# Insulating a partial earth sheltered home



## ddsrph (Nov 23, 2013)

My house project is all block filled with concrete and brick veneer. Many block houses are in Florida which at least north Florida has a climate very similar to my location in southern tennessee. How are those Florida block houses framed inside and insulated? I have a huge supply of recycled poly-iso board and want to use it to the max coupled with some soon to be purchased XPS blue board.

Thanks
JM


----------



## BigJim (Sep 2, 2008)

This is a good thread, since seeing your build, I have been doing some research on insulating masonry walls in colder climates like ours, which isn't as cold as way up north. So far it has been confusing what I am finding out.

Just sealing the masonry walls won't stop condensation from forming when cold masonry walls meet inside warm air. Some way, heat must be contained from coming in contact with cold objects. I wonder if Styrofoam will sweat? I know it is a very good insulator but will the back side of it sweat if cold and some heat meet?

One ideal way to get rid of moisture would be with a dehumidifier, but how could one be incorporated to work if a small space was left between the outside wall and an inside, well, insulated wall? I ideally it would be to insulate the entire outside of the outside wall and inside as well. That would cause some problems not to mention expense. This is an interesting study.


----------



## ddsrph (Nov 23, 2013)

Big Jim
The extruded polystyrene, like the blue board is supposed to be very resistant to the flow of water and water vapor. Look at the article I referenced in a recent post from building science corp. if you search for the authors Smegal and Straube and high R foundations you can find it. It gives ten examples of ways it can and has been done. Look at case number 5 which is what I was trying to copy in my initial plan. The overall idea is to use a lot of vapor impermeable board type insulation, in their case XPS against the block and poly iso over that.
One thing they never mentioned was leaving a space between block and wall.

JM


----------



## BigJim (Sep 2, 2008)

ddsrph said:


> Big Jim
> The extruded polystyrene, like the blue board is supposed to be very resistant to the flow of water and water vapor. Look at the article I referenced in a recent post from building science corp. if you search for the authors Smegal and Straube and high R foundations you can find it. It gives ten examples of ways it can and has been done. Look at case number 5 which is what I was trying to copy in my initial plan. The overall idea is to use a lot of vapor impermeable board type insulation, in their case XPS against the block and poly iso over that.
> One thing they never mentioned was leaving a space between block and wall.
> 
> JM


I haven't gone to the site you linked to, but I will. One thing that bothers me putting the XPS against the wall is there will be a space, be it ever so slight due to the imperfections and roughness of the blocks. In that slight space much mold can grow. If there is a mold resistant substance that can be applied to the wall, placing the XPS directly to the wall would work.

I just did a check and if this works it will be just the ticket:
http://www.rustoleumibg.com/images/tds/CS1770_1112_WRT_ZWT01_WaterTite_Mold_TDS.pdf

See what you think.


----------



## BigJim (Sep 2, 2008)

I went to that site and read part 5, sounds good. The key would to be doubly sure the warm air is totally sealed where zero air can get through. If the interior wall is absolutely sealed, if mold did get back there it couldn't get into the living area. 

I understand your concern and wanting to make sure to head this off now as later on down the road. This is an interesting project.


----------



## ddsrph (Nov 23, 2013)

BigJim said:


> I haven't gone to the site you linked to, but I will. One thing that bothers me putting the XPS against the wall is there will be a space, be it ever so slight due to the imperfections and roughness of the blocks. In that slight space much mold can grow. If there is a mold resistant substance that can be applied to the wall, placing the XPS directly to the wall would work.
> 
> I just did a check and if this works it will be just the ticket:
> http://www.rustoleumibg.com/images/tds/CS1770_1112_WRT_ZWT01_WaterTite_Mold_TDS.pdf
> ...


Big Jim
You are absolutely right about the space and the original comment from the other poster about finding mold behind the pink board was addressed in a article I read after his post. It seems that with a rough wall and or just using dabs of glue coupled with a little space directly behind the sheet rock will create a circuit of air flow and allow moisture to accumulate on the colder side.


----------



## ddsrph (Nov 23, 2013)

The watertite product you mentioned looks very promising. I am going to check on cost and where to buy. I was planning on using more drylock but this sounds better especially the mold proof claim.

Thanks
JM


----------



## iLikeDirt (Apr 27, 2014)

The right place to put your rigid insulation is outside the walls, not inside. You have a perfect opportunity, too, since you're still building the house and the foam will be covered up with brick veneer later. Doing it that way gives you a bunch of insulated thermal mass on the inside (the CMU structure), which will help with your A/C bills. Keeping the insulation inside won't help as much because the huge mass of brick and concrete-filled CMU that make up the wall will absorb the day's temperature extremes take a long time to heat up or cool down once you actually want them to. During the summer in particular, the heat in that mass from the day's sun will be pushing itself against the insulation long after the sun is down, resisting the wall's likely thermodynamic tendency to shed heat at that point.

It's not too late at all to decide to put your foam on the outside. You'll just have windows that are a little recessed. But that's the way they'd have been be anyway after you added your brick veneer. And they'll last longer being less exposed to the elements.

Even better idea: don't use foam at all, as it will eventually get infested with carpenter ants and termites, and can offer them a protected route to your (presumably) wooden roof structure. Instead, use rigid mineral wool boards. Insects don't eat rocks! But polyiso is probably fine, honestly. Especially if you decide to use concrete or metal SIPs for your roof.

If you build like this, your house will likely be outrageously comfortable, last 1,000 years, and laugh at many of the typical hazards and headaches that most homeowners deal with (high energy bills, termite infestation, moisture problems, flammability, chemical odors, etc).


----------



## ddsrph (Nov 23, 2013)

I am past the point for that option. What I am planing on is to put in two inches continous
Against the block(which will be coated with super thoroseal by the thoroseal company) the the two inches continous will be 1/2 inch blue board then 1 1/2 inch poly ISO, then frame against that with stud wall then fill stud cavities with 2 1/2 inch poly ISO plus one inch blue board. All joints will be overlapped by two feet and taped. That will give slightly over a 30 R value. The ceiling will be only poly ISO as high as I want to stack as I have a bunch. I will go at least R 50. I will run a dehumidifier and heat and cool with a 1 1/2 ton heat pump augmented by a small propane fireplace.


----------



## BigJim (Sep 2, 2008)

You got it looking good JM, now you can work any time you want, weather bad or not. I read that tape isn't very good sealing joints even if they are overlapped. Maybe they could be sealed with a butyl rubber sealant then taped. The butyl is some sticky messey stuff but it does a great job of sealing any water out.

This is just what I would do, seal bottom edges, side edges and top edges, plus tape, to keep any and all heat from reaching the blocks from inside and seal all moisture out from getting to the living area.

Maybe an over kill but I would want more over kill than under. JMHO


----------



## ddsrph (Nov 23, 2013)

Jim
That's a good idea about the caulking. Whats butyl rubber caulk normally used for to aid in finding? Also check out the Super Thoroseal and give me your opinion. It's similar to Drylock but I have read it is better and not very expensive which was a pleasant surprise.

Thanks
JM


----------



## concretemasonry (Oct 10, 2006)

Drylock is a lower quality, easy to apply "waterproofing" material. Thoroseal is far superior, but more work to apply since it become a permanent part of the concrete wall and not a coating with some claims for permeating.

I have used Thoroseal products when repairing architectural building details and restoration work on old small dams. My personal uses were on my own home for correcting old errors or sloppy construction while finishing a basement. I also used in on my 1600 sf. year-around lake home (3 year phased construction) to give an acceptable surface over 8" lightweight block until I got around to getting the brick veneer applied.

Dick


----------



## BigJim (Sep 2, 2008)

JM, When Dick speaks I listen, he knows his stuff. I was a contractor, I wasn't a specialist in concrete and masonry like he is. 

I looked up an article on the butyl caulk sealant to let you read for yourself. While I have used butyl caulk a lot of times and had absolutely no problems out of it leaking. Butyl is used to seal glass to aluminum frames, the gray stuff you see in aluminum windows. I have used it on my camper roof many times to seal around roof protrusions with good results. They do make a butyl rope which is really good but costs more.

Butyl caulk is like working with soft bubble gum and will stick to almost anything, it is very water proof and makes a good seal. The only place I have been able to find it now days in this area is Ace Hardware and then some of them don't have it.

I did read where some people are using the spray styrofoam in the can to seal styrofoam side to side and top and bottom which makes sense to me. I know that stuff will seal like crazy and is easier to use than the butyl.


----------



## Windows on Wash (Aug 30, 2011)

Looking great!!


----------

