Interesting New Stuff

[Aaron Miller]

New Roof-Attic Design Improves Efficiency (http://www.jetsongreen.com/2012/09/ornl-roof-attic-passive-ventilation-system.html)

[Jerry Peck]

Quite similar to a design I proposed many years ago in discussions on the old ASHI forum - I had many non-believer so-called 'smart people' there who did not believe it would work, including several 'hot-shot' now-past presidents and others. :rolleyes: :)

The retro-fit was the design I was proposing and discussing - anchor 1x2 furring strips on top of the existing decking to create a 3/4" air space from eave to ridge, then install new decking on top of that.

Of course, though, in Florida, that design would need to be run through tests to show that it would not be any more susceptible to high wind events than the current designs, and that would be a bit difficult as the design is open at the bottom and current designs nail that bottom edge of the roof sheathing to the fascia so no air can get in and to keep it down (this design intends air to get in, so ... ).

One would need to alter the design to allow the bottom edge to be nailed as is now required, however, another cut-outs would need to be made into the lower roof sheathing about a foot above the bottom edge to allow air to enter from the soffit area and matching soffit vents, then 1x4 strips run around the edge of the roof and the vertical 1x2 strips going up the roof would start there.

Okay, now someone with a sufficient reserve of money can build a test structure and take it to one of the wind machines to be tested ... :D

[Dan Harris]

This stuff is interesting.
I'm seeing a lot of new construction with sealed attics and foam on the decking ,with solar water and HVAC back ups . From customer feed back this option can add apx $20,000 to the cost of the home. The owners claim they are saving apx $100 a month, when comparing with neighbors with standard HVAC equipment and insulation .

Being the sceptic I am, I still question, why would I spend $20,000 or $2000 plus on something that will take 20 plus years to see a return. After seeing the life of the 80s solar panels and large water tanks, will this or any other energy device be effective/ functional before 20 yrs to see a return, or do I, or the next home howner need to spend another 2-20,000 in 10, 15 or 20 yrs.

Me, If I want to spend that kind of money I still prefer to take it to vegas , and see an instant return , OR loose it all in a weekend :D

[Garry Blankenship]

Adding ventilation paths seems like a good idea, but I am, ( aaa-gain ), confused. The design shown appears to require sheathing on the bottom of the truss bays and on top of the foil covered foam, ( as in OSB x 2 ), ? Sheeting the bottom side of the trusses would be some sport. The design requires slotting or opening both the lower sheeting and the foil covered foam ? The diagram appears to intentionally demonstrate no bird block venting but indicates some unknown "ventilation in" source in the same area, ( soffitt vents ? ), ? Last I am seeing three paths for bottom up ventilation - - - 1) under the lower sheating, 2) inside the truss bays and 3) in the spaces created by the foil covered foam and wondering how & why three paths makes things any better ? Why not have six paths and double the savings :rolleyes:

[Jerry Peck]

Adding ventilation paths seems like a good idea, but I am, ( aaa-gain ), confused. The design shown appears to require sheathing on the bottom of the truss bays and on top of the foil covered foam, ( as in OSB x 2 ), ?

There is only one layer of sheathing in that design for new construction - on top of the foam.

The performed foam, with foil faces, lays on the top surface of the top chords (or rafters) and dips down into the top chord/rafter space.

The roof sheathing is laid on top of the preformed foam where the foam crosses over the top of the top chord/rafters, the roof sheathing is then nailed through the foam to the top chord/rafter.

Here are my concerns for that type of installation - at least for locations with high wind events, or even like Washington or Oregon where winds greater than 60 mph are common (from what I have been told) - the nail sizes would need to be larger for a long enough nail to penetrate through the extra thickness of the foam, and the nails will be cantilevered from the wood through the foam to the sheathing and could bend, allowing the sheathing to move. Some engineering would need to be done to make sure the nails were sufficiently large enough to maintain the diaphragm of the roof structure with the sheathing on it.

[Rich Goeken]

My first question, outside of installation issues, is how long will it last? A new shingle roof will last 20 years, then you pull it off and start again. I have reservations about the foam lasting at least that long. Then it becomes a "rip the whole roof off to the rafters and begin again"... a costly procedure. Interesting concept though.

[Al Inspect]

It looks similar to this product from DuPont.

Attic Insulation – DuPont (http://www2.dupont.com/Tyvek_Weatherization/en_US/products/residential/resi_atticwrap.html)

Without the extra insulation but the same idea of ventilation channels provided at the roof decking.