On my personal home we had a plumbing leak that was found by my daughter and son in law. They noticed a dark spot on th garage floor (concrete). Turns out there was a plumbing leak and the water had leached through the foam from the laundry room above. Granted it had been leaking a while but it did show. Radiant barriers hender roof leak detection also.
My house's entire envelop is foamed. (2000) My personal experience with sprayed in place foam has been over the past 11 years. Retrofit and new construction.
It should not be an option, nor should it be codified, it should be the law. Like anything there is a learning curve and requires a commitment to the science.
KMac's statement of a 30% reduction (a/c only here) is a blanket statement that is structure depend. The foam gives you back the duct gain along with the gain of any knee wall exposure, skylight shafts and all attic exposed assemblies. The foam also reduces the infiltration which a blower door will confirm.
The foam has no effect on loads from internal sources, fenestations, or non foamed assemblies.
I'd still be concerned about roof leaks. A plumbing leak is an entirely different animal....constant flow of water that will eventually show up somewhere. A leaky roof will provide a sporadic injection of water into the decking and trusses. As far a someone never having a roof leak...interesting how there seem to be a fair amount of people employed re-roofing structures. Of course if you move from new house to new house on a regular basis you may never experience one but here in Florida I have seen many roofs that looked fine leak badly. I'd feel better if the foam could somehow be applied above the actual roof structure as on commercial buildings with flat foam roof. In those cases, failure of the roof membrane is obvious.
Something else that came to mind is how much better roofing materials perform now. i remember back in the 60's, as shingles got older they'd get obviously curled. Shingles nowadays maintain their appearance much longer and most leaks probably start a a tiny crack in the material. Of course we use underlayment but the heat dries it out too regardless of whether you use 15lb, 30lb, or icedam. Eventually water will get through it long before the roof looks bad.
That is a pretty good way of doing it.
5/8" decking applied to top of rafters.
self healing roofing membrane applied to that.
4" to 6" of polyiso foam insulation - 4x8 sheets - about $.50 a board foot.
1/2" decking on top of foam with long screws and washers going through 1/2" decking and foam into 5/8" decking
Whatever roof you prefer on top of that.
The top layer of 1/2" decking can be replaced as needed when the roofing is replaced.
Doing both is a waste of moiney, after you get the quote for the foam you will not be thinking about spending any more money in the roof.
To get the best answer, you need to state your approximate location.
Foam in the walls has it advantages also. A stud wall with batts of fibreglass insulation is a filtered fresh air intake, air will flow through the wall and short circuit the insulation value, how ever the fibreglass will catch the big pieces of dirt.
If you blow the foam into your wall you have stopped air movement
Yea John I was bragging a bit.... I fought all the HVAC guys for years and had them call me a idiot... When I was trying to get them to do their job
So I joined them
Yea when someone doubts my creditability I GET DEFENSIVE>
And yes I am bragging about my success in my insulation and HVAC companies...
I am not the one ripping my customers a new one... oversizing
I am not bragging about my home.... but 5 Tons doing 12,220 is impressive..
As far as my comment I am from the south.... and I enjoy life and I enjoy my job..... And when I sale a job.... I make sure my customers enjoys my presentation and not put then to sleep...
Why didn't you question the guys that was doubting me...
And I am a teacher..... why would I waste my time on this forum ?????
I don't doubt the value of the foam insulation. I doubt the sizing method of 2000 sf per ton. For many years I’ve fought the battle in western Arizona that 400 sf per ton is not a proper sizing method. The last thing I want to see is the new method to be 2000sf per ton.
What’s my sizing method? I’ve used Wrightsoft for many years and done thousands of loads. I’ve used blower doors, duct blasters, and foggers since 1995 and have a pretty good understanding of infiltration (to say the least).
I usually see 30% to 50% of the homes A/C load to be glazing, so in my part of the world on a 4000 sf home that’s about 3.5 tons. Using your sizing method that leaves me about 1 ½ tons short for the WINDOWS.
Here in Arizona I can take away ALL the wall, ceiling, infiltration and ducting load but will not get close to 2000sf per ton.
You say you use Wrightsoft, I would love to see your loads on your 12500 sf home (must be nice). Especially your internal, glazing and ventilation loads. Are you running an ERV or some other type of ventilation?
If I was building a new house today would I use foam? For sure. I’m doing the HVAC on the first homes to use foam in our town and yes it is being sized using Wrightsoft.
Right now I doubt seriously if even have R-19 in the attic. TVA and other outfits say that I should max out at R-49 for Northern Mississippi.
The quote on the foam is 3x as much as the blow in, but still wondering if bringing cellulose up to say R-30 and 5" of foam would be better or overkill.
In my opionion the best way to do an attic in a hot humid climate is to place your insualtion on top of the roof deck, then something reflective like white standing seam metal on top of the insulation. With a hip roof and sealed you are all set.
If you have a gable roof then insulate the gable walls.
With a sealed attic, and keeping the heat out on the first place, putting another layer of insulation at the ceiling plane is a waste of money. The duct leak of a typical hack job would more than condition the attic and you have a huge storage area available for no extra energy penalty.
The second best way in my opinion is to blow icynene foam along the underside of the deck. Still no need to have insulation at the ceiling plane.
The home I designed and built is a 3000 sqft ranch, full basement & an inlaw suite totaling 6700 sqft living space. It faces south with no windows at all on the east or west walls. Advanced Framed Walls, 2" Foam under slab, 5" CC Foam Roof, KES Hybrid walls, maybe .02 ACH. Heat Pump Water Heater, Induced Fresh Air, Tons of windows..... ALL METAL Foamed Ducts.....
With the attic, carport and counter levered porch ceilings which adds another 5500 sqft of conditioned attic. 12,200 conditioned space YES I have a Ton of air in the attic
The reason I am bring this to the table is to prove a point !!!! YOU CAN NOT SIZE any home by SQFT any shape, size or portion!!! PERIOD!!!
Temp diff. (delta t), surface area, window, type of insulation are the factors.
Jim and John think about that I have 1.5 ton unit for my inlaw suite, the inlaw is 700 sqft and called for less than 1/2 ton so I had to dump the other TON in the attic. It is a 12/12 Pitch 8900 sqft of roof.
Added up is 6200 sqft inlaw and attic with a 1.5 TON unit THAT is 4300 sqft per ton.
This is not bragging.... it is just facts.... I am going to start a tread soon with all of the details and let you guys beat me up
a well insualted home indeed, but you and paul would be good at convincing women 4 inches is 6