Back again with my insulation decisions. Talked to a guy who installs SPF in the high country of Colorado. He said they only apply 2 to 2 1/2 inches of foam to the stud walls. “It’s all you need” he says. Any more is overkill. Also suggested (if I can aford it) to spray underside of roof sheathing, making a totally sealed unit. No need for soffit venting etc. It sounds like a substitute for SIP panels. This would allow me to finish wiring, plumbing etc. all walls & ceilings in “comfort” during the winter. He said to buy the smallest wood stove I could find. It won’t take much to heat the place. Would an air to air heat exchanger be necessay? Has anyone had experience with SPF?
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If you are making a "totally sealed unit", then you certainly need to have a ventilation system, preferably with a heat recovery unit.
Tom
Douglasville, GA
I have an open cell spray foam insulation (your guy is probably talking closed cell if he says 2-2.5 inches).
You could heat the house with a lightbulb :).
A few considerations:
Roger
Consider your penetrations (no jokes, guys):
No jokes ?? None ?? C'mon, cant I even say that I always carefully consider all my penetrations ? Even the quick ones........ never mind. =)
Carry on.
I like the concept of spray foam insulation. My concern is that in the hot, humid south if you seal the house completely you have no way for the moisture to escape. If you spray inside the stud cavities, what about any moisture that could wick in thru the studs or etc. What about any pinhole moisture comes in thru. Wouldn't it then be trapped inside. The jury is still out. Plus, isn't it only cost effective if you are going to live in the house 7 years or more? Also, a manual j AC calc would become crucial.
Going with SPF (closed or open cell) essentially implies also having whole house ventilation, with heat exchanger, along with makeup air for fireplaces and furnaces.
If the pay back period is 7 years that doesn't mean you have to live there for that period to make it economically worth while. Why, when the house is sold the low heating and cooling bills will help getting a better price.
Of course Manual J calculations are virtually a must in any event. Code (IRC) requires it, though there are exceptions that could let the HVAC guy substitute some other "approved heating and cooling calculation methodologies".
In response to your seven year payback period. We finished a 3000 sf doctor's office this past year. Prior to the remodel the average monthly electrical bill was around $800. The building was insulated with Fiberglass. After remodel, which included Icynene all the way around, this summer's electric bill was $300 per month (100 degree days in Austin Tx.)
Payback in terms of cost difference for this project is 1 year. That is pretty good return on investment. This is the only pre and post data point I have, but I am convinced.
Bruce
all 1777 of them, Woody?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
if there had been 1777 of them...... wow, uh, ahem well maybee I wasnt always paying attention.....
What is the web site for Venmar? Cost?
Thanks
Sorry to be late getting back to you. Please explain the Titanium membrane. Was thinking of putting a standing seam metal roof on.
Thanks
If you are going with the standing seam metal roof you will not need the Titanium.
Titanium is a low perm membrane (something like < perm 1 for Titanium where felt is perm 15). That means that water can't get through it. For regular asphalt shingles, a small amount of water actually wicks between the shingles and can get the roof deck wet (through the felt); since with an unvented, sprayed roof there is no air circulation it can rot out the plywood. Enter Titanium: no water penetration, no rotted plywood.
On a different note: I liked the fact that the open cell spray foams allow water to pass through; so if I did have a roof problem, I would see the water come through. With the closed cell foams, the water would not come through or come through as easily, so it would take longer for you to find any problems; by that time, it could be a more serious problem. Also, the closed cell foam was quite a bit more expensive.
Hope this helps,
Roger <><
Perm does not have anything to do with liquid moisture (water).It is a measurement of how fast gasous moisture vapor can move through it.
Is SPF a brand name or an insulatin type? Impossible to comment intelligibly without knowing if this is an open cell foam or a closed cell. It sounds like a polyurethene close cell but it could be a salesman for icynene open cell which is entirely different as relates to your questions.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
SPF usually means Spray Polyurethane Foam and 2 lb density like Corbond, closed cell.
Stu
Thanks, these senior moments are getting to be more frequent. I guess that's so I can get practice for when I'm a senior
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Ooops - adding - what R-value does he claim? This is very telling.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I am in Lake Placid, NY, and we get wintertime lows down to 50 below occasionally. Our heat loss calcs are done using 7500 heating degree days.
It depends on exposure, glazing areas as compared to total wall areas and ceiling-under-roof areas, and a lot of things, but in general, we use closed cell spray-in polyurethane foam insulation to insulate houses this way:
Roofs are not ventilated.
Windmill,
Have your heat loss calculations done.
When we spray hard foam(closed cell, 2lb) 3-3 1/2" is the rule for walls, 5-7" for roof systems.
Soft foam varies, full wall cavities and enough to reach R-value requirements in ceilings.
Some soft foam manufactures have been approved by the IRC to spray less and still meet code.
Size your heating (including the wood stove) system according to heat loss calculations for your area and your floorplan.
Good luck
Garett
Just my two cents. Anytime someone, who's occupation is applying spay foam insulation, is not the right person to enlist for consultation on best building practices.