ICFs and Concrete

[GaryM]

The fellow who owns the concrete company built his home that way a few years back. And one of his drivers knows of another about 40 miles away. The owner of Stitt Energy Systems current home is built that way too. Can't tell any difference outside or in. Nice and quiet though. www.stittenergy.com

I wanted to use new building techniques, I guess just not that new!

[Pat]

Neat project! Congrats! I like the ARXX blocks but the nearest source is a ways away from me and no one near by uses them. I will be using Polysteel brand which fairly recently added another style block to their lineup. It is 13 inches wide over all and 2 ft tall by 4 ft long. Concrete is 8 inches thick with NO waffle grid and NO post and beam, just 8 inches of crete. It has steel "nailers" on 6 inch centers recessed 1/2 inch below surface.

I reproportioned my master suite to acomodate an integral number of blocks to reduce waste. It is 31x35 OD now.

Are you using any of the PanelDeck/LightDeck/whatever horizontal analogs to ICF for any ceilings or floors? I'm using PanelDeck for the basement ceiling which gives me a floor for the space above. I found out about the new block too late to use in basement which poured 2 days ago so cast the walkout basement walls in place (12 inches thick with 9 ft ceilings).

I'm just the reverse of you... You have 1 buried wall and three walls with windows in your "basement." I have 3 buried walls and one window wall.

We put a tad over 50 yds of 4000 PSI crete in the basement walls. The header beam over the window/door opening (16 ft wide) got 5 pieces of #8 (1 inch) rebar in the bottom and a couple #5 (5/8 inch dia ) higher up. The beam is 23 inches tall and 12 inches thick.

Keep us up to date with your project, it is quite interesting.

Pat

[GaryM]

Sounds like a great Master Suite. I guess you're including the bath and perhaps a dressing room or walk in closet in those dimensions. At least I hope so!

We are not using any of the horizontal stuff you mention. The floor joists are trusses with lots of room for services to run through. It's too late now, but if you have a URL, post it so I can learn. Stitt Energy usually builds a research house every year and tries new products. If they like the results, they then offer the new products to their customers.

Tomorrow we are going to mark locations for floor electrical outlets so that the rough-in can be done before the floor slab is poured. Perhaps by the end of next week we'll be able to start putting up walls.

[Pat]

Gary,
I meant to imply by "suite" more than just a bedrom. BOY that would be a B E D R O O M! Ya, it is bedroom, bathroom, sitting room, and his and her WIC. Bath has 5 ft Jacuzzi tub and a doorless shower. The "block" walls on all four sides of the master suite are 13 inches thick before sheetrock in the interior and veneer on the outside (brick-stone-vinyl).

In the floor plan the wall between the great room and the master suite is shown thinner than 13 inches. This is either a shortcoming of the cad application or a lack of ability on my part to make it behave. The interior walls of the sitting room are correctly shown at 13 inches (Pollysteel ICF with plain flat wall design). It is simpler to just go ahead and do them like the rest since I will be using them to support a cast concrete ceiling.

The entire master suite, less the sitting room with its French doors and windows, is a safe room. The two bedroom doors leading out of the space are FEMA doors with a lockset AND three deadbolts. If I decide to put any windows in the bedroom and or bath, there will be interior steel storm shutters of massive strength. I have done that for the guest bedroom/saferoom in the basement.

There is a small propane gas log in the upper right corner of the sitting room. Luckily we usually don't have simultaneous cold weather, power outages, and tornados so in case of a power outage in cold weather we can heat the bedroom with the sitting room's gas log and not compromise safety. I may run a duct with a small quiet, I mean, Q U I E T fan to circulate warm air into the bedroom from the sitting room. I have some solar electricity and batts for storage so a small draw like an efficient fan will not pose a problem.

I'm not quite approaching the max number of house building balls I can simultaneously juggle yet but I can see it happening later when several parrallel processes are running.

Best of luck to you with your adventure,

Pat

[GaryM]

Pat, i should have read your post before responding! I looked at the horizontal units and it look neat. Would make a great ceiling for the safe room!

At this point it's too late for us to use as there was not enough room allowed. We cut the budget a little, hope we don't regret it later, and are skimping on the saferoom ceiling. It's not going to meet FEMA specs. Can't have everything I guess.

[Pat]

Gary, I guess the good news is that the ceiling could be less important than the walls since the greatest damage is from wind tossed debris. Of course I saw the 18 wheeler in the movie "Twister" before I built my mom's safe room. I made her saferoom ceiling 14-16 inches with two rebar mats one atop the other 5 1/2 inches apart with rebar on 8 inch centers.

Pat

[Pat]

Gary, A couple questions... Did you use ICF for your stem wall or did you use conventional forms for it or what?

In consultation with my ICF source, I have decided to use ICF for my stem wall but will just thicken the slab under interior ICF walls. Makes insulation installation real easy.

I learned of yet another feature of ICF. With the concrete core of the ICF in contact with the ground or uninsulated footer, the concrete in your walls tends toward the temperature of the ground. In summer, the heat has to penetrate the outer EPS then heat up the cool concrete (mid 60's here but mid 50's in say, Wisconsin.) After warming the concrete then the heat has to penetrate the inner EPS. Similarly, in winter, the core is warmer than the outside temp and provides a little help.

I have ordered all of my PanelDeck and ICF. Deliveries should start arriving in a week or two.

Pat

[GaryM]

All the foundation wall, including the stem walls, are ICF construction. I had not heard the details you raise about the concrete acting as a "heat sink" of sorts, but it makes some sense. I wonder what the flow rate of heat through concrete is?

They were supposed to do the plumbing rough in on Thursday/Friday. May drive out this afternoon to see if it's so. If it's not it'll just make me upset. Why ruin a beautiful weekend!

Weather shows isolated thunderstorms for the four days starting Monday.

[Pat]

Gary, If the ICF stem sits on an uninsulated footing (at least uninsulated on the bottom) then that earth contact will tend to promote the effect I mentioned. The R-value of concrete is not very high. It is a decent conductor. R-value of concrete, tile, brick, and stone run around 1.0 +/- 20% with concrete close to about 1.0 in general (Wirsbo tables). Concrete has a fairly high specific heat also, not as high as water but still significant.

If you are "electrical" then think of the layers of EPS as resistors (R-value) and the thermal mass of the concrete as a capacitor that stores heat energy. Reference the sketch... An ICF wall lis a low pass filter. The applied voltage (outside temp), if higher than the concrete temp, forces heat through the R-value of the outside layer of EPS into the concrete core. If and when the core temp goes above the inside temp then heat is forced through the inside layer of EPS. As in the electrical analog, there is a phase shift and there are the equivalent of RC time constants.

As a thought experiment lets take the example of that time of year when the outside temp goes both above and below the inside temp. When it is hotter out than in, heat flows through R1 and begins to raise the temp of C1. If C1 is warmed above the inside temp then heat flows through the inside EPS into the house. It is likely that before much heat makes it to the inside that nightfall occurs and the outside temp falls below the core temp and heatflow is reversed. Heat flow continues from the core to the inside until the core temp is equal to the inside temp and then reverses direction as the core goes below the inside temp. There is a "phase lag" between the core temp and either the inside or outside temp.

The core exhibits a thermal flywheel effect, similar to a bare concrete wall but with significant differences, chief among which is the phase lag due to the high R value EPS. If you plot the outdoor temp and the core temp versus time you will find that the max temp ouside leads the max temp inside. The max temp in the core will be significantly later in the day than the max outside temp. The min temp will be similarly time (phase) shifted.

Being the curious sort, I will plant some thermal sensors in my ICF cores. It will only cost a couple bucks and will entertain me for a while. I will probably use a semi-conductor diode. Due to the still unrepealed laws of physics the forward voltage drop is a function of temp and a 10 cent 1N914 diode makes a decent temp probe for the temp range in question. I have designed electronic thermometers and temp controllers around them.

Pat

[GaryM]

Hey! More progress. SIP walls are going up on the lower level. Weather permitting, how many times have I said that in the last five months, they should be setting floor trusses Friday or Monday.

Attachment shows North and some of the West walls.