Point me in the right direction, small, new, energy efficient home

[juanni]

Well I have been searching and reading through the threads and really haven't stumbled upon my situation.

I will be building in Montana a single level 1200 sf ft home of ICF with a suspended concrete slab and hydronic floor heat. Very well insulated.

Only energy available is propane, heating oil and electricity,,, and wood lots of softwood only. Pine, fir and larch. I have lots of experience cutting wood and already have the saws, hydraulic splitter, trailer and the wood is free to almost free.

Water table is 8 ft below grade, so not sure it that is good or bad for geothermal?

So what kind of system is practical for my size home?
I gather that boilers really aren't made for smaller homes?

Somebody point me in the right direction.

THANKS.

 

[Bob Rohr]

Well I have been searching and reading through the threads and really haven't stumbled upon my situation.

I will be building in Montana a single level 1200 sf ft home of ICF with a suspended concrete slab and hydronic floor heat. Very well insulated.

Only energy available is propane, heating oil and electricity,,, and wood lots of softwood only. Pine, fir and larch. I have lots of experience cutting wood and already have the saws, hydraulic splitter, trailer and the wood is free to almost free.

Water table is 8 ft below grade, so not sure it that is good or bad for geothermal?

So what kind of system is practical for my size home?
I gather that boilers really aren't made for smaller homes?

Somebody point me in the right direction.

THANKS.

Run a heatload calc first. Don't be surpriced to find a load under 10 btu/ square foot on a tight ICF home like that. The last ICF home like that I was involved in, about 1700 sq ft, the floor rarely kicked on. The lighting, appliances and internal heat gains warmed the home on all but the coldest days.

I'm a long time radiant contractor, but I'm begining to think radiant may not be the best system for a tight home with low loads, especially with a high mass slab to flywheel up and down.

My idea would be some radiant in the bathrooms, maybe even electric mat under tile.

If you really want hydronic, consider panel rads. They respond quickly, are able to be easily zoned with TRV and easy to instally.

A heat pump mini split would be another option as you will need to move some air, and a heat recovery unit to bring in fresh air. Throw a couple KW of PV and offset the operating cost of the HP. With PV under a buck a watt and mini split HPs running 17- 22 SEER, that's a tough act to beat.

The load calc will help you nail down a few options. In a small tight home, if you want some wood heat consider a nice sealed wood stove. Or the gasification parlor boilers like they use in Europe. Those provide hydronic and DHW.

Don't forget solar thermal. Where in Montana?

 

[benjamin]

Turn around and go directly to builditsolar (dotcom). A great site with lots of cutting edge ideas and even more way over the edge ideas.

I agree that a small tight building loses lots of the advantages of radiant heat, but what else are you going to use? Unless you get efficient enough to only need a couple of electric baseboards, you're probably going to end up with a "central" heating system, and radiant can be very simple and effective. http://www.radiantec.com/systems-sources/open-system.php this system might work good for your situation, combined with water to water geo and solar instead of propane.

The water table is one factor in geothermal installation, rocks and available acreage are more often problems.

I'm wondering how a suspended concrete floor is going to work with ICF, are you going to have just the exterior insulation outside of the edge of the floor? skeptical of ICF's here, especially since all of that wonderful mass is is lost inside of insulation.

 

[juanni]

OK, I should have stated that I doubt solar is an option.
My property is located in the bottom of a very steep East-West canyon.
Directly to the south/east is a large knob which blocks out 3 hours of sunlight except during summer.
So I get 2 dawns for every morning. lol

From late fall to spring I would get very little direct sunlight, made even less so from the usual rainy/snowy weather of winter.

Because of the location, and construction of the the home I don't believe I would need or use cooling in summer.

The ground is basically alluvial fill. 1" of soil and nothing but peddles, rocks and boulders from there on down.

I should clarify that I am not exactly doing CIF, instead in will be site cast tilt up, 5" of concrete on the exterior face with 3" foam sandwiched between 3.5" non structural metal studs.

I want concrete on the exterior, not stucco over foam because of the woodpeckers and wildfire risks.

Oh and I am 50 miles west of Missoula, MT.

 

[Bob Rohr]

OK, I should have stated that I doubt solar is an option.
My property is located in the bottom of a very steep East-West canyon.
Directly to the south/east is a large knob which blocks out 3 hours of sunlight except during summer.
So I get 2 dawns for every morning. lol

From late fall to spring I would get very little direct sunlight, made even less so from the usual rainy/snowy weather of winter.

Because of the location, and construction of the the home I don't believe I would need or use cooling in summer.

The ground is basically alluvial fill. 1" of soil and nothing but peddles, rocks and boulders from there on down.

I should clarify that I am not exactly doing CIF, instead in will be site cast tilt up, 5" of concrete on the exterior face with 3" foam sandwiched between 3.5" non structural metal studs.

I want concrete on the exterior, not stucco over foam because of the woodpeckers and wildfire risks.

Oh and I am 50 miles west of Missoula, MT.

You might enjoy this site. (broken link removed to http://www.danchiles.macmate.me/rockspan/RockSpan/Shop,_Stage_4.html)

This is a friend in Missouri building a concrete tip up home for tornado alley. They installed pex tube in the concrete walls, ABC wall system. On the outside as a solar collector, the tube on the inside gives him radiant walls instead of radiant floors, but it is still a fairly high mass system.

I'm leaning more towards low mass, quick accelerating systems for tight homes where wide temperature swings are possible.

Radiant walls under sheetrock, or panel radiators are two systems that I have installed with excellent results.

Skip the AC in your climate, maybe a ceiling fan, but still look into an energy recovery unit to exhaust kitchens and baths and bring in fresh air.

"Heating a Thermos Bottle house" by John Siegenthaler is another good read,

www.pmmag.com/Articles/Column/c14ebdd039aae010VgnVCM100000f932a8c0____

 

[benjamin]

That Rockspan link makes Gary's builditsolar look kinda square.

Now, removing foot from mouth, no solar-got it. Have you considered ICF's, they're not great insulation and the mass is lost in the middle of the insulation, BUT they have the great advantage of continuous insulation, which I'm afraid you would lose with the steel studs and/or floor to wall connection, or am I missing something? everything?

I'd guess you've ruled out conventional ground loop geothermal, have you considered open loop/"pump and dump"? or do you just want to burn wood and figure out the best way to do it?

 

[PassionForFire&Water]

Look for hydronic wood stoves or hydronic fireplace inserts.
www.Hydro-to-Heat-Convertor.com

 

[juanni]

Have you considered ICF's, they're not great insulation and the mass is lost in the middle of the insulation, BUT they have the great advantage of continuous insulation, which I'm afraid you would lose with the steel studs and/or floor to wall connection, or am I missing something? everything?

I'd guess you've ruled out conventional ground loop geothermal, have you considered open loop/"pump and dump"? or do you just want to burn wood and figure out the best way to do it?

I am open to any practical, cost effective ideas.

I actually have used ICF before, but I don't think they are the best solution for my situation in my location.

I am pretty remote in a very low populated area, delivery costs for non mainstream proprietary products is expensive. So is bringing in skilled workers to do stucco, plastering etc.... That is why I want to use standard, typical building materials and products.

The same goes for anything too high tech, there is simply no persons or businesses close to advise, sell, install or service such products if they needed to be in the future.

So to my precast panels....
I have a small mini batch plant and equipment to lift and place panels. By casting them myself I can work around the weather and the obstacle of finding even unskilled labor.
Not having to include a redi mix company is huge plus too, since they are difficult to schedule.
As posted above, I want a hard concrete finish on the exterior surface because of the peckers and do not want to have to stucco it. The exterior of the panels will be finished when cast.

I plan on embedding threaded nuts in the interior face of the panels. Screwing in threaded rod 5/16" on 24" centers. Between the panel and the studs will be 3" of foam board. The metal studs will fasten to the threaded rod. I can't imagine much heat transfer though those rods, through 3" of foam board.
So yes the insulation is continuous.

I have plenty of experience with drywall hanging and finishing. Plus I like the ease of remodel repair if needed.

Geothermal is definitely an option.
There is a shallow 30' existing well in place,,,, right in the building footprint or close to it.
So I plan on drilling another deeper well. The old well could be used for the dump.

I would like to incorporate wood into the heating plan. The existing shop is wood heat so I already have to get wood anyways and as mentioned it is free or almost free at $20 for 4 cords on Forest Service land. And dead beetle kill is everywhere.

 

[juanni]

Thanks Bob!

That is a good article by John Siegenthaler.
I like the idea of partial radiant floors, placed only where they are needed.

 

[benjamin]

You're not afraid to get your hands dirty and try some new things on this one, huh?

Open loop geo seems like a good solution, just get your water tested and know what that means in terms of cleaning your heat exchanger. The units are relatively easy to install DIY (no freon hookups, just water).

I don't have any good solution for burning wood, unless you want to build it yourself? Kinda hard to justify $10-12k+in boiler-storage for such a small load.

I'd like to try tilt up concrete someday, but I imagined the thick section inside with a wood "larsen truss" with cellulose and real portland stucco on the outside. Your plan sounds solid, only thing I'd consider is cellulose, but that depends on a whole bunch of other factors.

 

[juanni]

You're not afraid to get your hands dirty and try some new things on this one, huh?

Open loop geo seems like a good solution, just get your water tested and know what that means in terms of cleaning your heat exchanger. The units are relatively easy to install DIY (no freon hookups, just water).

I don't have any good solution for burning wood, unless you want to build it yourself? Kinda hard to justify $10-12k+in boiler-storage for such a small load.

I'd like to try tilt up concrete someday, but I imagined the thick section inside with a wood "larsen truss" with cellulose and real portland stucco on the outside. Your plan sounds solid, only thing I'd consider is cellulose, but that depends on a whole bunch of other factors.

No I don't mind, I have a lifetime of getting my hands dirty. lol

I have lots of construction/metal fab/machining experience,,, but none in alternative heating. Everything prior was in the city, on city water, sewer, nat gas, etc...

Yes open loop seems a good solution, and I will get the water tested. I did pull the existing well's jet valve at the bottom of the well. Been down there for 10 years and did have some iron bacteria crust and slime,, but not gobs.

I really need to explore the wood options a bit more. It dawned on me today that perhaps I could put the woodstove/boiler in the shop and pipe the water to the house.

The shop is 1000sq ft, 2x6 framed, 9' ceilings, well insulated, but drafty with two 10' wide x 8' high rollup doors.
Even so, I typically only burn 8-12 decent size pieces of pine or fir a day to keep it quite comfortable for working.
And the stove is an "airtight" from the 70's or so,,,,,so it can't be too efficient.

It is about 75' from the shop to the edge of the house.

Perhaps I can find a model that would both heat the shop and supply hot water to the house? Without overheating/underheating one or the other.
Of course I would need an alternate method for when there is no need to heat the shop.

 

[Chris Hoskin]

I love the idea of a wood boiler with thermal storage located in the shop. Keep the wood out there, dry and warm and 75 feet to the house is no problem. You might even be able to get away with 1" pipes underground because your heat load is so small. Nice high ceilings in the shop so you are able to use a single 400 gallon tank (just over eight feet tall) for a super cost effective and elegant set up. With storage there is no need to worry about over heating the shop or house - just charge up the storage like a big heat battery and draw off to the shop and/or house zones as needed. I like Bob Rohr's idea of panel rads, but would also consider constant circulation in a radiant floor (at very low temps). If you like the idea of setting your thermostats back at night then panel rads, otherwise I like the radiant floor. Also strongly recommend ERV as indoor air quality can be a real concern in the kind of house you are building. Keep us posted and drop me a note if you would like more details about the system I am describing. Chris.

 

[maple1]

I was thinking a boiler wouldn't be the best solution for your small efficient building - but if you can do a boiler & storage without taking away much living space, I think that would be the best you could do. You could maybe burn something like once every three days to do your heating - with adequate sized storage. That would also handle your DHW in the off-heating season, maybe going over a week between burns.

The only thing that would make me think of alternatives or supplements to that would be possible need for A/C in the summer? Then again, you might get by very well with a single mini-split unti for that if required.

 

[benjamin]

If you do the geo and you have reasonable electric rates, then a boiler can be a low priority.

You could use your slab as the storage if you don't mind wider temp swings. Or a sand bed under the slab for more storage and stability.


I cobbled together a boiler with a masonry combustion chamber and a used cast iron boiler core. I wouldn't recommend putting an experimental boiler anywhere smoke will be a problem, but it might work fine in a shop. The "heiss" boiler, or a hybrid masonry heater/boiler is similar to what I'm thinking of.

 

[Como]

I think the first thing I would do is move it to where you do get good solar.

I am in a 10,500HDD climate so I am going to assume a higher load. I know people even here with well insulate buildings who have to leave a window open when the sun is shinning due to the solar gain.

I would in your location at least double the insulation. The next question is automation, a wood stove should be fine for your load, so what do you need to cover when you are gone?

So a Stove and whatever you need to keep the building from freezing when you are not there. There are a few stoves that allow you to preheat water.

Or get a Rayburn, cook, heat and hot water in one.

 

[StihlHead]

Solar seems to be a non-option with the east-west canyon location.

I would advise that you avoid heating oil like the plague. Spendy. Porpane is also spendy, but better.

Hydronic is the way to go with space heating. By far the best heat in my experience. My ex's place had hydronic on an electric and we retrofitted it with an OWB. She has more wood than she can burn in 10 lifetimes there, so an OWB was a good option. We went with Central Boiler. Not as efficient as Garn, Tarn or other large water storage systems, but half the price. You can run loops for hot water and space heating, and run 75 feet easy from the smaller OWB models available. If you have firewood, you are set. Fir is good firewood (doug fir that is), and larch is even better. Larch has about 20-22 MBTU per cord, about the same as walnut or maple. Pine is good shoulder season wood.

It seems to me that the higher water table would be good for a heat pump source. Water transfers heat really well (or robs it, depending). Find out if there are others using geothermal in that area and find out about typical costs.

 

[juanni]

I think the first thing I would do is move it to where you do get good solar.

I would in your location at least double the insulation. The next question is automation, a wood stove should be fine for your load, so what do you need to cover when you are gone?
So a Stove and whatever you need to keep the building from freezing when you are not there. There are a few stoves that allow you to preheat water.

Or get a Rayburn, cook, heat and hot water in one.

Huh?
5" of air entrained concrete is R19.5
3" of rigid foam is R11.5
3.5" of Roxul is R15
and you say to double it?

I suspect even a small wood stove without heat storage would drive me out of the proposed home, with the planned insulation.

In my drafty 1000sq ft shop with R22 on the walls and R38 on the ceiling with a 70s era stove Typically, I comfortably heat it with 8-12 decent pieces of pine or fir a 8-10 hr workday.

If I doubled the insulation in the house, I could heat it with a Bic lighter. lol

Here is the 1st paragraph of Bob's linked article...

Does the term “superinsulated house” ring a bell with some of you? It was a concept first hyped in the 1980s to describe houses with extremely well insulated thermal envelopes. Imagine R-30+ walls, R-50+ ceilings, R-4 windows, and so forth. When you put these R-values into heat load estimates, you may find a 2,000-sq.-ft. house with a design heating load of 20,000 Btu/hr. or less, even in a very cold climate. A superinsulated house might even have a lower overall heating load than the great room of a typical “suburbia” house built to minimum code standards.

 

[Fred61]

If I doubled the insulation in the house, I could heat it with a Bic lighter. lol

Or junk mail. But isn't that the point. Think about future energy costs or the work involved in cutting and handling wood when you're in your seventies as I am. Believe me, it isn't as easy as it used to be.

 

[JP11]

Remember that a tight house is great for heat.. not for air quality.

A HRV or ERV.. whatever you call it... You gotta have fresh air. Some ducts like central air.. even if you never use central air. Fresh air brought in to keep your house healthy. Whole house humidifier.

I agree with the boiler, storage, and wood all in one shop. Don't scrimp on the underground pipes. What you put in the shop to heat the water isn't as important as design temps and pump flows. All simple, off the shelf, controls and pumps. Easy DIY.

AND.. if you do it that way you don't give up any floor space in the house for your utilities. Heck.. I'd put my cold water tank out in the shop too. Back up heat source too! I'd go propane boiler and heck, put a standby propane powered generator our there outside the shop too. Main electric panel out there.. with a sub panel in the house.

It's easy to spend someone else's money.. but keep planning. Keep your mind on what you want it to look like and work like when you are done.

JP

 

[mikefrommaine]

Huh?
5" of air entrained concrete is R19.5
3" of rigid foam is R11.5
3.5" of Roxul is R15
and you say to double it?

I suspect even a small wood stove without heat storage would drive me out of the proposed home, with the planned insulation.

In my drafty 1000sq ft shop with R22 on the walls and R38 on the ceiling with a 70s era stove Typically, I comfortably heat it with 8-12 decent pieces of pine or fir a 8-10 hr workday.

If I doubled the insulation in the house, I could heat it with a Bic lighter. lol

Here is the 1st paragraph of Bob's linked article...

Does the term “superinsulated house” ring a bell with some of you? It was a concept first hyped in the 1980s to describe houses with extremely well insulated thermal envelopes. Imagine R-30+ walls, R-50+ ceilings, R-4 windows, and so forth. When you put these R-values into heat load estimates, you may find a 2,000-sq.-ft. house with a design heating load of 20,000 Btu/hr. or less, even in a very cold climate. A superinsulated house might even have a lower overall heating load than the great room of a typical “suburbia” house built to minimum code standards.

R3.9 per inch for ae concrete? Seems a little high to me. Is this standard 6% air entrained, or some other type of concrete?

If one could get that high of an r value out of standard concrete there be no point in ICF construction. Just use standard forms and pour 8" walls and skip the expense of foam forms... Presto r31 walls.

 

[juanni]

R3.9 per inch for ae concrete? Seems a little high to me. Is this standard 6% air entrained, or some other type of concrete?

If one could get that high of an r value out of standard concrete there be no point in ICF construction. Just use standard forms and pour 8" walls and skip the expense of foam forms... Presto r31 walls.

All I can say is that is the R value given in every reference I see.
I suspect if it was super air entrained it would say.

 

[mikefrommaine]

Every reference I've seen list concrete at .08 per inch. And air entrained as "slightly higher". Some manufactures of Autoclaved concrete have erroneously claimed 3.9 for their cellular concrete products which isn't a DIY process. But others now admit an "effective" r value of 1.5/inch is more likely for a cold climate for cellular concrete.


http://www.sungardenhouses.com/tech-aac.html

 

[Frozen Canuck]

Yes that number sounds kinda high for the R value of concrete. Typical weight/strength mixture of concrete in an 8" thick wall should yield R1.35 for an 8" wall, uninsulated of course. This may be an R value of an ICF & was simply transposed in the posters thoughts/typing. Makes sense that way. BTW if someone has indeed figured out how to achieve those R values in concrete please PM me with a few details, in my business that's money in the bank.

 

[EffectaBoilerUser (USA)]

Your system sounds ideal for a wood gasification boiler and water storage in your garage. When using storage you simply heat up the storage and then the heat loads pull off of the storage . By having this system located in the garage you are able to get the added benefit of using any lost heat from the boiler/storage to heat your garage.

 

[juanni]

OK, lets say R1 for a 5" concrete wall + R11.5 + R 15 = R 27.5 for a 12" finished wall.
The suggestion was to double the insulation to R 54 which would be a 18.5" finished wall.

Sorry that sounds way over the top, I am not building on the dark side of the moon. lol