Concrete home construction

[Paddy]

Highbeam,

I have done a little searching on Thermal mass and insulation. Found a neat site devoted to research on the topic. One paper in perticular that caught my eye compared 4 concrete and foam isulation methods;

Ext foam/concrete int
Ext concrete/foam/concrete int (my choice)
Ext foam/concrete/foam int (ICF)
ext concrete/foam int

Each configuration is simulated in 10 climate regions. Summary; foam on inside walls performed lowest and concrete on inside performed highest.


link to this overall website; Thermal Mass Discussion Forum

The paper can be found under "View presentations' at the botom. The paper is called; Calculation of Energy Benefits of Application of Thermal Mass in Residentail Buildings - Methodology

Be carefull, you can spend all day on this site!

 

[dfkrug]

The roof has no gable ends to speak of so maybe that helped it stay put.

Yes, hip roofs could survive; gable roofs were doomed.

The other reason that some roofs stayed on and some did not is the
quality of the top plate to roof connections. Post-mortems of
hundreds of failed newer stick-framed structures (mostly in FL in the
90s) showed that simple toe-nailed connections did not hold the
roof on. Simple truss-to-top plate connections were better, but not
enough. Codes changed to require steel strapping that extended
down the walls and in some cases, over the roof.

In ICF construction, the top plates on the walls are bolted to cast-in
connectors, similar to those used for foundations. Trusses or rafters
use steel connectors to this very secure top plate. Gable roofs of
all-ICF construction to the roof apex is also very strong.

Of course, the ultimate roof diaphragm is a concrete slab....

 

[Paddy]

dfkrug,

I agree, nothing like a concrete slab with conecting rebar to the walls. I plan on having short half walls so it will be safe to use the roof as a patio.

I have seen other photos where homes with concrete walls survived just to wall height. I think, if it had just gone all the way up!

 

[_RaT_]

Yes, hip roofs could survive; gable roofs were doomed.

The other reason that some roofs stayed on and some did not is the
quality of the top plate to roof connections. Post-mortems of
hundreds of failed newer stick-framed structures (mostly in FL in the
90s) showed that simple toe-nailed connections did not hold the
roof on. Simple truss-to-top plate connections were better, but not
enough. Codes changed to require steel strapping that extended
down the walls and in some cases, over the roof.

In ICF construction, the top plates on the walls are bolted to cast-in
connectors, similar to those used for foundations. Trusses or rafters
use steel connectors to this very secure top plate. Gable roofs of
all-ICF construction to the roof apex is also very strong.

Of course, the ultimate roof diaphragm is a concrete slab....

I remember framing my first project, a 4 plex. I was a bit suprised even though I knew nothing, at how little connection there was between the top plate and the ceiling/roof joists. Toe nailing, a little freeze block and that was it, we did not even use plywood on the walls, just led in bracing. Out here in CA, we have many Simpson type brackets to attach and create seismic panels, some seem a bit silly, but the rafter connection brackets make alot of sense. For me, ICF is the start of the future. There is so much more to "R" value then what you read on the bag of fiberglass insulation. Remember, with open insulation like fiberglass R13, R19 etc. measurements are static conditions where air movement is minimal at best. Put fiberglass on a vaulted ceiling and its R value will go down. Same in a walls. ICF pretty much eliminates many of those issues.

 

[bugstruck]

Ext foam/concrete int
Ext concrete/foam/concrete int (my choice)
Ext foam/concrete/foam int (ICF)
ext concrete/foam int

Each configuration is simulated in 10 climate regions. Summary; foam on inside walls performed lowest and concrete on inside performed highest.

Haven't checked the link out yet (I will though) but I would have guessed the all foam exterior to be the best. The thermal sink (concrete) is against the most evenly regulated thermal envirionment (inside) and acts a a buffer or delay to exterior temp swings. My guess anyhow? The only better place for that thermal mass could be inside the exterior walls?? I know that is often done on passive solar but I'm not aware of anyone intentionally putting thermal mass on the inside of the home in a conventionally controlled envionment. Not sure if it would be of real benefit or not. Seems it might though.

 

[_RaT_]

Haven't checked the link out yet (I will though) but I would have guessed the all foam exterior to be the best. The thermal sink (concrete) is against the most evenly regulated thermal envirionment (inside) and acts a a buffer or delay to exterior temp swings. My guess anyhow? The only better place for that thermal mass could be inside the exterior walls?? I know that is often done on passive solar but I'm not aware of anyone intentionally putting thermal mass on the inside of the home in a conventionally controlled envionment. Not sure if it would be of real benefit or not. Seems it might though.

Chris, I think you hit the nail head on, dead smack square in one swing.

 

[Paddy]

Rat/Bugstruck,

Internal thermal mass is very good when solar is used. It seams here in Indiana, when it's cold it's also cloudy

In some of the studies listed above, no insulation on the outside was best because of big daily temp varriations, Southern CA and AZ. In these cases, the goal is to "flip the temp cycle". That is to have the heat of the day being dumped in to the home as the cool of night comes. One main issue is timing. If your timing/ Thermal mass is to great, you can have the heat of Yesterday dumped during the heat of the following day. This will double your heat! Even in cases where the outside temp never gets below inside temp, the temp cycle flip is still good because the heat pump is pulling cooler air across the coils at night when the load hits.

Do check out the paper I reccomended, really neat material

 

[bugstruck]

Rat, I'm far far away from any mechanical guy so that was just a lucky guess based on some observations of construction types over the years. As for hitting the nail.... I'm a Carpenter before anything else, and before pneumatic nailing took hold, so I'd better Very interesting discussion here. I'm learning a lot from this thread and the links. Pretty humbling as there isn't a whole lot I haven't seen or experienced in the construction arena. Nothing the expert makes though, that's a rule I try to remember. I do favor the concrete home constuction idea for the reasons expressed here. If I do another home, that or timber frame is what I'd be inclined to go with. Now if you blended the two and did it well, that would be rather unique. I need to park that thought though or I could be distracted for hours...or days

 

[bugstruck]

Paddy, That is a very interesting description you gave on the CA and AZ locations. Makes a lot of sense. So is the ideal position of the insulation and the volume of the thermal mass inclined to vary from one geographical location to another? I think that's what I got out of that.

I'm the student on this one. I did poke around that link and there is a bunch of info as you said. I'll read some more over the weekend.

 

[_RaT_]

Rat/Bugstruck,

Internal thermal mass is very good when solar is used. It seams here in Indiana, when it's cold it's also cloudy

In some of the studies listed above, no insulation on the outside was best because of big daily temp varriations, Southern CA and AZ. In these cases, the goal is to "flip the temp cycle". That is to have the heat of the day being dumped in to the home as the cool of night comes. One main issue is timing. If your timing/ Thermal mass is to great, you can have the heat of Yesterday dumped during the heat of the following day. This will double your heat! Even in cases where the outside temp never gets below inside temp, the temp cycle flip is still good because the heat pump is pulling cooler air across the coils at night when the load hits.

Do check out the paper I reccomended, really neat material

Thanks Paddy, great info.