new construction - insulation (East Texas)

[3Ts]

is that builder mike, with dream homes?

how old is your home?
you aren't seeing significant savings in yer light bill?

No. Different builder. House is about 1.5 years old. Our house is a little under 2200 sq ft and we run about $160 for electric in the summer time with the air conditioner. I don't know what to tell you about energy savings we see since it's the only way the house has ever been so we have nothing to compare it to. It was also designed to use LED bulbs (regular bulbs will burn up the dimmers and blow circuit breakers). Those LEDs do not work as well with the dimmers as I'd hoped even though I matched the bulbs and dimmers and even tried them out in advance.

corkpuller - I sent you a PM

 

[Tractor Seabee]

Th only difference between southern climates is where you put the vapor barrier. I was involved for awhile with modular construction. We put the vapor barrier on the outside instead of the inside.Those were engineered designs for Florida, Gulf Coast, and Hawaii.

Ron

 

[Milo]

there seems to be a strong push towards this idea of making a house act like an igloo cooler with this closed cell foam insulation.
no ridge vents, no soffit vents. spray foam in walls and on roof decking i believe. no insulation laid between ceiling joists.

from what i understand, you dont seal the living area from the attic, the attic will attain close to the same temp as the living.

i just cant wrap my head around no attic ventitation in the east texas humidity. seems there would be a problem with mildew......

I know that technique is promoted by some but personally I don't like the idea for a couple reasons. Having to condition the attic, I don't want to heat and cool the attic. And the roof decking and shingles are going to literally bake without the benefit of any cooling air underneath. Otherwise I'm convinced spray foam insulation is the best way to go and used it in my house built in 2002 as well as the shop I just completed. Watching it done and seeing the foam completely seal to the studs and back side of the sheathing and fill every little gap is was pretty impressive to me. Places like electrical wiring, wall boxes and ceiling fixture boxes which are hard to get fiberglass effectively behind are completely filled. Headers were made hollow from (2) 2x12"s with 2x4 ends then filled with foam.
In both cases we framed outside walls with 2x6 but before insulation was sprayed the ceilings were drywalled and joints taped. After spraying the walls they went to the attic and sprayed down covering everything including the truss bottom chord.


It appears in the pic that the OSB attic flooring is on the bottom chord but actually 2x6's were scabbed up higher to the truss sides then the OSB was laid down after insulating.









Excess shaved off.

 

[Dave Pee]

In hot North Florida, I am sold on installing a radiant barrier. I put one under a new metal roof, and my vented attic stays at outside ambient air temps, as opposed to 120+ degrees , before3 the foil. 1600 sq ft double wide, electric bill is always less than $150.

 

[hawkeye08]

If I were building again (we have SIPs now for whole house (all exterior walls, roof, floor), I would look seriously at the t-studs and spray foam for whole house. I would put in mini splits and an air exchanger.

 

[Granthol]

If you’re going to spray foam everything you will need an air exchanger. Without one you are very likely to end up with serious moisture issues and mold. The air exchanger runs about $2000 that expense plus having to cool the attic I can’t imagine much expense saving. I’d install 24 inches of blown in fiberglass and a radiant barrier on the roof side and call it good.

 

[ovrszd]

If you’re going to spray foam everything you will need an air exchanger. Without one you are very likely to end up with serious moisture issues and mold. The air exchanger runs about $2000 that expense plus having to cool the attic I can’t imagine much expense saving. I’d install 24 inches of blown in fiberglass and a radiant barrier on the roof side and call it good.

I was scrolling down to type this response. Thanks for doing it for me.

 

[EddieWalker]

Something to consider. I went to look at a house with one of my clients who was thinking about buying it. Price was $750,000, which is really a lot of money for a house here. I didn't know how old it was, or what the value of it was. I was just there to see if everything looked right. The main thing was that the shingles looked worn out. Lots of discoloration and loss of rock from the surface of them. Just looking at them, I guessed that the house was 20 plus years old and that it had been through some severe storms. This didn't make sense because they where still building new houses in the neighborhood, and even on the lot next door. I went up into the attic and it was all spray foamed under the sheeting of the roof. When I touched it, it felt soft. They used open cell foam. It turns out that the house is 2 years old!!!!

There are some examples of using open cell foam on a house, but they are pretty detailed and not very easy to accomplish. There are also a lot of stories out there that I found for my client with this exact problem of roofs rotting away, deteriorating and failing prematurely because of the moisture held in the open cell foam. Fortunately she realized the severity of the problem and what it would cost to fix, and she walked away from that house.

 

[Corkpuller]

The more I read about it all, the more I think I'll build the next place with the "old way" of insulating. It's served me pretty well over the last 30 yrs.
It will be just me and the old lady, in a 1600 - 2000 sq ft. home. Not gonna break the bank if the August light bill is $175 compared to $100. And I won't be wondering if I got moisture trapped in my home or a roof leak that I can't detect.

I got another year before I have to decide, so still plenty time to investigate my options.

 

[Milo]

If you’re going to spray foam everything you will need an air exchanger. Without one you are very likely to end up with serious moisture issues and mold. The air exchanger runs about $2000 that expense plus having to cool the attic I can’t imagine much expense saving. I’d install 24 inches of blown in fiberglass and a radiant barrier on the roof side and call it good.

The more I read about it all, the more I think I'll build the next place with the "old way" of insulating...... And I won't be wondering if I got moisture trapped in my home or a roof leak that I can't detect.

If you insulate perfectly with fiberglass which includes a vapor barrier attached you'll need an air exchanger also. Fortunately, or actually unfortunately, fiberglass can't realistically be installed perfectly, there are so many little gaps and voids where air flows freely, especially in walls. Warm, moist outside air condensates in those areas of a wall cavity cooled by AC. So not only are you loosing AC or heat it's allowing moisture in the wall cavity. Just Google "fiberglass insulation and mold".


Eddie Walker described how to insulate the wrong way with the wrong type of foam.