of insulation: 0.25*4" + 2.7*12" + 0.25*4" => 34.4
4" of insulation: 0.25*12" + 2.7*4" + 0.25*4" => 14.8
weighted average (24" of 12" thick insulation for every 4" of 4" thick insulation):
    (34.4*24" + 14.8*4")/28" => 31.6

This predicts only a small 8.1% decrease in average r-value resulting in 8.8% of additional heat loss. Not bad given the huge amount of extra strength the micro-buttresses add.

Therm

I've modeled this wall system in THERM, and due to the conductivity of the CEB blocks the heat loss is actually much worse. A rough reading of the renderings THERM provides predicts roughly 50% more heat loss with the buttresses than without. This is because heat travels so well through the CEBs. In areas near to the 4" insulation gap, heat will collect over a large area of the CEB wall, funnel into the 4" thermal bridge and then spread out along the outside wall.

In the diagrams below, you can see the top half of the wall which has no buttresses, and the wall section below which does. The color indicates heat flow in BTU/hr*ft^2. High numbers are bad. I've set up the scale of the left diagram so that any white section indicates that the heat loss is more than 20% higher than it would be without the buttresses. This is most of the wall. In the second diagram you can see that large sections of the wall are loosing heat at 2.5x the rate that they would without the buttresses.

Conclusion

Adding buttresses can help with the strength of the wall, but detrimentally effect the insulating value of your cavity.

The Flip Side

On the other hand, CEBs high conductivity makes them great at quickly absorbing and evenly distributing heat throughout the house that is gained through passive solar design. They act as great heat sinks in the winter and cool sinks in the summer.

Here is the THERM model used in the above examples

Note to OSE Microhouse designers: I haven't run this example with your proposed 2" thermal breaks, but I imagine that they will loose heat at least twice as fast as a linear analysis might predict.

Simple, Cheap, Easily Adjustable Domestic Hot Water and Radiant Floor System

Here are the design requirements I used when searching for a home and hot water heating system:

• cheap
• simple
• passable by building department (Indiana code follows IBC)
• low co2/pollutant emissions
• expandable to include, but not require solar collectors
• provide domestic hot water
• provide 100% of backup heat (when the sun isn't shining) via radiant floors for 700 square foot, highly insulated passive solar house

Electricity

There are two primary ways to heat water with electricity. One is with a heating element which is how almost all residential hot water systems work, and the other is with a heat pump. Heat pumps can be 2 - 3 times more efficient, but are more complicated, expensive, and are most efficient when it is hot out - exactly when a solar hot water system would be better. Resistive heat is how most electric hot water heaters work. On this table, this kind of heat is both the most expensive and emits the most co2 out of all options. Though, this comparison doesn't take into account that all other forms of heat require that you vent some of your warm conditioned air to the outside, see Natural Gas below. It also doesn't take into account other issues such as local air quality (with wood), pollution and non-co2 environmental effects such as fraking and mercury rain. On the other hand, it is quite simple to set up a space or baseboard heater, and if you don't need much heat from it, it may be easier to go with that than to put a bunch of thought into a more complex system. Instant electric water heaters are simple to integrate into a simple radiant floor system.

If you don't actually want hot water all the time and you are only installing an automatic hot water system to meet code and don't intend to use it, electric hot water has one of the lowest up front costs, at around $210 (installed) for an instant hot water heater and $250 (installed) for a smallish 40 gallon tank heater. For the tank heater you will need a 50A 240V breaker which is $10 and some 8-3 wire to your box (15' is $30). An instant hot water tank will require a larger breaker and larger wire about $10 more expensive. Depending on the other appliances in your house, this could require a larger panel or service to your house, which could quickly add more cost.

Wood

Purchasing wood costs about the same as gas 2. Obviously, growing your own is also an option. I would be interested to see how much space and how many nutrients are required to grow enough wood to heat a home. I was hoping to be able to use a heat exchanger around the fire to provide hot water when the sun isn't shining, but code requires that we have hot water available at all times, and so this is not an option. They also disallow all forms of DIY water heating ... you must use only UL listed appliances. Even if code isn't an issue, another down side is that we couldn't use it to get hot water in the spring summer and fall without heating the house at the same time. In the summer, a fairly simple solar hot water collector should suffice for hot water, but it gets a little harder in the spring and fall.

Another down side to the wood stove, is up front cost. On craigslist I've found stoves for $300 or so, then at least another $400 for chimney, cap, roof connection, etc. In addition, cheap wood stoves on craigslist tend to be much larger than we need for our house, and very inefficient. We are building in a fairly high density area (30 adults / acre) and with everyone using this kind of heat, air quality would suffer very quickly. Stoves with a gasification step tend to have very low emissions and high efficiency. An efficient stove properly sized for our small house would be $800 instead of $300. Here are some small wood stove options:

• $300 + shipping - http://www.fatscostoves.com/ (unknown if it has a gasifier or is efficient)
• $1000 + shipping - http://www.jotul.com/en-US/wwwjotulus/Main-menu/Products/Wood/Wood-stoves/Jotul-F-602-CB/
• $1100 + shipping - http://www.marinestove.com/sardineinfo.htm

Another option for wood is to build a rocket mass heater. (unless code requires UL listed appliances like it does here) These can be very efficient, low emissions and built by hand using materials that cost less than $100 total. They are quite large, so they should be taken into account when designing a space. It is cheap, but requires you heat your house if you want hot water, which isn't always wanted. This kind of system could wind up being ideal if you have the time and space for one as well as the flexibility to try it out for a year in combination with a solar hot water system and try to balance them out so that your solar collectors heat the water in all of the times that you don't want to start a fire inside. I look forward to experimenting with this type of system.

Solar

A good solar hot water system is either quite expensive - typically starting at $1000 or will require a bit more time researching DIY systems. I think that in the future, I would like to do this research or spend this money, but right now, I have other priorities. This is the reason for the design requirement above of a system which doesn't require, but could easily be altered to take advantage of solar hot water. We are already incorporating passive solar heating ideas into our house, so heating with solar hot water doesn't make much sense. The only time we will need extra heat is when the sun isn't shining.

Propane

Propane is very similar to natural gas. It doesn't require a gas line, which can be helpful. The fuel tends to be 40% more expensive than natural gas and emits 20-30% more CO2 1. One of the other disadvantages of propane is that it is a bit harder to find cheap large used propane water heaters around here.

Natural Gas

In a small house like ours, a typical hot water heater is about the right size to use for heating water for a radiant floor heat system. On a very cold day with no sun, our house will need about 130,000 BTU per day 3. A typical hot water heater is rated for 36,000 BTU per hour or 864,000 BTU per day, which is more than enough to heat our house on a very cold day. It may also be possible to use a very small instant hot water heater. One problem with a natural gas heater is that it requires fresh air to burn and so most furnaces and hot water heaters suck warm inside air past the flame and then vent it outside. Not only do you lose warm inside air, sucking air through the heater causes cold air to be pulled in through cracks near windows and doors, which are already colder than the rest of the house. The vents for a small house tend to be around the same size as the vents for a large one, and so the effect is proportionately greater. That said, some small gas space heaters can be ventless and cheap ($120), but there are too many horror stories for me, especially in a well sealed house. People complain about high carbon monoxide levels, lots of condensation which wind up on the windows and rotting the wood, health problems, etc. There are some gas heaters which are direct vent, which means they suck outside air to burn and then vent the exhaust, but they are more expensive ($400) and of unknown efficiency. This heater could be a good option if there is already a gas line to the house.

Conclusion

We are building two houses this year. In our house we will heat with electric instant hot water through a radiant floor and in the rental, we will use a wood stove. Both will likely use electric hot water tanks (for code, with DIY solar hot water and wood heat exchangers soon to follow).

CEB Press Hydraulic Pressure Switch

Just spent an hour or two looking for low cost pressure switches to use on the CEB Press. I would like to add them as a way to add reliable sensing of end cylinder stopping points. This avoids the need for external sensors to determine when to stop primary and secondary movements. I will still need sensors to know when the primary cylinder should stop growing the compression chamber as well as one to know when the secondary cylinder should stop for a compression stage. However, with just 2 sensors instead of 6, it should be a fair bit simpler to use physical switches instead of the unreliable hall effect sensors.

The sensor I found to use is this one. It is $32 adjustable from 1000-3000 psi and rated for maximum 6000 psi overload.

There is one at the surplus center here, but the one they sent me was used and broken, there is no datasheet that exactly matches what they sell and there are only 3 left in stock which means that they aren't going to be able to be used by many more people. I'd rather find a solution that can be easily replicated.

WX-1B-4200J/WLAU Datasheet

Spent a while looking for the datasheet for Nason's WX-1B-4200J/WLAU. Here it is: pdf, see page 15.

Sound Absorbing Qualities of a CEB Wall

Sound absorption is measured in decibels where the higher the number, the greater a silencing effect the material has. I looked around for the sound absorption numbers on a few materials and found these:

Plastered Straw Bale     | 20 inches            | 59.8 db
CEB Wall                 | 15 inches            | 56 db
CEB Wall                 | 10 inches            | 56 db
CEB Wall                 | 16 inches            | 45 db
Plastered Concrete block | 7 inches             | 53.3 db
Insulated Glass          | 1/2 inch             | 28 db
Glass in General         | 1/8 inch - 7/16 inch | 22 - 35 db
Doors                    | ---                  | 28 - 34 db
Rice Hulls               | ---                  | ???

There are some good more wall and material types along with their ratings on the Sound Transmission Class wikipedia page. For reference, at 50 db, "very loud sounds such as musical instruments or a stereo can be faintly heard; 99% of population not annoyed" and at 60 db, "superior soundproofing; most sounds inaudible".

It seems that with both straw bale and CEB walls will provide significant sound proofing and that the weakest link is likely going to be in the windows and doors.

This is how people who are really picky about sound proofing do it:

Screwing and Nailing Into CEB Blocks

I've been weary of screwing and nailing into CEB blocks for a long time, but have had no good evidence to support my worries. I was pretty surprised by how well they grip the block and am not as worried about hurting them as I used to. I was able to lift the block using two screws which means they were each holding around 15 pounds. I am still a bit weary of attaching anything very heavy like shelves, cabinets or counter tops to them, but I'm thinking that hanging mirrors, pictures, etc should be fine. More experimenting to come. Any experiments you would like me to try?

Apparmor, file locks, MySQL and Innodb

In my syslogs I was getting this:
Oct 10 23:48:51 dwiel-srv kernel: [ 141.664049] type=1503 audit(1349927331.203:107): operation="file_lock" pid=2192 parent=1 profile="/usr/sbin/mysqld" requested_mask="k::" denied_mask="k::" fsuid=113 ouid=113 name="/home/mysql/ibdata1"

It turns out that the problem was that the problem was because in /etc/apparmor.d/usr.sbin.mysqld I had the lines:
/home/mysql/ rw,
/home/mysql/** rw,

instead of the lines:
/home/mysql/ rw,
/home/mysql/** rwk,

Note the k at the end of the second line which enables mysqld to make file locks

Window Building Musing

On the one hand I don't want to deal with the time and complexity of building windows, on the other and, especially on the south wall, I like the idea of being able to build them all our selves and make them fit well ...