Yes, our attic is now sealed from the ridge down to the 2x6 plates with 3" of closed cell polyurethane foam. Where we had overhangs, there were knee walls from the outside wall up to the roof rafters. Any spaces were covered with roofing felt to create a surface for the foam to transition from the roof sheating to the knee wall.
To my knowledge, the code does not require covering the foam in an attic space that will not be used for living space.
Regarding the wires, there are some short lengths (up to 2') of romex that were foamed in. Should I be concerned?
be concerned with any wiring which has high amperage demands for 3h or more, and is under insulation for a distance over 3 inches. esp in the attic, pull the wiring out of the insulation -- say for elec heat strips.
I studied the effect of fire stopping material around wire & cables -- got a trip into Boston in 1976 to deliver an IEEE paper [took family]. said material seriously entrapped heat when the thickness along the cable length was over ~2 inches! The study included power & control cable.
Within 2y, we studied an insulated mock wall section with type NM [ took me 2y to learn the word "Dutrex", the Anaconda trade name for NM -- Romex is a GE tradename].
understand that there are hundreds of thousands of miles of NM cable within insulation. There are also thousands of deaths EACH YEAR from house fires, many of "unexplained elec orgin".
Most of the wiring in the attic along the bottom of the roof rafters is for a few light bulbs and utility outlets, but I did extend a circuit for the new dehumidifier, which is about 12 amps at 110 volts. All the wiring is 12 gauge. The foam on the wires is mostly incidental from having to spray around it and is about 1" thick in a few places. Mostly just overspray, but I will remove as much as I can. It's pretty easy to slice off.
On another interesting note, we have lightning protection on the house, consisting of heavy gauge bare twisted copper wires running from the roof down to a ground rod. That definitely got foamed in. Of course, there was no guarantees on that working anyway, so I guess there is nothing to do about that now. I wonder if it would have been prudent to cover those affected wire runs with felt to protect them? Oh well, too late now.
On to the next project: new supply ducts and the Ultra-Aire H135 dehumidifier.
Then, providing all this works, I get to do it all over again for the first floor system, the ducts for which are in the garage ceiling.
I never heard of lightning streamers inside a wooden frame structure -- only where the building had a steel frame, eg: Empire State bldg in NYC.
seems scary to me -- heavy current traveling along that wiring -- and bound to have some right angles in that wire! = BAD BAD BAD BAD.
Welcome to South Carolina! Where the most popular bumper sticker is: "We don't care HOW you did it up North!"
Anyway, when it comes to 50,000 amps, or whatever lightning is, you'd probably need about two feet of insulation to do anything. I had never seen an installation before, so I didn't know what to expect. I am pretty sure they are all done that way.
design for lightning protection is NOT determined by which region of the country a system is installed, except for the grounding electrodes.
BTW, I own property on Edisto Island & Hilton Head -- & have seen lots of lightning rods & down streamers exterior to houses & historic trees, including in Charleston SC, Gulf Shores AL.
What was your final configuration:
I live in similar climate.
Here's where we ended up:
1. 3" closed cell foam on roof down to 2nd floor plates
2. Ultra-Aire dehumidifier
3. New supply ducts with 3" R-8 insulation (was cheaper than just reinsulating existing. Sized for added 300 cfm from dehumidifier.
4. HVAC control is thermostat/dehumidistat, so we used that to control air handler (with its own dehum. setting)
5. added transformer and contactor in air handler to activate Ultra-Aire when HVAC control called for dehumidification.
6. dehumidifier has two returns: one from 2nd floor, 1 from attic with manual dampers to adjust mix
7. dehumidifier has two supplies: one to main trunk (with auto closing back draft damper) and one to attic, (both with manual dampers) all dehum. duct runs are insulated.
Above config allows dehumidification of attic if/when needed. as it turned out, I estimate dampers to attic are open about 20 percent, but that's using swag method. I have monitor up there and if humid rose too high, I adjusted accordingly. Seems to have settled around 20% though.
we added (but never used) 1 supply and 1 return to attic from air handler plenums (just in case)
Note: we originally used, but later sealed off, the outside air intake to the dehum. Bringing in the corrosive and humid salt air had more downside than up to me.
Bottom line: we maintained 45-50% rh in attic. In heat of the summer attic stays between 85-95 and is actually quite comfortable if you have to work up there. Keep in mind Dehum. adds heat. (We never removed R19 fiberglass from attic floor) Dry as a bone up there.... no condensation. Dew points in attic and moisture infiltration are controlled.
Energy consumption is down year over year (summer and winter) and comfort level is up. Still would take decades in payback. If I ever build again, I would use this process during construction when everything is so much easier (and cost effective) to do. But it did solve our problem and it's done.
Hope that helps.
One aspect not mentioed here is comfort, in my experience ( over 25yrs building with sips, and nearly 10 with spray applied closed cell polyurethane) there is no comparison to a home with fiberglass and one with foam. Energy is what it is all about, there are so many problems with fiberglass I wont go into here, but a couple are mold, and formaldehide, glass sucks in my opinion.
Tightness of the envelope, sound deadening, and enhanced structural integrity are but a few of the positives of foam.
As to the roofing issue, air core roofs can be constructed to allow thermosiponing of air between the sheathing and insulation.
Most top brand foams have waivers that allow foam application directly to sheathing from roofing manufacturers, but I still use an air core.
Icenene R 3 p/in Most urethanes R 7 p/in, Icenene is less expensive p/ applied inch. Really depends on your use
Bluestone, I am interested in hearing how you do the air core. Do you have a double set of roof decking, with an air space between them?
Thank you -- Pstu
OK I haven't read all the replys here so forgive me if I am repeating something...
To make a long story short, I have been envolved with this extensively for over 6 month. I live on the Gulf Coast and we know about humidity problems first hand! One of my good customers had a large home damaged by Katrina. He is a fairly big roofing contractor and has inhearted a contacting business. We got his house A/C system(S) half installed and he then decided to BUY a foam company. I got dragged to all the factory BS and to the power company REGIONAL school on this stuff.
Here is the scoop as I see it.
Flame Spread or fire rating = Don't worry about it. All foam today have fire retardents and you cannot set it afire, it will only melt.
The Bad - A totally foamed home will build up heat way faster because of the insluating factor and the home will have a HOTTER fire. I come from a FD family and that means more things will get destroyed!
Close cell foam is more expensive! It will not absord mosture (as dunked in a pale of water) if it is put into a flood prone wall. This is why FEMA is pushing it. Open cell foam is just fine for other applications.
My friend the roofing contractor contacted roofing Mgf. and was sorta told that cheap shingles will have a problem anyway, bur quality (i.e 30 yr. ) shingles will not have a problem.
If you foam the attic, the underside of the roof rafters. The attic becomes just another room of the house with a 0 wall height. Even tho this cuts down on the A/C load infiltration factor, you have to have a "vent" in the attic with X CFM to condition the attic. You will not need ceiling insluation and will need a return air somehow back to the unit.
And bvecause of the above this will help your ducts sweating. Now having a "tightly" (as of foam) insluated attic and a regular possible loose home may have other problems.
You really need to get with an A/C guy who knows his stuff to check your house before plunking down big bucks....
Life is too short, Behappy!
OOOpps ... Oh Well.
Life is too short, Behappy!
One way to do this is strap the roof vertically (some may call it furring) and apply a second roof deck. I cant go into all the details regarding valleys and such, here, but you get the idea. Just make air flow from bottom to top, soffit vents, and I use coravent for the ridge. I don't use roll type ridge vent as I fell they don't have enough free area.
Originally Posted by pstu
Another way is from the inside with prefab plastic or EPS foam insulation chutes, stapled up, this is a good choice for retrofits. cheaper by factors and slightly to moderately less effective but I would still highly recommend it.
My house is done with the chute method, only with custom , site fabbed, chutes made from fan fold insulation normally used for vynil siding. I saw an ad in Fine Homebuilding for rafter clips to hold ridged insulation to form air cores recently, another way to go