Helpful? 0

Review my home insulation plan

I'm building a new house, and would love to hear feedback on the insulation plan. It can be found here: http://lazukars.bitbucket.org/house.png

DESIGN GOALS:

- Have a consistent insulation pattern up from the basement and up through the roof. In this case XPS on the exterior and ccSPF on the interior.
- Eliminate thermal bridges wherever possible.
- Double the insulation required by code

CONCERNS WITH THIS DESIGN:

- Foam Sandwich: The current sandwich of XPS on OSB on ccSPF will create OSB rot. The OSB will not be able to dry to the interior.
- Venting the roof at the Ridge is going to be challenging with this design. Any ideas?
- The exterior XPS, the XPS that comes out of the ground from the basement, will attract insects and become a insect highway into the house.

If any changes are suggested, please keep the design goals in mind. I really appreciate any and all help!

Asked by Ryan Lazuka
Posted Mon, 08/18/2014 - 12:54
Edited Tue, 08/19/2014 - 09:34

Tags:

26 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
Helpful? 0

With only 2" of XPS on the exterior you still have over half a perm of drying capacity toward the exterior. The depth of the ccSPF is not specified, but at even 2" would be sufficient protection from interior moisture drives.

The potentially high thermal performance of ccSPF is severely undercut by the thermal bridging of the framing- you'd be better off going with an inch thicker exterior foam and using open cell foam or cellulose between the studs. (Open cell foam air seals better than closed cell, due to it's greater expansion ratio and higher flexibility.)

Both XPS & ccSPF do quite a bit of enviromental damage if used at high-R (or even code-min R), due to the heavy global warming footprint of the HFC134a & HFC245fa blowing agents (1400x & 1000x CO2, respectively). Switching the exterior foam to 1 EPS on the exterior + 1" polyiso (or 2-3" of rigid rock wool, no foam) on the exterior, and open cell foam or cellulose for the cavity fill would be a lot greener. EPS & polyiso are both blown with pentane, which is only ~7x CO2, and open cell foam is blown with water, which has even lower global warming potential than CO2.

It's possible to install borate- loaded EPS for use below grade. Installing copper flashing or copper-foil clad plastic sill gasketing that extends beyond the foam layers on both sides of the assembly creates a mechanical barrier forcing the termites to daylight, and leaches copper oxides that (like borates) are toxic to the gut flora of wood boring insects. Using damp sprayed cellulose cavity fill is also good for mitigating termite infestations due to the high borate content of the fire-retardents used.

Answered by Dana Dorsett
Posted Mon, 08/18/2014 - 13:56

2.
Helpful? 0

@Dana

Thank you for your detailed answer. I can't tell you how much I appreciate it.

You mentioned:

. The depth of the ccSPF is not specified

The plan is to put as much ccSPF insulation in there as budget allows. So say, for arguments sake, the ccSPF is 5". The concern is that any interior insulation, whether it be 2" or 5", of ccSPF will not allow interior drying. Do you have to worry about the OSB board drying to the interior. Or is that not a concern, since the OSB will dry through the exterior XPS layer, like the one in my plan?

The potentially high thermal performance of ccSPF is severely undercut by the thermal bridging of the framing- you'd be better off going with an inch thicker exterior foam and using open cell foam or cellulose between the studs

In my original plan, won't the exterior XPS layer prevent the thermal bridging?

Thanks again, and I'm definitely going to look into the greener options that you laid out as well.

- Ryan

Answered by Ryan Lazuka
Posted Mon, 08/18/2014 - 14:22

3.
Helpful? 0

The XPS prevents thermal bridging... but only through the XPS layer. The stud/SPF layer still suffers from thermal bridging which cuts down the spray foam's usefulness quite a bit. It's an expensive material to be compromising like that, which is why it makes more sense to spend more on continuous exterior foam and spend less on cavity insulation.

Answered by Nick Welch
Posted Mon, 08/18/2014 - 14:47

4.
Helpful? 0

Nick has it right- only the continuous foam layers deliver the full R-value.

With 5" R1.2/inch of wood thermally bridging the ccSPF foam the wood is only about R6. With the framing wood being ~25% of the total wall area (typical for 16" o.c. studs) that 25% of R6 is conducting more total heat than the 75% of wall area that is ~R30. So while the center cavity R at that layer of the assembly is about R30, it's average performance is only about R15, due to the thermal bridging of the wood. Adding R10 of foam on the exterior doesn't change that, but since it is not thermally bridged it adds about R10 to the total R.

As long as it's a full-fill (no voids or compressions), the difference in whole-wall-R between 5.5" of open cell or cellulose (~R20) and 5" of closed cell (~R50) is only about R2 after factoring in the higher thermal conductivity of the wood. That's a very expensive R2 when comparing it to the cost of an additional 1/2" of EPS on the exterior.

Bottom line- save the higher cost foam for the exterior where you're not cutting it's performance off at the knees with framing, and put the cheap stuff between the studs.

Answered by Dana Dorsett
Posted Mon, 08/18/2014 - 15:56

5.
Helpful? 0

@Dana @Nick

Again thanks for the help.

Here's what I don't understand. How do you prevent thermal bridging at the studs when using ccSPF on the interior?

Dana mentioned:

(Open cell foam air seals better than closed cell, due to it's greater expansion ratio and higher flexibility.)

Is that the answer to reducing thermal bridging on the interior? Use open cell foam to reduce the thermal bridging at the studs.

I'm not dead set on using ccSPF on the interior. I'm just curious on, how the heck to prevent thermal bridging at the studs with ccSPF. My research has been getting me nowhere.

Answered by Ryan Lazuka
Posted Mon, 08/18/2014 - 16:16
Edited Mon, 08/18/2014 - 16:17.

6.
Helpful? 0

Studs are thermal bridges. You can't really change that, unless you move all your insulation to the exterior (e.g. many inches of rigid foam). That solution seems to not be very cost effective since it is rarely done.

Answered by Nick Welch
Posted Mon, 08/18/2014 - 16:46

7.
Helpful? 0

Ryan- you might look into recycled xps. It is widely available. Typically, it was used as roof insulation and removed when a new roof is installed. Cost is about half of new and recycling keeps it out of the landfill. Just google "recycled xps insulation."

Answered by stephen sheehy
Posted Mon, 08/18/2014 - 16:57

8.
Helpful? 0

@Stephen @Nick

Studs are thermal bridges. You can't really change that, unless you move all your insulation to the exterior

That is the reason I put XPS, on the exterior of the house, in the design ( http://lazukars.bitbucket.org/house.png ). However Dana suggested this:

The potentially high thermal performance of ccSPF is severely undercut by the thermal bridging of the framing- you'd be better off going with an inch thicker exterior foam and using open cell foam or cellulose between the studs. (Open cell foam air seals better than closed cell, due to it's greater expansion ratio and higher flexibility.)

In conclusion, the best way to deal with thermal bridging at the studs is to add exterior insulation, and use open cell insulation on the interior? Am I reading that right? There is no way to prevent thermal bridging on the interior?

Answered by Ryan Lazuka
Posted Mon, 08/18/2014 - 17:24

9.
Helpful? 0

The studs are thermal bridges and it's true that it simply can't be prevented, only mitigated (by insulating over the edges.)

But with a full cavity fill of 5.5" with open cell that thermal bridge is now R6.6 instead of the R6.0 it would be with 5" of closed cell. The extra half inch of cavity insulation depth provides a 10% reduction in heat loss through the framing.

Unfaced EPS on the exterior is better than using XPS, since it has a much higher permeance, offering a faster drying rate toward the exterior for the sheathing & wall cavity. At 2"/R10 XPS runs about 0.5 perms, whereas at 2.5"/R10 type-II EPS is over 1-perm, about as permeable as the OSB itself. Over the next 5 decades or so the R-value of that 2" of XPS will fall to about R 8.5 as it's HFC134a leaks out doing it's climate damage, whereas 2.5" of EPS would still be delivering R10.

If you really need/want a full R10 at 2", you can beat that with 1" of polyiso next to the sheathing with 1" of Type-II EPS on the exterior. The nominal labeled R of the foam layer would be about R6.5 iso R4.2 EPS for a nominal R10.7, but since polyiso performance drops when it's average temp is below 40F, the average mid-winter performance won't be quite that good. The performance of EPS rises with lower temp, so putting the EPS on the exterior to keep the average temp of the polyiso warmer optimizes the winter performance of both.

Most 1" polyiso sold comes with foil facers which has extremely low vapor permeance, so the cavity fill insulation would then have to be high-permeance to allow better drying toward the interior. Local climate also matters- in US climate zone 7 (or even the cold half of climate zone 6), you may need to go a bit higher on the exterior foam layer to go with an inward-drying-only stackup. What's your location?

Answered by Dana Dorsett
Posted Mon, 08/18/2014 - 17:39

10.
Helpful? 0

@Dana

Wow, all that info from your last answer is really helpful. Thanks so much.

I am leaning towards the EPS insulation on the exterior, after reading your last answer. So the only issue now is getting a consistent envelope around the entire house, not just the exterior walls. So to recap and per the drawing http://lazukars.bitbucket.org/house.png if XPS is swtiched to EPS, and the ccSPF is switched to open cell foam, will that work throughout the entire structure of the house, from basement to attic. That is one of the design goals with the insulation. That is, a consistent design.

Answered by Ryan Lazuka
Posted Mon, 08/18/2014 - 22:40
Edited Tue, 08/19/2014 - 11:24.

11.
Helpful? 0

The link in your last post isn't working.

Open cell foam is somewhat risky on the interior side of foundation walls, depending on how likely flooding events are, and the quality of the capillary break between the footing and foundation wall.

Applied directly to the foundation wall with no thermal bridging you get the full R-value out of closed cell foam there. But unless you are looking for an unusually high thermal performance at the foundation (say, PassivHaus style), it's probably cheaper to use insulated concrete forms and a poured concrete foundation, or rigid EPS held in place by furrring through-screwed to the CMU. Closed cell polyurethane costs about 17-18 cents per square foot per R, installed price, EPS cost about 10 cents/R-foot plus installation.

The sub-slab foam can be EPS too, as long as it's Type-II (~1.5 lbs/cubic foot nominal density) or Type-IX (2lbs density.)

The ratio of exterior R to total R in the above grade studwall matters from a moisture control point of view at the sheathing layer. The minimum ratio necessary to be protective also varies by climate. So to fully specify the insulation we need to know your location. If you are in the US or Canada, all we'd need to know is your climate zone:

http://www.greenbuildingadvisor.com/sites/default/files/Climate%20Zone%2...

Answered by Dana Dorsett
Posted Tue, 08/19/2014 - 10:57

12.
Helpful? 0

The link as been fixed and the Climate zone is 5. Cleveland, Oh is where the home will be built.

Answered by Ryan Lazuka
Posted Tue, 08/19/2014 - 11:25

13.
Helpful? 0

The designer of homes with all six sides of a continuous rigid foam insulated is Bruce Brownell. He does not insulate between framing.

Google: Bruce Brownell Adirondack Alternative Energy

Answered by aj builder, Upstate NY Zone 6a
Posted Tue, 08/19/2014 - 12:46
Edited Tue, 08/19/2014 - 12:51.

14.
Helpful? 0

In Cleveland with 5.5" of open cell foam (R20-R21) in the cavities and 2" of EPS (R8.4) on the exterior you would be fine from an exterior-R/total-R ratio point of view, and would not need to use interior side vapor retarders.

With 16" o.c spacing that would come in at about R24 whole-wall, which is about 20% less heat loss through the walls than an IRC 2012 code minimum wall for that climate. If you bumped the stud spacing to 24" you'd be at about R25 whole-wall.

In a zone 5 location you may want to go higher than that for the above-grade whole-wall R values, especially since you're going higher than code on the foundation walls & slab-R. A good starting place for consideration can be found in Table 2, p.10 of this document:

http://www.buildingscience.com/documents/bareports/ba-1005-building-amer...

Note those are whole-wall R values, not center cavity, and they are recommending R30 as being cost-effective in the longer term.

An example of an ~R30 wall would be a 2x4 wall 16" o.c. w/open cell foam, with 1.5" of polyiso (R10) on the outside of the sheathing, and another 1.5" of EPS on the exterior of the polyiso. That wall is just an an inch thicker than what you were contemplating, but comes in at about R29, and has HUGE dew-point margin at the sheathing layer, and is fine just drying toward the interior.

Or you could stick with the 2x6, 16" o.c. plan and make it 3" of EPS instead of 2" which comes in at about R28 whole-wall, with somewhat better dew-point margin at the sheathing, and the ability to dry in both directions.

Answered by Dana Dorsett
Posted Tue, 08/19/2014 - 14:47

15.
Helpful? 0

Or you could call Bruce and get a great home designed for you.

Dana, Building Science quotes very little to no R value loss when comparing insulation R value in a wall to the whole wall R value. In fact some of their proposed walls show more R. Dana, you post that the loss is high, very high compared to Building Science.

Are you wrong or them or do I need to read more better-er.

Answered by aj builder, Upstate NY Zone 6a
Posted Tue, 08/19/2014 - 19:11

16.
Helpful? 1

Why are you using foam at all? What is the R-value warranty for XPS and ccSPF? Why not blow the the walls with BIBS and then install Roxul Comfortboard IS? Use ProClima Mento on the outside over the Roxul and use Membrane or a similar product from ProClima on the inside and you then have a vapor open wall assembly that will outlast any foam and will be better for IAQ and the environment. You can also save some money.

Answered by Tim Johnson
Posted Wed, 08/20/2014 - 21:53

17.
Helpful? 0

First thank you for all the help to this point. My architect, insulation consultant, and I had a meeting last week to iterate over the initial design, seen here: http://lazukars.bitbucket.org/house.png

    After, going over all of the feedback here, on this q/a page, and by doing some more research, we came up with a revised plan. That is, to use 3" thick Roxul Comforboard IS in replacement of the XPS board on the exterior walls of the house. So the breakdown is as follows:

      Basement:
        Closed cell ccSPF foam on the interior wall
          House Walls:
            Use 3" thick Comortboard IS on the exterior of the house over the OSB. The interior wall will be filled with ccSPF creating a vapor and air barrier. The Roxul board is used, so that the house will be allowed to dry to the exterior. This setup greatly reduces the chance of OSB rot that could occur with the initial design. That is, XPS on the exterior walls over OSB, then ccSPF on the interior. Plus, this design helps with thermal bridging at the studs.
              Attic:
                Use closed cell foam insulation with an additional layer of cellulose or batt if needed.

                    Critics of Closed Cell Foam

                      Many people mention to forgo closed cell foam. However, after doing a lot of research, it doesn't make a lot of sense not to use it IMHO. Well..., let's hold on for a second. There isn't a reason forgo using closed cell foam insulation, unless greeness is important to you. But even then, closed cell foam is not completely ungreen. The materials used to make the closed foam have been recycled.

                        However, we could debate the importance of greeness all day, so let's get back to the point. The main benefits of closed cell foam is that it has the highest R value per inch of all the major insulation materials on the market; It fills hard to reach crevasses, places where cellulose or batt might not reach; and it adds structural strength to the house. These benefits are hard to argue against.

                          Now, other argument to ccSPF, other than it's environmental impact, is that it's expensive. Yes, indeed, it is. However, if you only have so much room, in-between the wall cavities, then R-value per inch has a large value in and of itself. That's worth something.

                            Please leave Feedback on the Revised Plans

                              So after seeing my thought process, above, and seeing my list of material choices, what do you think? And please, even if you don't like closed cell foam b/c of environment issues, please leave feedback without that in mind. I greatly appreciate any help it.

                Answered by Ryan Lazuka
                Posted Sun, 08/24/2014 - 23:13
                Edited Sun, 08/24/2014 - 23:24.

                18.
                Helpful? 0

                Ryan,

                In my opinion, you apparently have not read these links below before you wrote about the benefits of SPF. Here's what they are not telling you...

                http://www.foamrun.com/wp-content/uploads/2009/10/foambook_ch5-fire_and_...

                Before you compare a home to commercial look at this spfi fire from July 03,2014. This is Larry Janesky's home founder of Dr. Energy Saver. This fire started from the installation of SPFI.
                How many have told you it does not burn?

                http://www.rescue9photography.com/Fires-2014/Middlebury-structure-fire-7-3/

                http://www.epa.gov/dfe/pubs/projects/spf/spray_polyurethane_foam.html

                2014....Canada is proposing a ban on consumer use of two-part SPFI.... Coincidence?
                http://www.ec.gc.ca/ese-ees/default.asp?lang=En&n=7DDFCE16-1

                In 2011 the United States EPA proposed an all out ban but could not finance the fight the chemical industry was willing to wage.... http://www.ens-newswire.com/ens/apr2011/2011-04-16-092.html

                and then the CDC exposed the B-side hazards in 2012....

                http://blogs.cdc.gov/niosh-science-blog/2012/03/21/sprayfoam/

                and then CPSC exposed the B-sides Amine which suggests the amines contribute to long term health effects..
                http://www.cpsc.gov//PageFiles/129845/amine.pdf

                and then in February 2014 NIST publishes a paper which they are trying to come up with indoor air testing of residential structures which contain SPFI...
                http://www.nist.gov/customcf/get_pdf.cfm?pub_id=915634

                Amazing all these scientist are not saying the product is safe or speaking about it's benefits when used in a private home. Only the chemical makers and their hired gestapo CUFCA and SPFA are. After all it is your home and if or when you come down sick you can not say you were not warned. Been there.. Done that. There's my opinion for what it's worth.

                Answered by Richard Beyer
                Posted Mon, 08/25/2014 - 00:11

                19.
                Helpful? 0

                Ryan,
                It's your house, and if you want to install closed-cell spray foam between your studs, go ahead. The exterior mineral wool will allow the wall sheathing to dry to the exterior.

                Answered by Martin Holladay, GBA Advisor
                Posted Mon, 08/25/2014 - 11:07

                20.
                Helpful? 0

                Thank you for the feedback.

                  I didn't mean to start some kind of flame war. Right now, I am looking for feedback on the design without worrying about the greeness impact.

                    I look forward to more feedback. Thanks in advance; all the feedback is greatly appreciated.

                  Answered by Ryan Lazuka
                  Posted Mon, 08/25/2014 - 11:16
                  Edited Mon, 08/25/2014 - 11:17.

                  21.
                  Helpful? 0

                  Ryan,

                  I did not mean to come across so harsh. Just be informed and smart about your choices, after all it's your health and as Martin said, "it's your house".
                  Should you elect to choose SPFI, here's a good article published today about installation and how to avoid the pitfalls of a bad install.

                  http://www2.buildinggreen.com/blogs/foam-place-insulation-7-tips-getting...

                  Answered by Richard Beyer
                  Posted Mon, 08/25/2014 - 11:41

                  22.
                  Helpful? 0

                  Martin,

                  Why not specify mineral wool inside and spfi outside? Wouldn't that make more sense since it has been tried and proven in the commercial sector? Or, spray the entire exterior of the building with Grace Vycor's new vapor permeable product to air seal the entire exterior envelope and then insulate the interior with your insulation of choice.

                  Answered by Richard Beyer
                  Posted Mon, 08/25/2014 - 11:50

                  23.
                  Helpful? 1

                  "Right now, I am looking for feedback on the design without worrying about the greeness impact. "

                  Which is why you would post the question on a GREENbuildingadvisor blog, right!? :-)

                  Would a bang/buck argument work?

                  " However, if you only have so much room, in-between the wall cavities, then R-value per inch has a large value in and of itself. That's worth something. "

                  It's worth a heluva lot less than you might think. At 5" that high-R foam thermally bridged by the studs isn't buying you much additional thermal benefit. With only 5" of cavity fill the thermal bridging framing fraction is is now 5"/ R6, rather than 5.5"/R6.6.

                  Take these two examples.

                  *At a 25% framing fraction the whole-wall R-value of the studs + gypsum + sheathing with only 5" of R6.5/inch ccSPF is R16.5.

                  **If instead you installed 2.5" ccSPF on the sheathing and 3" of 1.8lb density JM Spider (damp sprayed fiberglass) you'd be at an identical R16.5 performance level.

                  But in the second option you would retain as much drying potential toward the interior as a kraft facer on batt, and have an easier time dealing with any electrical & plumbing that might need to be run in those stud bays. It's literally half the amount of foam and comes with lower installation risk, since it's thin enough to be installed in one lift (no waiting time between lifts to be sure you don't burn the place down or have shrinkage issues.)

                  (And even though you couldn't care less about the environmental impact issue, it's about half the lifecycle global warming hit. (ust sayin'... )

                  Answered by Dana Dorsett
                  Posted Mon, 08/25/2014 - 12:03
                  Edited Mon, 08/25/2014 - 12:04.

                  24.
                  Helpful? 0

                  @Dana

                  "Right now, I am looking for feedback on the design without worrying about the greeness impact. "
                  Which is why you would post the question on a GREENbuildingadvisor blog, right!? :-)

                    That's a good point Dana! Let me try to explain. Since this is indeed a GREEN site, it can be easy to focus too much attention on greenness. Believe me greeness is a major factor in my decision, but the technical details of the materials used and how they work in terms of insulating the house are just as important. And right now, that's what I'm trying to get info on, the technical details of materials used. Once I can wrap my head around those tech details, the greeness factor will also be a an important factor in the final choice.

                        @Dana

                        **If instead you installed 2.5" ccSPF on the sheathing and 3" of 1.8lb density JM Spider (damp sprayed fiberglass) you'd be at an identical R16.5 performance level.

                          Dana, I never thought of that, and that makes a lot of sense. I like that idea.

                              There's one worry I have about that design. That design being Roxul on OSB on the exterior and ccSPF on the interior with the damp sprayed fiberglass. The problem might be that wall is too vapor permeable? Meaning Roxul is already very vapor permeable, and by giving oup 2.5" of ccSPF for damp sprayed fiberglass, the overall wall would be too vapor permeable overall. This might not be the case at all, but I'm looking for some reassurance for peace of mind.

                                  @Richard

                                      No worries! LIke Dana said, this is a Green site!

                                          @Martin

                                              I like your idea of placing the spfi on the exterior of the house. The problem, however, is that finding installers in my area, who are competent to work with new materials in a non conventional way. Non conventional when it comes to residential at least.

                                                  Thanks again everyone!

                  Answered by Ryan Lazuka
                  Posted Mon, 08/25/2014 - 12:27

                  25.
                  Helpful? 0

                  Ryan,
                  You wrote, "Martin, I like your idea of placing the SPFI on the exterior of the house."

                  But I didn't have that idea.

                  I wrote, "If you want to install closed-cell spray foam between your studs, go ahead." I'm pretty sure it was your idea.

                  Answered by Martin Holladay, GBA Advisor
                  Posted Mon, 08/25/2014 - 12:38

                  26.
                  Helpful? 0

                  Hi Martin. Oops! I meant @Richard

                  Answered by Ryan Lazuka
                  Posted Mon, 08/25/2014 - 12:40

                  Other Questions in Plans Review

                  Add R-14 Roxul between the garage attic and the house?

                  In Energy efficiency and durability | Asked by Mike Lucas | Oct 23, 14

                  Minisplit - One indoor unit for two adjacent rooms?

                  In Mechanicals | Asked by Steve Robertson | Oct 23, 14

                  How do deviations in average winter temperature affect energy consumption?

                  In Energy efficiency and durability | Asked by norm farwell | Oct 24, 14

                  Will spray foaming my basement rot my sill plate?

                  In General questions | Asked by Chris McLean | Oct 24, 14
                  Register for a free account and join the conversation


                  Get a free account and join the conversation!
                  Become a GBA PRO!