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Archive for the ‘Single family’ Category
Thursday, March 5th, 2009
I am looking for sources, info, anything that will help concerning building an energy efficient retirement home, off the grid if possible, east of Dallas, Texas. Prefab companies, plans, books, anything to help me get started.
We have had numerous articles about solar system design, solar system types, how solar works, etc. Many can be read online. And the Backwoods Home Bookstore has two good books on solar systems including one I reviewed in the last issue. Order the back issues on CD if you no longer have these issues.
Thursday, February 19th, 2009
My 1928 stucco frame house has I believe no insulation in the walls. I do have blown insulation in the attic. I’ve done some research on installing expandable foam in the walls so as not to have to remove the interior plaster walls. It’s going to be expensive and the payback is about 6-7 years. Any comments on the foam issue?
Yes, older homes are a real problem to heat, but on any home the most heat loss is usually out the roof and air infiltration. Wall heat losses are far less if you can seal up all the cracks around windows, doors, wall outlets, and anywhere else the wind blows. In other words, I would first put the most money in insulation for the attic and sealing all the cracks. We did tons of computer energy modeling that showed it made sense to install thermal windows in new construction, but the high cost to retrofit them in an existing older home with many other problems was not worth the high cost.
As far as spray in foam insulation, its a great insulator, but if not done right, you can get voids if the mixture is too little, and you can blow off the siding if the mixture is too much. They also have to drill lots of holes around the exterior walls and I am not sure how well those can be patched to look good after.
Saturday, October 25th, 2008
I recently stumbled onto your website. It is very helpful! You have great articles, and therefore, seemed like a person I could send my energy “situation” to for advice. Here it is:
My wife and I live in a large (4500 sq ft), 3-story house in northern Maryland. Our two energy sources are electricity and propane gas for heating. The main shape of the house is square. But from that body it has two “wings”. The first wing is a 2-car garage, with a room above it. The other wing is a large bathroom and walk-in closet.
In the summer the trees that surround the house aid in keeping the entire house relatively cool in the summer. I recently added ceiling fans to the first floor (study and living room), the second floor (3 bedrooms and a movie room) and the third level (the roof was designed with trusses, allowing an arts and craft room). The fans keep the air flowing –and the house cool enough–where air conditioning is not necessary except for days where it is 100š or higher.
The problem is heating the house in the colder months (primarily late November through early March). I have a 1000 gallon propane tank and can go through 250 -300 gallons of propane a month during this time. At roughly $2 a gallon, this amounts to $500 – $600 a month.
Beyond the wings of the house, which are very cold in the winter, the other challenge is that the central part of the house (the 20′ x 20′ living room) has 20′ cathedral ceilings. To cut our heating costs, my wife and I are considering a wood stove for this room, We are also considering buying a tankless instant propane hot water heater.
I’m looking into solar hot water system, but it doesn’t appear to be a viable option, especially given the cost to install it, and the low return on heated water in the winter when we would really need it.
Any further suggestions on cutting down on my heating bills?
Thank you in advance.
You have a very large home and it costs more money heat and cool than a small home, no matter what you do. Your cooling costs are low because the high ceilings allow space for the hotter air to rise, and most likely lots of cracks around windows or open windows to provide good ventilation. I have visited many very high end large homes that the owners just could not afford to heat. Most put up barriers and sealed off all but the main rooms they lived in during the winter. They even had plastic sheeting at all doorways inside you had to push aside to go from one room to another. I could not live like this and feel very strongly that if you cannot afford to heat the home you have, maybe its time to move.
It sounds like you need to either get a wood stove for your large living room, or maybe one of those outside wood boilers that can heat your entire house, assuming you are able to keep it loaded with wood all winter. Just for the record, solar is out of the question for your situation due to the very high cost and high energy demand.
Sunday, September 14th, 2008
I have a 4,000 sq ft Victorian home that built around 1900. I purchased it 2 years ago. It came with aluminum siding and a new roof with a ridge vent. I soon learned that it had no insulation in the attic or walls so contracted blow-in insulation and soffit and proper vents to make the ridge vent function properly. We also replaced 11 of the 43 windows and tightened up most of the drafts. However, my oil bill is still about $3,000 per heating season. I was going to update the hydronic hot water generator after last season but the oil company stuck me with a full tank in April. So here I am spending another 3K on oil.
My dilemma is this, the hot water system consists of a 4 inch supply header (around 60 feet long) with individual feeds to each radiator that go back through another 4 inch return header. I’m sure this is great for getting the same temperature water to all of the radiators but I’m concerned that the modern generators aren’t suited to Header type systems. I have a summer cottage at the shore that has a modern Weil McClain generator and noticed that there is no such header. It works great making all of the radiators quite hot and heats the house very quickly. If I go to a modern High Efficiency gas system, will I have to change the whole piping arrangement ?
I should also point out that I invested about $600 on piping insulation and insulated both supply and return headers as well as the accessible portions of the branches to the radiators in the basement and crawl spaces. I figure most of the energy I’m wasting is heating up this large volume of water in both the generator (probably built in the 40’s -General motors, Delco heat) and headers.
Thanks for your help.
Sounds like you have a real problem.
You first need to decide if you want to stick with oil or switch to gas. I assume your existing oil boiler is very old and past time to replace. Many boilers designed for gas firing can be converted to oil or even use both, but if it is over 20 years old it is time to replace. Your piping headers and piping distribution layout is a function of the heating system design, not the boiler.
You did not say if your system has a pump, but most systems using large headers in residential systems are designed to operate without any pumping, so most likely this is a very old system which did not use pumps. If the radiators are OK, I would scrap the boiler, headers, and replace with new high efficiency boiler, zone valves, and circulating pump. With a pump your piping will be in the 1″ TO 1-1/2″ size range at the boiler, and most likely 1/2 to 3/4″ run-outs from the mains to the radiation. With a pump system, you can have several zone valves and wall thermostats to allow having different temperatures in different rooms to save energy. Finally, decide if oil or gas in your area will be your best long term best choice and go with that fuel type boiler.
Thanks for your input. Here are some more specifics about my system that should clarify things:
Yes, there is a large circulator pump on the return side of the boiler. It apparently forces hot water out and into the main supply header. The supply header runs the length of the house 4 inch most of the way and then 3 inch for the last 15 feet. Then 1 ” and 1 1/2″ branches go to each individual radiator. I have to say, this seems like a good system to evenly distribute the hot water to all of the radiators. And I have to ask, without a header, how is this accomplished ? Do modern systems run like a daisy chain, with each successive radiator downstream from the next ? Doesn’t that make the radiators early in the chain too hot and those at the end too cold ? What I was hoping to hear from you is to be able to just replace my boiler with a new Modern (I have gas service in my house now) gas high efficiency boiler and still use the header system for distribution. Especially since the piping is now freshly insulated. I also can’t replace the run-outs to the radiators with smaller piping because those pipes are mostly buried in the walls. Thanks again for your help.
I was trying to say that most of today’s systems do not require large header piping which saves pipe and insulation costs. For most residential hydronic heating systems, a 1-1/2 to 2″ main piping header is more than large enough to handle any water flow a typical residential circulating pump can handle. You will never see a 4″ main header pipe today unless the facility is a school or large office with much larger boilers and circulating pumps.
I still bet this system was originally designed to operate by gravity flow (heat rises, cold falls) without a pump. Many of these older systems worked this way by using over-sized piping. If this piping is in good condition, the only real problem is the higher heat losses due to the larger pipe surface area and related higher pipe insulation costs. If this piping is in good condition, you can use almost any size pump and boiler without any heat distribution problem. However, if it is old, you better hope you never have a leak as this old piping is almost impossible to repair due to thinning pipe walls or corrosion. Once you try to un-screw a fitting something else will break or leak and it never ends.
Saturday, September 6th, 2008
Having recently bought some land in Missouri that is located out the the sticks and very much at the end of the power grid. I have pretty well deduced that I will need some back up power.
Recently I have discovered the backwoodshome.com website and a number of your articles. As one who is not totally familiar with alternative power like wind and solar, everything I read seems only to confuse me more.
With interest I have read about l-16 industrial batteries for a battery bank in some articles. In an article about adding a solar cell to a truck camper a RV/marine battery is recommended. Since RV/marine batteries are easy to find and will take to repeated charging wouldn’t they be logical choice for a battery bank vice the harder to find L-16?
I have noticed too that with wind power most often suggested is a dc wind generator that requires upwards of 6 or 7 knots of wind to operate. In searching around I have found a source for a AC wind generator that begins operation in the sub 7knot range. AC generators have to best of my knowledge a big advantage over DC generators and that is in size of the cable between the transmission line from the tower to the battery bank. An ac generator can use a standard ac power cord and suffers no loss in current between the tower and batteries.
I have to admit that my understanding of the way a ac generator works is taken from the following website: http://www.tlgwindpower.com/default.htm On the opening page there is a photo of a customer using 9 ac wind generators on his farm in Wisconsin. Although wind power as such is confusing to me I believe that this ac system must be quite good or the farmer who had added to it and bought these generators would not be doing so if they weren’t efficient.
Perhaps you can give some insight into battery banks and DC versus AC generators in a future story. Also the battery bank issue of l-16 versus marine batteries is very confusing to a novice seeking information like myself.
Any information you can provide along these lines would be greatly appreciated.
Lots of questions! Actually you are talking about “L-16” batteries, not “I-16”. When I suggest using an RV/Marine battery, you will find that it is for a small 12-volt DC system that does not have a large load that would fully discharge it each day. These batteries are much heavier duty than a typical car battery, and most have re-combiner caps and do not need to add water. However, they will NOT hold up to a daily deep charge/discharge cycling like a solar powered home or cabin. For these larger loads and system sizes, the lowest cost battery designed for a heavy charge/discharge cycling each day is a 6-volt golf cart battery ( T-105 size). These are less than $100, and can be found at most big box stores during the summer months. They are about the same size as a car battery, but because they are 6-volt, the plates are very thick and very heavy.
For a 12-volt system you will need two 6-volt batteries wired in series, and for larger systems you will need 4, 8, or 12. When you start getting above 8 batteries of any size, its better to switch to a larger amp-hr battery and stay less than 16, as this can cause problems with un-even charging and dis-charging when you have multiple strings of parallel batteries.
I think you are caught up in the AC or DC debate as a marketing ploy. There is no engineering difference in the amount of wind it takes to turn a wind turbine based on AC or DC output voltage. Wind energy is a “cubic” function of the area of the blades, and below around 7 MPH I think you will find most small-scale generators will not provide any real power, although the blades might turn. There are now both AC and DC wind turbines and each has its advantages, but only in wiring and additional equipment that will be required.
A 24 or 48 volt DC output wind turbine is very easy to add to an existing solar-power system, and some models have built-in charge controllers and can be hooked directly to the batteries. Yes, this will require a larger wire size since the voltage is lower, but the ease of wiring is its real advantage. Also, unless you are talking about some huge wind machine on a 150-foot tower, the difference in wire costs would most likely be less than 50 cents per foot for the larger wire caused by using a lower voltage DC model. An AC wind turbine can use a smaller wire size since the voltage is higher, and these are usually designed for grid-connect systems without batteries. There are a few other issues, but you cannot say an AC unit works better than a DC unit having the same size and blade design, and the reverse is also true.
Tuesday, August 26th, 2008
I’ve been working on a solar trailer design similar to yours for a few months now. I really loved finding your article last month. I also plan to generate a surplus of power to help out at a group camp, event or disaster.
Is there a way I can plug the trailer in to supplement my home electrical supply to knock down my electric bill when the trailer is sitting unused at home?
Steve Sonntag MD
Lame Deer, MT
The short answer is yes, the long answer is this may be more trouble than its worth. Your state has had a net metering law since 1999, so it is legal for a homeowner in Montana to sell back to the utility. However, each state has allowed the local utility to set up specific requirements that must be met to ensure the safety of their service people and the quality of the power for the other customers.
Normally, in most states these requirements include filing a form with the local utility that describes the system, the installed hardware, indication that this equipment meets grid-interaction safety requirements (usually listed on nameplate), and the wiring into the electrical system was completed by a licensed electrician who also signs the form. Some states also add the requirement for an exterior dis-connect with a lever handle that can be locked-out by their service people. Again, these requirements vary from state to state, and you can contact your local utility for more information.
However, it does not matter that the source of the power that will be “back-fed” into the utility line is coming from a portable trailer, you will still need to meet most if not all of the states requirements just as if the solar system was mounted on the roof of your home. THey may omit the dis-conect at the meter since you or they could “un-plug” the trailer from the house, but I am betting this will be too complex a decision to make for the non-technical person you will most likely be dealing with and they will still insist on meeting all of their requirements.
Keep in mind that many inverters will meet the requirements for grid-interconnect and can easily be switched manually over to the “sell” mode. However, your trailer will most likely only have an “input” cable to allow charging the batteries from the house or a generator, so your trailer will need a second cable to connect its output to the house and this should NOT be a standard “male” plug with exposed pins since these exposed pins will be HOT at 120 or 240 VAC, depending on the model inverter you install.
If you want to stay “legal” but not go through all the hoops, why not just run a heavy extension chord from your solar trailer into your home and plug in a few appliances like a freezer or other load that closely matches the output of your trailer. This will remove this load from your utility bill, yet keep your trailer wiring from connecting into the other house wiring.
Hope this helps and good luck!
Friday, August 8th, 2008
I am reading through your BHM archives looking for rules of thumb to develop my plans for my last single family home.
I’ve been to look at solar and the formulas they use have more than one ridiculous assumption – i.e. the tax bracket is 40% and that electricity will inflate at an average of 3.8% forever (ours hasn’t here in Georgia) and that the house will increase in value 25% of the total cost of project and the house will appreciate at 6% over the next 30 years ( I’m not wanting to take more of your time, just trying to convince you I am putting in my homework and trying to be functionally literate)
I don’t particularly like the looks of the solar homes I have found on the web.
I am not really willing to take 2 min showers and go with the flushless composting commode.
I do want a cistern, backup propane, plan ready for when solar really becomes almost reasonable, energy efficient refrigerator, non glowplug gas oven. I think I can get our electric use down to around max at any given time under 3500 watts if what is said about concrete walls and roof and proper sizing of HVAC cuts those two elements to a third and oh yea a solar hot water heater.
I haven’t bought the land yet and I am looking for an architect that has experience and references designing and orchestrating the building of low carbon footprint homes ( know anyone in the Atlanta area). I know about southface here in town and leed and earthcraft stickbuilt guidelines (but I don’t want a stickbuilt)
Hope you have time to respond
I am not sure what you want me to say. You have listed several areas that will reduce your energy requirements which is a good first step. The “rule of thumb” finance advice you are finding is a joke and a total waste of time. The last page of my earlier book titled Achieving Energy Independence – One Step at a Time (now out of print) had a solar system sizing chart. You start with the number of solar modules you can afford and then the chart will tell you how much energy the system will produce.
The reason for working backwards is that I spent years making very detailed computer models and engineering analysis on each solar-power system I designed to determine what system size would be required for the given loads. I always was then told by the client after doing all this analysis that they could not afford a system that large. Finally I just asked how much they were willing to spend then I designed the best system I could for their given budget, and at least I know they will consume all the solar power their system will generate without being over-sized!
Keep in mind that if you purchase a quality inverter that is large enough to also handle future loads, you can always install only part of the solar array at first to keep costs down, and add more modules later since these represent the highest cost items in the system. You will use what you generate and rely on the utility grid or a generator to make up any difference until you can enlarge the solar array.