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How to insulate a lifted floor properly?  RSS feed

 
Posts: 28
Location: Chillan, Chile, zone 9b, 475m above the sea
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Im planning on building a 60m2 house with a 17m2 chinese style greenhouse, paired to the livingroom with a rocket mass heater. ¿How can i effectively insulate the floor of the building, if its gonna be, lets say, 2 feet off the ground? The minimum temperatures range from 26F to 32F but remains mostly cold for the rest of the year, at around 50F.
Im very much thankful for all your ideas, suggestions and overal effort
This is a drawing of the lateral view of the greenhouse, the measurements are in centimeters.

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Facing north / geocoordinates 36°36′00″S 72°07′00″O
 
Posts: 155
Location: North of France
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Sorry for not answering your question.
Nice drawing, what did you use to make it?
 
gardener
Posts: 1484
Location: Ladakh, Indian Himalayas at 10,500 feet, zone 5
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I love living with an attached greenhouse. I've lived in houses heated by nothing but an attached greenhouse in a climate with cold but sunny winters, for more than 20 years. In our earlier houses (and the one I've lived in the whole time) we didn't insulate under the floors. I'm sure it would have helped a little, but other things would have helped us more, like insulating the roof better.

I'm not sure I understand your idea. You have a very narrow window of temperatures over the whole year? No cold winter, no hot summer, only chilly all year round? Are you in the southern hemisphere, so that's why the house faces north?

If you are in the northern hemisphere and facing north, then the plants in the greenhouse will be in the shade and might not bear fruit.

How to insulate with under your floor depends on what the floor surface will be made of.
 
Agustin Arancibia
Posts: 28
Location: Chillan, Chile, zone 9b, 475m above the sea
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André Troylilas wrote:Sorry for not answering your question.
Nice drawing, what did you use to make it?



I used autocad 2017 but the autocad 2007 should work just great, plus its really lightweight and easy to obtain for free in many sites .

Rebecca Norman wrote:I'm not sure I understand your idea. You have a very narrow window of temperatures over the whole year? No cold winter, no hot summer, only chilly all year round? Are you in the southern hemisphere, so that's why the house faces north? 



Heya, im sorry i explained myself poorly, the window of temperatures aint that narrow and in the summers it gets considerably hot for the places %RH, Ill attach the link of the forecast website.
Recinto's Accuweather Report in July (coldest month)

And yes, its in the south hemisphere, located in the parallel 36°S. The parallel 40°S, used as a greenhouse-orientation limit-paramenter, is located about 400 miles south. Ill also add that im from Chile, the country of parallels.

Regarding the floor construction type, Im not entirely sure yet, since im not the one who decides the technical side of building. We are trying to work with a local company who builds small houses at a quite reasonable price, since the house is gonna be floor-lifted and the house wont be neither concrete nor with metallic beams, i guess the options of floor reduce quite considerably, to a point wether we willl be using mineral/rock whool some kind if high density EPE (expanded poliestirene) or some kind of Polyurethane foam. Since its hard to find the higher densities of HDEPE (20 to 25kg/m3) and the polyurethane is the pricier option, i might end insulating the floor with the mineral whool, aswell as the walls and roof.

Im a total noob when it comes to construction regulation or codes, thank so much for the time and interest, thanks a lot.
 
Posts: 33
Location: On a Farm
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Sorry I can't add more to your own thoughts on this. Underfloor insulation is kind of limited in scope and I'm not familiar with your regions availability of supplies. Your other option is to not insulate the floor itself but insulate the foundation walls which in turn makes the air space beneath the floor insulated. Just a thought ...
 
pollinator
Posts: 2019
Location: Cincinnati, Ohio,Price Hill 45205
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The rock wool should deal with potential moisture quite well,so that would be my choice.
You still don't want it wet ,but at least it can get wet and dry out and be fine.
You don't mention perlite or vermiculite, but they also could be good solutions.
 
Agustin Arancibia
Posts: 28
Location: Chillan, Chile, zone 9b, 475m above the sea
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Thank you so much for the repplies, both seem like really good ideas.

The foundation will have no walls, since it will be a lifted house, like the image Ill attach below, but it was indeed interesting to consider.

I too think rockwhool would be the best, I read that a combination of "glasswhool" and rockwhool is the best, since the glass one is impermeable and the rock isnt. Which allows you to circulate the absorved moisture thru the rockwhool layer, out of the house. Somehow

Thank you all so so much for the repplies, i invite you to check the post on my signature jojojo im needing help there too. Im considering using a BBMH to heat both living-kitchen and greenhouse

Take care
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:v
PI-21.jpg
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My updated drawing
 
gardener
Posts: 2609
Location: Upstate NY, zone 5
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Letting the wind blow under the house will drastically increase the heat loss. You would be much better off with perimeter "walls" shielding the floor from the weather, even if they allow some air movement to keep it from getting humid.
 
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If you insist on having an open space below, then redesign your floor to used engineered trusses as wide as you can.   Staple tyvec to the bottom of the trusses, and put enough 1x2s across to support the insulation.  (1 every 6"?)  Fill the space between the trusses with cellulose insulation.

If this is a green house and not a sunroom, you will have a LOT of dirt in there.  Dirt is heavy.  Do you really want to suipport that mass up in the air?

However a better solution is to use the earth below as part of your temperature moderating system:

Enclose the space, insulate the walls of that enclosed space, and extend insulation 2 to 4 feet underground.

This however leaves you only loosely coupled to the ground mass.

Another option would be to make a 'sunken greenhouse'  The greenhouse is at ground level -- easy access with a wheelbarrow to the outside.  The greenhouse is on top of the thermal mass, and directly connected to it.

Also:  Google "SHCS greenhouse"
 
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Location: Iowa
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I used a Metalized Mylar Double Foil Bubble Wrap, available at Amazon.  It's like bubble wrap packing material.  They claim R22 in an under floor installation.  One layer goes between the joists, with a four inch space below the floor.  A second layer goes across the bottom of the joists.  The more air-tight it is, the better.  I sealed mine with caulk and an aluminum tape they use for furnace ducts.  NOT cloth duct tape, the glue dries out and it peels away.  The insulation comes in 24 and 48 inch widths.  I found it easy to staple in place and I liked that I stayed clean.  
 
Sherwood Botsford
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Richard Arnold wrote:I used a Metalized Mylar Double Foil Bubble Wrap, available at Amazon.  It's like bubble wrap packing material.  They claim R22 in an under floor installation.  One layer goes between the joists, with a four inch space below the floor.  A second layer goes across the bottom of the joists.  The more air-tight it is, the better.  I sealed mine with caulk and an aluminum tape they use for furnace ducts.  NOT cloth duct tape, the glue dries out and it peels away.  The insulation comes in 24 and 48 inch widths.  I found it easy to staple in place and I liked that I stayed clean.  



Those claims are bogus.  It is a radiant barrier but the temperature isn't high enough for a radiant barrier to matter much.  Thermal radiation goes as the 4th power of the absolute temp.  When you have a 160 degree black roof it makes sense. But for a 65 degree crawl space it doesn't.  Mylar bubblewrap is effectively R2 to R3
 
Agustin Arancibia
Posts: 28
Location: Chillan, Chile, zone 9b, 475m above the sea
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Glenn Herbert wrote:



As I fear too, the flow of hair will drastically increment the amount of radiated energy. Yet, how is that nordic styles and many other cold weather buildings are lifted?
Arent they losing too much energy? (maybe they didnt know back then?). Lifting the house is only for water insulation. Maybe it does help that it doesnt contact with the cold humid soil?
If Im gonna raise the house, but will be placing perimetral walls in the beneath space, wouldnt it be better to raise the house as little as needed to fight the water?

S. G. Botsford wrote:



I really apreciate your ideas. I firstly was thinking of a lifted greenhouse, aswell as the house, but then I realized that not only the structure will need to be strong enough to deal with all the additional weight, but also be able to deal with the air leaks and the humidity insulation problem, since I expect it to be quite more humid than the interior of the house, aswell as getting constantly wet during the watering proccess or other procceses alike. Therefore, the greenhouse is now planned at the ground level, but not sunken.
Thanks for the SHCS information. That is precisely how I expect to build mine. I intend to prepare the soil beneath the surface level: composition and underground pipes.
After build the greenhouse itself on top of this area, aswell as leaning-on the house.
¿Should the walls that go below the house be insulated aswell, or are they only to stop the wind? I might think that insulating them would be good, but might be unpractically expensive given the amount of materials and their price. Its effectiveness might also be considerably reduced if there is an opening that makes air flow thru this enclosed space, removing gathered moisture.

Richard Arnold wrote:



Thank you so much for your idea. However Im from chile and the pannels of the material, that I have seen on sale, were outrageously expensive. They are that expensive that people tend to buy the pannels which conform the medicine transportation chambers, as vaccines in ship containers, in order to be able to afford them. I nearly bought some to build my own refrigerator, but I didnt. I will keep watching the market's products and their pricing. Thank you so much for the considerations and details in the procedure.



Is there any possible use to the area thats covered by the house? The area of ground underneath the house?
How thick should the glass be in order to achieve a minimal state of insulation?
Ive picked the lifted style because its building price is like 15% less than the one with foundations. Also, the zone is quite humid and rainy and Im NOT the one who will be looking after the damn humidity leaks each day (nobody either is, since Ill live alone; I might aswell train some chickens to do the chores).
Maybe Im being too dramatical, I come from a city which is surrounded by the driest deserts in a radius of at least 600 km. The precipitation is something like 10 minutes of really really light rain a year; and thats only because a phenomenom that has place in the crest of Los Andes, many kilometers up into the mountainous chain. So, maybe, the lifted-floor makes no real differece apart from the price of the building.

I will let you guys know which system I end up using, among with its collected data and pictures. Id really appreciate if you could lay an eye on the thread thats on my signature.
Thank you all for the kindness and good will; aswell as the good ideas :P
PI-21.jpg
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Side view of the building.
 
Glenn Herbert
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Your description of the rain you get in your area makes a big difference in the answers. I would guess that there is a lot of bare ground between plants, and if you dig down, you still find dryish soil, not wet?

In this case, I think you will be much better with the floor sitting on the ground, with some insulation under it perhaps. If you can get lightweight stone like pumice, that would probably be ideal. If not, simply making a layer of six inches to a foot of loose stone all similar size so there are air spaces between stones would give you a decent separation between floor and ground temperature, while preventing moisture from wicking up to the floor.

Cold humid climates where the ground is always wet, and freezes solid and heaves in winter, are good reasons to raise the floor far above the ground. So are hot humid climates, to avoid mold.
 
Sherwood Botsford
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One of the advantages of a raised building is that you have cheap space under it. 

I suggested in a forum discussing the aftermath of Katrina that it would make sense to require all construction to be on stilts that were taller than the previous flood.  Further any wiring for that space was on a separate sub panel, and that no utility service (gas meter, hot water heater, furnace.

This area then becomes a place for kids to play on wet days, a place you can keep the car, the boat, and the lawn mower, but everything under here is either mobile, or you don't care.

If you are in a cold climate, then basements make sense.  This is true for a very hot climate too.  In northern Idaho where I grew up, we lived in the basement during those 110 degree days.
 
gardener
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Location: Okanogan Highlands, Washington
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Here are a couple of articles on the methods used in North America:

http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/best-way-insulate-floor

http://www.finehomebuilding.com/2012/03/08/how-to-insulate-a-cold-floor

(I'm guessing that in Chile, you have a lot of the Central/South American masonry methods, and some of the materials and techniques for cold climate conditions may be less common.  However your southern climates are definitely cold enough to benefit from them.  Eurasia still has the advantage of big smeared-out regions of similar climate zones, where a design like your Chinese greenhouse can be copied from east to west.  Chile has the opposite situation, being smeared out from north to south where the appropriate solution in one region may be useless to other regions.)

For those who haven't seen it already, my new favorite article on what a building IS, "001: The Perfect Wall."
https://buildingscience.com/documents/insights/bsi-001-the-perfect-wall


I agree with those who have suggested enclosing the space under the floor, by any means necessary.  An exposed floor can have colder temperatures than the outdoor average, due to being shaded, whereas an on-ground floor typically benefits from the soil's stored heat.  Ground temperatures below the surface gradually approach the annual average temperature.  So in my climate, it can be -10 outside and still 40 or 50 degrees F (15 C) in the ground under the house. 

Unless you are storing valuable things in the space, or someone has convinced you to build the house in a hole without adequate drainage, the small amount of added moisture exposure will be less of a concern than the constant heat loss.
In fact a colder surface under the building can contribute to moisture problems, through condensation of indoor moisture (or leaks) in the cold, outer layers of the building materials.


One advantage of the perimeter wall is you have a lot more ways to build it.  You don't need panels if local labor is cheaper.

For a low-tech, possibly local enclosure solution:
You could potentially use a 30-cm foot of dry stone, or concrete block or brick (anything that won't allow moisture to travel upward).
Then use earthen brick or cob (with a LOT of straw and a little clay-mud mixed together) above that.  Monitor to ensure that there is no wicking of moisture up from the ground. 

Another option is to get perlite and mix it with clay or cement, to make insulating cob/concrete.

Even a skirting of wood without insulation will slow air movement, reducing heat lost to evaporation and colder air temperatures.

Part of our home is suspended floors, the rest is on a concrete slab, and every layer we add to our perimeter around the sub-floor space has been worth it. 
Our climate is Okanogan / Okanagan Highlands, USDA zone 4-5, winter low temperatures sometimes as low as -25 F (-30 C), and summer highs up to 105 F (40 C). 
Our valley gets about 12 inches of rain per year, on average; however we rarely have an 'average' year (more common is alternating extremes).
Your problems with temperature may be less, and with damp possibly more, if your climate has marine influence.

yours,
Erica W
 
Posts: 1
Location: Nubeena, Tasmania, Australia, USA Zone 3
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"Staple tyvec to the bottom of the trusses, and put enough 1x2s across to support the insulation.  (1 every 6"?)  Fill the space between the trusses with cellulose insulation."

I am currently researching insulation solutions for our wood-floored cottage that is also up from the ground, so glad to see your design and questions here!
I am posting because I found some very important safety information regarding the use of STAPLES to attach FOIL type insulation.
New Zealand, my neighbour country, has banned foil and staples in underfloor insulation because some people have been killed when repairing underfloor insulation due to the metal in the staples and foil coming into contact with electrical wiring.
We have used earth-wool in ceiling and so far I plan to insulate floor with a combination of this and maybe some expanding foam in parts.

Good luck with your project, I like how the greenhouse is attached to the kitchen and goes to the ground...

here is a link to the New Zealand site: https://www.energywise.govt.nz/at-home/insulation/underfloor-insulation/choosing-underfloor-insulation/
 
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