While "R" value may be slightly higher with interior foam, I still stand firmly behind exposed interior thermal mass. Statistics alone can be misleading because of so many variables. Compare real world experience of comfort and the energy bills from two exact buildings side by side and that would tell much more than a computer program that can't possibly account for all the possible variables like windows, overhangs, climate, system mechanicals, etc., etc., etc. There is much more than "R" to the equation although I applaud your accomplishment in that area.

I wish that radiant or swamp cooling were practical options, but we are going to be in one of the few counties actually even designated as a warm humid zone in NC.  We have to keep the interior temperature around 70 or below for my son to be able to sleep, so we're staying well below dew point most of the time. 

The radiant solar is definitely an idea we're trying to incorporate.  We will have a pool, so there's a summer heat dump.  Radiant heat is also something we'd like to do - looking to see how it fits.

If we do the ICF footers, shouldn't we be able to have continuous exterior insulation if we drop the inner EPS height to seat the slab on grade, or even the monolithic slab interior?  Is the Buildcrete suitable for below-grade, or any other suggestions for protecting the EPS from termites that don't involve pesticides? Or should I consider doing a separate heated slab above insulated sheathing, which would eliminate the exterior slab insulation completely (there's no slab insulation requirement in this zone if it isn't heated)?  We've even considered using radiant pads under area rugs.  I think the insulation under the slab would end up being best here for winter, but the real problem is summer, and I'm not sure I want to give up that cool concrete floor to have a heated slab when we can use another method of radiant heat. 

Posted By mojoe on 11 Apr 2016 07:09 AM
OK, sure, whatever you say.

What was that comment in reference to?

Posted By mojoe on 11 Apr 2016 11:48 AM
While "R" value may be slightly higher with interior foam, I still stand firmly behind exposed interior thermal mass. Statistics alone can be misleading because of so many variables. Compare real world experience of comfort and the energy bills from two exact buildings side by side and that would tell much more than a computer program that can't possibly account for all the possible variables like windows, overhangs, climate, system mechanicals, etc., etc., etc. There is much more than "R" to the equation although I applaud your accomplishment in that area.

Sailawayrb uses scientific analysis to get her results. Exposed interior thermal mass walls don't perform as well vs standard form ICF walls (2.5" foam + 6" concrete + 2.5" foam). That's been proven with science. Outdoor climate temps, indoor temps, etc. have all been taken into account with the calculations. Sailawayrb has free software calcs that you can use to determine what results you will attain with ICF.

Not to confuse exposed interior thermal mass WALLS with exposed FLOORS. We are talking about WALLS here.

Mojoe, you are absolutely correct...I meant say stay ABOVE the dew point...and I have edited my previous statement accordingly. Thank you for pointing that out. If a surface gets BELOW the dew point, it will indeed cause condensation. BTW, we also have software to forecast where condensation will occur and how much will occur within any build up:

Borst Building Assembly Moisture Analysis Software

No prob sailaway, I do it all the time myself. I know you know what you're talking about. I'm just trying to point out that there is more to the equation than "R" or than a computer can determine. The computer says that essentially it makes no diff whether you put the insulation on the inside or the outside [as far as "R"] but I think we all know that there would be a major difference if you lived there and paid the bills. "R" is a consideration, but it isn't the only one.

maria, I don't know your heating vs cooling season exactly but if you dual purpose the radiant tubing for cooling in the summer it might work out. The dew point you need to stay ABOVE is the indoor dew point, not the outdoor, so if you are using a/c also - it would probably work out and maybe reduce the a/c load. That's why I questioned what the most efficient way to dehumidify the interior air was. Were you planning on insulating under the footings? If not, you would still have some connection there.

Actually Mojoe, our ICF performance software will tell you exactly what the effective R-value will be for any ICF build up and any given temperature profile. This was precisely why we developed it and we have found it to be very accurate. We needed more accurate ICF R-values to accomplish more accurate ICF building heat transfer analysis (e.g., ASHRAE or ACCA Manual J8). As I wrote previously, for our Rogue River OR Summer temperature profile, placing all the insulation on either the exterior or interior side results in a decrease in performance from R66.15 to R44.05. We have found that the standard ICF build up has provided a higher effective R-value for the temperature profiles that we have exercised.

We also do passive solar heating designs for commercial and residential buildings and we have had clients who have wanted (or perhaps have accepted...) exposed concrete interior walls. Exposed concrete walls (like exposed concrete slab floors) can provide significantly increased thermal mass performance, i.e., the ability to absorb/store more irradiance energy and then slowly release this stored heat energy at a later time. This passive solar thermal mass buffering effect is very useful in preventing a building from overheating while still using the available irradiance energy to heat the building. Passive solar thermal mass performance has more to do with the thermal mass area, thickness, density, specific heat capacity, absorptivity and emissivity than with the R-value. Perhaps that is what is causing some confusion. You can find a simple sample passive solar building analysis/design (including thermal mass analysis/design) here:

Sample Passive Solar Analysis/Design

We also have a full suite of passive solar design software (including passive solar thermal mass performance software), to allow one to accomplish this sort of passive solar building analysis/design:

Borst Passive Solar Thermal Mass Performance Software

Hey Mojoe, I think you meant to say "stay ABOVE the indoor dew point"...LOL!

sailaway, I'm not doubting your numbers and I'm not confused. If "R" was the only consideration, then foam-concrete-foam would be the way to go. That however is not the case - as you recognize at the end of your post. To determine a method based on "R" alone is shortsighted and a folly - as is wasting all that thermal mass by isolating it behind insulation. What is really gained by the increase in "R" in the wall by the interior insulation compared to what is gained by the massive increase in exposed thermal mass? Unless you live in a cave, because I haven't seen any windows that have R44 let alone R66. Like I said, put the 2 methods side by side in an equal comparison and let the results speak for themselves. Real life stats trump virtual stats. I like your info but it doesn't tell the whole story. This is probably the wrong forum but I have no dog in the fight - just what works best. You're right - ABOVE - See, I told you I do it all the time myself. It's counter intuitive. Thanks.

Interior walls don't have to be exposed concrete in order to benefit from exposed thermal mass. There are many choices that are both visually appealing and beneficial. Any brick, stone, slate or tile would work and so would plastering or stucco. There are some very durable and visually interesting coatings as well as natural choices like clay - and there is always stain and paint. I'm sure there are many others as well.

Our cooling load is going to be the much heavier season, especially given that we need to keep the house cooler than most year-round and are in a rather warm climate to start with.  Using any cooling system that takes the load off the heat pump will likely end up with humidity being a problem from short-cycling.  That's one of the toughest problems we have where we are now, and it's not nearly as humid as where we're moving.  I'd rather keep the cooling load on the HVAC to maximize it for dehumidification, otherwise I'm using a supplementary dehumidifier (which adds heat as well) or trying to make up some with ERV.  We picked the minisplits because the testing we've seen shows that their cooling efficiency is excellent, and that they run long cycles at a fraction of cooling capacity, showing even greater efficiency when they are slightly oversized for the space.  Basically gives us a solution that runs well and can potentially handle more, even if one conks out for some reason.  Between my son's extreme temperature sensitivities for sleeping, the asthma, and then adding a large IT storage array that probably currently uses about 50% as much as the whole house, we need the flexibility and ability to respond to any failures without an oversized HVAC system that won't wring out the air.  I went around this issue a bit with our HVAC contractor, and that's the most effective option we could come up with during that meeting that didn't destroy the budget. 

I'm not planning to insulate under the slab at all, that's another source of cool that I can just cover with rugs during the winter.  Adding the radiant to the slab makes slab insulation a requirement, which I don't want to do.  Ultimately, I don't think the tradeoff is worth it when I consider the insulation cost, the tubing cost itself, and then the loss of the cool ground contact in summer.  I'm thinking I'm going to try to find a way to work in a few radiators in sleeping spaces.  Maybe I'll be able to afford one of these or something like it - or that can be something we try to build.  J does love welding and plasma cutting projects...

http://www.archiexpo.com/prod/radox/product-49786-1675850.html


http://www.archiexpo.com/prod/bleu-provence/product-74617-716786.html

IT Storage array? I am storage engineer so just have to ask what kind it is and what are you using it for? You don't have to answer what for if you don't want but that could heat your whole place if it is big enough :). Had an HP array in my garage in CO during winter and it made a nice heat source. Power bill was pretty high those few month tho that I had it.

J is an IT consultant - he uses it for his own personal stuff, testing for client environment configurations with virtual servers, and a bunch of other stuff I don't understand very well.  Yes, it really does eat up power, and does help quite a bit with heating load in winter!  That's another plus of the ICF setup - the sound dampening with having the IT dude with the odd hours and the need for quiet is a phenomenally difficult match with a special needs child at home and on the move most of the time.  Having a Cape Cod is basically like having a megaphone in the center of the house (stairwell), and it's virtually impossible to effectively share space.  J has lived in the cinder block garage for over a year now, so this move is a long time coming for us!

Don't you think all storage will be ssd in a couple of years or so? These things don't get nowhere near as hot as 15k rpm drives. So all that heat that you count on just won't be there. If it will still be there, then how are you going to get that heat dissipated in the air since opening up the space will also bring the noise they make and they are freaking noisy.

I'm starting to think that all the smart people in the world hang out on this site - no sarcasm.  I don't know what SSD is - when I summarize what J does I give sort of a canned response that I understand very little of.  One thing I will say is that even over the last year, he has almost doubled his storage and processing capacity and cut the power draw and heat generation at the same time, so I'm thinking that the trend, as it's always been, will be towards smaller/cooler/faster - though I still don't know what an SSD is...

This is a roundabout answer, but here 'tis - One of the things we're really trying to accomplish in this design is the ability for the structure to evolve as we do.  Essentially, we have a large rectangle with four consecutive blocks - kid space, kitchen, master space, and garage/shop.  Each of the squares, though containing different spaces, contains very little permanent wall separation (with the exception of bathrooms).  There's a convertible furniture movement that uses pieces like large, moveable, folding cabinets that form separations of space without the permanence of framed walls, but with many of the benefits.  For people like us who don't have too much concern for convention, the lack of crown moulding at every turn doesn't make us terribly sad.  On the other hand, the spaces are large and flexible, using storage pieces to separate space and mount small furnishings (like coat racks, mirrors, electronics, or artwork).  As our needs change, so can the space.  We're trying to design the mechanical systems to be somewhat flexible as well.  I am really impressed with the ductless minisplits from the perspective of the consumers with severe allergies and such, not to mention the potential for supplementing or upgrading if need be.  Fortunately, the recent testing showed their efficiency increasing with the ratio of load-to-capacity, so if we need less later, that's not a problem. (If I'm missing something here, please feel free to point it out)

The noise, though - that's a problem when everything's cranked, so leaving everything wide open isn't really an option we like.  Fortunately, having addressed air flow to closed bedrooms with ductless HVAC, we're installing air circulation loops into the closed rooms (total of four, so not an intense undertaking we hope).  I'm trying to decide on whether to allow vent placement to try to drive movement or whether to circulate mechanically based on a temperature differential, or both.  J is completely immune to the noise, and fortunately at least I sleep pretty heavily, so having a bit of a noise bleed won't be awful. 

I wish I'd picked some sort of degree and career path in construction.  Not only would it be really helpful in general, but working on this build plan has been fascinating, and quite honestly just plain fun. 

maria, that first radiator looks really nice but also really climb-able. What about radiant in the exposed walls instead of the floor? Just a thought. SSD is IC chip vs spinning disc drive for storage - google it. Unpowered vents, unless huge, are unlikely to move enough air. I've noticed that things are way more fun when you don't have to do it for a living. When you add the financial necessity to the equation it definitely changes things. I know a lot of creative people who work with their hands [and heads and hearts] and it's a widely held realization. I got a job building furniture right out of school and my first day on the job the head guy after quizzing me on my classroom knowledge told me right to my face to forget all that **** and this is how it's done in the real world. I was shocked but he was very knowledgable and experienced and knew what he was talking about - not that there aren't things you can't learn in a classroom but that's not the end all. I also have a manual of carpentry from the 70's that has good info on the inside but shows a guy nailing an asphalt shingle in the middle of the tab on the cover.

I've also seen towel rack radiators for supplemental bathroom heat - nice looking, functional, DIY-able, but still very climb-able as well.

And Lbear strikes again with some coenabling from sailawayrb. What we have seen demonstrated here is that interior foam is an aid IN ROGUE RIVER, OREGON, which tells zip about coastal NC, high desert AZ or Appalachian PA. In fact, since sailawayrb lives in the mountains, it doesn't tell us much of anything about her neighbors who live substantially higher or lower than she. Those who live higher, who chance upon this will ask "Air conditioning? Huh?" Weatherspark.com doesn't have averages for Rogue River, but Grants Pass nearby has a range of 55-75 on July 30, the hottest day of the year.

And, no, it is not scientific. She has a rough check on her figures by gauging her energy use. But it's pure guesswork to parcel out the effect of glazing, attic insulation, air infiltration, internal heat generation, insolation on roof and walls, and on and on. Scientific is building the wall section in a hot box where you can measure the temperature on both sides over time in controlled conditions. Those would be the basis of simulations your cohort (employer?) TexasICF says are misused.

But you're right that a slab is sufficient surely in NC, or pretty much anywhere else that isn't the desert southwest. That said, I think OP has health concerns about interior foam rather than energy concerns.

Posted By toddm on 12 Apr 2016 07:40 PM

And, no, it is not scientific. She has a rough check on her figures by gauging her energy use. But it's pure guesswork to parcel out the effect of glazing, attic insulation, air infiltration, internal heat generation, insolation on roof and walls, and on and on. Scientific is building the wall section in a hot box where you can measure the temperature on both sides over time in controlled conditions. Those would be the basis of simulations your cohort (employer?) TexasICF says are misused.

And ToddM strikes again, the forum curmudgeon. Discrediting & disparaging Sailawayrb's study as "not scientific" just shows how little ToddM knows on this topic. "Pure guesswork" ? Are you kidding me. Her software and calculations are scientifically sound.

Sailawayrb scientifically verified on how ICF performs and the science is sound.

Maria, your unusual floorplan (my favorite thing) begs for some good research on disentangling your utilities. It's something that really has never caught on, I guess for the same reasons that contractors are resistant to ICF. You can save a LOT on a tight budget if you do it right.

Thanks for posting those swoonworthy radiators. Now I *want* that bathroom.

Disentangling utilities - expand on that Robertson?  Definitely need to hear more about that if you can!

Sorry about the radiators.  I know, they are beautiful.  I've never had the desire for purely decorative stuff (I happily used hand-me-down garage shelving as an entertainment center for years to my mother's absolute horror), but taking function to a level of sheer beauty is just awesome.  Robertson - check out Archiexpo.  It's pure crack for finding cool stuff like that.  I don't even know if any of the manufacturers or suppliers are in the US (looks like they're all in Europe), but I don't look at it for anything beyond enjoyment. 

And just when I thought I couldn't love this site more, thank you for seeing and commenting on the climbability of the radiators.  Yes, that would be a horrifying idea - which is why they would only be on the grown-up side of the house.  Fortunately, the kiddo is so unbelievably hot-natured that there's no need at all for that on his side.  He's perfectly happy at 68 degrees everywhere, and completely oblivious to cold feet as well.  Which is another reason why our current setup (him in the hottest room in the house needing to sleep under a 15lb weighted blanket plus several others) is just really not working.  I looked at towel radiators online, and was really surprised to find several that were pretty cool and very affordable, which solves the bathroom problem for me and J-man on the grown-up side who are not quite so hot-natured.  Found a great little floorstanding ceramic heater for the bathroom too - nifty

Thank you for the information about removing the interior insulation.  I've battled in my head about this as we've gone through this thread, and ultimately, I have to take that hit in R-value.  The little one requires some extensive safety measures that include a locked bedroom door at night, plus locked windows at all times, which has caused me a great deal of fear.  We've gone through this with both the local Fire Department as well as Human Rights professionals, and ultimately the risk of injury from of his waking and "exploring" unattended are much higher than that from fire.  The end result, though, is that in the event of a fire, I have to eliminate as much fuel as possible - hence another draw for concrete walls, because I have to give myself more time to get to him.  The burn temp of EPS is much lower than the average temp of a house fire (400ish versus 1100ish), so I can't do it.  That also plays a big part in electrical wiring for the home on his side - very little of it will remain after we move in anyway, so having it exposed with conduit doesn't matter much to us either way just to get a certificate of occupancy.  Anything remaining will all be at around a height of 6 1/2 feet and only in a couple of spots.  The frequent incidents we have of water damage are a big deal too - I detest babysitting drywall.  I never even thought about drywall before dealing with this stuff.  And even though I actually find steel kitchen shelving and countertops pretty cool, that's not the only reason I'm choosing it.  Hopefully, this should pay off for us in insurance costs too, but even if it doesn't, it's a mommy decision.  If there was a phenomenally effective, practical, cost-effective way to maintain the interior insulation with fireproofing materials, I'd say great, but given that I like concrete walls anyway it kinda makes all that extra work daunting.  If we move again one day (which we hate, so hopefully we won't), that'll have to be a "wow - take this super versatile space and make it your own" sale.  Having a child with special needs has made managing lots of everyday aspects of life a lot different than they used to be - it just changes everything.

Radiant in the walls sounds cool!  I don't know if I can pull that off - I'm going prescriptive on reinforcements, and beyond hiring a concrete contractor, all of the design falls on me (even the drawings).  I worry that I would create additional obstacles that would obstruct a good concrete pour?  That said, though, maybe I could imbed some in plaster cladding here and there if it's a bit thicker, depending upon the width of the pipe?  Worth a gander in the mind for sure, especially since that can be done after the initial build.  Then I wouldn't have to insulate the slab and lose that cool floor in the summer.  I'll have to look into that.

Thank you for the answer on ventilation - that makes a couple of decisions easier to make.  I think my response in design to that will likely be to combine my son's living and sleeping space, since that ultimately reduces the total space requirement anyway, and makes a lot of daily living issues much easier to manage.  It'll cut construction costs significantly as well, and eliminate the need for a west-facing window that was really giving me some serious irritation, which are both HUGELY lovely developments.