Thursday, May 31, 2012

Getting Closer to smaller living: Stage 1.2 - Insulation and Heat

Insulation...  A lot of Tiny Home people gloss over this, but to make a really efficient tiny home you have to think about it.  If you use typical construction using 2X4 and 2X6 boards.  that gives you the ability to have 3.5" of insulation for outer walls and 5.5" for the roof and floor.    Rigid foam board insulation is the easiest to deal with and the lightest.  And interestingly it also delivers the highest R value per inch.  The higher the R value the better.  The cheap white beaded foam board is about R2.5 to R3 per inch.  so you can stack  two boards in the wall cavity, 1 2" thick and 1 1.5 inch thick to get the wall full,  this will give you and R of 8.75.  Typical homes have a wall R value of 10.  You want higher than that.  So we look at the Blue or Pink board.  This is extruded Polystyrene and it has an R value of 4.5  to 5 giving a 2X4 wall with 3.5 inches of it an R value of 15.75.  Now that is a wonderful insulation value for the wall.   If we want to go further, we can buy the high end foil faced Extruded.  That has an R value of 7 to 8 which delivers a Whopping  R24.5 for that 2X4 wall.     The drawback is that the last two use CFC's in their production which means they will outgass.  so you need to be sure to have a sealed vapor barrier inside the home to stop the CFC outgassing from going into your home.   Now round down to figure losses for you cutting into the insulation to run wires and  using the pink/blue board you can have R15 outer walls, and a R24 ceiling and floor.  This is better insulation than most Mc-Mansions.  What I recommend is using the cheaper Blue or Pink board for the walls and the foil faced for the ceiling and floor.  Yes you can use it everywhere and you will save more on Heating and cooling. but the foil faced stuff is harder to find and is 2 times the price of the pink or blue board.

Figuring on lower numbers,  assuming I cant get 1.5" thick board so I have to only use 3" in the walls and 5" in the ceiling and floor.  R13 wall and R22 ceiling, 1 door and 4 windows.  a typical Micro home will lose about 5000 Btu per hour.   A person at rest puts off 222 Btu per hour, yes you are a heat source, so we can remove that from the 5000 Btu/h number for heating.  So I need to make up 4800Btu/h to maintain the temperature in the home, this is assuming 70 degree inside and 10 degree outside temperature.   So how do we heat the house?  Well a typical 800 watt electric heater will deliver about 2,750Btu/h and a 1500 watt electric will produce about 5,100Btu/h.   You can easily heat a 180 sq foot micro home with a 1500 watt oil filled portable heater.  If you had electrical service then assuming $0.10 per Kwh cost.  running your heater 12 hours a day drawing 1.5Kw means it will cost you $1.80 a day to heat your home when it is 10 degrees out and you are not getting any heat from the sun coming in windows or hitting the house. and remember, the sleeping loft will be warmer than the floor, so night temps can be set lower to save energy.

So my idea of a 12,000Btu/h RV furnace is really overkill, but probably not a bad idea.   Excess capacity means it will run less, and when solar power is considered, I would rather heat from a Propane source than an electric source.

Air conditioning is the opposite,  5000Btu/h heat gain rate from outside and add in the 222btu/h per person in the home and you need to get rid of 5222btu/h.  luckily  tiny AC units are huge.  The smallest one I can find is a 5000btu/h AC unit.   but if you have friends over you can quickly overwhelm it by the additional heat, plus heat from cooking also adds to the load.

So how much propane?   well,  Propane has about 21,500 Btu per pound.  so a 5 pound grilling cylinder has about 100,000 btu in it. (rounding down for losses)  that means that I can run that 12,000 BTU furnace for  8 hours 20 minutes before the 5 pound tank (if it has 5 pounds in it) is empty.  That is total run time.   If I   need to make up 4800btu per hour, that means I have heat for 20 hours 30 minutes.   A 20 pound grilling cylinder gives me 89 hours of heat (again assuming a full 20 pounds)  that means in the dead of winter you need to get a 20 pound grill tank refilled every 3 and a half days.  This also means that the tiny coleman 5 pound cylinders can be used as an emergency gas source  for 8 hours of heat if you needed to.   This is assuming only Furnace use.  this does not account for hot water heater or cooking.   RV water heaters use as much as the furnaces, they just dont run as often or as long.

This is where insulation really kicks in.   If you were to increase insulation and reduce heat loss by only 500btu/h That 20 pound tank will last an additional day plus 4 hours.   All of this is assuming worst case.  dead of winter in the arctic circle with no sunlight at all.  in reality it heavily depends on the weather and your location.   sunny days reduce heat loss significantly, even when it's 10degrees F out the sun can give you 1300btu/h through a typical 32" by 32" window.  also heat gain through the wall as the house heats up from solar radiation, etc..   plus if it's only 40 degrees out, your heat loss is a lot lower than  the calculated, etc...

By my estimates, a 20 pound grill tank can easily heat your home to a normal 65-68 degrees for at least 7 days in the winter. Spring and fall are looking at a monthly cylinder fill.  Worst possible case,  $80.00 a month heating bill in the arctic circle using only R13 walls and R24 ceiling.  if you were to add storm windows, triple pane instead of double pane and higher insulation, you can do a lot better.

Again, this is assuming that the home is off the grid.  no electric except for solar, and you have to cart in your own propane in your car/jeep on your own.  If you will be in a location that has full hook ups or you can have electrical service ran, these issues are not a bother to you.   But it's good to know what the effects are,  remember your monthly expenses in living are tied to the decisions you make before you build.  spending more when you build means you spend less while you live there.

In my off the grid case,  the loft will be a lot warmer on it's own and if I was to run 12V outlets up there to use a  12 volt heated blanket even more gas can be saved.  However, they use about 80 watts of power.  So now that is a higher load on the solar storage system.   80 watts over 8 to 10 hours is about  800 watt hours used out of the storage system.   Everything in off grid living is a trade off.  And if you want to be portable, you can not use alternative systems like wood heat.  I have seen tiny wood stoves, but honestly I cant see them being used safely in a micro home.  the only small ones are the old cast iron pot belly type and they utterly scare me.   If someone made a tiny modern type I may change my mind.

Monday, May 14, 2012

How to figure out solar or wind power needs.

One of the hardest things to figure out if you want to go Off grid, or be self sustaining and make your own power is how much power do you think you will actually draw or use?    You would be suprised at how much the things you own or use drink electricity, and when you have to make it yourself, suddenly everything matters.

Below is a table of items I have measured with my Kill-a-Watt meter and calculated out for a daily power use.

 1000 Watt Microwave oven.  Uses 1110Watts per hour. used 30 minutes a day.  555WattHours a day BUT it also consumes 2 watts every hour all day long. so add in another 48WattHours for it just sitting there plugged in.
Your cellphone charger,  Consumes 12Watts per hour.  a typical charge time is 4 hours.  48 Watt Hours a day BUT it also consumes 2 watts an hour just sitting there plugged in.  That's another 48 Watt Hours!

Everything that is plugged in today consumes power while sitting there.  At least if it's electronic  it does.   your toaster might not, and a old style turn knob timer Microwave also may not consume electricity when not in use. But you need to check to see.   That is why everyone even thinking of living off the grid needs to buy an energy consumption meter.  so you can check to see if it uses power when off.

You can combat the wasting of power by these devices two ways.  One is to simply unplug it when not in use.   The other is the new "timer outlets"  that you can set to only stay on for 4 hours and then it shuts off.   OR a old fashioned Light timer set to only turn on your chargers for 4 hours at night.  But remember that timer will also use power 24 hours a day.  From 24 to 36 Watt hours a day just for that timer.

All of the above not only is important to help determine how many solar panels you need, but how big of a battery bank.  Until you know how much power you will be using a day and then multiply it by 125% or 150% you cant begin to calculate what you need for solar.

So let's go with a hypothetical small home.
1 800Watt microwave with old style timer.
1 cellphone charger
1 ipad or other tablet charger.
4 5 watt LED lights
A laptop that uses 95watts
and a clock radio, 10 watts typically.  I am assuming you will probably use the clock radio as a radio at times.

440Wh for the microwave (30 minutes a day with 10% added for power loss)
48wh for the cellphone
72wh for the ipad charger
380wh for the laptop that takes 4 hours to charge a day.
264wh for the clock radio that is plugged in all day long.

This is not figuring in Lights, water pump use and any fans for heat or cooling.  Those really are important as well.

1204WattHours used per day.  so you need to make MORE than that during the 6 hours of daylight you can count on having.

Typical 100 Watt solar panels make 600WattHours per day.   2 of those panels will make 1200WattHours.  3 will make 1800Wh per day..   But wait, it's not that simple.  If I was living in Arizona, Yes that will work.  But I'm silly and want to live in Minnesota.  If I double the number of panels, they will make the same wattage in 1/2 the light.  (really general of an assumption)  The sun is not as bright up there compared to the desert, and there is more opportunity for cloudy days.   So I am closer to right by simply doubling the number of panels, on bright sunny days, I will make a lot more power than cloudy days, but you need to make power every day.

But that is 1/3rd of the system. I also need battery storage for when the solar panels are not making enough power.   At a minimum you really want to have 3 days of battery capacity.  so that is 3612Watt Hours of storage.  Watts divided by volts = amps.   301Amp Hours of battery storage is needed for the 3 days.  But you cant discharge a battery 100%, you really want to stay above 50% discharge for the longest battery life.  so let's go for 650Amp Hours of Batteries.

That is a large battery bank.  It's not going to be in the home and not easily carried.  Solar power starts looking bleak when you waste power like a typical consumer.

So look at reducing power use at home.  Laptop,  charge it at work or elsewhere.  Clock radio, fond one that uses a lot less power, a LCD model that has almost no features will use 4Watts That saves 168Watt hours right there.

You can also offset it with wind, a  small 400 watt sunforce wind generator is only $600.00 and those work when you have wind.  All night long in a windy location you are generating electricity which is typical on cloudy days.

But the thing is, you cant rely on having sun and wind 24/7/365  you have to plan for the days when you have none for long stretches of time.   This is when you either have a larger battery bank, or you supplement with a gas generator.

I probably raised more questions than I answered, and Off grid living is a complex topic.   Check out for some detailed info on off grid living as well as Home power magazine.

Sunday, May 13, 2012

Quickie: Gardening in the tiny home.  has a really good article on Tiny home gardening.    This is a great idea, and if you did the right kind of containers, you would be able to pull up stakes and put all the planters in the home and drive off.

No you wont be growing watermelons and Pumpkins, but you can fill some of your daily needs from a garden you grow all on your own.

Saturday, May 12, 2012

Getting Closer to smaller living: Stage 1.1 - Planning

I have been thinking about power consumption a bit more.  A microwave oven takes 1000 watts,  but a coffee maker does as well.  electric hot plate, etc... a LOT of appliances that would be used for cooking all take a LOT of power to run.   Granted, it's not for a long time, but even a Crock Pot draws 600 watts and people leave those on for 8 hours.

Cooking in a tiny home will have challenges,  going 100% solar increases the challenge quite a bit.  I need to see if a smaller crock pot uses less power. If I can find a 350watt crick pot that makes enough food for 3 people, that would be satisfactory, but solar needs to be scaled up by at least 35-40%   I am thinking 5 panels now to generate 500 watts per hour.  This can still be easily stored in the home when it is being transported.  The other advantage is that now the house will generate 200-300 watts of power on cloudy days.  electric cooktop is right out.  I will have to use a Propane 2 burner cooktop.  that means having to install a RV stove hood with vent fan.

I was looking at the all in one kitchens Like the Summit C301 or the Avanti CK301 but  I feel that a custom built kitchen with slide in dorm sized fridge is a better idea for serviceability.  and I still do not have any answers for bathroom yet.  it does seem that my 3' by 3' size is plenty large if I make it a wet stall where you straddle the toilet to shower.

I also still need to research heating.  The RV furnace is expensive and may still be overkill.  RV's are poorly insulated,   the typical tiny home will be better insulated and had fewer air leaks.  I need to find some HVAC calculations to see what kind of heat loss and heat gain the house will have.  I am certain that the smallest window AC unit will be overkill for the house.

I also have decided that the whole house audio will simply be a car stereo that has a remote.   Car stereos can drive 6 speakers easily, so that means 4 in the home to cover any and all areas, and two out on the porch with a switch to turn them on or off gives the tiny home a rich mans whole house stereo with patio speakers!  Car stereos run off of 12 volts so it will use very little power, and it will take up almost no space in the house.     Lighting will be via modified fixtures.   I cant find any house fixtures that look normal but have 12V light sockets.  So I will buy regular ones and change the sockets and wiring.  That way the porch can have a nice coach light that is LED and not use much power.   Inside Indirect strip lighting and  task lighting will be used to reduce wasted energy and power use.  RV Lighting fixtures  have very nice looking Wall sconces and other nice looking fixtures that will work very well in the home.

Finally, if you are looking for some basic tiny home plans for free, check out  They have a few sets of free plans to get you started.  They are not comprehensive, but they have enough detail that someone that is competent in carpentry can build the homes.  One that I find really cool is the 8X8 tiny home.  If you had permanent land, you could build that as a guest house, library or office separate from the main house.   Built as-is would be perfect for a single person.

Also watch out for the website  He simply harvests email addresses and mails you a link of other peoples information from their websites.  Do Not waste your time filling out his email link for any house plans, because all he will send you is the plans from  Honest sites will give you the info freely without making you sign up.  Stay away from ANY website that makes you give them your email to download something free.

Tuesday, May 8, 2012

Getting Closer to smaller living: Stage 1 - Planning

I am planning on a mobile version of a micro home.  I want it to be 14 foot by 8 foot with a 13 foot height.  but I may do an initial test building smaller.  I can use a pair of harbor freight 4X8 trailers to make a light tandem that is 12 feet long.  This can hold a 6 foot wide micro home on it.    This would be more of a "camper" than anything, so  it will be easy to sell when I am ready to go full scale.

Planning out the design is a bit tough.  I want to be self sufficient in that I do not need to be hooked to any utilities if I do not need to.   That means solar for power, and propane tanks for gas.  Along with having to have water and sewer storage on board.  This means building like a RV is built.  I also need to think of weight of the whole thing. Typical micro homes like the tumbleweed homes are incredibly heavy.  5800-7500 pounds means you have to own a 5mpg gigantor truck to move it.  SO compromises can be made and changes in design to decrease weight are needed.    Interior walls can be 2X2 lumber to save 1/2 the weight, and instead of expensive hardwood, buy cabinet grade 1/4 inch thick plywood to sheath it.  you get a luxury wood wall at 1/2 the weight. You can go even lighter if you use composite paneling.  And save a ton of money.  Outer walls can be 2X2 walls just like how a RV or Camper is built, but you space the studs closer together.  again thinner plywood for sheathing and to add more insulation, you attach foam board on the OUTSIDE of the studs and then attach the sheathing.  this way you can have 3 inches of hard foam board insulation in the outer walls and cut a lot of weight.  Ceder shake siding is light, but pine is even lighter if you plan on staining and sealing it.  look at your siding choices and weigh them.

Wood windows are nice but vinyl is lighter.  steel roofing is also a lot lighter. and unless you plan on walking on the roof, you do not need 3/4" sheathing up there as well.  you can save 40 pounds per 4X8 sheet if you go with 1/4 inch thick everywhere.

Solar power.  If I figure that a mini fridge, a small microwave, a laptop, and other smaller electronic and electric items are used, I can get away with about 300 watts of solar,  that is 3 100 watt panels that can easily be packed up into the home when travelling and produce 1800 watt hours of electricity in a 6 hour day.  6 batteries will give me 3 days worth of power and a single 2500watt inverter/charge controller will give me AC power for the Microwave and other items when needed.  All lighting will be 12V low voltage LED as well as the wireless router with 4G for internet everywhere.  Typical power consumption at it's worst will be less than what I generate per day so the batteries will stay topped up unless I get a week of darkness.

I am trying to figure out if a 12,000btu RV furnace is enough for a micro home.   This would give me the ability to have "central heat" in case I want to spend a month in Minnesota during January.  I have also discovered that bathroom and kitchen  vent fans can be created by using Marine Bilge vent fans.  they are 12 volts and are standard 3" and 4" duct sizes.

One added idea I have is a ventilation fan.  adding in cold air intakes under the home that will be duct-ed inside.   IF I open the loft windows and the vents hot air will draw in cold air from near the ground and make the home cooler in hot weather without spending any money. I just have not figured out how to insulate them for colder weather.

Friday, May 4, 2012

Getting closer to small living - The start of a project

I have decided that this year is when I start building my "tiny home"  we are going to use it mostly as a deluxe camper, but it will be my experiment and my first build.   I am basing it on the design of the Tumbleweed homes  first design but with changes taken from the camper world to make it lighter and add more infrastructure.  Like adding Low voltage wiring for 12V lighting and  a solar panel setup, plus a 110V wiring with a inverter for making the Ac power when needed.   I am thinking of the possibility of installing an RV toilet and grey water tank so that a shower and real toilet is possible.

I need to aim to save 800 to 1000 pounds on the tumbleweed design of 4800 pounds.   I want to be able to tow it with a v6 jeep or other smaller and far more affordable vehicle instead of a monstrous v8 9mpg super duty truck.  It will be built for year round, so it will have a propane furnace and a very tiny AC unit.  But design for lots of cross ventilation so that AC is not needed unless it is 110 degrees out.

I also aim to add in "fancy things"  like a whole house audio system,  built in AV gear like a "home theater" in the main location and a bedroom TV.  house network with server and internet live webcams to share our fun with friends.

Design phase is in progress.  And unlike everyone else out there doing this. All of my documentation and plans will be available 100% free under a creative commons license.  But a heavy disclaimer that you will kill people and lose billions of dollars if you do what I am doing.  Everything is for Entertainment purposes only.

Right here is where it will be documented...  It will take from 2-3 years as I don't have a lot of money to dump into the project unlike the people that have a few grand sitting around.