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JoeK

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Reply with quote  #21 
Oh and thanks for those links! they are full of great info! I love the simplicity of the passive design from MU, and that whole thing was built with $1,500 material outlay.  Direct gain on a large mass of water (with high surface area) is a tried and true plan that seems to provide great temp stability without any active power consumption.  They could certainly keep a BIG fig or a couple dwarf trees under the 11ft peak if desired. Winter greens are highly valued too though and it obviously suits their goals/needs.

mattie

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Reply with quote  #22 
Hello Joe and anyone else interested.
Yes the glazing is a key area in trying to balance  r values with light transmittance, it would be interesting for to look into what product holds the best balance of both. Earth berming might be a consideration on the north wall your site is at considerable elevation (at least in comparison to where I live anyway) as far as I remember it’s a drop of 1 degree c or so with every 100m you go upwards.Later in the post you describe wind tunnel conditions so maybe exposure is a concern.You do however have natural wind exposure reduction with the presence of the trees surrounding the site.

You also seem to have long spells of cold and cold air is not generally associated with lots of latent thermal energy, as the temperature drops the airs capacity to store moisture will too.(you prob allready know this) Air filtration may be worth looking into (otherwise the outside cold air mixes with the warmer inside ; then when the dew point is induced in the ground the amount of latent energy given off during the phase change may drop). If anyone wants to delve further into this topic look up psychrometric charts.Maybe you want to see how well the system performs over the colder spells first before looking into this more.
I found this link for a SHCS in northern hemisphere http://www.permaculture.co.uk/sites/default/files/Solar_Greenhouse_Article_Web_Ed.pdf  Small solar pv panels were used to power the intake and outake fans which is useful.   screenshot.123.jpg
Straw is a good insulator but it would be advisable to ensure its raised slightly to reduce moisture contact, here’s a company http://www.modcell.com/technical/passivhaus/ that uses it in passive homes .I’ve seen elsewhere the use aerated blocks(reduces Thermal bridging with ground) another feature used in passive home detailing, on top of block sits DPC and then straw (this may be overkill although they are not hugely expensive and is worth mentioning for others too).
You mention bubble wrap in the post ,you can increase the r value of your windows using the bubble wrap


Temperatures of -17f  or -27 c and -22 f or -30c sure is cold a lot colder than what I would see here Im not too savvy on snow conditions ,how well does the snow insulate the ground? And will the frost play a role is helping energy cross your insulation and into the surrounding subsoil?  Not many issues with clouds certainly helps with passive solar gains. Mongolia seems to do well because of this(not harping on about passive solar greenhouses just used as and example of good year round sunlight conditions)

 


Nice find on the Degree day’s website I could do with a looking again at the topic .
Regards Mattie
JoeK

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Reply with quote  #23 
Thanks for your interest mattie. Keep the passive greenhouse links coming, I'm a big fan of passive to the greatest extent. Mike Oehler wrote an excellent book titled The Earth-sheltered Solar Greenhouse Book. He has a phenomenal design for an earth sheltered passive greenhouse that performs in very cold climate. He lives, underground, near the Idaho/Canada border and reports tomato plants still alive into december with cold hardy crops surviving year round.

Berming the North wall would be nice, but It's not in the cards at this time.  At least not a real berm. There is a sort of mini berm around two feet high piled up against the bottom of the N extrerior. And the 4" layer of dirt I sandwiched between the insulation and "siding" of the vertical section.

I don't really understand your point about air filtration. I don't even know what to ask for clarification, but I just spent 9hrs getting the siding up on the curve so I'm a bit tired. Maybe I'll just have to look up some of those psychrometric charts sometime...

I have been considering an attempt to make a Heat Recovering Ventilation box (HRV).  I know there has to be some air exchange in the greenhouse for the plants to be healthy, but there will inevitably be infiltration despite my best efforts. And on warm sunny days some vents could be cracked open, though it would sacrifice heat.  So I'm thinking about installing a small vent to the outside exiting the battery/control enclosure and see if I can make a half decent HRV for it. The vent would draw air from the greenhouse through the battery box and exhaust it outside. Perhaps via tiny CPU fan. The batteries should be vented anyway so it seems like two birds with one stone.

Referring to straw insulation and passivehaus construction, What is the DPC?

The "bubblewrap" I got is not clear like for packing. It is opaque and made as insulation with one side plain white and the other mylar/silver. It's pretty thin but every bit helps and it was a bargain price.  Plus it will be easy to install wherever there's an opportunity. I think I'll at least put a layer on the interior of the door. It's a metal door so thermal bridging is definitely an issue, even though the two pieces of metal(In/Out) are seperated by a layer of foam with a wood frame. Still looking to insulate the door further.

Snow is a certainly a fair insulator.  R-value can vary widely based on the consistency. Often on charts its rated ~R-1 per inch. Of course fresh fluffy powder is better than the condensed icy layer left as it melts. When it piles up a foot that should be ~R-12. Makes a HUGE difference buffering the soil from sub zero temps and winds both.  I do believe in general frost encourages heat transfer, but don't have a lot of specific about that. I do know that to melt off frost in the morning you have to add enough energy to change phase to liquid. Typically the frost is only a very little bit of water though so not that big a deal.

Window shades/blankets would likely be the most effective measure to reduce loss through glazing at night. I looked it up and the glazing is only ~R1.9. For this site, particularly with me leaving soon, maintenance and upkeep needs to be as minimal as possible.  My friend who's paying for this installation is simply not about to draw shades down at night and raise them in the morning every day. Probably be willing to do it sporadically during extreme cold spells though.  If I have enough time I might rig up some rolling blankets similar to what you see in the above mongolia vid link.  They can stay rolled up out of the way while remaining at the ready when temps really get cold. It's a thought, we'll see if it actually comes to fruition or not.  I certainly recommend something of the sort to anyone who can accommodate the twice daily chore, or set up automation. Its probably the most value you will see from any sort of insulation. Plus if its not that cold they can stay rolled out of the way and only need to bother with it during the coldest times.

Been making lots of progress lately, and snapping some photos as I go. Took me around 15 hrs over the last two days to get all the N wall wrapped in Tyvek and covered with galvanized siding. Even managed to get some painting done a couple days ago too. Tonight I won't muster the effort to load pics and write up a proper update. soon enough though.

Bless
Joe

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Reply with quote  #24 
Hi, Joe,

Quote:
I have been considering an attempt to make a Heat Recovering Ventilation box (HRV)


FWIW, I started one of these also, U can take a look HERE:

http://simplysolar.supporttopics.com/post/diy-airair-heat-exchanger-for-economic-hrv-6282653?pid=1277502795&highlight=heat+exchanger#post1277502795

So far I just have the outer case, not yet gotten round to adding the internals, but I need to get on with so much other stuff !

In this design I aim for the best heat exchange possibe, since the TD is pretty small (around 3°C) So I went for lowest-inertia tubes I could think of...

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
mattie

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Reply with quote  #25 
Hello Joek and G_H.
Nice plan G_H. Heres another HRV system i looked at that might be a possibility or useful on some way http://www.builditsolar.com/Experimental/DIYHRV/DIYHRV.htm
Not much time here now be back later for a better reply.
Regards Mattie




Garage_Hermit

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Reply with quote  #26 
Very nice link there, Mattie, Cheers !

G_H


__________________
(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
mattie

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Reply with quote  #27 
Good idea(Whoever was responsible) on the topic move this was drifting off in a new direction with HRV
Thanks for the name of the book Joe will have a look for it.
DPC is damp proof course it is used in building to control or prevent moisture.
Regarding my comment on air filtration i can understand the headache, psychrometric charts are notorious for this lol.Typically where you live the air is cold and relatively dry? If so you don't want it mixing with the greenhouse air which is warm and moist this mixing will result in drop in the energy released when the dew point is met or the phase change occurs in the ground.I realize you will have to have some ventilation and the HRV is a great route to take.
Good point on the blanket at night although this becoming part of a daily routine may not suit all.
Looking forward to seeing the new photos of the build progress.
Regards Mattie
JoeK

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Posts: 135
Reply with quote  #28 
I still don't quite understand what your getting at about not letting the air mix.  I don't see How would I prevent the mixing? I'm probably overthinking it.

I looked up the term psychrometric and while the charts might be a little tricky to interpret for some the concept itself seems very simple. Its the basic concept behind the phase change advantage in this system.  More humid air carries more "latent" thermal energy. This latent thermal energy is dispersed to the surroundings when the vapor condenses at dew point. Drier air obviously has a lower capacity. It may seem like a complex chart but the oversimplified basics are that moist air has higher thermal capacity than dry air yes? It seems to be basically a specific heat curve, correlated to humidity though I'm not sure about the exact semantics for these terms...

In other news progress is continuing rapidly. N wall was wrapped in Tyvek and covered in galvanized roofing/siding, Large 15" exhaust vent installed over 12" ductwork, cause that's what I had and it fits a radiator fan easily too.  Last two days I took down the polycarbonate around the glass windows on the E wall and painted all the exposed 2x4 framing with rubberized roofing paint. Snow Roof by Elastomeric. Probably throw another coat on before I put the polycarb back up, but we're supposed to get some snow tomorrow and I doubt I'll be able to work on it much this weekend. Should be picking up some batteries and equipment for the PV setup tomorrow.

I have received this charge controller:

http://www.colemanair.us/vp_asp/scripts/shopexd.asp?id=660

And I ordered the maxdtc8 here:

http://www.mydtcstore.com/

This seems like a really nice versatile controller for this application and it has built in datalogging for 8 temp sensors and 4 extra inputs, I ordered an RH sensor and one for Solar Irradiance. This logging is a HUGE plus and really sealed the deal on this product.  The 8 output relays are only rated for 5A so I had to order some additional relays to handle the power to the fans.

http://www.ebay.com/sch/i.html?_trksid=p2047675.m570.l1313.TR0.TRC0.H0&_nkw=New+Solid+State+Relay+SSR-25DD+25A+DC-DC+I%2FO+3-32VDC%2F5-60VDC&_sacat=0&_from=R40

Both coleman customer service and Brian smith @ mydtc were helpful in determining that these products should fit the intended application.

getting real close now...


JoeK

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Posts: 135
Reply with quote  #29 
Heres a few pics
3-15-14.jpg  3-15-14-2.jpg 
3-16-14.jpg  3-16-14-2.jpg 

mattie

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Reply with quote  #30 
Hello Joe
Regarding the air topic is was just explaining my earlier comments,you have addressed the air mixing issue with your plan for a heat recovery system.In the case of passive home a design criteria is to ensure that all air that leaves the home passes through the HRV system in order to ensure it performs efficiently.Air tight membranes or sealing is used to get much tighter control over where air leaves a home.Another technique Ive seen for colder climates is to run ventilation intakes underground to boost your inlet air temperatures.

Spot on with the psychrometric charts, I wasn't concerned in your abilities at all.I just giving others who are new to the concept some hope (its ok to laugh if they seem confusing at first).They are actually highly useful.I had a really good interactive chart somewhere but have no idea where it is now,here's another link for anyone interested,https://www.educate-sustainability.eu/kb/content/anatomy-psychrometric-chart
There's good animated tutorial in the teaching resources tab, when it downloads double click on the .html file for it to start

Really great find on the controller the you tube video is really informative on its abilities this is a highly useful tool thanks for sharing.The fact that you are making the effort to monitor performance data of your SHCS is a step in the right direction and will give others plenty of insight into how well it runs over time.
In the you tube video its says 4000 ticks if that's over the course of a year you have 2 hour 20 min intervals or if you want to have smaller intervals does the unit allow transfer of the data over wifi ,usb or memory card?
What would be really nice here is to set up remote monitoring of the system, on a web page that you could check from a smart phone or laptop when away from base,then again maybe this is turning into the start of a whole new project.
Regards Mattie


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