We are building a house in climate Zone 4C zip code 97502. I have been reading all your insulation posts for a couple of months and hope I am not asking too many redundant questions. I have several different roof and wall types going just to make things more complicated. We have finished framing so I'm finalizing insulation stack up. Here goes: Roof stack up 3rd floor 1.2:12 pitch - exterior metal roof snap lock sheating, roof sheathing (OSB), vented purlins or 2x2 furring through screwed 24”OC, 2” of 1” polyisocyanurate staggered with bottom layer next to sheathing fiber backed and and top layer taped with housewrap tape, roof sheathing (OSB), 1” cc spf coating in continuous layer over rim joists, fill with 3lb or denser stabilized wet sprayed cellulose to bottom of 12” trusses, membrain, t&G finished cedar. Alternative to ISO and purlins would be 4” EPS (2” on top 2” staggered with nailer deck) at R 16? 2nd floor main same pitch - exterior metal roof snap lock sheating, roof sheathing (OSB), 2” cc spf coating in continuous layer over rim joists, fill with 3lb or denser wet sprayed cellulose to bottom of 17” trusses (may need to go with spider fg due to weight), membrain, t&G finished cedar. HVAC ducts located in this ceiling. 2nd floor sundeck - 4” concrete over plywood sheating, 12” truss filled with 2” cc spf and dense packed wet spray cellulose, 2” of EPS, ¾ through screwed drywall taped, latex paint 1st floor garage - 4” concrete radiant floor, pandeck, 2” cc spf in groove, 2” xps attached to drywall and through screw to pandeck. Wall stack up 2x6 and 2x8 wood framed walls. exterior metal roof sheathing, 1x3 furring OR purlins through screwed 24” OC, 1” ISO fibre backed, 1” cc spf continuing from roof, dense packed cellulose for remainder of fill, drywall. 8” above ground concrete wall in living space - 1” ISO fibre faced, 2x4 wall filled with dense packed wet sprayed cellulose, drywall, latex paint. Also thinking about ½ SIP 8” curved above ground concrete wall in living space - 1” cc spf, 2x4 wall filled with dense packed wet sprayed cellulose, drywall, latex paint. Garage area turned into living space- (partially above ground - 8” concrete wall 3” xps (only because I already bought it), 1x3 furring through screwed to concrete, drywall. Wall partitioned garage - 1” fibre faced ISO, 2x4 wall filled with dense packed cellulose, drywall. Would peal and stick ice and water make sense in any of those layers? Have a spf (Demilec) installer lined up. Have not met the cellulose or fg guy yet. The roofs are butterfly shaped with one cricket each but no other gables. Thank you in advance. Denise

What is the truss spacing under the OSB sheathing on the 2:12 roof?

I hope you have a builder who can properly integrate all that, including proper air sealing so that you get the value out of it.

All of my trusses are spaced 12"OC. I realize a certain trust will have to employed. My contractor said he was going to set up a tent for me to stay in til the insulation is complete. What would be your simplified and/or more realistic solution?

I realize a certain trust will have to employed

Nearly impossible. A substantial amount of money goes into quality construction, not to mention your personal time and then, the builders and subs are simply unwilling/unable to follow through with the application end. If they think they can cut corners, they will. As painful as it might be, you need to personally inspect (particularly the details) if you want it to come out the way it looks on paper. I am sorry that solution is not simplified, but it is "realistic". I have seen builds do well with architects, but that's probably because they can feel as personal about it as an owner. A hired manager would have to be passionate about the concepts and the build in order to do a good job for you.

One thing you might try is goal-based contracting. For example, even the best insulation contractor was all about lip-service and promises, until he was told that the build was absolutely going to have an IR camera survey and anything found would be his to fix. That got some real attention like nothing else. If they are convinced there will be an inspection or a measurement, they will put more effort into it. Even good companies have varying levels of competence and diligence among their employees. If they know that you will be a squeaky wheel, they will send out their best guy to do or oversee. If they don't think you will check up on them, you will get the junior varsity crew. There is a difference.

You seem to have an awful lot of insulation for your zip code. I hope your heating plant is appropriately sized and efficient.

Oops my trusses are 24"OC except for the sun deck which is 16". Should have double checked before I wrote.

Thanks for the advice. Funny you mention IR because I already have someone set up to do just that. Plus I have the blower test in my back pocket. I will make sure to spread the word.

We don't have access to Natural Gas which is the reason for the extra insulation so I can downsize the heating/cooling tonnage. Which is geothermal. And from what everyone has mentioned every ton counts.

Do you really need geothermal there in CP? Looks like you have some radiant floors already. Did you evaluate the relative costs of quality air-source heat pumps or water radiant all around?

Once I finalize my insulation plan and see what I come up in the heating/cooling load department I may change my mind. In fact you're probably right.

What I want to know right now is to know if a cedar ceiling with 2" of cc spf under the roof deck plus 15" of dense packed cellulose will stay put or will my boards look like the waves of the ocean. And will 2" be enough to keep the condensing surface out of my cellulose.

4" of EPS sandwiched between two pieces of OSB should permeable enough to allow the upper nailer deck to dry to the interior. Or is it just too much stuff in the stack up and not enough ventilation? The only time I have seen this stack up mentioned was with a furring striped ventilation layer. Maybe that's the only way.

I do seem to be chasing my tail.

I do seem to be chasing my tail.

It's all beautiful stuff, but I think you need to define what your goals are in your climate area. And maybe reformat the original post. There is a lot of stuff in there and it's hard to follow.

There is a lot of complicated stuff in your post, Denise. Maybe you need a more versatile insulation solution that can offer the sealing and energy efficiency necessary. I'd suggest using Owens Corning EnergyComplete. One of the great things about that is that no hazmat suit is required and it doesn't require an evacuation of the site while it's being installed, which is great. More info can be found on the OC site here: http://bit.ly/K9kvBP. Hope this helps and good luck!

ICFHybrid, thanks for the reality check. I was really driving myself nuts with all this.

alexbest27, took a quick peak at the site. Looks perfect. Dana1 inspired me so do a better job of insulating but I think I jumped off the deep end. And found that I couldn't swim very well.

Thank YOU!!!!!

Posted By Denise1 on 12 Jul 2012 10:35 PM
Once I finalize my insulation plan and see what I come up in the heating/cooling load department I may change my mind. In fact you're probably right.

What I want to know right now is to know if a cedar ceiling with 2" of cc spf under the roof deck plus 15" of dense packed cellulose will stay put or will my boards look like the waves of the ocean. And will 2" be enough to keep the condensing surface out of my cellulose.

4" of EPS sandwiched between two pieces of OSB should permeable enough to allow the upper nailer deck to dry to the interior. Or is it just too much stuff in the stack up and not enough ventilation? The only time I have seen this stack up mentioned was with a furring striped ventilation layer. Maybe that's the only way.

I do seem to be chasing my tail.

I have a hard time reading your stackups in the original post- white space counts...

As I understand  your roof stackup is something like :

Metal roof / underlayment or vent gap / nailer OSB / 4" EPS/ strucural roof deck / 2" ccSPF / 15" dense-packed cellulose / MemBrain /  2x cedar

If that's the case you have ~R30 between the metal roof and the interior face of the polyurethane (the condensing surface) and ~R55+ of cellulose between the condensing surface and the interior.   Assuming a 40F wintertime dew point for the interior air and a 70F interior temp, the condensing surface doesn't hit the dew point until it's below ~24F outside.  If your average January mean temp averages above 24F, you won't need the MemBrain, and in Central Point/Medford your mean temp is about 39F, which is PLENTY of margin.  Yes it gets below 24F every year, but it doesn't dwell below 24F for weeks.

The coldest surface abutting an air-permeable insulation layer (such as cellulose) is where all of the condensation occurs, because as soon as it hits the dew point of the entrained air in the cavity the moisture begins to deposit there. As the temperature of the condensing surface drops, the dew point of the air in cellulose layer tracks the temp of the condensing surface, but the temperature of the cellulose is above the that dew point.  The liquid moisture is concentrated at the cellulose directly in contact with the polyurethane, but since it can wick quite a bit of moisture into it's hollow fiber structures, it won't be wet to the touch or lose R value. Only when it stagnates below the dew point of the interior air for weeks would you end up with anything resembling damp insulation.

The nailer deck can still dry slowly to the interior through 4" of EPS + 2" of ccSPF, but if there's any type of vent gap or air-permeable underlayment for the metal roofing it's capacity to dry to the exterior will be orders of magnitude higher.  If the roofing is mounted on 1x or 2x purlins the nailer deck has a HUGE capacity for drying to the exterior.

The cedar ceiling won't warp under the weight/pressure of the cellulose, but it's always a good idea to use fasteners with sufficient pull resistance for the load.  At a minimum use ring-shank nails, but screws would be even better, particularly in an earthquake scenario.  (But of course those never happen in OR. )

You might want to cut back to a 1" flash of SPF for cost reasons, saving about a buck a square foot.   With a semi-permeable but non-wicking SPF as the condensing surface moisture doesn't condense on/wick-into the roof deck you're trying to protect, and with your winter temps there still won't be enough condensing hours to matter.  Replacing the inch with another inch of cellulose means the cellulose layer is now R58, and from the condensing surface out you have about R23, which means it now only has to be below 28F outdoors with 70F interior temp 40F dew point interior air.    Even on the very coldest days you would still have some drying-hours, and even on the coldest cold-snap weeks you'd have more drying hours than condensing hours, looking at WeatherSpark data.

Sorry to all who tried to sift through my original post. THis one will be better.. I have 3 completely different roofing situations on one house. Hind sight is 20/20.

Situation 1:
metal/peel and stick ice and water/OSB nailer/2"ISO(maybe 4"EPS)/OSB structural roofing/1" cc SPF/11" dense packed wet spray cellulose/3/4"x finished cedar

Situation 2:
metal/peel and stick ice and water/OSB structural roofing/2" cc SPF/15" dense packed wet spray cellulose/3/4"x finished cedar

Situation 3:
4" concrete/2" cc SPF/11" dense packed wet spray cellulose/2"ISO/Dry Wall

Dana1, I have made some adjustments based on the information in your post. Situations 1 & 2 have 1.2:12 pitch. Situation 2 includes HVAC ducting. Another 20/20 hindsight moment. My goal is insulation above industry standards. And to kill the blower and IR tests. I will also be installing an HRV. I think I'm still missing air-permeable underlayment. Where would that go? Would love to give the purlins a miss if the stack ups would still work without them.

Thank you!!!

Might help to know where I am in the process. Trusses, framing and OSB structural sheathing are on.

Glad I could help Denise! Good luck with everything!