Yes, FBBP, firing a stove is an active task. So is shivering. It's called passive solar to distinguish it from active solar (PV or hot water.) Supplemental heat is a given. If I got even 25 percent of my heat just by pointing my house the right way, would you say passive solar failed me?
Nor are firewood and coal equivalent. Wood is the product of living organisms that sequester carbon into perpetuity given good stewardship. Burning it releases that carbon more quickly and completely than decomposition, but one doesn't necessarily weigh the alternatives when lightning strikes a 100-year old oak at the head of one's driveway. By contrast, coal is carbon that is otherwise safely held in storage and that can't be readily replaced.
While smoke can be a local issue, masonry stoves pollute less because they're meant to operate at full blaze.
Jonr, given enough mass in a very tight house, there aren't any changing conditions that need to be addressed quickly.

Posted By toddm on 10 Dec 2010 09:53 PM
Yes, FBBP, firing a stove is an active task. So is shivering. It's called passive solar to distinguish it from active solar (PV or hot water.) Supplemental heat is a given. If I got even 25 percent of my heat just by pointing my house the right way, would you say passive solar failed me?
Nor are firewood and coal equivalent. Wood is the product of living organisms that sequester carbon into perpetuity given good stewardship. Burning it releases that carbon more quickly and completely than decomposition, but one doesn't necessarily weigh the alternatives when lightning strikes a 100-year old oak at the head of one's driveway. By contrast, coal is carbon that is otherwise safely held in storage and that can't be readily replaced.
While smoke can be a local issue, masonry stoves pollute less because they're meant to operate at full blaze.
Jonr, given enough mass in a very tight house, there aren't any changing conditions that need to be addressed quickly.

I don't necessarily disagree with anything you say here. However my point is that firing the wood stove is not different from setting the thermostat. One is just more automated. Also while most improvement over the last three decades come from people who are willing to split the firewood, ultimately we want a building for the masses that has the same efficiencies as some of the doers and shakers are getting. So please do not take my points as a critisism of the people that do but as something to think about as to how we can deliver to the masses. In this case, as suggested earlier, some active storage collecting heat from solar collectors, instead of the wood stove might make you home ready for any buyer that walks in off the street.

Oh, but setting that thermostat is very different if it is connected to the power company or a fossil fuel boiler or furnace. At least it is in my part of the world, where firewood falls from the sky. My goal is to pay $600 a year for energy.

And the trouble with providing for the masses is that everyone has a unique story. Solar hot water is a tossup for me, for example, because of the aforementioned trees. On the plus side, wood heat is common here, and if my design proves out, I'll be splitting a fraction of the wood my neighbors are. I suspect that SierraSkier's neighbors are already a cord or two ahead.

But you are right that passive solar isn't for everyone. It's the Goldilocks dilemma: heat without overheating; wood supplement without a hernia; active management without a PhD. And I don't want to suggest that my design is just right because I don't know that.

I'll have a 300 gallons of heat storage, but it is no substitute for the house's 100 tons of mass. Modeling says it will lose a bit more than a half a degree an hour at its design day heat loss (25k btu/hr at 10 degrees). A single burn flat out burn in my stove -- 40k btu/hr for six hours -- would add two to five degrees depending on heat loss and wood quality. My aim is civilized passive solar/wood heat. Everyone remains fully clothed at all times.

At any rate, the world is headed in my direction. Today, the USGBC requires builders to provide a basic owners manual and a walkthrough as a part of the LEED certification process. If they want an extra point it takes a comprehensive manual plus training.

"ultimately we want a building for the masses that has the same efficiencies as some of the doers and shakers are getting". This is exactly what the founders of the Passive House movement had in mind - affordable homes that anyone could afford, could build and live in (without a comprehensive multi page manual). Homes that required very little supplemental heat, that did not require a certain orientation, solar panels or any other expensive technology. What they found was that by insulating the building well enough that goal is achievable. Through their calculations and then trial and error they identified the important aspects that the builder has to follow to achieve that goal. We in the US have a ways to go to make the affordable part a reality; the materials we need aren't all available easily and the methods aren't all worked out yet, but there are hundreds of Passive House followers and others interested in energy efficiency, like those on these forums that are all trying different methods and combinations of methods. We haven't gotten there yet, but we will. It is doable.

Bob I, if I like to look out windows and I have something worth seeing, is a Passive House design for me? Never been inside one so this is complete ignorance on my part but I'd rather not live in a bunker.

Also, passive solar costs less to build than conventional construction. SierraSkier's windows cost thousands less than standard U factor windows, for example. (I am guessing.) Slab on grade is cheaper than basement. The bulk of the mass in my house is AAC block that cost $6 to $7 a square foot as a semi DIY. (Hired a moonlighting mason; served as his helper.)

I doubt that that there is a one size fits all, except to say that extraordinary insulating and sealing should be the base of any approach.

The Passive House Institue doesn't specify design, insulation levels or how many windows you should have, but rather it gives standards the buidling needs to meet to qualify for PH designation. It is true that extensive windows are probably uncommon in PH's simply because it is hard to overcome their heat loss and still meet the standard. My point wasn't that every home built should be a PH, but that using the techniques that PH has found to work will help every building be more energy efficient. Ideally, though, we could all approach PH standards by these methods and "extraordinary insulating and sealing" is a good place to start.

What is the appropriate metric for an energy efficient house? btu/year? btu/heating degree day? btu/HDD/sqft? What does PH use?

PH has three basic metrics: 4.75 (thousand) btu per Sf per year for heating and cooling, .6 air changes per hour at 50 pascals, and 11.1 kWh per Sf per year of primary energy (primary meaning at the power plant) to meet all of the building's energy needs. To be certified, the building's construction plans must be OK'd by PH and must be verified during and following completiion. A building must make use of these practices: superinsualtion. elimination of thermal bridges, a continuous air barrier, mechanical ventilation, high performance windows and doors, minimize energy losses, manage energy gains and use the PH modeling program.

These are described in a new book: Recreating the American Home, A Passive House Approach, by Mary James. I should mention the book contains has a directory of PH consultants in which I am listed.

Thanks. It follows that a PH is much easier to achieve in a mild climate. It also encourages (or perhaps doesn't discourage) larger houses - ie, it measures "per sq ft" and larger houses can have less surface area per volume and less power usage per sq ft (for example, hot water usage is more a function of the # of occupants). A 10,000 sqft house for two people isn't very "green" even if it is a PH.

How does one measure btu/sq ft without waiting a year for the results?

I can tell you that houses that are certified by Passivehaus in Germany are required to be small and cannot exceed so many SF per occupant. That requirement was dropped from the American version as it was thought no one would put up with it. You can estimate energy useage with an energy modeling program, but you do need to compete a heating season to actually measure the results. The PH modeling program (PHPP) is an extremely detailed program and they have found that the results are pretty close to actual results.

It's too bad that they didn't leave in some accommodation for smaller houses. Ie, perhaps not a fixed max sqft per occupant but something that meant you had to go to greater, not lesser extremes to meet the standard in a large house.

Amen. What America really needs is a 1500 sf house with the curb appeal and livability of a mcmansion. Suzy Homebuyer wants arugula. PH is serving up spinach.

toddm
Well, I have to tell you you're wrong about that. Passive House leaves the design and the curb appeal up to the builder/designer/owner. A PH can be anything you want it to be except an energy hog. Anyone that has followed the writings of Sarah Susanka and her "Not So Big" philosophy knows that you don't need 3500 Sf to have a neat home with tons of curb appeal. Kaplan Thompson Architects in Maine has designed some "net zero energy" houses starting at 1200 Sf which are being offered by a local modular plant. I displayed the brochures at a conference and one of the first people I spoke to was "Suzy Homebuyer" who was attracted by the design and the size and is moving forward with buying decisions. There may be some differences between a ZEH and PH, but the point is that small well designed very energy efficient homes can and do attract buyers.
Bob

Sierra Skier,
Would some solar water tubes help smooth out some of the variation in temps?

-Rosalinda

Thank you for the information. This could be very helpful. It only proves that the sun helps us a lot.

We've built a lot of Passive Houses, while they have high comfort levels with minimum temperature fluctuations, they still require a back-up heating system for really cold weather. We find clients are scared of not having sufficient back-up heating so generally go overkill with heating systems. That's why I developed this 100 day solar heat store http://www.viking-house.ie/hydro-th...store.html and under house heat dump,  I welcome critical comments on this solution!

SWH systems are design to deliver the optimum amount of hot water for most of the year. However,in winter there sometimes may not be sufficient solar heat gain to deliver sufficient hot water. In this case a gas or electric  booster is normally used to heat the water.

40,000 l of hot water?

Hasn't that been done before?

Posted By ICFHybrid on 13 Jan 2011 08:31 PM
40,000 l of hot water?

Hasn't that been done before?

We used water storage a few times already but found the large tanks expensive, the stone store within the foundation system is a lot cheaper, if its been used before I wouldn't mind seeing a few links.

After looking at all the other measures addressed in your designs, I can see how a BIG hot water tank could make sense where it hasn't done too well on this side.

Is it really designed to be charged in Summer and carry all the way through the Winter, or what is the rationale there?

I might find the same to apply to the stone store, but I didn't consider it as closely as the water. Stone stores were done here back around 1980 or so. I remember helping fill up the basement of a 5500 sf home with stone. It was a total failure, too. Luckily, I wasn't around to have to remove the stone.