FURNACE-FREE HOUSES. The Gaia House. ecology

FURNACE-FREE HOUSES

SITES:
. . Oikos (www.oikos.com)
. . Environmental Building News (www.ebuild.com).
. . london@sunSITE.unc.edu
. . london@nuteknet.com
. . http://sunSITE.unc.edu/london/renewable-energy.html
. . http://sunSITE.unc.edu/london/permaculture.html
. . free energy-modelling program Solar 5:
. . http://www.ced.berkeley.edu/cedr/vs/inf/rps.html
. . http://www.waterwiser.org/books/ulft.html

. . Healthy House Institute: http://www.hhinst.com/
. . Cement can contain up to 5% inert or unclassified material which is generally ash from fuel used in its manufacture. Depending on the plant, the ash could be a byproduct of garbage incineration and could be high in toxic contaminants.

The paper facing on the front and back of gypsum board makes an excellent nutrient for fungal growth. Carbonaceous materials will generally be supportive of fungal growth in the presence of moisture. Wet sheet rock can provide a fairly sustained source of moisture at the paper facing --back or front.

The house has fresh air supplied continuously at the rate recommended by ASHRAE 62-89 standards (15 cfm/ bedroom, 30 cfm/master bedroom—60 cfm total). We make the house airtight. In addition, by providing a slight positive pressure (max. 3 Pascals), we will control pollutant entry (radon, soil gas, etc.) into the house.

FURNACE-FREE CONSTRUCTION
. . I loved this exchange:
. . http://www.buildinggreen.com/elists/furnacefree.cfm
. . Amory Lovins (world famous energy expert). It began when Amory told Donella that it was possible to build a passive solar home in the Vermont climate which required no heating system or back-up heat. Marc was very skeptical, and went on to do computer modeling to verify this claim. The actual project is a 22 unit cohousing/organic farm/institute being created in Hartland, Vermont.
. . I assumed: a 1344 ft2 house, one story, R-40 walls, R-70 ceiling, R-40 floor over a basement, very tight construction. 200 kWh monthly internal gains from people, appliances, lighting. 68F thermostat setpoint. Burlington VT weather data file.
. . Thermal mass: 350 ft2 of 4 inch thick concrete floor, plus 500 ft2 of 4 inch thick concrete wall exposed on both sides to the space (interior walls). Net glazing 80% of gross rough opening. 225 ft2 south glazing, 25 ft2 on north, east, and west, each. Triple layer glazing with two low-e layers with high solar gain low-e, argon fill. R overall of windows just about 5, glass-only: R-6.
. . Annual back-up heat required = 6.6 MMBTU
. . With setpoint of 60F = 3.7 MMBTU
. . In Eagle, CO = 1.4 MMBTU
. . In Denver, CO = 0.8 MMBTU
. . 6.6 MMBTU is very low, just under half cord of wood. But you still need something to provide it! A woodstove with chimney costs real money, it's not free. And it doesn't make hot water.
. . BTW --I played with adding more mass, more glass, changing other parameters-- very little impact. the issue is that our weather has occasional long cold cloudy spells, in which passive solar doesn't carry the load.
. . Save the expense of chimneys, stoves, or heat-distribution systems.
. . First thing, make all the glazings at least R- 8.1 center-of-glass (like Hurd Insol-8), and preferably R-11 or -12. That would typically mean three selective films -- either a double-sided Heat Mirror 88 or two separate single-sided HM88 films, plus (say) Cardinal low-E softcoat on one lite (try inner and outer separately to see what's best), all filled with krypton with optimal (around 10-12 mm as I recall) spacings. If necessary, go to wide sashes like Pozzis. Be sure to use krypton, which insulates twice as well as air, not argon, which is only 1/3 better than air and has a wider optimal gap. Extra cost is zero to negligible, because you use not 99.999% lab-grade krypton but only first-distillate-stage Kr (around 60-70% Kr, rest Ar; indistinguishable thermal performance). In your climate, R-7 is roughly the threshold above which north glass provides a net winter gain. With such good glazings, you could also consider using a bit more glass. You now have 22% glass-to-floor-area ratio. Ours is 26%. Normal for nonpassive houses is about 10-12%. A bit more gain than 22% wouldn't hurt if you've paid proper attention to glare management and luminance ratios.
. . Next step, use Wolfgang Feist's trick for eliminating edge losses so the entire glazing assembly has the same R-value as the center of glass. You do this by adding about a half-inch layer of foam, dressed with a plastic or textile cover so it looks nice, that overlaps the entire window frame and goes about 1-1.5" onto the glass all around. You lose a little aperture that way, but it looks good and has terrific thermal advantages. (Also eliminates any leftover frame infiltration.) You do it at least inside and preferably also outside. You can design it to be removable in summer on operable units.
. . Next, make sure you're using a good air-to-air heat exchanger. We use Carrier's Venmar (Quebec) condensing polypropylene-core crossflow units, but counterflow would be even better, and we want to retrofit the Venmars from constant to variable speed. In any event, spec several fold oversized (i.e. right-sized) surface and slow, efficient fans at variable speed, ideally with CO2-sensor control, so you have a very low face velocity, and you can readily get efficiencies well up in the 90s of percent. If necessary, use the further Feist trick of tempering the outside air up to at least 50deg.F by bringing in through an earthtube (suitably sloped, drained, screened, etc. to avoid fungus, rodents, etc. --standard drill for earthtubes).
. . Mean radiant temperature is half your perception of warmth --indoor drybulb air temperature is the rest.
. . Passive really will carry the load even in Burlington. But finally, if you do need any residual heating, or want a control margin, for those long cold/cloudy spells, just run a radiant coil in the slab and heat it if needed with a hydronic loop from the water heater, which you'll need and pay for anyway. You might like to consider a simple French Aquastar (the U.S. distributor is in Vermont and is excellent) for both those functions --run on bottled gas or biogas. (We cast such radiant coils into our floor slabs, but never needed to hook them up.)
. . Of course, there's a lot to be said for a miniature (watermelon-sized or less) woodstove anyhow, run through an outside wall, because you have to burn the junk mail, bad poetry, incriminating correspondence, and energy studies somewhere; but if you don't want one and prefer to shred and recycle your cellulose, that's fine too. A 50-watt dog, adjustable to 100 W if you throw her ball, also works fine.

. . From: Marc Rosenbaum: I don't like earth tubes because it is clear that condensation will occur in them --which means mold to me.
. . Electricity as an obviously inefficient option.

. . Not necessarily. It can be very efficient with the right pots, superinsulated ovens, induction cooktops, microwave ovens, etc.. <

. . It looks like we will be talked into gas cooking and probably even gas water heating, though I have said as a mandate: No Fossil Fuels.
. . We will probably have PVC pipes, though I have declared: No PVC. The alternatives are too expensive.

. . From: Marc Rosenbaum: The enclosed Excel 4.0 spreadsheet shows the results and the input assumptions. You'll notice the windows have center-of-glass R values of about 11, and the overall R is just under 8. You'll notice that the air leakage is lower than any house I know: 5 CFM.
. . Using the current TMY2 data, you will notice that E-10 doesn't think zero heating energy can be achieved --for a variety of mass levels and south glazing areas. As I have stated, it is clear that you can get close, but close doesn't buy you no heating input. And the house as modeled is almost impossible to build --incredibly airtight, almost the entire south wall is glass, and most importantly, the amount of mass modeled couldn't be practically be built into a small house like this (6750 ft2 of 4 inch thick concrete wall.) And the internal gains are actually higher than I expect we could easily achieve --my own home is lower, without extraordinary measures. With internal gains half as high (1178 kWh/year), the back-up heat need rises from 688 to 1030 kWh.

Some additional points:
. . * TMY data doesn't represent the worst weather year possible - it is an average. Even if Energy-10 concluded that zero heat was possible, it wouldn't guarantee that this would be true every year. Norman Saunders used to say that to reach 100% solar heat you needed to take the average December and add 30% to the solar system to cover weather variations.
. . * The best realistic result, still achieved with extraordinary measures in glazing and airtightness, and using a pretty massive building construction, is 944 kWh/year. This saves 1262 kWh/year over the base case superinsulated building, at fairly high cost (mass, airtightness, super HRV, the most costly glass, which needs to be installed in large pieces to keep the high R value.) This is about $140 in electricity, $55 in propane, or less than $30/year with wood. Why bother, when you still need a back-up source for domestic hot water? A woodstove is a poor idea --it doesn't make DHW, and it costs a lot to install, with chimney and hearth.
. . * Note that in Seattle, which is the closest US city to the Darmstadt climate Amory cites, the house uses 1/5 the back-up heat. Average temp in Burlington in January is 16F, Darmstadt is 32F. This makes a difference, even though Darmstadt, like Seattle, gets less sun.
. . * Note that in Eagle, CO, closest to Amory, you can get incredibly close to zero heat. VT is slightly colder but much less sunny.
. . Thus far, I conclude that Amory doesn't understand the climate here well enough to make these assertions.

. . From: Amory Lovins
. . My reaction is that actually you're getting the results I'd expect for your climate (I used to have a house in the NE Kingdom, spent a lot of time in NH/VT over 15 years, and do know a bit about the climate). You're really close to converging on the results I hoped for. What I'd suggest you add next is the following small but important details: - Check that you've included heat gains from lights and appliances. If my recollection of the ASHRAE Fundamentals is anywhere near right, your internal gains might be just for people, not people plus equipment (even very efficient equipment: our superefficient household lights and appliances average about 110-120 W, but that's about 1/10 of normal). A 110-W internal gain from these sources is 964 kWh/y, which approaches your resistance-heating load in the better cases. Most of the lights-and-appliances heat, too, is normally released in the evening when you want it. Putting the kitchen on the north side helps too.
. . I'd have thought you could use the performance rather than prescriptive option for ach/replaceance and get plenty of fresh air with considerably less than 50 cfm. (Of course, you can also make the heat exchange so efficient that 50 cfm hardly matters:...)
. . - Temper the air-to-air heat-exchanger input with an earthpipe, so all air coming into the hx starts at 8+ deg.C. Then specify the hx for low face velocity, i.e. big, slow fans and extended surface area, for average efficiency ~92-95% with, say, Venmar crossflow, even more with counterflow.
. . - Don't be afraid of the "extra" airtightness We did <0.03 ambient ach -- almost unmeasurably small -- after dampering the a-a hxs. (air-2-air heat-exchanger)
. . - Do go for the "extra" glazings --well worth it.
. . - If you want to get fancy, you can use a small heat pump to recapture latent heat from the exhaust air, discharging it saturated at 0deg.C, and bring it back into the space as sensible heat. Also a good way to do water heating. You can also normally do graywater heat exchange from showers etc..

From: Marc Rosenbaum
. . We run about 50 cfm continuously to keep RelHumidity down to about 40% in the cold months. Much higher RH risks dust mites.
. . - Internal gains are 0.269 kW continuous, 2355 kWh/yr, which exceeds my own not-super-efficient house. Some runs cut this in half, which is more realistic as lights and appliances get more efficient.
. . 0.03 AC/H is harder in little houses.
. . - air to water heat pumps are poor choices --complex, low COP, noisy-- the one on the market uses a glass-lined tank, which won't last as long as this kind of appliance should.
. . His is still based on average weather data. It assumes virtually unavailable construction: R-11 overall windows (how are they operable and yet remain R-11 overall?), huge amounts of mass, earth tubes, very large ventilation heat exchangers with active controls, all the south facade in glass, etc... As soon as you put any device on site which makes thermal energy available to heat DHW, you may as well use it for heat, too, and then why take the building far past the economical point of construction to save tiny amounts of energy (as well as making it into an unlivable energy machine instead of a house?) The payback on increasing the glazed south area from 228 to 312 ft2 is on the order of 100 years, yet the glass itself has seals which are likely to fail in 10-20 years. Investing in equipment in which the payback greatly exceeds the service life is not good!
. . It probably does make a lot more sense to leave a small residual heat load and to handle it with a hydronic loop from the water-heater (which you'll need anyway) into a radiant slabcoil. That's cheap, effective, and probably a lower-total-capital-cost solution than fighting for the last iota of heat savings: it still eliminates the furnace, but adds very little capital or operating cost for the backup. (Perry Bigelow has done over a thousand tract houses in IL this way for a decade with no furnaces and without even using superwindows.)
. . The basement subslab insulation is 400 mm (16") of loose Foamglas, providing an R-15 insulation. The Foamglas was apparently dumped and spread as though it were gravel. Foamglass is also used for the roof insulation (10") over the waterproof membrane but below the vegetated roof.
. . The south wall is fully glazed fixed direct set panels --heat mirror TC88-- including krypton gas.

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