ASHRAE Tiny Houses HVAC Discussion

[sailawayrb]

Thought some here might find the attached subject discussion useful.  Do to the file size, I had to break it up into two files.

[sailawayrb]

Second and last file.

[mobile_bob]

Hiya Rob, ltns
thanks for the pdf files, they are quite timely in that i am having a renewed interest in tiny house design

my original thinking some 20 years ago now, (wow, i hate to admit that it has been that long) was something about 400-500sq/ft, being single, and then after getting remarried maybe as much as 750 sq/ft.

my wife is less than enthusiastic about the prospect, however since moving back to kansas, and buying a place that is two story, with the lower floor to be remodeled from 2 car garage to living space... shhhh don't tell here, but for the last 6.5 years we have done just fine in 750sq/ft the upper floor has afforded us.

yes i would need a larger shop for all my finery... (crap in her words), but hey i don't have to climate control that space save for weather like we are having, then i could control a sub space where i am working only.

as mayor of this little town, (got re-elected to a second term too) i am pushing for a vacant city block to be developed into a tiny house community. 

as proof of concept i have more than enough space on my home spot here in town, to plant a  couple tiny homes without much trouble at all... and am seriously considering doing one.

paying 300bucks per month to cool this space during the heat of summer,and likely over 200bucks to heat it, is the definition of insanity in my opinion. especially when i know that a well designed tiny home could be cooled with an icecube and heated with a kitchen match... relatively speaking of course.

i really think with all the attention given to the tiny home movement, we ought to be applying what we know to that area of design.

doesn't take more than a 3 or 4 light bulbs to light a tiny home, in some cases 1 or 2!   with all that has been done in refrigeration, hvac, etc over the years... even a 6/1 would be overkill in most applications.

i live for the day that someone comes on to this forum having built a tiny home, and is powering it with 100 watts of solar, and a harbor freight 2 stroke generator (yup the little 89 buck jobs) in a co-gen setup, showing how he is living comfortably.   i know for a fact those little generators are at least very quiet and cheap, if not long lived.

takes me back to our old friend here on the forum,  another bob, who had two 20ft shipping containers, one as his home, one as his shop, his 6/1 as a cogen running at around 350rpm burning waste motor oil and doing just fine.

anyway, nice to see you up and around!  how is life down in "oregon" was it?

bob g

[Hugh Conway]

Tiny house??

Not new, we just used to call them cabins. We lived (wife, dog, myself) for 10 years in a 225 sq ft cabin. The 50psi gravity water supply was a barrel on top of a bluff filled by a ram pump from the creek. We had a couple of batteries for the truck and swapped them out to provide electricity in the cabin. Could not afford a generator. 35 years later, the cabin still stands and is occupied........they have electricity now though.
The main issue with small dwellings is zoning laws.

And BTW, no matter how small the house, the sewage issues remain more or less the same. We used an outhouse, but that won't fly in town.

Cheers,
Hugh

[sailawayrb]

Bob, we are doing well in our remote southern OR location.  We built the shop building that has guest quarters two years ago and we built our new house last year and putting finishing touches on it right now.  The house is 2400 sf, the guest quarters are 400 sf and the shop is 1400 sf, so not "small house" living by any means.  We do use a hydram to harvest our drinking and irrigation water from a creek.  Also have a good well.  We will also eventually have hydro and solar power to supplement the grid power.  Both buildings were constructed using ICF and use passive solar and hydronic radiant floor heating.  The house also has a masonry heater.  I still need to get the Listeroid moved into the shop and operating again.

Hugh, I share your thoughts...cabins, RVs and small mobile homes came first.  They are tolerable for a while, but not something I would be drawn to for long-term living other than necessity.  Yes, sanitation always gets more problematic as the space is reduced...but it can be adequately managed to some degree.

[Henry W]

Thought some here might find the attached subject discussion useful.  Do to the file size, I had to break it up into two files.

Rob, I just read the attachments again and find them to be helpful.

I think tiny homes will get more popular in the future.

Henry W

[glort]

This Tiny house talk always leaves me feeling Claustrophobic!

I just renovated my Kitchen and I well know the floor area of that is 72 Sqm Or 775 Sq Ft.  My " Tiny" Holiday house is 52 Sqm which is 560 Sq Ft and there is only enough room in that for essentials.
My home is about 4000 Sq ft and we constantly wish we had another bedroom as a storage room. Really would like a bigger laundry as well. It's not small but by the time you put all the appliances in it and a cupboard for cleaning things, ironing boards and a bit of bench space.... It adds up.

As far as the Heating and cooling goes, I have just achieved a goal since getting here.  We are all electric, No gas, no sewage here so we run an air pump 24/7 as well as a circ and  pump out.
We have no other form of heating than the AC and some little fan heaters. The place isn't badly insulated but the 40 odd large/ double windows and 6 outside doors are not the best sealed nor double insulated. I get a bit sick of people talking about double glazing and better insulation because they are really talking out their arse and just parroting what they have heard with no idea as to what is involved.   I looked at it recently just to see if I was wrong or anything had changed. I was wrong allright. I thought it would cost me about 30K to redo this place. based on a couple of estimates I got couple of months back it's much closer to $50K. It makes NO sense what so ever to pay that out when my bills are $200 or less and I can keep them to that or even less by adding more panels which I could add about 25% capacity for $1000 now.
Yes, sometimes inefficient IS cheaper long and short term. Better insulation does not remove heating and cooling costs, it simply reduces them somewhat.

Sure, if you are building,  good design ( something this place is NOT) and insulation are a no brainer. When building you can incorporate these things at far less cost than you can retrofit.  Retrofitting places that had minimal attention paid to that is a different matter. Here sadly  a well designed house is a VERY rare thing Indeed. Most people when building are on a budget and want to get a roof over their heads first and foremost and any extra cost is not wanted. That's an aside from building on suburban blocks makes it DIFFICULT  to do a good house design often by council rules and regs. You'd have to find a street that faces the right way for a start and then hope you had enough space to do what you need to do a truly energy efficient home.
You could do insulation, double glazing and solar (although they are cutting back on that now too)  but that's about it.

I put another 6.2 Kw of solar the other day ( and took some ground mount panels down)  which brings me to about 25Kw of solar.  Pretty much the middle of winter here now and yesterday I did 81 Kwh of generation and today 84.  Yes, nice sunny days BUT, we have had a lot of crappy ones too latley  but I am now gaining on my power use.  And we are using an average of around 70-75 Kwh a day.  It was my goal to cover winter power use which I didn't think I could but seems it can be done.

As my power is effectively free now bar the little I run up to keep the power co happy, about $200 a quarter, ( over $100 being " connection" charges) I don't really care how much we use.  I did figure that at this level of winter consumption here it would cost around $140 a WEEK .  The heating/ Cooling is the killer, in Spring/ autum when we don't  use either for 3 Months we are down to sometimes 20 Kwh a day, average more like 25.

Telling people these numbers often causes a freak out and they will tell you how little their bill is..... and the fact they have gas hot water, cooking and heating or wood heating.  If it's gas, the cost of that which they never tell you makes their numbers blow out a lot.  Where we are  Often gets below freezing in winter and a week straight of over 40oC (100F+)  is Common rather than rare. It's a temp range a lot of people don't have and makes AC use essential rather than a Luxury.

I have done all my own solar using all 2nd hand panels and inverters up until recently where I bought some New old stock 4 KW inverters of which I have one running atm.
Currently I have only got 15Kw of inverters hooked up so my system is pretty well over clocked but that enables the inverters to run 75-100% even now on a decent day.  What I am behind on the cloudy days I make up ( slowly) on the sunny ones.
Although I usually shut down half my inverters in summer as I make stupid power thanks to the long daylight hours, last summer was not the usual walk in the park. The weeks of Hazy overcast smoke filled skies and the ash that piled up like a light snowfall REALLY knocked the output around.  Making far more now as a percentage than I did most of summer.

My reasoning is that with very modest investment ( I have probably just spent about $2.7K on my setup)  You really don't have to concern ones self about worrying how much a plug pack uses or switching everything off all the time.  Heating and Cooling isn't an issue either.

As you chaps are talking about decent amounts of land, you have plenty of area to do ground mount systems if you don't have the roof space.  Rather than count every watt, I thing the sensible way to go these days is just offset what ever you use. Is you make a few small ajustments to lifestyle, You need very little power at Night. All the things that do need power can be done during the day.  One thing I did was put a Voltage relay on the water heater. I Took it off the off peak and put it on the regular power. When the solar kicks in and forces the line Voltage up, the relay activates the hot water heater. I had a PWM on it as well Taking the power down to about 1000W so it worked longer but with less draw. Don't really need to do that now but it was effective with lower generation in winter.

For me the investment in solar was worth the peace of mind as much as the cost saving.
I don't care a shit if My daughter tries to empty the 400L water heater. I don't much care about leaving lights on and even less so since I bought a box of LED downlights and changed every one in the place ( even the fridge light is LED now! ) and I don't care if she runs the Dryer for one outfit for work tomorrow. Not having the stress and arguments is worth it.
And, I enjoy a warm house in winter and a cool one in summer and not worrying what the bill will be.

It would take a fraction of the solar power I have in a normal house with a Modern AC let alone a small one.  I just don't see the point these days in worrying about it.  When My AC Dies, I'll replace it with an even Bigger one to make the cooling and heating even faster.  The new ones work a LOT better in the cold for heating. I have mine on now and I can tell it's struggling.  I could probably go out and find the Condenser iced up as it's a cool damp night and that happens on occasion.

A decent solar System is definitely the way to go for anyone concerned about home power costs.

[sailawayrb]

Henry, I posted that info a couple of years ago, but I am glad that you found it useful!

I may get hydro here before too long and perhaps even solar PV too.  The hydro is the lowest cost option as I can easily fabricate a cross flow turbine which is the most suitable option for our site.  And it is 24/7/365...  Yes, I wouldn't consider doing anything but ground mount for solar.  Roof mount makes little sense to me, but I guess if that's your only option and you really need solar, that's what you have to do.  Frankly, I haven't been especially motivated or felt any urgency to do either as we have grid power and generator backup.  Our grid power is relatively low cost and given the passive solar cooling/heating design and the high energy efficiency of our buildings, the ROI for doing either really doesn't exist.  It only costs us about $40/month to heat both buildings using an electric boiler as the heat source for hydronic radiant floor heating.  When we fire up the masonry heater in the house for about an hour every other day like we typically do (which also provides us a free white oven for bread, pizza, etc), this goes to about $20/month.  The passive solar cooling design totally eliminated any need for AC so there's zero cooling cost.  It is 102F here this week and the house doesn't go above 68F.  So if I ever do the hydro and solar, it will be more for the fun aspect and getting the place completely to a self-sufficient state.  But the bride sees the landscaping, fenced in vegetable garden, and chicken coop as higher priorities...and I am not a Spring chicken anymore either.  

[glort]

I may get hydro here before too long and perhaps even solar PV too.  

Do you have any idea what sort of flow and head you have available?

What would be your preference for a an alternator? Automotive, F&P....?

Never had the chance to play with Hydro but I'd sure love to even if I could find someone's property to set something up on.
Would be nice to be able to do some hands on learning with this rather than just watch Vids and look at websites.

[Henry W]

Hi Rob, The reason It's so useful is I have a 21ft car hauler (not including the Tongue) that has a 10,000 Lbs. GVWR rating. I'm thinking that possibly, someday, if my body is able, to build an efficient mini home on it. If would be roughly 10 sqft. Larger than I have now. Having it made with 2x4's instead of 2x3's and 2x2's should help with the r-value. It would be such a nice project. The total height would be up to 12ft.   The width of the trailer will be right at 8'-6" and that is measured at the outside of the fenders. The trailer is equipped with dual 5200 lb axles with brakes and the tires are load range E. It's not a bad trailer for $500.00.  I would like to have the trailer set up with 120volt 30 amp service. It's working now so why change? And at least here, any trailer that is at 25ft long or shorter monthly price is about $150.00 to $200.00 less than larger trailers.

Here are a couple pics of the trailer.

Henry W

[sailawayrb]

Henry, I have some course information that I will PM you and try to get to you that way.  Unfortunately, it isn't something that should be shared in a public domain and I fully trust that you will treat it accordingly.  I could see how this would be a great project for you and I think this additional info might be helpful/useful to you in that regard.

Glort, I have a minimum of 8 feet of head (which can vary well above that during flood season) and a permit to divert 3000 GPM for hydro power use.  So my hydro site is ideal for a DIY cross flow turbine (I have fabricated many of these for folks over the years) which has a flat efficiency curve over what would be a relatively low but variable turbine specific speed range.  I would use a fish screen bypass tank design at the diversion inlet.  My max theoretical would be about 4.5 kW with an estimated usable power of about 3.5 kW.  I would likely use a PMG (for similar reasons they are used for wind power) to generate wild AC (because actual turbine speed will vary as stream conditions vary), step it up to some high voltage (to reduce transmission loss), transmit the couple thousands of feet to my shop, step it down, rectify it to DC, feed it to a simple DIY charge controller, charge some simple DIY Edison batteries (I have fabricated a couple of these for folks over the years), and invert it to AC.  I already wired my shop for generator backup and with future hydro and solar PV in mind when I built it and everything else myself a couple years ago.  I brought 400 A of grid power into the shop and it feeds all the other power usage locations (our house, guest quarters, sheds, well water system, stream water system, etc) so I can easily isolate, combine and branch power sources as needed from that location.  But again, my motivation level is pretty low because there isn't any significant ROI, I still have a long "honey do" list of other stuff to complete around here and I am not exactly retired with my Borst engineering stuff either...I am in the middle of a small dam removal project right now.  But yeah, hydro is fun for sure and the best path to go if you have the opportunity...provided you don't harm any fish propagation in the process!  You can find hydro calculators and photos of our place on the Borst engineering website if interested.  But this topic is about Tiny Houses and NOT about hydro power...so this will be my last digression here.

[Henry W]

Henry, I have some course information that I will PM you and try to get to you that way.  Unfortunately, it isn't something that should be shared in a public domain and I fully trust that you will treat it accordingly.  I could see how this would be a great project for you and I think this additional info might be helpful/useful to you in that regard.

Thank you! It will be lock boxed.