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PostPosted: Mon Sep 12, 2005 5:46 pm 
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Recently I attended the High Performance Green Building: The Future of Affordable Housing conference at UNT.

The conference was excellent and the presenters from Building America and EEBA were particularily good. I have had a lot of exchange with the Building America folks as they are a partner on www.heathershome.info project with my firm. There is general agreement that insulation in our Texas climate is effective. However, wall insulation is not as effective as you might think.

The most critical issue is shading. Windows on the south and west must be shaded.

Secondly, orientation. If the builidng is sited poorly it will absorb too much solar radiation or too little.

Third is quality of the attic or roof construction.

Fourth is the SEER rating of the HVAC cooling systems, the higher the better.

Fifth would be the amount of glazing or the area of the windows as compared to the area of the floor plan. Too much and your living in a greenhouse that will overheat. Too little and you are living in a cave with the lights on all the time.

Sixth is the quality of the windows. They should be thermally broken with 1" insulated, southern low-e glass.

Seventh would be the insulation in the walls. Typically in our area R 23 is plenty. Too much glass area and the insulation value of the walls is irrelevent.

There are highly regarded professionals in this field who would argue that insulation in the walls in our climate isn't relative. However, the City of Lubbock has proven that ICF constructed homes are about 45% more energy efficient than stick built homes with batt insulated walls. They have a home replacement program for those who qualify financially. Lubbock has built over 150 homes simply using Insulated Concrete Walls and tight construction to achieve this level of performance. What this tells us is that thermal mass can do more to achieve comfort with the least amount of energy expended rather than insulation.


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PostPosted: Sun Sep 18, 2005 7:27 pm 
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Location: Bartonville,TX
Gary,

I had hoped to attend that seminar but work prevented. I thought I'd offer this, which I had posted under as a new topic, until I read yours...

As the price of my home which is still to be constructed increases I'm reconsidering ICF construction.

To preface my question, let me describe the house as designed:

The structure is oriented on an east to west axis, in most areas only one room deep to allow maximum solar penetration in winter, situated in the shade of large trees for protection from summer sun, protected with a near house-length porch on the southern exposure, no glazing on the east or west elevations. The attic space will be conditioned, insulated between the rafters with Icynene and the structure will be airtight as possible.

Having said that, I realize the pro's of ICF, such as strength, quiet, pest resistance, and insulation quality. However, I've recently heard a notable "green" architect quoted as saying that when considering 2x6 stick construction as an alternative, ICF is not cost effective.

This expert advocates a thin layer of Icynene between the studs on the exterior side of the void between the studs, followed by a blown cellulose resulting in a greater R value than ICF.

Where do you stand on this?

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Last edited by stuart on Mon Sep 26, 2005 12:48 pm, edited 2 times in total.

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PostPosted: Mon Sep 19, 2005 10:22 am 
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From the information you gave me the "noted" Green Expert was probably Peter Pfieffer from Austin. Peter has recently been using the thin Icyene followed by blown cellulose formula for awhile. The logic is good and the system functions well. The Icyene seals the moisture out and the blown cellulose absorbs the interior moisture and then gives it back to the interior space when needed.

Cost effective, maybe. It seems to me that if designed properly the AC system can handle the moisture just fine. I've got issues with cellulose - another topic of discussion. I have used 2x6 framing at 24" O/C and simply filled the cavity with Icynene. Why bring in another subcontractor to insulatethe same house twice.

Either system is certainly much more cost effective than ICF construction which typically is about 15 - 30% more in terms of just wall cost.

However, the ICF methodology does perform exceptionally well in this climate, it is also tornado resisitant, water resistant, pests can't hurt it and fire resistant. I built the first floor in my new home with ICF wall construction, knowing full well it was more expensive. The Heers rating by Energy Star was in the top 1% in terms of tightness of the envelope.

The comfort level is incredible. The interior space never seems to vary more than a couple of degrees. From my experience, the ICF construction is the best way to build in our climate. It does cost more but it boils down to the long vision and sustainability. The ICF walls will last generations and don't use any wood in their construction. Stick framing is conventional and slowly giving way to other methodologies that just make more sense. The effort to build a stick home with the proper building science as EEBA recommends, in my opinion, just seems like a bandaid on an archaic method of building that's been around for a couple of centuries.

It comes down to making a decision about whether you want to build with the best wall system for our climate by taking advantage of the embodied energy of thermal mass or using the alternate SIP methodology or getting even more cost effective and conventional with the sticks and foam. Peter is a conventional guy and finds ICF and SIP "interesting", that's his mindset.

Personally, and based on performance experience, ICF while more costly is the best way to build in our region.


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PostPosted: Mon Sep 19, 2005 10:43 am 
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The ICF sounds like it just may be the way I need to go, thanks.

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