Earthships

good point, the sun rooms role is to provide some insulation for the livingspace at the cost of some solar radiation, so I guess depending on the number of panes used there, originally I planned doubles on both walls, but there was not much thought behind that. at the same time the heat loss we calculated earlier was at 75F base temp, for the outer wall the delta should have been half, maybe if I could match the input rejected by the second glass wall with the heat loss of the first, whatever makes it into the living area is a total gain, but than it may be too much too.

from what I saw in some tourist videos of NM earthships (my inspiration), the living space maintained about 70F over night due to the thermal mass I guess, while the sun room may swing widely one winter video I saw by 10 am the greenhouse was pushing 90F, they had window vents above to the rooms to let some of that 90F air into the living space, the design is not a total passive solar, it involves some user input if you will opening certain vents at certain times, I would not consider it Active means but kindof.. a smart HEV I read about could come in handy but those are details, opening vents is fine at the moment

guess I am looking at a middle of the road solution, the rooms require some curtains for privacy if nothing else, maybe single panes on the inner wall is not such a bad idea provided some thick curtains be pulled at night?

 

I was just going back and reading through and althou I am still not serious about expensive windows for the weight and cost factor I think I found an error in your math still.

presumably double panes let in the 1800 WH, that is 0.85x0.85 =0.7225 of the total available which is 1800/0.7225 =2491wh now presuming a tripple lets in 0.85x0.85x0.85x2491 = 1530wh, the third pane filters 0.15 of the 1800 not 2 thirds so heat gain is only reduced 230wh, guess all those german scientists were on to something, go figure

 

funny definately not the bunch to do this, I doubt the coating does much for heatloss, so you can call this exercise for coated glass.

I need to do this all over, I grew up in Europe the thought has crossed my mind to draw this whole project in metrig the imperial is such a pain but than again when you go to buy stuff like windows it's all rated in imperial.

still as interesting as this has been, I have yet to see a tripple window pricetag and a real R 10 rating, in theory a third pane may bring it up a bit but its a log shot to 5 times the insulation, the gasses make a bit of a difference but they tend to leak out at some point, I'd like to see a real window with real ratings before we debate this further, I loked at some of those sites lots of fancy pictures no real numbers.

it has been a good exercise at least I have a clue about how to figure the net input of a glass wall, picked up some interesting framing teckniques along the way insulation too

 

ok so lets start with some real numbers, I tried to look up the code requirement for conversation sake but came up empty, curently my thermostat is showing 71F furnace is off and my bouy is running arround barefooted wrestleing the dogs so 70f is comfy enough, outside is 34 at the moment, here's my HDD:

Description: Fahrenheit-based heating degree days for a base temperature of 70F
Source: Heating & Cooling Degree Days - Free Worldwide Data Calculation (using temperature data from Weather Forecast & Reports - Long Range & Local | Wunderground | Weather Underground)
Accuracy: Estimates were made to account for missing data: the "% Estimated" column shows how much each figure was affected (0% is best, 100% is worst)
Station: DETROIT METROPOLITAN, MI, US (83.33W,42.23N)
Station ID: KDTW

Month starting HDD % Estimated
2/1/2013 1199 0.04
3/1/2013 1099 0
4/1/2013 718 0.03
5/1/2013 270 0.06
6/1/2013 105 0
7/1/2013 56 0
8/1/2013 65 0.03
9/1/2013 225 0
10/1/2013 529 0
11/1/2013 965 0
12/1/2013 1326 0.03
1/1/2014 1642 0

totals 8199






wow look at januarry

 

Description: Fahrenheit-based cooling degree days for a base temperature of 70F
Source: Heating & Cooling Degree Days - Free Worldwide Data Calculation (using temperature data from Weather Forecast & Reports - Long Range & Local | Wunderground | Weather Underground)
Accuracy: Estimates were made to account for missing data: the "% Estimated" column shows how much each figure was affected (0% is best, 100% is worst)
Station: DETROIT METROPOLITAN, MI, US (83.33W,42.23N)
Station ID: KDTW

Month starting CDD % Estimated
2/1/2013 0 0.04
3/1/2013 0 0
4/1/2013 1 0.03
5/1/2013 67 0.06
6/1/2013 84 0
7/1/2013 164 0
8/1/2013 124 0.03
9/1/2013 46 0
10/1/2013 8 0
11/1/2013 0 0
12/1/2013 0 0.03
1/1/2014 0 0

total 494 thou 70F is a bit too much to ask for cooling I honestly like heat, below 80 I am unconfortable

 

looking at july arround 73-74F hdd evens with cdd so in theory a properly designed house should even up right arround there on it's own, this pos I live in will push 100f in mid july if unassisted opening it up at night and closing it and shading during day I can keep it at 85f real world data lived in in for 10 years this way.

 

november through march is what concerns me 5132 hdd, now want there a way to figure heatloss based on hdd after all is a delta temperature measurement 5132/120days, 42F average x5/9 was it, I read this somewhere, 23.75C, I think Corwin rated a plain double pane at R 1.8

5132 HDD in your coldest month, 0.5 U value double pane clear glass window:
5132*0.5 = 2566 btu per SF per heating season
= 2566*10.76 = 27610 btu per square_meter per season
= 27610/120 = 230 btu per square_meter per day

Convert btu to Wh:
180/3.14 = 57 Wh (per square_meter per day)
27610*0.293071= 8092 Wh/sqm/season?
hope I got this right

as for gain pvwatts say 322kwh solar radiation /sq m that is counting the shgc of 0.7225,

so what have I done wrong a 9kw loss compared to a 322kw gain, for plain double panes, I guess it does not apear too unrealistic



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that is very different than my latest math

 

yes it is but something is not right, the way Corwin was doing it 1600 hdd * 0.5 U=600 btus loss, I need to look into this something is not right with one of the formulas, pv watts shows 2.87kwh/m2/day solar radiation I guess the 1800 is based on the ac energy projected which accounts for tilt angle 214kwh per season etc

 

you bring up some good points, the weight for example, in all honesty I havent yet really considered any kind of fancy window including tripples just took on the conversation for debate's sake just

what is wrong with this equasion and why is your math produce such a different result, math is math should have the same result

 

so 0.5*53=26.5btu/sqft/hr? 7.8wh*24=186wh still not right far cry from the 2k the metric method came up with
wait * 10.76 = 83wh/sq meter thats what your metric came up with
so its more like 8 kw*24 per season 192kw lost hmm bit better
1600*0.5*24 = 19 200 btus lost that mont 5627 wh lost in january *10.76, 60 KW/ sq meter/januarry
1800*31=55800 no $hit, guess the expert kew his stuff

 

the other thing corwin brought up for my design the buffer temp will be about half way between the living space and outside, that changes F to 26.5 different storry

 

yeah the tripples work out to about 25kwh/jan, granted I figured he had a point to make, him and all the german engineers involved in Passivhaus, just had to get to the bottom of this math is math regardless how you go about it cant have 2 results, U value is a rate per hour, to compute it with HDD you need to multiply it by 24, that was the issue I guess, hmm
I need to reevaluate my plans here, I guess if you count the buffer to be half way between it changes things, actually it gets even more complicated as in real life examples during the day the buffer is hottest probl half between after sunset