I want to building an ICF home, basement and two-stories, with a brick wall bisecting the building. The floorplan would be about a 30'x40' rectangle and the wall would bisect the long way, trying to take advantage of passive solar. My question is this: Would it be smart to build pipes or coils into the wall and run water through for cooling in the summer? I fully realize that condensation would be a concern, but it seems like it could be almost free air conditioning. Ground water in the area is 46 degrees and very plentiful.

So, is that brick wall going to receive direct insolation?

No. It would be entirely interior, from the slab up through the second story. It would through the middle of the house bisecting the house into two long, thin rectangles. My idea was to add a lot of mass and try to take advantage of the ground water supply for cooling. I just can't find where anyone has tried something like this before, and I wonder if there is a reason.

We build high mass walls on a regular basis and use them for cooling and heating as part to the radiant system. You need about 1 foot of 1/2 inch PEX per cubic foot of mass wall and or floor. When cooling the external surface must never reach the dew point. The control system needs to be smart enough to properly adjust the mixing valve, supply, pumps based on the thermal lag, internal and external weather and ventilation so that no issues arise. You are in a pretty cold climate if your water is 46 degrees. Where are you building?

We do net-zero that cost no more than a standard custom home all the time.

Brian

I wonder if there is a reason.

You're not going to get enough cooling while you are trying to avoid the dewpoint to make it worth your while.

ICFHybrid do you make high mass heated and cooled houses? Because your statement is incorrect.

The wall has to have a large enough surface area so that the temperature does not have to be below the dew point. The example given is a wall 40 feet long down the center line of the building. If vaulted ceiling and two stories that’s 20 feet of height that gives you 1600 square feet of exposed mass wall. With that much surface area the effective temperature only needs to be a few degrees below desired temperature to maintain desired temperature while cooling the home. In such a case the issue is distributing the energy adequately to not have cool spots. Making the wall one foot thick and massive, cooling to accommodate the thermal lag and the PEX in the middle would eliminate surface cool spots and spot condensation issues. It is a matter of understanding high mass cooling and heating and how it works. We have been making high mass homes for 30 years, they work. Few people understand how to design, build and use them.

Brian

This kind of cooling is rare because AC isn't needed in climates where cold water is abundant. I have to wonder how abundant your supply is. My well water is cold by virtue of being 600 feet deep. But the well had to be that deep to get an acceptable recharge rate. You can pump it back into the well but but storage in mine is only a couple hundred gallons.

Thermal mass does nothing for humidity, which plays a major role in comfort. The ICF pros can correct me but I believe RH in a new ICF house will be high until the concrete cures.

Aesthetics is an afterthought around here, but one hopes you are building this wall because it suits your design and energy efficiency is secondary.

Brian, it would be nice if you could supply some evidence, or maybe even some calculations in support of your statements. Or, maybe something you have built that does this. I have seen radiant systems used for cooling, but only in very limited circumstances and under limited conditions. Moreover, those systems were designed as radiant heating, so the extra cost to get some cooling is nil.

At this point, we don't even know where this home is located. The notion that there is widespread application in this manner for "almost free air conditioning" as the OP suggests, is a bit ethereal.

Posted By ICFHybrid on 28 Feb 2012 08:33 AM
Brian, it would be nice if you could supply some evidence, or maybe even some calculations in support of your statements. Or, maybe something you have built that does this. I have seen radiant systems used for cooling, but only in very limited circumstances and under limited conditions. Moreover, those systems were designed as radiant heating, so the extra cost to get some cooling is nil.

At this point, we don't even know where this home is located. The notion that there is widespread application in this manner for "almost free air conditioning" as the OP suggests, is a bit ethereal.

I would assume it is the same math for radiant, just in reverse. You remove heat instead of adding it. The size of the wall allows you to spread that heat removal over a large surface therefore not having to drop the temp of the wall so low that it causes condensation. Seems simple enough to understand.

Posted By 2pdhall on 26 Feb 2012 01:30 PM
I want to building an ICF home, basement and two-stories, with a brick wall bisecting the building. The floorplan would be about a 30'x40' rectangle and the wall would bisect the long way, trying to take advantage of passive solar. My question is this: Would it be smart to build pipes or coils into the wall and run water through for cooling in the summer? I fully realize that condensation would be a concern, but it seems like it could be almost free air conditioning. Ground water in the area is 46 degrees and very plentiful.

When we build again, it is our plan to have a wall that we will use in the same way. We however plan to put vented air chases in it or a central air shaft between two concrete walls. Ours will have the ability to vent to the outside in summer so as to move the warm air out. Winter it will be a solar heat sink.

Whether you can cool the wall sufficiently to handle the sensible loads without condensation depend a lot on the summertime outdoor dew points and the magnitude of the actual sensible load.

You get on the order of 2BTU/hr of radiant cooling for every degree below the room ambient very exposed square foot of chilled wall area. Say you have a sensible cooling load of 8000 BTU/hr and you have about (20' x 40' x 2 sides =) 1600' of chilled wall surface, the temp of the surface of the wall has to be 8000/1600= 5F below the ambient room temp to handle the load. If it's 78F in the room, you need a 73F wall. But if the load is 24,000BTU/hr (a plausible peak number), you need to bring the chilled wall down to 63F. Since outdoor dew point peaks tend to coincide with outdoor air-temperature peaks (at least for the eastern 2/3 of N.America), it's quite likely that 63F would be below the dew point of even the ventilation air on those days, which would mean the chilled wall would start taking on moisture/condensation during those periods.

Whether that's a problem depends on what's attached to that wall, and how long that condensing condition persists. Masonry walls would tend to wick in condensation as rapidly as it forms as long as it doesn't have sealers or paint on it, and can absorb quite a bit of moisture before it's saturating. Cooling with a chilled masonry wall has many advantages over chilled floors, since the insulating air-films are constantly convecting away, and won't usually be covered by mold-susceptible objects like rugs, etc.

Before calling it "almost free" cooling you need to consider the pumping power used for achieving this though, and compare it to how much power would be used by a mini-split heat pump for the same amount of cooling. If 200 watts of pumping buys you 12,000BTU/hr of cooling you're doing very well, but it it's only buying you 2400 BTU/hr it's the same range as a window air conditioner. At part-load the coefficient of performance of mini-split can approach double-digits. Idling along at 200 watts with a COP of 8-9 a mini-split delivers ~5500-6000BTU/hr, and even at 110F outdoor temps at full load the COP can be north of 3. See figure 14 in this document: http://www.nrel.gov/docs/fy11osti/52175.pdf

In addition the mini-split handles latent loads (humidity) as well, whereas the chilled wall does not.

Whether you use the wall for active cooling or not, it's thermal mass will lower both peak & average heating & cooling loads.

ICFHybrid

Data is strongly site and house specific. Dana is pretty sharp. He has explained a fair amount though I would assume the floor would also be usable in the system which could add another 1200 square feet of surface area. Internal thermal mass gives the home a thermal lag that eliminates peak loads and changes them to the average load over a day or longer depending on the whole home design. If you design a 24 hour worst case thermal lag into the house than the HVAC system only has to handle an average 2 day peak. This typically halves the size of the HVAC system. Adding a thermal lag of 6 months to the house usually eliminates the need for standard HVAC completely. Obviously it is climate, site and house dependent.
So what data do you want? I have been engineering, designing and building self-heated and cooled high mass homes since 1976. I have gone through dozens of different alternative construction methods. I have built underground in a dozen different configurations. I designed a stressed skin arch system out of OSB in 1977. It was a passive annual heat storage system with earth tube heating and cooling. It worked great but did not have mass appeal. Temperature stability wise they out performed Earthships. I cannot tell you how many times I was told that it looked like a Hobbit hole.

I usually recommend against building underground now at least beyond a live roof. Generally I restrict live roofs to areas that have less than a one foot frost depth. This is because freeze thaw cycles can affect the water proofing layers. A client that wants a live roof in a cold area can have one but they are expensive standardized products.

I have experience with SCIPs, SIPs, Tilt-ups, double wall, double envelope, concrete post and beam with foam in-fill, Earthships, PAHS, AGS, earth tubes, natural convection, thermal earthen storage, high internal thermal mass, passive super insulated designs, gabion ballast base construction and others.
Material wise I have used rammed earth, straw bale, stuccos, sand filled bags, earth filled bags, contained ballast, sod, cob, earthen plasters, modified earth cretes, surface bonded cement over polystyrene, polyurethanes, polyisocyanurates, cellulose, pumice, pearlite, recycled crane cable, shipping containers and others. I have also used standard construction systems, material and designs.

I have tried many things beyond standard. I enjoy experimenting and have spent 10,000s of hours studying and learning all that I could about the different systems, materials and designs. I have continuously been trying to optimize performance, cost, self-sufficiency, embodied energy, local processing, and mass appeal.
All of this has loaded my quiver with a lot of options. I believe I can now build a self-heated and cooled house in any normally habited environment in the US with a life cycle cost that is lower than a standard home and an initial cost no higher than the average custom home in the area of the same quality finishes.
All of the issues you are concerned about are worked out based on climate, envelope efficiency, air exchange, relative humidity issues, isolation issues, total thermal mass, thermal lags and other details.

The condensation issue can be taken care of by installing a solar driven desiccant based dehumidification system on the intake air manifold. Ideally humans are most healthy in an environment in the 30 to 40% relative humidity range.

If the mass wall is 2 feet thick you can cool the wall day and night due to the thermal lag in the wall. Assuming you are collecting weather information you can pre load the mass. Given the ability to pump 24 hours the rate of pumping can be much smaller. I built an 8000 square foot house in Utah where the total pumping system was done with high efficiency DC variable speed pumps filling an upper reservoir which gravity fed through the mass. The feed to the reservoir has oversized piping and the total consumption never exceeded 200 watts an hour. The house is a very efficient build, off grid, PV electrical etc.

Assuming an efficient envelope and a system designed for the climate, high mass systems work. The whole point is to get the envelope efficiency high enough that a non-compressor based thermal mass system can work and be dramatically more efficient. I am a proponent of very large thermal masses that annualize the climatic effects. When dealing with such designs you can do some very interesting things for example elimination of all standard HVAC systems. This requires engineering, designing and construction of the building to a high standard. It requires an understanding and working knowledge few have. I have successfully built in many climates. I perform a dynamic thermodynamic finite elemental analysis of the climate and building modeling. I can design a home that will function in any climate with very low external thermal input. Hot and muggy, the arctic circle, or in between can all be accomplished.
Complete climate data, micro-climate, site, shading, plant life, wind analysis, isolation, deep earth temperatures, sub soils, the aero dynamic profile of the house and any other pertinent information has to be taken into account.

I am currently writing a book documenting all of the above and explaining how it all works. It will include ways of calculating the insulation, massing, air handling, humidity control, and engineering of the homes as I now recommend them. It will also have a discussion of the various systems I have built and the reasons that led me to the place I now occupy from a building standpoint.
If you have a specific question I would be happy to answer it.

Brian

If you have a specific question I would be happy to answer it.

Yeah, I didn't ask about hobbit holes. I asked about calculations supporting the feasibility of a cooling brick wall in a 30' X 40' "passive solar" that doesn't see any insolation. Am I going to have to wait for your book to come out?

Seriously, 2pdhall, unless you have some other use for the wall, or you want to evoke the row house of your youth, this heat exchanger, a pump, a controller and a valve gets you AC for under $1k, not counting ductwork, and the chiller handles humidity as well. http://www.ebay.com/itm/14x14-Water-Air-Heat-Exchanger-NEW-front-mounting-/250957473797?pt=LH_DefaultDomain_0&hash=item3a6e3b2805#ht_2291wt_952

But if you're pumping that 46F water from a a 300' deep well your COP will be truly wretched, whether it's a fan-coil or a mass wall. Without knowing the amount of head your pumping against there's no telling where the average efficiency of a mini-split vs. that of the mass wall + groundwater loop might be.

But there are plenty of good reasons to build in a modicum of thermal mass that is fully inside the thermal envelope of the building though, even if tall brick walls aren't necessarily the cheap & easy way to get there. Having a decent surface area to that mass exposed toevery room helps from a comfort and even-temperatures point of view.

ICFHybrid,

As I said I stopped building underground 20 years ago. So I am not sure why that is the only thing you flippantly mention. Full disclosure of the house, lot and climate are necessary to go beyond the speculation that I and Dana have already done. There are simply too many unknowns to give specific answers in this case. Though an efficient shell, with a high mass interior can be engineered to work in any climate in the US. Examples exist from Alaska to Florida, from the Arctic Circle to the tropics.

I can build a home of any style that is self-heated and or cooled with my current state of engineering knowledge. You do run into architectural style limits at the extremes like a 14000 HDD climate like Fairbanks Alaska. The question is how can I help you, or are you just being contrarian?

Brian

The question is how can I help you, or are you just being contrarian?

I'm not buying or selling; just supplying a homeowner answer to a homeowner question. Maybe that's the problem, huh?

And my answer to the OP, based on what info has been given is still the same; there is no value to be had in building a groundwater cooled brick wall in the middle of your ICF residence.

As I said I stopped building underground 20 years ago. So I am not sure why that is the only thing you flippantly mention.

If you look carefully, that is what I said I DIDN'T want to hear about, yet, you keep bringing it up.

I was trying to help answer the question. That is not buying or selling. If the load is small you can cool with ground water. If the load is big probably not. This agrees with Dana communicated as well. Since the ground water is so cold it is unlikely that it is in a hot climate. Likely cooling load is small. Therefore your answer is likely wrong. The full answer is not possible to complete without additional information.

Brian

Likely cooling load is small. Therefore your answer is likely wrong. The full answer is not possible to complete without additional information.

It's also likely the humidity in such a place will interfere substantially. You could build this animal and it might work in selected places at some times, but it is unlikely to be a cost-efficient or sensible thing to do under the circumstances given.

I have spent the last 30 years studying how to tame that animal so it is always of benefit. Understanding the climate, lot and home dynamics and variables and using them to engineer a solution which is the most economical solution to luxury living with as low of energy consumption as possible is the whole point. Done right it is economical and works in any environment. You do not build unless it makes financial sense. All such homes outperform standard homes and provide a healthier environment in a more sustainable manner at a lower cost. The holistic integration using natural engineering systems approach looks at all the related variables and takes the time to make the entire home-nature system work for the specific case.

Standardized materials, make money for the advertiser, media, harvester, manufacture, packager, warehouse , trucker, shipper, wholesaler, seller, contractor and tax collector. Using more natural less processed materials where appropriate are often better solutions but are not promoted by industry because there is not a lot of money to be made for most of the above people. They are by passed and not needed.
Clever use of materials gives you more options. You can use standard materials where you want to but 70% of the mass of a house can use more economical solutions to quality housing.

Brian