Has anyone build a passive barn?

[wanderer]

I’ve been intrigued by the passive house movement and really haven’t understood why more of this has it been adopted into the design of outbuildings. I’m in the planning stages of an approximately 60 x 60 barn and would like to design it to approximately maintain a temperature of between 50 and 80°. In houses this is done with heating and cooling systems but my desire would be to have a building that stays at a moderate temperature without any heating and cooling and if I decide to heat and cool it I would be able to do so with a modest sized unit.

My first job growing up was in a manufacturing company that worked at two buildings. Both were pole buildings built by the same manufacturer but one had 12 inches of insulation in the walls and ceilings. This alone was enough to make the people much more comfortable in summer and winter both. I don’t recall it ever getting below freezing in the insulated building despite temperatures that were much lower and a complete lack of any heating system at all. All this despite the fact that it really wasn’t a very well insulated building.

So I would like to incorporate some of the principles of the passive house movement such as south facing solar windows but I’m a little bit concerned about the effects on the interior space such as UV damage and moisture damage. I’m looking most heavily into ICF construction for this. This is pretty appealing to me because pretty much the entire building would be concrete except for the roof.

Does anybody know if there are any kind of design standards for unconditioned buildings using any of these principles?

 

[matt_i]

I think you basically need to design it just like that..."foot thick walls". The ICF is easy to do and has automatic structure. I think one could do pretty well with 2x4 walls built 12" apart and fill the center with loose fill insulation, with some way to manage the shrinkage/settling over time.

Soapbox: My prediction is that someday in the future either all of the "old" (meaning current) houses will be torn down or else rebuilt with new inner walls that shrink the space for the sole purpose of insulating it 3x-5x or more than present-day. Currently there's no economic justification for any of this but when fossil fuels start to wind down it will be a mad business that involves everyone worldwide because of the high energy costs driving it. /Soapbox

In all designs trapping air in dead spaces both in the wall cavity and inside the building are key principles.

Once well-insulated the prime-mover for heat transfer in and out of the space can become very small, like a mini-split. For heat: Passive solar as you mentioned, or the lighting...or the work going on inside the space...

 

[Copymutt]

A few thoughts as I've built SIP passive homes.
In a barn your heat will stagnate up top, so large slow fans are in order.
The more south glazing the better. Helps tremendously with interior light.

My last build i insulated 4’ of crusher fines, then vapor barrier, then a full course of 8x16 CMUs, and 4” slab on top of that. CMUs were absent the last foot on N. & S. w/ a face block against the stem wall to create a chase running along both the N.& S. Walls, 1’ wide. CMUs are arranged so the holes terminate into the chases N. to S.. A lot of the CMUs were seconds and I preferred split face as it increased the integrity of the slab, block bond.
Formed through the slab are floor vents every six ft. Used marine plywood to support the poor in these runs.
Mine is totally passive, however I'm positive low wattage squirrel cage fans below the floor vents would increase the stored BTU. Spec your eaves to max interior sun in winter and min. in summer. This dictates a southern roof slope above the glazing. I also think you have the option should it get too warm in the summer to breach the stem wall on the east and west and again employ squirrel cage fans to run nightime, thus discharging the floor.
At 1600 sq. ft. my heat costs have been less than $400.00 per year at 7000’ Co.
Hope i made this understandable.

 

[Kaizen]

Cost is why it’s not done in garages. Yea it could be but it turns a 50k project into an 80-100k depending on the extent. Perhaps more. Houses the roi is worth it but not in garages.


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[wanderer]

It was never a $50,000 project......My estimate is quite a bit higher. If I didn’t want to insulate it and I didn’t care what it look like and I didn’t wanna concrete floor, maybe.

It’s not really ROI I’m looking for. If it’s designed properly I will be more comfortable and everything inside will last longer.

 

[tboy]

I have a friend that has several barns, and in one he built an insulated room. He insulated it with bales of hay. Essentially he stacked them and framed the wall against it. I'm not sure what he did for the ceiling though (that would be quite heavy!)

Sure, would be quite a fire hazard but such are old barns, and he does no hot work in this one, he has other places for that.

 

[theoldwizard1]

Better do some more research ! 12" of "typical" insulation is about R38. To achieve similar R-factor, your would need ICF with 4"+ of foam on each side (2" in typical). More foam = more $$$$ ! ZIP System sheathing over a double 2x4 wall with 2" of "dead air" in between and an additional interior vapor barrier might be cheaper.

You don't mention your location. 36" of fiberglass insulation between the ceiling and roof is not out of the question for what you want.

Assuming you are going to have a slab on grade, plan at least 4" of foam board underneath. The foam board needs to run down the inside of the concrete footer wall to below the frost line.

If you are going to use windows to store heat, they had better be the best money can buy and triple pane. The inside where the sun is striking, the surface should probably be 6" of concrete. You also need something to block the sun in summer.

People and animals radiate a lot of heat. If you build a super-"tight" building, you will have air quality issue and you will need fresh air run through an air-to-air heat exchanger.


All this is do-able. The technology exists. I would still want some kind of backup heat and you had better have DEEP POCKETS ! Someone much smarter than I will have to figure out the payback time. It could be long.

 

[theoldwizard1]

ICF vs SIPs vs Framing - Pros and Cons

 

[jives]

We built our house mostly that way, planned for the barn to be built that way, but not enough cash . . .the roi would not be worth it given how often the barn would be used.

We began our plan with what I think CopyMutt was describing. Essentially, the soil/gravel underneath is a giant thermal mass. Air channels underneath collect the warmed air and distribute to building. Slab can work as a passive solar collector if the windows are right, but it needs more. We considered a solar wall/collector that would pump heated air into the thermal mass. This is simple in concept, but to make it work it needs some reasonable engineering. Also to be considered is how much the slab is covered by junk.

If windows are used for passive solar gain, think carefully about what they should be. highly insulated windows may actually block solar gain.

Massive insulation is key to the rest.

 

[Pluribus]

Hope this continues as a discussion, as I'd also like some tips to incorporate in my "someday" shop.

My winter-time sun exposure isn't great, but it would be nice to have some ability to moderate temperature swings and gain/preserve a little bit of warmth.

 

[John in OH]

Yeah! I have a totally passive workshop on one of my farms!

It's got thin leaky walls so there is plenty of natural passive air flow in and out. And the uninsulated steel roof provides lots of radiant passive heat in the summer and allows for plenty of bone-chilling passive cool air in the winter! And the un-insulated, non-vapor barrier, concrete floor allows for lots of passive humidity year round.

 

[SGKent]

Capture the cow methane and use it to run a generator to heat and cool the barn made with normal construction materials. That would be more beneficial than pouring a ton of concrete. Concrete releases a lot of CO2 when creating the lime, surprising no one ever talks about that. Methane is 23 X as powerful an atmosphere molecule in trapping heat than CO2. When methane is burned it reduces the effect by a factor of 23. Trap the methane from the cows and save the planet. Need to get catch all the termites passing methane too though because I've read they produce more methane globally than the cows.

 

[ZRX61]

I think you basically need to design it just like that..."foot thick walls". The ICF is easy to do and has automatic structure. I think one could do pretty well with 2x4 walls built 12" apart and fill the center with loose fill insulation, with some way to manage the shrinkage/settling over time.

I think that's called a Larsen Truss design

 

[ZRX61]

Found it:


https://www.greenbuildingadvisor.com/article/all-about-larsen-trusses

 

[RPH]

Also consider going passive solar. This is a simple system designed and built by a guy in Montana. If it works there it should pretty much anywhere

https://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Passive

 

[MushCreek]

As mentioned above- cost. I built our house with ICF, and even DIY, it was relatively expensive. My big barn is framed, and we barely had the money to do that. 8 years after the fact, I'm slowly finishing off the barn, but it will never be energy efficient, nor does it need to be. If I were using it for a business, and was making enough money, it would be a different story.

As for effectiveness of ICF- I think it's at its best in a moderate climate. We're in upstate SC, so pretty mellow much of the year. I put a lot of study into this, and have been looking at the 'numbers' to see how it's performing. My walls are only rated at about R-24, but perform much higher than that. One factor is air infiltration. Between the ICF and my careful detailing, our house is very, very tight, which is a big factor.

The other factor with ICF is thermal mass. Our house is about 1400 sq ft, and has about 100 tons of concrete in the walls. This can work for you, or against you. In a moderate climate like ours, that core stays at a pretty manageable temperature year round, but I think that in areas of extreme heat or cold, it could work against you. Our first year in the house, we shut the A/C off in mid-September, and didn't turn the heat on until January 4th.

More numbers- The house is about 1400 sq ft on the main level. Ceilings are 9-1/2', with lots of windows. We have good shade to the east and west, and the house has large roof overhangs. Further, the attached garage shields the house from the western sun. Our design A/C load is 9,000 BTU (3/4 ton); the heat load is 12K BTU. They don't make central systems small enough, so we use mini-splits instead. The A/C adds about $20/month during the heat of summer, and the heat adds about $40/month during the coldest months. Our total cost for A/C and heat is about $250 a YEAR! Granted, we are pretty thrifty with the thermostat, running about 78 in the summer and 65 in the winter.

Other things about ICF- It's obviously very strong. It's also very quiet. Trades often whack you with significant upcharges to work with it. Electricians seem to think it's a major challenge, although I didn't think it was any more difficult. Plan all of your wall penetrations, then add a few extras. I had to drill a 3" diameter hole for A/C lines when I changed the location- NOT fun. Some localities have never seen ICF, and might hit you with significant engineering demands. My local inspectors pretty much ignored it. They've either dealt with it before, or (more likely) just didn't care.

As for passive- as you can see, it would never pay for us to do any more with our heat/A/C. I looked into geothermal, and the payback was in many decades. Same for solar. If I were rich, it would fun to play with, but the ROI is nowhere in sight. Why aren't there more energy efficient, or passive outbuildings? Money. Heck, if they don't bother to make a multi-acre home improvement store energy efficient, why would anyone do it to a private outbuilding. I wonder what it cost to heat/A/C a Home Depot?

 

[Falcon67]

IMHO will be hard with a "barn". My 24x40 never gets below mid 40s in winter without any heat running. If I want to store up passive energy in winter, I'll open the big door on sunny days to let it heat the slab. There's 62,000 lbs of concrete in the floor and that will keep it up in the 50s~60s for several days. Also, the building is built tight - R13 insulation, ceiling panel seams caulked, ceiling caulked to wall covering, insulated overhead door, 8' ceiling to reduce conditioned air volume.

I'd do some reading on passive solar to get some ideas. Mostly, passive comes down to using a lot of mass to regulate swings in temperature. Concrete, walls made of steel tubes full of water, trombe walls. etc.

 

[Innovate1]

I did some minimal passive solar items - basically just sizing the south overhang to shade the windows in summer. And went with energy heel trusses for better insulation. I have a HVAC system but that will save a bit and was easy to do.

 

[wanderer]

I did some minimal passive solar items - basically just sizing the south overhang to shade the windows in summer. And went with energy heel trusses for better insulation. I have a HVAC system but that will save a bit and was easy to do.

At the end of the day this is most likely the strategy I will use. I am curious about ICS but don’t have a price tag to attach to them yet. If I did a conventional stick framed build it would be well insulated. Also, no animals. This barn will be for machinery storage and a party barn.

A couple notes… I’m in Northeast Kansas. It’s almost mid November and the heat still hasn’t been on the house yet. I burned a little bit of wood in the fireplace but that’s it. January February and March can be pretty cold, well below zero for short periods and below freezing for weeks at a time. Other than that it’s pretty moderate. My thinking isn’t actually to build a completely passive barn, but rather incorporate many elements of it so that it stays moderately warm inside and I can only kick on the heat when I’m out there. My experience with well insulated structures in the area leads me to believe that some modest improvements on them would go along way.

That said, I’m not interested in things like Air exchanging fans or anything like that. I would just like it to stay moderately warm without mechanical heating and cooling and not creating any moisture issues.