Wednesday, November 26, 2008

Cottage heat loss coefficient

On my list of things to be thankful for, category wonk, subcategory building science, is a thing that happened during the first few hours of Nov 16 - the cottage settled into a thermodynamic steady state with the boiler running full out and all four radiant floor loops turned on.  (I was trying to warm the greenhouse floor for painting.) Because of steady state I know that the boiler electric power, the heat delivered by the distribution loops, and the heat leaking to the outside are all the same.  That plus the air and water temperatures from the monitoring system allow me to estimate the building "UA" or heat loss coefficient, and the flow rate of the hydronic circulation pump.

Data from the 2-3 am hour of Nov 16:

Boiler power 17061 Btu/h (5000 W)
Outside air temp 22.72-23.31 F
Inside air temp 70.3-73.78
Greenhouse air temp 55.53-57.69

Inside to outside temp difference 49.025 F, 27.236 C.

Building UA = 17061 Btu/h / 49.025 F = 348 Btu/hF
Building UA = 5000 W / 27.236 C = 183 W/C

Lower is better.  It would probably look better if I hadn't been heating the greenhouse, but in order to get steady state with just the cabin zones heated, it will have to get colder outside.

I'm actually more interested in the circulation pump right now as I'm trying to figure out the solar hydronic system.  The data I have is:

Boiler outlet 97.85 F
Cabin return A 90.27
Cabin return B 91.41
Greenhouse A 94.05
Greenhouse B 90.09

I really wish now I had a sensor on the boiler inlet to measure the mixed return water temp.  As it is I don't have much choice but to assume all the loops are carrying an equal share of the flow, and use the average of the four return temps.  

Distribution loop temp difference: DT = 97.85 - 91.44 = 6.395 F

Qdistrib = m cp DT = Pboiler, in steady state.

m = Pboiler/(cp DT) = 17061 Btu/h / (1 Btu/lbF * 6.395 F) = 2668 lb/hr * 1 gal/8 lb * 1 hr/60 min = 5.6 gal/min.

I looked up pressure-flow curve for the Taco 007 circulator, which is (irritatingly) labeled curve number five (dark green).

At 5-6 gpm the 007 is almost maxed out on pressure.  I wanted to put flow meters in the distribution loops but I can't find any (cheap) ones that drop less than about 1 psi @ 4 gpm, which is like two feet of water and it looks like that would choke this pump off entirely.

Friday, November 21, 2008

Must-read septic system update

It looks like the septic-line-insulating-dirt-berm-operation (SLIDBO) on the 18th has halted the coldward temperature trend on the east-west section of the line (middle trace on the graph below).  That is good because it is only 4 degrees from freezing.  Air temp outside has been below freezing for a week.  Now that there's more dirt on top I hope some heat from the ground can migrate upward and warm the line or at least offset the cooling trend.  It's only November.

Wednesday, November 19, 2008

Solar Water Heat, Phase Uffda

J and Grandmaster-J, from, swung by today with Solar Water Heat parts, including the two 120-gallon solar storage tanks.  Lookatemgo.
These are Richmond S120HE-1 tanks.

In other exciting news, our pal Pigpen replaced the seal on the toilet and "retrained the operator."  
[Photo omitted.]

I on the other hand had a rough day of sitting in my cozy cabin and working on the computer.

Survival spud diet update

As Jerry Reed sang in She Got the Gold Mine, "why didn't you just learn how to cook?"

My many loyal readers (hi Mom) will recall the 600 pounds of potatoes I grew this past summer.  I think I'm running behind on eating them, at a rough guess maybe 30 lbs so far.  It occurred to me that if I made a big batch of mashed potatoes ahead of time it would be more convenient to reheat them for quick lunch breaks etc.  Mashed potatoes make a great extender for canned chili, soup, hash.

This is a form of what I think of as Bachelor Chow, where you take a processed food product and bulk it up with extra vegetables, usually in a one dish.  Here's another example: a breakfast salad I made from a gas-station breakfast sandwich and broccoli:

Actually that one didn't turn out that great (a little dry).  

I once saw KP making potato pancakes; it looked like she was just frying patties of mashed potatoes.  I haven't been able to get that to work, they crumble when I go to turn them.  Adding milk and even egg makes the potatoes smoother and creamier but they don't add any strength to the patty, and seem to make it even more likely to stick to the pan.

What did work was adding mashed potatoes to corn muffin mix and making pancakes out of that:

Here's my recipe for Corntato Pancakes:

2  1/2 cups Bob's Red Mill Cornbread Mix
2 cups mashed potatoes
1  1/4 cups water
1/4 cup oil
1 egg

Makes about 1 dozen.  Yummy.

I've also been working on mastering the no-scramble, one-egg cheese omelet:

Tuesday, November 18, 2008

Another round of freeze protection

Mr. and Mrs. Universe donated their trailer home.  Last week the nice men came to take it away, ha ha.  (I mention this in case you'd wonder where it went in subsequent photos.)

I'd been monitoring the septic line temperatures via the sensors Neo and I installed t'other week, and got a bad feeling.  I showed a chart like the one below to Edie D. the Executive Director, and Pigpen, learned with drain expertise.  The light blue line shows that from noon on the 4th to midnite on the 11th, the outside air temperature dropped from 65 to 17 F.  The dark blue line shows the temperature on the downstream leg of the septic line which we recently bermed over, that temperature barely moved.  The gray line shows the temperature on the upstream leg which was only about a foot down.  It responded much more quickly to the air temperature and had dropped into the thirties already.  We decided maybe we'd better hurry up and throw some more dirt over the upstream leg of the septic line.

That dirt-berming operation took place today.
I decided we'd better bring the berm right up to the house.  Glad I didn't spend too long setting the pavers for the walkway.
Pigpen must've brought out at least a ton of straw - four or five of the 8-foot bales.  We talked about throwing some manure on it in the spring and planting it.
I had to reroute my walkway which looks a little goofy now.  

Monday, November 17, 2008

Greenhouse floor sealing

Next week the Rural Renewable Energy Alliance comes to install solar water heat equipment.  It'll be one for the ages, the heat storage tanks will hold one ton of water and once installed will not be moving for a while, God willing.  I thought it would be a good idea to do something about the greenhouse floor before they went in.  The cob-crete floor has been wearing away into a fine powder.  Redbeard came up with a scheme to seal it using ordinary water-borne polyurethane and came out to do a test patch.  

It seemed to basically work.  Not a super-tough surface but it was a lot better than before so I went ahead and did the rest of it.  Redbeard says to me, "try and mix the poly and dirt into a slurry and fill the cracks in the floor.  And don't get ahead of yourself."  I sort of did that, but as much dirt and dust as there was on the floor, it still wasn't enough to fill the cracks, and it seemed crazy to dig up more dirt outside for that purpose.  That could still be done some time I suppose.  It took three gallons @ $40 to do the whole floor.  I wanted to hurry up and finish it so I could stop using electric boiler heat to warm the greenhouse floor.

I had a lot of stuff stored in the greenhouse which I had to move inside.  The upside of this is that there's much less floor to sweep in the house.

Tuesday, November 11, 2008

Freeze protections

When I got back from the Passive House Conference on Sunday it was down to 53 F in the house.  I hadn't left any heat on, the weather had turned colder, and I wasn't there to open the door to the greenhouse to let the solar heat puff in.  So far this fall I'd been getting by with said passive solar and a 1500 watt space heater on cloudy days.  It was sunny on Monday and I got a lot of good heat into the house, but come the night the little space heater couldn't keep the house above 60.

I find if the temperature is below 64 my nose gets cold, which I dislike.  So late Monday night I decided to torch the planet's future for the sake of my short-term personal comfort, and turned on the Big Heater.  That's the 5000 watt electric boiler and the in-floor hydronic radiant heat.  Right now there's no thermostat control - a simple on/off thermostat probably wouldn't work very well anyway, because of the huge time delay between turning on the power and heating the air.  There is an aquastat for controlling the boiler outlet water temperature, which I set at it's minimum of 90 F.  Over the past day the boiler has been cycling on and off.  On the HUGnet monitoring it looks like the boiler outlet water is averaging about 88 F, the return about 78 F, and the air temp in the house about 64 F.  This was with the water heat loops to the greenhouse floor shut off.

The temperature sensors on the septic line have been trending down, faster on the E-W section which is the shallower leg now.  It's now about 37 F.  Typically it is coldest at around 1 pm and warmest at around 1 am, that is, there's about a 10-hour delay from the daily cycle of the air temperature above.  It seemed like a good way to run the deicing cable might be, to turn it on for awhile midway through the daily cooling-off period, which would be about 10 am.  I've set it on a timer to run from 9 am to 11 am each day, we'll see how that works out.

I also set up a heater to keep Big Foamy, the aboveground root cellar, from freezing.  It's just a work light with a piece of polyiso insulation board taped over it to keep the potatoes in the dark.  I've got a little line-voltage winter watchman thermostat to control it, set at 40 degrees.  It's also plugged in to a Kill-a-watt meter so I can monitor how much energy it's using.

Sunday, November 9, 2008

The future of housing

I'm yust back from the North American Passive House Conference in Duluth, Minnesota.  Redbeard recommended I should go and he was right.  It was a small conference but very good.  I thought the presenters represented the best thinking on sustainability, and the audience participants also had smart questions and comments.

Passive house is a super-insulation concept for buildings (which originated in the U.S. and Canada in response to the oil shocks of the 1970's) was formalized and so-named about 15 years ago in Germany, and is now reimported/revived in the U.S.   The key concept is that as you add more and more insulation and air tightness to a building, you can take more and more cost out of the heating system, therefore you can get dramatic (90%) reductions in heating and cooling energy for little extra cost - a true win, not just a tradeoff.  Or, to put it in my accustomed sarcastic and curmudgeonly terms, it is ridiculous to continue the stone-age practice of burning stuff to heat the house, now that we have so much better insulation...than in the stone age.

The Passive House Institute has set a Passive House Standard.  It is a performance-based standard which I think is focused on the right things.  Being German, it sets very stringent requirements for air-tightness, total annual heating and cooling energy per square foot of usable floor area, and total household energy use including all appliances.  They derive these allowances from a concept of per-person fair share of the earth's capacity to absorb greenhouse gases.  The Germans have about a ten-year lead and have thousands of buildings meeting this standard; in the U.S. there are only a few yet.

It's interesting (I'm sure you'll agree) to compare and contrast the stereotypical German Passivhaus, the two examples we toured in Duluth (the Isabella Eco-House and the Skyline House), and the HDT Eco-Cabin from which I am broadcasting here.

The big difference is that all three U.S. houses are considerably fancier.  All three are tricked out with solar water heat systems for both domestic hot water and space heating.  Two of the U.S. houses also will have solar electric systems.  Two also have attempts at long-term (seasonal) heat storage in the ground under the building.  Partly this is because of the harsher climate of Minnesota as compared to Germany, and partly because of lingering bias in the U.S. towards adding renewable sources of energy instead of efficiency measures.  The canonical German Passivhaus is a super-insulated, super-tight house with full time mechanical ventilation through a heat-recovery ventilator, and a small (1000 watt) electric heater also integrated into the ventilation system.  

The Isabella Eco-House:

The Skyline House:

Compared to these places our HDT cottage here is relatively modest, and uniquely intended from the start to be 100% solar.

There was also some great stuff on retrofitting existing houses, how to achieve deep reductions in energy use without breaking the bank.  Things like super-insulating only a portion of the house, or building a small super-insulated addition.

There was also a very interesting presentation on straw bale construction.  The presenters had basically given up on making the straw bales load-bearing, and had evolved basically to a double-walled wood frame house construction with straw bales as insulation.  They were even cutting the strings on the bales to eliminate the gaps between them, essentially turning the straw into a dense-pack insulation within a wood structure.

Wednesday, November 5, 2008

Battening down for winter

Since the hard freeze of Monday-before-last? we've had another nice little stretch of Indian Summer, good for getting in a few more outside jobs:

Back on Cob Spraying Day (see 30 October) while the Cottage Cob Crew was at their labors, Pigpen and I worked on freeze-protecting the septic line with gutter de-icing cables.  This was not a photogenic process.  Basically, the process was to run fish tape or plumbing snake downhill to the tank or cleanout, tape the plug end of the heater cable on and pull it back through.  I repaired the existing 100 ft cable which because it is shorter is now 700 watts instead of 600.  It protects the E-W section of the line.  A new 375 watt cable protects the N-S section of the line, and the tank.  As I described previously, we've also got temperature sensors buried just outside the pipe so I can tell when freezing threatens and the heaters need to be turned on.

As I went about mentioning to people about the temperature sensors everyone pretty much said "sure would be nice to get a bit more insulation on top of that line..."  Pigpen was like "Yah, let's get crazy with the Cat.  Two hours I can build one of my patented two-foot-high six-foot wide dirt berms on it.  I'll even drop a straw bale on top you can spread out for extra insulation."  This plan was speedily approved and boda-whang, he got 'er done.  

Looking north:

Looking east:

The straw ended up about six inches deep.  I fluffed up the old straw over the tanks as well.

The extra dirt is helping - I can see a difference on the temperature traces.  Before there was about a five degree daily temperature swing, now it's less than one degree I'd say, on the N-S section of the line.  

I think we are in pretty good shape on this, with the sensors, the electric heat, the partial berm.  Also when the solar water heat is hooked up I may be able to use free solar hot water to warm the line.  Multiple elements supporting the function.  Permaculture.

* * *

We also moved Big Foamy, the insulated box now serving as a root cellar, to my Originally Designed Root Cellar Location just outside the west door.  Now that it's out in the sun it should stay unfrozen a bit longer.  Mr. Universe also pointed out that because it's so insulated, it wouldn't take much electric heat to keep it unfrozen, twenty watts maybe.

I also tried various things to fix the leak in the lid.  I found some heavy black plastic film which Redbeard later told me was "root barrier".  I tried gluing it to the lid (which is made of pink polystyrene foam board) using expanding foam.  It didn't stick.  Next I tried gluing it on with roof tar, that caused the edges of the film to curl up.  I gave up on it for now and turned to the sides.  I wanted to cob the outside of the box, basically to make it look nicer.  It then would match the cottage, both in appearance and in the manner of construction being comprised of wood, styrofoam, and mud.  I got as far as stapling on two layers of chicken wire, and cobbing about one eighth of it.  

* * *

Fancy finished up cobbing around the windows and doors, and declared a seasonal end to major cob operations.  She says it's better if it dries before it freezes, but the forecast is for wet weather through to a hard freeze on Saturday.

I can report some qualitative evidence that the door and window resealing is working: before I could smell straw inside when the wind blew hard enough, I don't notice that any more.  I'd still like to get a blower door test done to quantify the air tightness of the house.  Hopefully when the new building is tested we can piggyback on that operation.

* * *

Another thing I had designed but not gotten to was the beltway path around the cottage.  The main point being to better protect the floor inside from tracked-in sand.  Mrs. Universe had a couple pallets of patio pavers she wasn't using so I grabbed 'em and started hastily throwing them down.  I guess ideally the ground should be fluffed and leveled and tamped before setting the pavers.  That I did pretty half-assed.  Most of it's not too bad.

Monday, November 3, 2008

Solar electric

I made some progress on my solar electric system - I built a rack to hold the panels.  I have the same modules as KP and the Skipper have out on the Island:  BP Solarex MST-43.  They had gotten their rack from Power Fab and gave me the part number for the rack to match these panels, but when I asked Power Fab for a price, they ignored that, asked for all the module specs, and came back with a quote of $2770.  For a rack! This was more than twice what I paid for the solar panels!  Clearly this was custom, hand-made-by-union-Ph.D.-plumbers pricing.  I was so disgusted I didn't even call them back but I thought about saying something like, you did hear me say rack, not crack or rock, right?  Mr. Universe joked that it would be cheaper to buy a Cadillac and bolt the panels onto to it - it would be long enough to hold all seven, and heavy enough not to blow away.

So for one-fortieth of that price I built my own rack, out of wood and deck screws because that's what I know.  This was a solid three-day project.

I designed the basic cross section in Sketchup, for a 60 degree angle.  The instructions for the modules recommended latitude-plus-fifteen-degrees tilt for this location.  They also recommended using the middle set of mounting holes (on 2-foot centers) rather than the holes at the corners.   The back leg of the rack is also at a 60-degree angle.  This suggests an equilateral triangle shape which I thought would be pleasing.
I worked out the 3-d details and added extra bracing as I went along.  It's made in two eight-foot sections and the center module spans over the joint.  
The basic strategy was to screw horizontal crossbars tucked inside the rails on the back of each module, and then to screw those crossbars to horizontal rails on the rack.  I figured this would be pretty forgiving of inaccurate construction and wavy wood.

Pocketing the face of rails for the screw heads.
I left a good inch between modules.  This helps it look okay even though the panels are not laser-parallel, and gave me space to clamp.
Because of wavy rails I had to shim here and there.  
It's ballasted with 4x4 timbers and concrete blocks.  I don't know if this is enough.  I positioned it as close to the house as I could in hopes of reducing the wind load.  There's no gutter on the front yet, the drip line is right above the concrete blocks.

I would have preferred to paint or stain it but I settled for caulking all the glue joints.  Now it's ready for some grounding & wiring.