optimum value engineering wall cavity


Old 12-28-03, 06:46 PM
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optimum value engineering wall cavity

Can anyone describe this? I saw it mentioned on the dept of energy web site but couldnt find an explanation. Im interested in building a highly efficient house and the best thing ive found so far is the SIPS panels. Are there any other ways to achieve the efficieny of these panels with other construction types or insulation?
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Old 12-29-03, 06:49 PM
Join Date: Nov 2001
Location: USA
Posts: 1,873
Structual Insulated Panel Systems (SIPS) is where two OSB panels sandwich foam. They are usually 6 to 8 inches thick and 4 feet wide by 9 feet high. They do come in different sizes depending on the use. For example, if they are for a cathedral ceiling, they are quite longer. They are structual because they are load bearing elements of the structure.

The foam is injected between the OSB panels under high pressure. This supposidly eliminates shrinkage of the foam and improves the R-Value of the panel. Nailers are provided along the edges to secure them. Standard lumber is also inserted for rough openings for windows and doors. Chases are also provided for wiring. The SIPS are fabricated off-site and then brought to the site.

After you have decided on the design of the house, the foundation is formed and poured. Then a platform is install over the foundation walls. Once this is done, the manufacturer of the SIPS sends someone to take measurements of the platform and then and only then are the SIPS fabricated. The exact measurements are feed into a computer along with your design. This process is quite fast, much faster than a stick built home and it uses less people and manhours to accomplish.

There are some disadvantages to a SIPS building. For example, these structures fall below ASHREA's Minimum Ventilation Guidelines. Which means that in every case an Air to Air Exchanger (HRV) is installed to provide adequate Indoor Air Quality (IAQ). Since these panels are structual, wood destroying insect can create havoc on the structure. I know of only one structure that was condemned. However, what was so unusual was how fast the structure was affected by the wood destroying insects. It has been said to me and never experienced by me, is that fire results in more total losses than with conventional structures.
Old 12-30-03, 02:51 PM
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Thanks but i was looking for more info on other forms. Ive found all kinds of stuff on SIPS building. THe insects and fire comments were new though. Any idea how the little buggers got in there or what could be done to stop them.
Im also concerned about the cost of the panels. Thats pretty much why Im looking for alternatives.
Old 12-30-03, 10:09 PM
Join Date: Nov 2001
Location: USA
Posts: 1,873

This Dept. of Energy site discusses SIPS and other alternative building methods. Such as Rammed Earth, Straw Bale and more. They provide links to them that are too many to list. Out of all the different types of energy efficient construction methods, the only one I am actively involved with is "Whole-Building Design". This is also discussed on this site and I wrote an article on it titled "Whole House as a System" which you can read on my site by clicking on the "www" below and then scrolling down to that subject.

This subject is indeed very complicated. The phrase for every action there is a reaction, clearly has made its point here. What makes it even more complicated are those involved refuse to admit their part in this problem. They even go as far as to profess adamantly that they are not part of the solution. We know that if we insulate a house, the amount of heat required to heat the house is reduced. We also know that the amount of air exchanges in this house is reduced by the insulating of the house. We can also apply this to air conditioning.

Unfortunately, the vast majority of the trades people stop there. Some people argue that the point I am trying to make is if the house is energy efficient and the HVAC system are too, then the distribution system must also be energy efficient. This maybe true because I am an Energy Conservationist, however, the reaction of an inefficient distribution system in a house that is energy efficient can be devastating to the occupants. And health and well being supercedes energy conservation.

Today most energy conservationists are involved in measuring and verification. This stems from the fact that utilities have been able to predict their energy supplies to meet future demands for years. Some utilities have been so good at predicting demand that they saved their companies millions of dollars a year. So if we have a fairly good estimate on how much they will supply in one year and know the number of household consumers there are in an area, we can calculate the estimated usage and size for a single average household in this area. If we compare this to actual fuel histories, number of occupants, age of house and much more, we can rate each house. Believe it or not, this has been done for years, if not decades. One would think that after all the improvements people have done to their homes concerning energy conservation that not only the overall rating for these homes improve but also their energy consumption should have gone down. Well the ratings may have gone up but the consumption did not go down as much as expected. For example, I was involved in a project several years ago where a city which had a very large housing stock that averaged to be 70 years old. The vast majority had no insulation in them. It was believed then as it is now, that attic insulation is by far the most cost effective measure one can take in a house of that vintage. The objective of this project was to insulate every attic in this city, at no cost to the occupants. The results were not that impressive and certainly not what was expected.

There are literally thousands of papers on studies and research out there on every single aspect of building design and performance. They are there to hammer a point to the trades through redundancy. Because it is them that have to change their methods of installation. To me it does not matter which building method you choose, what does matter is how everything is installed. In other words, I can take a 100 year old house and make it more efficient than a SIPS house and I can take a SIPS house and make it more efficient. But to a true energy conservationist, it does not matter what I can do personally, it does matter if what I do affects what the construction industry does.
Old 12-31-03, 05:37 AM
Join Date: Nov 2001
Location: Taylors, SC
Posts: 9,483
The results were not that impressive and certainly not what was expected.
I think that one point made here is that the process is energy conservation, and conservation as a mindset. There are many things that are done to waste energy. Correcting one of them often makes an incremental difference, but not overwhelming. I suspect that even the best insulated house still costs energy to heat and cool. Moreover, there is a point at which you never regain an investment on some improvements.

For instance, DOE recommends R-49 insulation in new homes here, but R-38 in existing homes. The only reason I can see for this difference is the labor costs of retrofitting a house. I suspect that you could never recover the cost of increasing the insulation to R-49, but could recover the costs of increasing to R-38. The incremental material costs are not too different.

From my perspective, attic insulation is the first step, but will not solve the overall cost by itself. My house is 64 years old. Wonderful insulation would not necessarly make the utility costs low, because the HVAC was retrofitted rather than designed for the house. The house was built in a time when energy use was much different and standards of personal comfort were different. The design of the house does not consider the use of central systems. But what I do my house won't change the overall picture when my neighbor does nothing and just deals with the inefficiency.

My house was built to take advantage of sunlight and ventilation. In the south, heat management in the summer is a bigger issue that cold managment in the winter. Our house picks up sunlight in the kitchen because of the position of the house and the windows. Always plenty of light. You just about don't need electric lighting during the day in the kitchen. The central hallway and high ceilings facilitate ventiation for cooling in the summer. Using only screen doors in the summer provides plenty of air flow. The four fireplaces were the solution for the winter. I bet it was an uncomfortable place in winter with them. They would have heated the living room, dining room, and the two bedrooms. The kitchen would not need any heat because of the waste heat from stoves of that era coupled with peoples' eating earlier in the day than now.

In general, air circulation in the house is poor because it is kept closed for heating and cooling. If the house were better sealed, it might be a miserable place to live because of the lack of overall design. Economically, it would not make sense to abandon the current HVAC system and replace it, ducting and all, with a new one. I will continue to work on improving the insulation, attic to R-49 because I can do it myself, blowing the uninsulated walls and insulating the crawlspace. I will likely not replace the windows because there are so many of them that the cost would be prohibitive. In the meantime, we manage the thermostat settings and keep sweaters handy.
Old 01-09-04, 09:08 PM
Join Date: Mar 2001
Location: Kansas City Area
Posts: 215
Right at a year ago I began to look into building a ICF home. ICF stands for Insulated Concrete Forms. I spent a good 4 months researching it and am convienced it is one of the best ways to build a home. I toured ICF houses, interviewed contractors and discussed home specifics.

Currently I am building a new house, standard stick building process. The problem I ran into was finding enough ICF contractors to work with me & give me accurate pricing on the home I wanted built. While all the press & internet information says ICF is only 2 - 4% higher than conventional (stick built) homes, I was finding that not to be true and the contractors I talked with wanted considerable $$ just to give out quotes & estimates. Basically they wanted a complete set of plans delivered to them, already engineer for ICF const., then they would give me a price after I paid them a $500 - $1,000 fee. I was unwilling to spend the $$ for both arch costs and the estimate not knowing if it was even feasible to build the house I wanted.

I ended up building (stick built) my house 3200 sqft, two story with full basement at around $81.50 per sqft. That is everything except the land lot cost. Nearly everyone of the ICF contractors said I was dreaming if I thought I could do it under $95 - $100.

While I did not use it to build this house, I am still convinced that ICF is probably the best building method out there, but is not used becasue of the learning curve for the contractors, plain stubborness by local area home builders, it is different thus not as readily accepted in the marketplace, and its cost is slightly higher. While the initial cost is higher the ongoing operating costs (heat & cooling) than a traditional house such as I am building.

The internet has a lot of info on ICF building and even a lot of ready to purchase plans, however the choice was very limited in the 3000 - 3200 sqft range & two story style was wanted.

Good Luck.
Old 01-12-04, 07:47 AM
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If I ever build again I am going to use the sprayed in place foam insulation. The house is traditionally framed, wired, plumbed, so the only non-traditional trade is the insulator. I have heard that wiring and plumbing costs can go through the roof with those SIP panels. The sprayed in place foam gives excellent R value and also seals air infiltration points. I hear the cost is considerably more than fiberglass or cellulose but I don't think you can beat the insulating value. You'll probably want to consider an air-to-air heat exchanger, however in my very tight house, we simply crack a window or 2 and we have never had a problem with odors or humidity even when it's well below freezing.

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