Been sorting and filing my training materials over the last few days and have found some of the documents I may have referred to in a post somewhere on these boards. Here are some exerpts from Thermal Mass and R-Value: Making Sense of a Confusing Issue , an April/1998 article in Environmental Building News: (revised Jan/99):
“Nearly all areas with significant cooling loads can benefit from thermal mass in walls” (Note: my bold emphasis)
“In nothern climates, when the temperature during a 24 hour period in winter is always well below the indoor temperature, the mass effect offers almost no benefit, and the mass-enhanced R-value is nearly identical to the steady state R-value”
Edited 5/13/2006 12:28 pm ET by experienced
Replies
I disagree. The blanket notion that mass in Northern climates does not help ignores the very valuable contribution that mass and solar heating can make by taking advantage of the thermal flywheel effect.
There is a house in VT reported on in the insulation book by the Taunton press, high up in the mountains that does not have to be winterized as even after several days of cold and blizzards it still maintains 40 degrees F inside. Mass and insulation make it possible.
The key is to design homes to take advantage of the sun, using siting, architectual features, insulation, mass, etc. That is the sort of straightjacket that most consumers and architects have been unwilling to wear (to date) when it comes to designing homes.
Edited 5/13/2006 2:19 pm ET by Constantin
ICF's do not have all the mass on the inside which is good for solar heat storage and quick release. Most ICF's I have seen are just like the house next door- not designed for solar. Even if an ICF was designed with a large solar aspect, how would the day's solar gain get into the concrete......there's an R8-10 layer of insulation blocking it from easy entry to the mass!!! The house would overheat- another solar cooker from poor solar house design.
Who wants to live at 40 degrees? This example has nothing to do with regular comfort or energy consumption. The btu's in the concrete will not re-enter the house until the interior temp is below the middle-of-wall temp which will be somewhere about 35-40 deg F in Jan/feb (approx. 1/2 way between 0 and 70F) in most of Canada and colder US states. There are highly insulated (with fiberglass batts of all things!!), airtight, non high mass houses in Canada's prairies that have not froze up in tests of up to 2 weeks during January at -5 to -10F.
I am not against ICF's, just the outright over-embellishments by those who bought the story from the manufacturer. These are another example of "smoke and mirrors" being used by promoters of certain products
There are quite a few papers/articles on the mass enhanced R effect and every thing I have seen says small effect in northen climates.
I agree that ICFs are not ideal homes for passive solar. If I were to build new, it would be concrete with a PERSIST system on the outside, maybe R20-25 on the walls. R8 windows, and the like. But no can do with my past project.As to the question of overheating, allow me to disagree. If designed properly, the place will not overheat. That's a matter of preventing summer rays from entering and metering the amount that the winter sun can also. Use a solar collector farm and a big storage tank and you have everything you need for a comfortable home. See the latest Home Energy Mag for a write-up on a 52-unit development in Canada that uses "regular homes" heated by solar collectors on the garage roofs, 30,000 gallons of intermediate storage and a well-field as a thermal battery.As for the 40 degree comment, it was a reflection on a mountain cabin that sits in the wild, is only accessible in the summer, and that needed either standby power (power outages) and heat to make it through the winters without winterizing. Proper design allowed the place to remain heat-less and got the HO a special rider on his insurance making it unnecessary.ICF's have their place but like you, I do not consider them to be miracle cures. Their uniform insulation wall-thicknesses is one ding against them though nothing prevents you from using an PERSIST approach to beef up the exterior insulation before sheathing/stucco'ing/etc. the outside over. Concrete floors then give you ample opportunity to act as passive and active emitters for heat in the night.As for the mass comment, I suggest asking the authors to explain why aircraft maintenance facilities swear by floor heating. The answer is simple: mass, which allows them to open the doors, tow a bird out, bring a new one in, and still have the place back up to temp in a few minutes, even in the middle of winter.
So then....
The overheating I was refering to was for poor solar design. While talking generically of ICF's so far no one mentioned that they were talking about good solar design, concrete slabs for heat storage, etc.....just talked about ICF's like any other house..... which in my area are regular homes built and made to look and act like the one next door. If you take any of those ICF's and turn the side with the most windows south, you'd have a poorly designed solar home.
From what I read.....the mountain house had good solar design for heat storage in the slab. A well built high efficiency house would perform about as well as an ICF. Its not the ICF factor but solar design, storage and highly efficient house shells.
I wonder if the average person can afford a house in the 52 home development here in Canada without a gov't subsidy. These items have to offer a decent return to the average person before they move to it. Only 3-5% of people make green choices for the sake of being green; the rest of us move by being pushed by the pocketbook.
"As for the mass comment, I suggest asking the authors to explain why aircraft maintenance facilities swear by floor heating. The answer is simple: mass, which allows them to open the doors, tow a bird out, bring a new one in, and still have the place back up to temp in a few minutes, even in the middle of winter."
You're mixing using mass for heat storage and heating types. If that radiant floor was low mass gypcrete at tempertaure, the effect would be the same......you have a huge radiator with a surface area of a few thousand square feet.
Why the quick reheat happens is:
(1) air has a very low specific heat per cubic foot and thus requires very few btu's to heat a significant volume. ( for example- the specific heat of air is 0.018 btu per degree per cu ft; water has about 3,500 times higher sp. heat at 62.4 btu per degree per cu ft)
(2) Aircraft hangers, due to construction techniques, are quite air tight so little continuing air exchange once the doors are close again.
(3) when the doors are open for a few minutes, not much of the interior gets a chance to cool down, just the exchanged air. Other planes, tools, etc did not have a chance to cool.
So once the doors close again, basically the whole floor is a heater of a substance (air) that requires very few btu's to re-heat- an easy trick to repeat. In many homes, it used to be a practice of the woman of the house to open up doors/windows and air out the house in the morning. This cooled it down for a few minutes only as heat was stored in the plaster, furniture and floors that quickly re-heated the air!!! This phenomenon is only a small function of the mass really but really a function of the low specific heat of air!!!
Edited 5/13/2006 4:11 pm ET by experienced
Hey, I'm not disagreeing with you, I think we're on the same page. All I was trying to point out re: the use of big slabs to re-heat large hangers is that the same thermal flywheel effect that allows a slab to re-heat a hanger after the doors open/close can be used to continue homes well after the sun has gone down. The larger the thermal mass on the inside, the more margin you have in terms of taking advantage of insolation.I see the same effect in my home which is a balloon-frame with Corbond and Icynene + RFH. You can open the doors, the place cools down, but as soon as the doors are closed again, it heats right back up.As for subsidies, I'd like to understand the extent to which the electrical power generation, fuel, etc. industries have been/are being subsidized. If all subsidies were to be removed, I doubt renewables would be that unattractive. Just look to Yucca mountain for a HUGE subsidy, for example.
The insulated thermal mass in the ICF walls are not part (or such an insignificant amount that the drywall is larger) of the well designed daily solar storage/release system in cold climates and provides very little extra R except for what the concrete is rated for!!
I've only been quoting what minds greater than mine have been saying but people want to take the examples of use of mass for solar and heat storage to make their case for mass enhanced or "apparent" increase in R. Works in certain applications in the south.
Edited 5/13/2006 4:40 pm ET by experienced
You're right, the mass has to be exposed to the warming rays of the sun and/or the heat emitted by the heating system to be useful. When it comes to ICFs it's not the mass in the walls that I would take advantage of, it's the possibility of installing high mass floors (i.e. 4" of concrete on a steel deck) and letting them flywheel the home through the night. It is precisely the very low delta-T's that these floors need to keep a well-insulated space warm and cosy that make high-mass systems so attractive.Lastly, from a control perspective something like the warmboard system combined with a large solar collector farm, a large storage facility with phase-change technology, and a dumping ground for excess BTUs may make the most sense. But that's way off in the future for most homeowners.
I have to agree with Experienced that ICF houses will perform just like the stick house next door in a pure heating situation. Physics supports his statement. In Nova Scotia, where he lives and where I also live, that is the situation for maybe four months of the year.
On either end of the heating season, though there is a period of time when my neighbour will be heating his stick house at night and my boiler in an ICF house is stone cold and we're still comfortable.
In addition, my concrete house leaks less air that the stick house and it was easier to make it airtight. It is unlikely that anything will ever happen in the way of something shifting or rotting to make it less airtight than it is now.
You can't take the picture of the house at mid-winter and say that's the whole story. I don't know how I'd prove it but I'm pretty sure this house would consume less energy on an annual basis than the same house with the same R-value built on the same site out of wood even though the heat loss on a windless mid-winter day might be the same in both.
And the concrete house is going to be the same in a hundred years, so that's what I want to build anyway instead of the flimsy R2000 style crackerboxes with bits of bent sheet metal holding them together until you get the structural drywall inside them and the structural vinyl siding outside. There's little satisfaction to be found there. You could kick your way through any wall into one of those places in three and a half minutes.
One disadvantage of an ICF house is that you feel somewhat isolated from the weather when you're inside. You can't hear the wind blow unless it's really howling outside and you can't feel the house shaking. (I can hear the wind when I'm on the top floor.)
Ron
>One disadvantage of an ICF house is that you feel somewhat isolated from the weather when you're inside.We're not ICF, but fundamentally the same. I always liked that feeling of isolation. For our family, it translates as "safety" or "security". Seriously, there's a difference in how the other family members react to storms when in a strong house like that vs a conventional frame house, and it's something I never fully understood till I lived in one.
I was just looking at the "Warmboard" site aand found this:
The importance of low thermal mass Fast response is one of the most important characteristics of a radiant heating system. The amount of heat required by a home or an individual room changes over time and the changes can be fairly rapid. Cloud cover can clear in just a few minutes causing rapid changes in the warmth provided by the sun. The outside temperature can change significantly in just one hour due to normal daily variations. For these reasons, fast response is essential to the performance of a radiant heat system. Thermal mass, on the other hand, will cause significant delays between when heat is needed and when it is finally delivered. It is not unusual for the owners of slab-based systems to wait many hours before their homes are warm. Warmboard starts heating up within minutes of heat being called for and rapidly responds to changing needs to provide the right amount of radiant heat right when you need it.
Guess it just depends on what you have to sell!!! LOL
Holy Smokes! That's a wee bit disingenuous.
You're right, the mass has to be exposed to the warming rays of the sun and/or the heat emitted by the heating system to be useful.
Gotta disagree. We store a significant portion of our annual heating needs in mass that gets no insolation, is only exposed to our interior air. Our next house will have 50% more of that un-insolated mass.
Furthermore, there's a not-small movement, centered in the Pacific NW, that's utilizing mass through something the originator calls Annualized Geo Solar (AGS). They think using the house as the collector, ala PAHS, is a poor choice. Both clearly work, with no insolation to a large majority (or all) of the dirt mass.PAHS Designer/Builder- Bury it!
What's the max. temp of the storage mass? How are you getting the heat in/out? Is it insulated on the exterior?
Edited 5/14/2006 7:44 pm ET by experienced
http://www.axwoodfarm.com/PAHS/UmbrellaHouse.html is an excerpt from Hait's book. He relies heavily on earth tubes. I don't.
As a result, our house has greater annual temp extremes (at 13º) than he got. Our mass is simply exposed to indoor air, no insulation between. As was noted, interior insulation of ICFs wouldn't help. But as you know, insulation only slows down heat transfer, doesn't stop it.
Is it insulated on the exterior?
We have an insulation umbrella, similar to Hait's in performance but not in shape (our house looks nothing like his). It extends 20' beyond the foorprint and keeps that mass dry in addition to insulated from outside air temps.
What's the max. temp of the storage mass?
Hait recorded highest dirt temps of 72º in Sept. and lowest of 66º in Feb. I didn't bother to bury sensors. As he points out, it's not very interesting to watch the dirt change maybe 1º/month.
How are you getting the heat in/out?
Simple, slow, flow through the ceiling, floor, and walls. This is totally passive, no moving parts, nothing to break or maintain. Takes a lot of dirt. The reason for that 20' is Hait found that heat takes 6 mos to move through 20' of dry dirt. Big thermal flywheel here. Takes a couple of years to stabilize.
PAHS Designer/Builder- Bury it!
I am finding this thread extremely interesting and very well debated. No name calling, just experience and alternatives broadly brought into the examination of finding optimum comfort and affordability for home owners. I'm curious about the difference between insOlation vs. insUlation. You mention interior walls and I'm curious how these are heated via direct solar energy. Are the majority of your windows south-facing, does your neighbourhood design permit unimpeded access to the sun? That is, are there no large trees or a future two-storey house that will act as a shadow and thereby reduce your solar gain? Do you factor in the damage the UV rays cause to such things as fabrics?
I like the idea of concrete floors complete with heating coils embedded in them. If the occupants feet feel warm than they can often tolerate cooler air temps.
As far as the ICFs are concerned, there certainly has been a lot self-serving hype produced by the concrete industry and not all of it is accurate. The strength of the homes is definitely a no-brainer, but to argue that homes built with ICFs in a hurricane-ridden area would withstand the awesome forces of nature gives me pause. Roofs can still be lifted off, hundreds of gallons of rain water can pour into the structure, windows can be blown out and foundations can be undermined by running water. You might end up with a well-insulated concrete shell, but at the end of day you're still dealing with virtually a complete rebuild.
But back to the thermal mass debate...as noted by another contributor to this discussion, how does the concrete absorb and give off heat when it is "isolated" by the foam that forms the walls? Surely you would have to superheat the interior of the home to see an appreciable gain in radiated heat later in the day? The exchange of energy would be quite limited and slow, unlike the exposed concrete slab in the airport hanger or the brick fireplace in the centre of the home.
And lastly, some of the examples use static air masses and don't take into account the importance of a well-designed HRV systems or the radiant heat that emanates from such things as televisions, computer monitors, fridge coils and ranges.
Anyway, the discussion is very informative. Some of the design aspects might be more relevant to more northern climates but with energy costs continuing to spiral upwards we need to take a good hard look at how we build our houses. The amount of energy expended to manufacture concrete vs. the cutting down of trees is another consideration but not immediately relevant to this discussion. Thanks for bringing this up. It's been on my mind for several years now.
Cheers!
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
>Surely you would have to superheat the interior of the home to see an appreciable gain in radiated heat later in the day?I don't think anyone's meaning that the walls are radiating heat in the sense of a radiant heated floor at typical rfh temps. There's no heat gain of that magnitude happening that would support that contention. Remember than any heat gain will come from the sun and from the exterior ambient temperatures. Even if the thermometer hits 100 during the day, the concrete isn't going to rise that high that fast. Heck, it would take full sunlight falling on 1000 sf for 5 hours to heat 10.2# of concrete 10 degrees, so you aren't going to superheat the mass in the fashion your question presumes.Here's our experience. We have an exterior foam, interior concrete assembly. Think icf without the interior foam, plus continuous everywhere including overhead. If we start from some arbitrary condition, and have full sunlight on a spring day, then the structure will experience some amt of heat gain during the day. The insulation will provide some amt of resistance, but some energy will reach the concrete, and that mass will experience some temperature increase in proportion to the strength of the sun that day. This energy will not radiate into the interior space to any significant measure during the day because the delta-T won't be that high.At night, the temp of the mass is likely higher than either the interior of the house or the outside air, and so, the stored heat will radiate to either space at a rate determined by those temps and the effectiveness of the insulation in resisting transfer to the exterior. The mass isn't radiating heat in a way that you can feel with a steam radiator, for example. Rather, it's buffering the daily (or seasonal) temperature fluctuations so that you aren't having to cool the building during the day or heat it at night to the same degree that you would have to in a low-mass house. The mass smooths out the interior temperature fluctuations. Throwing some numbers at it, my neighbor has similar house size and similar glazing and siting. Their interior temps would fluctuate 15 degrees in the course of a sunny afternoon, while ours would change 3 or 4 degrees. They needed to condition the space as a result, while we did not. The reverse would happen on a cool night, with their house cooling much more than ours would, and needing evening heat on nights that we'd need none.Different mass wall assemblies will have different results from each other, but will differ from non-mass structures in a comparable fashion to each other. Results will be affected by all sorts of other factors, including orientation to sun, overhangs, berming/burial, glazing, etc. ICF's are interesting (curious?) in that a large part of them--their roof--is typically low-mass, conventional construction. I think their greatest benefit is limiting unwanted air infiltration, rather than providing the benefits we've come to expect of a more completely high-mass house.
>but to argue that homes built with ICFs in a hurricane-ridden area would withstand the awesome forces of nature gives me pause.I agree that's a fly in the ICF ointment. But that's not the only way to get effective hurricane resistance. We do reinforced concrete (exterior insulation) assemblies that work anywhere from the mountains to the plains to the beaches. The walls and roofs are monolithically connected (well, they are one piece, so "connected" isn't the best term...just trying to get the point across), so one can never separate from the other. You get all the benefits of mass walls with all the engineering required to resist natural disasters. Certainly you need a solution for doors and windows, as they are the weak link. And you need to design for some target tidal surge. But if you do that, the results are dramatic. One of these houses survived two hurricanes on Pensacola Beach intact with just a basement washout (it was designed to do that in a 10' surge) while the conventionally-constructed houses on either side literally disappeared.Another experienced three hurricane eyes in two years with major damage to all the traditionally-constructed out buildings, but zero damage, inside or outside, to the residence.It can be done if that's the goal.
"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
After inspecting/working on/doing estimates on thousands of homes over 31 years, I've been saying much the same. My ending is "and I'm glad they don't"
Yep, that's what Dad meant too!
Cheers!
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
I'm curious about the difference between insOlation vs. insUlation.
Insolation: exposure to the suns rays. Per cent of insolation (per cent of possible sunshine) is the critical climate determination for design of solar heating. Then you look at degree-days and see what you can do. For instance, we get 48% of the possible sunshine in January. I don't have Canadian numbers readily available, but Detroit gets 31%, Alpena and Marquette (Mich.) 28%.
You mention interior walls and I'm curious how these are heated via direct solar energy.
Heated by our indoor air, provides our cooling system in an ac climate. We do get winter sun, but by the time the leaves come out we're very shaded by large trees. I guessed correctly that we didn't need summer insolation to raise interior temps to charge the dirt flywheel. We have large glass (all directions but N), nearly 25% of floor area. Low e helps immensely with uv degradation. The glass is more esthetic than heating system. Not to discount winter solar gain, but we never bother with window coverings. Means that same glass is by far our major heat loss. If we bothered with window covers we'd cut out annual temp extremes by 38%, but we don't bother. No "neighborhood" in your sense. We live on top of a mountain, closest neighbor is 1/2 mile.
And lastly, some of the examples use static air masses and don't take into account the importance of a well-designed HRV systems or the radiant heat that emanates from such things as televisions, computer monitors, fridge coils and ranges.
And occupants, often the largest heat source. I've been criticized for under-valuing these heat sources (in addition to using a lot of concrete). In fact, our house has no temp difference when things are turned off and nobody's home for a week or few. We don't have a particularly well-insulated place. Nowhere near "super-insulation" by anybody's standards. Our house uses a huge amount of heat keeping us comfortable. Same heat (loss) that makes our place fine during our summers. Hait, in a different climate, had different design parameters, closer to what you'd need. PAHS works admirably for both.
Brevity I'm not good at. Hope I mostly answered your remaining questions.
PAHS Designer/Builder- Bury it!
You answered everything very well. Thanks. My main interest is how we can incorporate these improvements into a regular Joe's house. They big builders are still stick framing, insulating with leaky batt insulation, using the cheapest windows you can imagine, then turning the home over to the happy buyer who will be flabbergasted at how often his heating or A/C system is cycling off and on. So frustrating.
Thanks again.
Cheers!
Ken"They don't build 'em like they used to" And as my Dad always added... "Thank God!"
Tom, I think we're in violent agreement, but I should have phrased it better... Any interior wall that is exposed to your heating system will have a measureable capacity to absorb heat via convection, radiation, and conduction. That is because the wall has not been isolated from the interior of the home. An ICF wall by contrast has a lot of things working against letting the mass in it work to your advantage.While a wall encased in multiple inches of styrofoam will have the same heat capacity as the comparably-massive walls elsewhere, such a wall inside a ICF block will have a lot of difficulty picking up heat because it's encased in in several inches of styrofoam. Then, when the time comes to release the heat, there are several inches of styro the heat has to travel through. Furthermore, the delta-T across the interior vs. the exterior wall surface will make more heat flow towards the exterior on cold days. Only if the exterior insulation is much thicker and the interior insulation is quite thin will the mass inside those walls start to play a measureable role in terms of thermal mass to flywheel with. So, I agree that interior walls can add a lot of mass, but only when that mass has not been decoupled from the interior of the house.
I think we're in violent agreement
LOL... so it would seem. Thanks.
I recommend ICFs for owner-builders (or others) if they won't do what I did (mass inside, insulation outside). There's a thermal penalty, but it still strikes me as better than most alternatives.PAHS Designer/Builder- Bury it!
Most ICF's I have seen are just like the house next door- not designed for solar.
And that is the failing, the lack of design, not the material for the walls.
The trick in passive is to be able to "throttle" the gain, you have to be able to control solar gain on warmer winter days as much as in the summer in some cases.
For many northern climes, a "sun room" set upon a large collector bed would seem to be ideal. This would be a separate element from the rest of the body of the house (and therefore, a bit of a design "bonus," something the client will 'want' to have; not an ugly "solar thing" forced upon them). The rest of the house can then be built with just about any building system, as long as one details that construction for the appropriate heat loss/gain.
I'm just not comfortable with blanket statements about any one construction system. We could also say that SIP is bad construction for thermal mass, too. That would be equally true and false, as well.Occupational hazard of my occupation not being around (sorry Bubba)
Aw Shucks CapnMac, study after study has shown direct gain passive is far superior to any sort of "sun room" strategy.In the book "The Passive Solar House" by Kachadorian, there is a chapter on sun rooms, and the the final conclusion is "if you want a sunny room for daytime use, OK, but don't expect it to heat your home"My take on it is that if you need pumps or blowers to try to get the passively collected solar heat into your actual living space, then just install a conventional active solar system in the first place.
"if you want a sunny room for daytime use, OK, but don't expect it to heat your home"
I'm guessing he was not writing about living down here at 29ºN lattitude. <g>
But then again, it gets to definitions, too. If we design a "conventional" house in a "U" around a very large sun collecting room, that's a tad different. Pave the collector room appropriately, some nice heavy masonry walls to line it, it makes a great collector (nice architectural feature, too), and you could use ICF or stick framing or whatever for the rest of the structure.
With due apologies to the Bard, the design's the thing.Occupational hazard of my occupation not being around (sorry Bubba)
That's certainly not always correct. Only with poor design will you not get better performance with more mass.
The original passive annual heat storage (PAHS) house, 1981, was in Montana with 8125 degree-days. Never dropped below 65º inside with no supplemental heat.
As Constantin notes, pretty much everywhere gets solar gain. What you want is to design accordingly. David Thomas once opined that he saw no reason PAHS wouldn't work in Alaska. I didn't work the numbers, but it seems likely.
PAHS is clearly beyond your ICF question, but the same principles apply. Your author seems to only want to consider btu loss. There's more going on than that.
Anecdotally, ever talk to someone living in a log home? They'll often mistakenly claim high insulation. What they have isn't well insulated, just comfortable from the mass. Much more so than a low mass house.
PAHS Designer/Builder- Bury it!
Tom:
Just happen to have something on the log mass effect also!!
From Energy Design Update- Sept/1993:
The (Non?) Advantage of Thermal Mass in Log Homes
Log homes can be as energy efficient as stick built homes but the heavy mass of the logs provides little beneifit in cold climates according to a report prepared by Ecotope inc. for the Washington State Energy Office.
Six log homes, all located in Idaho, were analyzed and closely monitored for various time periods up to 16 months.
The results show that when compared to a conventional stud framed house with the same R values, the log house should use between 1% and 3% less energy for heating due to the effects of the thermal mass. The actual savings would vary with the amount of solar exposure-- the more sun , the greater the benefit of the thermal mass.
The Ecotope report concludes that the performance improvement attributed to the thermal mass in these homes would would be equivalent to increasing the R-value by 4%.
Edited 5/13/2006 2:41 pm ET by experienced
I understand. But it apparently ignores the effect of a warmer wall on the occupant. Not insignificant, unless you have no occupants. That glowing pride of log home ownership isn't the only thing keeping residents warmer.
Pretty sure I mentioned that there was more than btu loss going on.
Thought there was an old thread here that went into more detail than I want to attempt. Didn't find it, but I may be mistaking forums. PAHS Designer/Builder- Bury it!
The quotation makes sense, that the additional mass does essentially nothing to enhance the apparent R-value of an insulated wall.
Thermal mass can be helpful in specially designed homes that make use of, for example, solar gain during the day. But in homes of more conventional design it seems to me that thermal mass is more of a detriment.
Say you have a lot of thermal mass in a home. Your thermostat is set to kick up the heat in the home some period of time, say, half an hour, before your alarm goes off in the morning. If the home has high thermal mass the heat gets sucked into the mass and the house is still cold when you awaken. To counter that you'd have to crank up the heat much earlier or set the thermostat higher. Then, an hour after you're up you are out of the house so all that heat that got absorbed into the mass radiates back into the house and is wasted because you are not there. Same thing happens in the evening. The heat kicks up before you come home, but the house is still cold when you arrive because the mass has sucked up the heat. By bedtime the mass is finaly warm and the heat and radiates it back into the house when the thermostat drops at bedtime. But again it's wasted heat because you are in bed and don't need a warm house.
So thermal mass, unless it is part of an intentionally designed system to store free heat, not heat you've paid for, works against comfort and savings, increasing cost.
It really doesn't work like that. Just as when you have a high-mass rfh assembly, you don't play the nightly setback games. You aim for constant and steady temps with the mass as a buffer. The mass will temper fluctuations, so your strategy should not be to try and out-think it with setbacks, etc. A high mass building with thoughtful use of glazing and overhangs, smart insulation, and a properly sized and controlled hvac system, is the most comfortable building there is and will absolutely conserve energy.
"A high mass building with thoughtful use of glazing and overhangs, smart insulation, and a properly sized and controlled hvac system, is the most comfortable building there is and will absolutely conserve energy"
The bold section reminds me of many R2000 and other well designed low energy homes here but very few of those so far are high mass. Some make use of solar storage in an existing needed interior slab. Or install a bit of acid-stained, stamped concrete over wood joists or one I saw recently, enclosed a propane fireplace in a tall large mass of masonry that picked up solar gain from noon on, especially in the low sun afternoon.
Maybe this is a highjack, but it did get me thinking. All of this talk has been about heating a home in the colder regions. What about cooling a home in warmer regions that have mild winters?
The home we live in now in a solid brick home three layers thick and this week we have been in the high 90's. Because of the thick brick, it does talk quite a while to warm the interior if you keep all doors/windows shut. But the problem is the heat continues to radiate through the walls until 2:00am or even later if the nighttime temp doesn't go below 60-70*. This makes for pretty uncomfortable nights if their is no breeze blowing to help circulate the air though out the home. Opening widows with wife and kids allergy problem doesn't help much either with the air circulation problem.
So the question becomes how to cool the home. Right now, we use a swamp cooler, but I really don't like the higher moisture. We are in the process of putting in a AC unit and because of the brick walls, I am starting to question the size of the unit needed in comparison to stick framed homes. My mind says a smaller unit would be more efficient because of the radiant heat transfer through the walls is a slow process, versus trying to "cool the walls down" with a larger unit. I also think that a larger unit, to run more efficiently, would have to set set at a higher temperature swing just to prevent more start/stop cycles. Is this the correct thinking???
I have thought of adding a layer of insulation and framing a new walls against the interior brick wall, mainly on the south and west facing walls, that would only slow down the heat transfer, if at all. More than likely, it would just delay the transfer maybe an hour or so.
Not a hijack at all! I started this since manufacturers/vendors of ICF systems have been promoting/transferring the mass-enhanced or "apparent" higher R-values (up to R50 with 4" of foam and 6" of concrete) that occur in the highest cooling degree-day areas to the cold areas as if there was no change in the apparent R values. As well, they have been talking about how green the system is by saving trees. BS!!! A tree grows with little human energy input and not to much energy to manufacture.
"I have thought of adding a layer of insulation and framing a new walls against the interior brick wall, mainly on the south and west facing walls, that would only slow down the heat transfer, if at all. More than likely, it would just delay the transfer maybe an hour or so."
Yes, exterior high mass works well in cooling climates and if you add an interior R10, it may be as good as having R20+ in a stick built wall, depends on the climate. If I were to start with the interior walls, I might go ahead and do them all- heating is costing you money also. A 3 wythe brick wall may only be R4-6 depending on if there are any airspaces left between a wythe.
Yes, there is a airspace between the first exterior course and the 2 interior couses. There are vents at the top and bottom of the walls. I don't know much other than that since this is the 1st brick home I have ever worked on. It definetly has it's challenges
The only thing keeping me from putting up a rigid intulation and drywall is the thickness and the rooms that get the most sun are the smallest rooms. One room in particular is the master bdrm and as it is right now, it's only13'x14'. Soon to be enlarged if the their is money left in the kitty after the AC, Roof, new electrical/plumbing, etc.
I wouldn't mind finding out the energy savings vs. material/labor costs first because I think that the initial costs would take many years to pay back.
Have a look at the cavity thickness behind the plaster. It may have been strapped with vertical 1" strong 1"x3" material to fasten the lath to. You may find that by adding another full 1" of strapping, you can get the R10 (or 12 if you use polyiso or polyurethane rigid board).
If you do decide to add insulation consider it as as part of the re-wiring. The narrow inside cavity along the outer walls may not accept a regular depth switch/receptacle box, making the wiring a pain for the electrician (I know!! wired for 3 years in the mid 1970's) To have to drill up from the basement along outside walls to find this small cavity is painful and costly as it takes longer, you have to chip out some brick to get a shallow box in, etc. Ask the electrician if having the outer walls open and ready for deeper boxes, where junctions can be made and multiple wires run, will lower your rewiring costs?
The exterior walls are not strapped for plaster, they are plastered right over the bricks. Makes for some tight shallow boxes and a little brick chipping. I'll probably go 1-1/2" rigid and flat stud the walls. That's ONLY 3 5/8".
As for asking the electrician, That's what they called talking to myself.. There is practically no electrical in the exterior walls except fro the switches by the front door and maybe two receptical boxes. Other than that, the the only other is the main service feed electrical "mast" is built into the brick, along with the main panel, meter and disconnect. Makes it a real pain to upgrade to a 200 amp panel.
Ask the electrician if having the outer walls open and ready for deeper boxes, where junctions can be made and multiple wires run, will lower your rewiring costs?
You still haven't answered my question!!! (LOL)