iMarc

The drawing also appears to show the rim joist bearing on nothing but the foam insulation board. No blocking or squash blocks; and no connectors shown to provide a continuous load path for wind uplift, either. If the 2nd floor wall is supporting a roof load, the engineer and the building inspector won't be likely to accept these details.

If New Hampshire summers are anything like Wisconsin summers, there can be periods of hot and very humid weather, and it's not really possible to seal that humidity out. It enters through windows and doors every time they are opened and, even in a very tight house, the ERV or HRV will bring in some of the humidity.

The humidity becomes a problem when it rises enough that cool interior surfaces, like poorly insulated foundation walls and floors slabs in a basement, are cooler than the dew point of the humid air. At that point the humidity begins to condense on the cooler surfaces, creating damp, musty conditions and a potential for mold and mildew.

Excluding insulation below the floor slab will only make the problem worse. Better to put more insulation under the floor slab so that it's surface temperature will be warmer and less prone to condensation.

The heat created by a small portable dehumidifier in a cool basement space isn't usually a big problem. A ducted dehumidification unit as part of the homes heating/ventilation system might another story and may not be a good solution, depending on your climate. The other big problem with running a dehumidifier is that even the highest efficient units use a fair amount of electricity. I don't know of a good solution to that problem. I'm hoping someone else will have a better suggestion.

This isn't the place for spam messages. If you want to advertise your products, contact the appropriate department.

What's with all the spam messages? I don't see anywhere to alert the site administrator to it. Maybe you need a spam button?

My mistake, DingusMcPhee. I was looking at the photo posted at the top of the article. I hadn't clicked on the underlined "showcase house" text.

"Copied from Wright's Fallingwater"? What photo are you looking at DingusMcPhee? Just wondered; What happened to the brick? Is that haphazard pattern a new style? Looks more like painted out graffiti. Wouldn't you think the IBS committee would have had enough foresight and imagination to build something more inspirational than this generic multi-gabled stilty-posted-entry McMansion? It looks like the first page from any 1995 home planning magazine. They must not read Fine Homebuilding.

I just received some free promotional literature in the mail from James Hardie, along with a sample of their new Artisan siding, that included a surprisingly well done design book, "The Value of Design", by Marianne Casuto. Builders looking for some inspiration and what-to-do/what-not-to-do ideas can go to James Hardie's Artisan website to request a copy for themselves at: www.artisanluxury.com/request.shtml. Just fill out the form and check both literature request boxes.

One more issue to consider that probably wouldn't occur to a builder or homeowner while in the process of planning for the construction of a new home is that the building will not last forever. What is done with any particular construction material at the end of its useful life span is also a totally valid factor to consider when evaluating how green a material may be. When a building insulated with spray-applied foam insulation is demolished, will it be practical to remove the adhered foam from the lumber, the copper wiring and plumbing pipes so that they can be reused or recycled or will it be so difficult to separate the materials from the foam that the whole thing will go into the landfill?

I was hoping the FHB#204 article on spray foam might include some discussion of Peter Pfeiffer's detail that shows a 1" flash coat of closed cell foam sprayed onto the backside of the exterior sheathing with the remaining depth of the stud space insulated using damp-blown cellulose.

I have my doubts about considering any type of spray foam to be a truly green or environmentally friendly product, yet it does have some specific advantages that other loose-fill or blown-in products don't have. I think there's some validity to the idea of using minimal quantities of spray foam specifically for air sealing and for insulating at rim joist and difficult to access areas, but I would prefer to use cellulose for the bulk of the insulation. Cellulose uses less energy in production than any other insulation material, it contains no petrochemicals, it's recycled content is 100%, it's blowing agent is simply air and it further minimizes greenhouse gas emissions by diverting newspaper from landfills.

Another issue that is rarely considered when building a new home is that the insulation won't be used forever. What is done with any particular material at the end of its useful life span is a factor that must also be considered when evaluating how green a material may be. When a foam-insulated building is demolished, will it be practical to remove the lumber, wiring and plumbing pipes from the adhered foam so that they can be reused or recycled or will it be so difficult to separate materials that the whole thing will go into a landfill?

I would be very interested to hear more from Peter Pfeiffer about his theories behind the detail shown in the article.