Is concrete block a suitable building material for walls of a house?

We are thinking about building a solar house and thought that concrete blocks would have a good thermal mass if filled with sand.

I think some people are missing the point. The thermal mass works as a heat sink, absorbing heat during the day, releasing it at night. And it works during the summer and winter. So the R-value isn't the point. So yes, a good deal of thermal mass there.

I'm no expert. Just fundamental knowledge, so do some more research. If you just fill it with sand, it is a passive system and therefore won't radiate much to the rest of the house. You may want to look at an active system in conjunction with thermal mass. It would consist of hot water heating, the thermal mass would supplement the heating of a boiler. Then you could build on a slab and use radiant floor heating. You have a range of possibilities. For example, you could build a trombe wall. It is an interior masonry wall and acts like a heat sink. It requires special consideration of your region, but so do all solar homes. You need to know the latitude and do some trigonometry to determine the best orientation for sun angle, soffit overhangs, etc, so you maximize solar gain in the winter and minimize gain in the summer.

Also if you use a thermal mass, you insulate the exterior of the thermal mass. Then find a way to keep the heat in during the winter, "vent" the heat out during the winter. (Opps meant vent out during summer)

But just as a material and disregarding design consideration, CMU's are good for thermal mass.

Edit: Some people still aren't getting it. Thermal mass as a heat sink. Of course, masonary doesn't insulate well. That's not the point of a solar home. It's thermal mass. The point is configuring the soffit overhang, so during the summer day when the sun angle is high, the soffit blocks solar gain and the thermal mass absorbs the interior heat, which can be released at night. During the winter the angle of the sun is lower, and now you use solar gain to your advantage, so the thermal mass absorbs the gain and releases back into the house during the night. The very fact that masonary materials have a low R-value is a benefit, not a libility, when it comes to using thermal mass in this manner. But it requires special consideration of the amount of mass, and design criteria. You still have to insulate, but the exterior of the thermal mass.

That is the whole point of a solar home. Using materials and thier properties to minimize use of fuels to heat and cool. As such CMU's are good for the use of thermal mass. Just search "thermal mass construction"

Here's a start:
http://www.consumerenergycenter.org/home...

There is ton of information out there.

Huge thermal mass! I think this would be great in the Southwest (warm days/cool nights, lots of sun). I don't know about New England, where in the winter we can go days without seeing the sun. If you are gonna fill the block webs anyway, why just not pour the walls?? That way the exterior and be formed to look like any number of stone products (instead of looking like, well, cinder block.)

remember thermal is a double edge sword.

yes it is a great building material for your house but make Shure that you have a experienced block layer show you the proper way to use them the material is only as good as the builder.

Interior walls?
Yes -
especially if they contain copper piping w/circulating 'water' from
exterior mounted solar collector panels in the winter
and
underground water in the summer.

http://www.solarexpert.com/heatpanel.htm...

Don't forget to include beams to handle the radiator wall's (concrete block) weight when building the house foundation...

The heat sink in a solar house must be insulated from the outside heat and cold. The concrete blocks on the outside walls will not work very well as a heat sink unless you put a very good insulation system on the outside of the concrete blocks.

You need your heat sink to be internal to the house.

Because you are getting some many answers here that are at odds with each other, I suggest you do some serious research on solar homes before you make some decisions that might be counter productive.

You might even consider using a consultant. If you are going to invest in a new home, that might be a very good first step. You are going to be investing a lot of money and for a solar home to be successful, you need to get it right.

Yes, but... there is NO R factor in block. As a matter of fact it's minus -15 i think. Therefore the inside of your house is cold in the winter and hot in the summer. However, they do make a good insulation for block so you must use this. Sound also echos inside a block house. Sorry about all of the negatives as block is great. You just have to insulate it properly. I live in a block house in Cabo San Lucas, Mexico so i have some experience.

All your answers are great. However, I don't know where you live. In places such as Florida, it quite common to use cinde block because of the expense of lumber and there are many block contractors. In other areas, you might have no residential block contractors, therefore, you'll have to resort to a commercal contractor. More expensive.

YES, I BUILT MANY IN FORT MEYERS FLORIDA....BEST FOR MODERATE CLIMATE, LITTLE R-VALUE...VERY GOOD FOR HURRICANES. THEY POUR A SOLID CONCRETE TIE BEAM AROUND THE TOP & FILL HOLLOWS AT WINDOWS & DOORS & INSERT METAL ANCHORS TO ATTACH THE TRUSSES. MAKES THEM PRETTY MUCK IMPERVIOUS TO HURRICANES ( ASSUMING IT IS A HIP ROOF & YOU NAIL THE DECK WITH 3 INCH NAILS & USE HEAVY SHINGLES.

filled with sand? that will be one well insulated house, yes, it insulates, yes it is a large thermal mass, and, if a tornado comes near youll be relatively safe

I don't know. Most of the wall would still be concrete and the r value won't be vary high. I would go with standard construction maybe 10 inch walls with spray foam. If you want a greener house, check out the straw walls............... The R-Value of an 8" concrete block is 1.11 PEOPLE. The sand wont help at all. It will lower the R-Value because it will fill in the dead air space. The problem is the concrete will take on what ever temp that is out side. In the summer it will get hot, and stay hot most of the night. In the winter it will get cold, and stay cold. You will have to insulate the inside to counteract this, defeating the purpose of the construction...

Yes they are and fill them with styrofoam beads for insulation.

If you are thinking about concrete blocks, which are actually a great building material, why not go all the way and research into concrete homes, which are really the way to go. Hurricane and tornado proof, they are super insulating, save a fortune in heating bills. Just click on the concrete homes ad at the right of this question and get a lot more information. We were going to build one but decided to stay where we were; however if we ever do build a new home, that would be it.

I don't think that block (with or without sand) is a good choice of material for a solar house. The R-values are small. The temperature of block pretty much follows the ambient temp. and stays that way. You would get more R-value if piled dirt around your walls. At least the inside temp would be more constant and you could temper it with heat or cooling.