Set back is akin to thermal mass. There tends to be a mania for both but perfect comfort is rarely served nor "achieved" by either.

Yes, you will use less fuel if you let systems idol and/or have a lower indoor temperature, but comfort (the reason we don't live in tents) is always compromised by such stratetgies. If you can't afford, won't pay for or don't mind large temperature swings; then heat load analysis, modern HVAC control strategy and IAQ or not for you.

Opening windows gives you perfect IAQ and humidity is not an issue for most humans in good health - though your flooring, furniture and baby grand may not agree.

Often confused with out door reset (ODR), set back on hydronic systems - especially high mass radiant floors and cast iron radiation - is of little or no use. ODR by contrast will operate at lower average water temperatures saving fuel and increasing comfort at once. This control can be added to practically any boiler with great effect. On the most sophisticated system the supply water temperature can be set back to achieve the extra fuel savings without compomising comfort.

Of course Masonry heaters can not be controlled to this degree.

You still seem stuck on this "perfect comfort" and control.

We don't live in a bubble of perfect comfort 24 hours a day. We are outside, at work, in the car. We put on clothes , we take them off, we move a little bit faster or a bit slower to keep warm or cool down. This relying on the "perfect comfort" does not work when the electricity is off.

You must be one of those guys wearing heated underwear, boots gloves and hats when you leave the house. Do you wear a helmet with the perfect humidity as well?

Be a real man - don't use any heating system!

Posted By BadgerBoilerMN on 16 May 2011 09:07 AM
Set back is akin to thermal mass. There tends to be a mania for both but perfect comfort is rarely served nor "achieved" by either.

Yes, you will use less fuel if you let systems idol and/or have a lower indoor temperature, but comfort (the reason we don't live in tents) is always compromised by such stratetgies. If you can't afford, won't pay for or don't mind large temperature swings; then heat load analysis, modern HVAC control strategy and IAQ or not for you.

Opening windows gives you perfect IAQ and humidity is not an issue for most humans in good health - though your flooring, furniture and baby grand may not agree.

Often confused with out door reset (ODR), set back on hydronic systems - especially high mass radiant floors and cast iron radiation - is of little or no use. ODR by contrast will operate at lower average water temperatures saving fuel and increasing comfort at once. This control can be added to practically any boiler with great effect. On the most sophisticated system the supply water temperature can be set back to achieve the extra fuel savings without compomising comfort.

Of course Masonry heaters can not be controlled to this degree.

After living in our house for the last 23 years, a completely wooden (PWF) stick built house, superinsulated and passive solar with an air tight wood stove, I really do understand the meaning of temperature swings. A lot of thought has to go into whether to light the stove or not, durring the day the sun comes out right after and ends up overheating the house. We have learned how to cope and the indoor house temp rarley moves between 68 and 74 degrees Farenheit and is quite comfortable, but you do have to pay attention and hope the weatherman is right!

John

My point exactly and your local climate and construction will dictate the individuals experience.

If no one is home for 10 hours and sleeping for 8, control can be an issue. If you are retired and don't travel, no problem.

The people of the South West have used high mass adobe constuction for some time. I worked on many of them while living in Albuquerque (where putting humidity IN the house is the norm).

I am not against passive homes or "Masonry Heaters" but suggest they are not a panacea for Green or comfortable living.

For people building GREEN, HVAC are things to be considered.

The French delivered promptlly, Jonr, and as far as I know, no woman was mistreated in the process. BTW, thanks for validating my manhood, but the folks who actually understand passive solar will tell you that the one essential ingredient is a real woman.

The Burch study is as described, and Ashrae members will find at Vol 90.2-1984, pp 184-206. Burch built four houses in Gaithersburg Md at what was then the Natl Bureau of Standards. Otherwise identical in SFage, fenestration and static R, No.1 was conventional stud wall, No. 2 was high mass with interior insulation; No 3 was a log house; No. 4 was high mass, exterior insulation. He heated the homes with the same thermostat settings during the winter of 1983: a 10-degree setback from 68 degrees from 11 p.m. to 7 a.m. Measuring energy use, he graphed kW consumption against average ambient temperatures. The result was the one you'll find in YOUR link earlier in this thread (an ORNL paper on thermal mass): the difference in setback savings between low and high mass houses are "very insignificant." Burch's graphs lack grids, so specifics would be estimates. Let's just say that if I reproduced them as transparencies and overlaid houses 1 and 4, the result would be a slightly fatter line. He also measured performance with and without interior partitions and furnishings. With furnishings resulted in less difference.

There is little discussion of how these results could stray so much from conventional wisdom. Suffice it to say that my musings earlier in this thread were wrong in almost every particular. A big part of it appears to be enhanced dynamic benefit. That is, if mass saves energy in 24-hour periods when the average daily temp is 70ish by buffering daytime heat and nighttime cool, then it will save more energy if the acceptable range is 70ish minus 3 degrees. Thus the difference in setback savings between conventional and high mass structures in mild climates is miniscule on to nonexistent (and also insignificant in $ terms.)
For that reason, Burch plugged his results into the Thermal Analysis Rearch Program software and predicted savings in Madison, Wis. -- a climate featuring full-on winter. Before you quibble about predictions, open YOUR link and read what ORNL has to say about the correlation of TARP simulations and actual results from high mass test buildings. In Madison, setback savings in the stud wall home with interior walls and furnishings was an estimated 14.9 percent a year, compared with 12.1 percent for the interior mass home. If we add 3 percent savings as the annual dynamic benefit of high mass (your link, Minneapolis projections at R10), well then, high mass works slightly better in Madison than conventional construction. If we go crazy with R25 over high mass, then we have a substantial edge: 20.1 percent annual savings vs. 14.9 percent. And yes, you'd bother, even if the results were the same. The savings from passive solar can be 100 percent, but you need substantial mass to buffer extremes.

One last thing: Burch used the Fanger Comfort Model and bar graphs to gauge the impact of setback in the four houses. In conventional stud wall, setback temps spiked in the "cold" range. Setback temps in interior mass didn't exhibit a spike, but I'd eyeball the median as the warm side of "cool." If it got to "cold" at all, the bar is indiscernible from the baseline.

Alas, Badger demonstrates both the hammer holding principle and its corollary. (When you are holding hammer, the whole looks like a nail, and you prefer blissful ignorance on the properties of screws.) The first generation of passive solar homes missed the importance of thermal mass. Mass changes the picture completely. For what must be the ninth time I've written this, my modeling predicts that my house will never be colder than 55. Gotta say I'll be more comfortable leaving it than any previous home I owned. Power failure on the second day of a month-long winter vacation? No problem.

Granted it will take a day or two to warm up, which is why you want aux heat that can pour the btus directly to some part of the mass, to reclaim comfort by the square foot. Like a masonry heater.

Finally, where is it written that a passive solar houses can't have HRVs, ERVs, dehumidifiers, automatic blinds run by electric eye or remote, solar hot water, storage, PV? I am building the house I want on a lot with plenty to see out the windows and no one looking back. On a different lot -- on most lots -- I'd be building a passivehaus with equal attention to IAQ, humidity, temperature constants and low or no energy use. Oh yes, and no conventional HVAC in it, either.

setback savings in the stud wall home with interior walls and furnishings was an estimated 14.9 percent a year, compared with 12.1 percent for the interior mass home. If we add 3 percent savings as the annual dynamic benefit of high mass (

As I read the paper, your first sentence is almost correct - just remove "setback" and replace with "total". In other words, high internal mass + setback is significantly (~20%) less effective than low mass + setback. This means that you don't get to add the effects of high thermal mass on top of this - it is already accounted for in the comparison. Edit: for the seasons and locations measured.

Myopic or not, I am not arguing the affects of mass, rather the significance thereof as it relates to comfort. Most (save real men with the aid of real woman) are not comfortable in a 55°F room and allowing a couple of days to catch up may leave a real man without a woman.

In my own experience I have found a relatively low mass heat source to be a better match to passive solar designs where setback - rather than comfort - is the goal. Where the goal of comfort is followed by reasonable economy, high mass can be nearly perfectly controlled with outdoor reset-all naturally dependent on the climate.

Since humidity is critical to comfort in many area fenestration should be considered seriously.

When I think of conventional HVAC an ERV come to mind since it is both conventional and common stick frame as well as passive solar design. One can rail against the psychometric chart, seeing his neighbors or civilization in general, but the laws of physics don't change.

With outdoor reset no compromise is necessary. I have several conditions in my home and many ways to affect them - as that is my business. But I would not use a high mass heat source such as a masonry heater as it is too hard to control. Storing and emitting heat are two different things entirely.

Passive solar requires high mass in most climates, whereas high mass emitters are of little value where comfort is the main goal. Unlike a slab of concrete heated by hydronic radiant tubing and condensing boiler with flame modulating on outdoor temperature, the high mass fireplace has no such control.

It is all very quaint and I love a fire but won't call it efficient. I prefer my little Morso for the walkout that likes to be 62°F even today when the temp will hit 86 here in Minneapolis.

Anybody can go off the grid, just flip the main breaker and open a window.

Badger. What is your definition of comfort?

What would your definition of comfort could you live with to reduce your heating/cooling bill?

I am not talking going off grid ( I don't know who was).

The definition of comfort is the lack of discomfort. My customers define what comfort is and I have noticed the older they get, the more refined their definition.

I use science to lower my fuel bill and that of thousands of others across North America.

I keep my shop much cooler than the house (where six zones control nearl every room) as this is more comfortable for vigorous work.

By the way, I love to be outdoors and dress according to the weather.

"The customer defines what comfort is"

Assuming you really believe that, why do you keep saying that passive solar and a high mass heater( masonry stove) are not suitable choices for a customer that has done the research and knows the variables? It is science, just one that limits the use of mechanical HVAC systems.

I think you have missed my point.

I can see the merit in both but the combination thereof is unacceptable for most. I own a fairly simple wood stove but know it's limitations and would not recommend it as primary heat for a passive solar or any other home. My Morso would be a better choice for many passive solar designs coming up to heat quickly and not retaining heat as this the job of the high mass stucture.

Amazing, jonr. That I can admit my mistakes apparently is a testament to my training in a discipline other than engineering.

Burch tested the four houses through a WINTER, during which there is no dynamic benefit because the heat is simply flowing out. Dynamic benefit happens in Gaithersburg, MD, in the SPRING and FALL, and during a much abbreviated spring and fall in MN. Hence, it is perfectly legit to add the dynamic savings to the setback savings and say that high mass/setback in Madison, Wis marginally outperforms low mass/setback. And while there might be a modest degree of overlap, I think we can agree that the dynamic benefit that saves cooling load is clearly outside the scope of Burch's work. Was it hot in Mich this week?
Also, you are still missing the big picture. I am not building a high mass home for either dynamic benefit or setback. My goal is 100 percent saviings, as in zero $ for heating and cooling. I want my windows to heat my house without being baked out of it. Visitors this week -- with "feels like" temps pushing 100 -- included my electrician, the building inspector and the cabinets guy. To a man, they walked in and said "cool in here." If you want to know how mass works, trek down to your basement. Apparently, a degree in engineering interferes with this sensory process.

I also have to disagree with badger. Concrete is a relatively poor heat sink. To reheat it with air, in my view, is an invitation to excessive cycling in the case of conventional HVAC or alternate periods of throwing the windows open and closing them again in the case of a radiant stove. There is a reason why masonry heaters are standard issue in passive solar circles. Might have something in common with the steadying effect of radiant heat.

I don't have the paper in front of me, but I concede that its results (and my discussion of them) only apply to the weather and location that it measured. I'll edit above to clarify that. As I said earlier (07 May), other conditions add or subtract from the results (and season is a significant one).

One is tempted to say, go down to your basement on a 90 degree day, and if it's 95 down there, say "right on, jonr."
The fact remains that it does come down to what your build and where, and what your notion of comfort is. There is no substitute for independent research. If you want passive solar and you don't visit builditsolar.com, woe on you.i