R49 insulation--not enough space, how'd you solve?

kirkhallOctober 24, 2012

I heard from my GC today that the codes have changed since phase 1 of our remodel/addition 2 years ago and new codes require R49 (I think he said)--17 inches of insulation.

We don't have 17 inches.

What are my choices? I'd like to hear some of the collective wisdom of this forum before I talk to him some more about this... He'll be subcontracting out the insulation part, so at this point, I don't really have anyone to discuss this with.


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There are lots of different kinds of insulation. It's been a while since I dealt with insulation but I'm pretty sure your GC was talking about the standard fiberglass batting (the "pink stuff") when he said that you would need 17 inches of insulation to reach your required R value of 49.

Obviously, if you don't have 17 inches of attic space, then you'll have to use some other kind of insulation.

For example, Owens Corning also makes a High Density version of the fiberglass batting that provides a higher R-value per inch. We had specified R-15 fiberglass batt in our walls and our builder tried to tell us that R-11 was the maximum we could get because our walls were constructed of 2x4s so only had 3.5 inches of space to insulate. But I already researched and knew that with high density batts, 3.5 inches of insulation was rated at R-15. End of argument. You would THINK that the builder and insulation subcontractors would KNOW these things but apparently ours did not. Or maybe it is just that the higher density batt is more expensive than regular batt so my builder "know" about it...and hoped that I didn't either. (sigh...)

And higher density batting is only one option. I'm linking to a document that talks about all the various types of insulation, gives their R-value/inch, and some pros/cons of each.

Hopefully this will give you a starting point to figuring out how to insulate your space.

Here is a link that might be useful: Handbook of Insulation

    Bookmark   October 25, 2012 at 1:35AM
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Where the IRC 2009 recommendations for cold climate attic/roof insulation have been adopted, R49 is the minimum.

As noted above, there are lots of higher R value per inch alternatives to fiberglass. If there's still not enough room, you can always add a layer of foam board or closed cell spray foam to the top of the roof topped by sheathing or other protective layers.

Use care when reading the above linked un-sourced handbook.

For instance, it contains this howler: "The choice between faced versus unfaced [batts] is usually a matter of personal preference." NO. The facing is a vapour retardant and its use and positioning is climate specific.

    Bookmark   October 25, 2012 at 2:24AM
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our vapor retardant/barrier in the addition 2 years ago was our interior paint. I don't think we had faced insulation in the addition. Sound right?

    Bookmark   October 25, 2012 at 10:28AM
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And, thanks Bevangel... I started to find info on "compressed"/high performance insulations (and also, I think, that cathedral ceilings only need R38) last night. Will keep researching.

    Bookmark   October 25, 2012 at 10:29AM
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The "un-sourced handbook" to which I linked was put out by the State of Virginia's Department of Mines, Minerals & Energy (Energy Division). It is chapter 3 of the Virginia Energy Savers Handbook. Links to the rest of the handbook, including the cover page showing the authors and their bona fides can be found here...

Here is a link that might be useful: Virginia - Energy Conservation Handbook

    Bookmark   October 25, 2012 at 1:33PM
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I liked the descriptions of insulation materials
in the link. very comprehensive.

OP check out different R-value per inch of
different insulating materials.

best of luck.

    Bookmark   October 26, 2012 at 4:24PM
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I figure this is known but you shouldn't have to comply with codes that go into effect after you have a permit (at least usually).

    Bookmark   October 26, 2012 at 8:26PM
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The city was very specific when they issued the permits for phase 1 that phase 2 had to have separate permits... Bloodsuckers.

    Bookmark   October 26, 2012 at 9:42PM
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No building department could be expected to issue a building permit that would be in effect for over 2 years.

However, it is sometimes possible to get a permit for all of the work and then ask for the permit to be extended after the usual time limit has expired but to stretch it to 2+ years can be difficult. How would you like to look at your neighbor's partially finished addition for 2+ years?

Blaming those who work to protect the public is not a good way to motive others to offer their help.

As for insulation for an addition, you haven't said what state you are in or what the energy code is or what the configuration of the roof and attic is but if the code is the 2009 International Energy Conservation Code (IECC), it is possible that your contractor does not know how to interpret the insulation requirements.

For an addition the usual approach is to use the Prescriptive method. For ceilings with an attic space above, Section 402.2.1 allows the reduction in R value for your zone from R-49 to R-38 "wherever the full height of uncompressed R-38 insulation extends over the wall top plate at the eaves."

For a ceiling without an attic space (like a cathedral ceiling), where the insulation requirement is greater than R-30 and the design of the roof/ceiling assembly does not allow sufficient space for the required insulation, "the minimum required insulation for such roof/ceiling assemblies shall be R-30. This reduction of insulation from the requirements of Section 402.1.1 shall be limited to 500 square feet (46m2) or 20 percent of the total insulated ceiling area, whichever is less."

Of course, you should ask the building department if this is the proper code and if so are there any local amendments to it.

    Bookmark   October 28, 2012 at 12:13PM
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I would prefer to use dense-pack cellulose instead of fiberglass batts where possible and to use foam in rafters when there is HVAC equipment or ducts in an attic.

    Bookmark   October 28, 2012 at 1:26PM
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"No building department could be expected to issue a building permit that would be in effect for over 2 years. "

Many do exactly that, and in some places you can even pay a 'renewal fee' to keep one active (often only required if obvious progress has not been made).

    Bookmark   October 28, 2012 at 4:37PM
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This is what the 2009 IRC says about time limits on residential building permits:

"Every permit issued shall become invalid unless the work authorized by such permit is commenced within 180 days after its issuance, or if the work authorized by such permit is suspended or abandoned for a period of 180 days after the time the work is commenced. The building official is authorized to grant, in writing, one or more extensions of time, for periods not more than 180 days each. The extension shall be requested in writing and justifiable cause demonstrated."

In the real world, not a hypothetical or fantasy one, the desire to avoid meeting new code requirements later would not be a "justifiable cause."

Even if a town has amended this code section it would still be nearly impossible to get a permit for work that the building department already knew would not begin within a year or two.

    Bookmark   October 28, 2012 at 5:02PM
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so why would you consiter code & permits to
be bloodsuckers?

because they mandate the legal minimum you
can safely build to?

why would you only want the minimum that
the law allows??

I don't get it.

    Bookmark   October 28, 2012 at 5:30PM
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It's not clear what the building department did to the OP. Until he tells us the applicable energy code and location it's not even clear that the insulation requirement has increased.

I would never take a GC's opinion as fact regarding the building code and I don't mean to disrespect GC's; designing buildings is just not what they do for a living. Successful GC's are busy people and many of them repeat what they hear from sub-contractors instead of reading the code for themselves especially when the code changes as often as the energy code.

If the Op wants to be sure what is required he should read the code for himself or ask the local head building inspector for an interpretation for this situation, you know, the guy who patiently answers homeowner's questions ... I think he's know in the office as the head bloodsucker.

    Bookmark   October 28, 2012 at 7:40PM
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I wasn't alerted to all the activity on my post! I'll try to catch up here below--

I am in Washington state, the west, wet, milder side. I live in a city which is known to permit the heck out of you...unless you are a developer, then you can get away with much more... And, every one of their permits asks for how much it costs, rather than what is being done, to determine the permit fee. If I DIY'd it (and therefore, probably spent more time bugging them, having inspections, etc) my permit fee would be lower than having a GC do it because it is based on project cost. It doesn't make sense to me.

I have no HVAC in my attic. In fact, until recently we were baseboard heat. We upgraded to minisplits. The new space will have a second 3 head minisplit system to keep it conditioned. There will be only bathroom vent fan penetrations in the ceilings and the occasional light electrical box (but no can lights). So, there should be limited flow through the ceiling.

My house was a rectangular cape with the upstairs under eaves and having a partial "cathedral ceiling" (ie, under the eaves, the slanted ceiling. Nothing cathedral about them except the slope). We added on a 2 story addition perpendicular to the original shape of the house. Upstairs, we gain the square footage of the addition plus the un-utilized space of the eaves on the backside of the house.

We never expected to permit the upstairs work at the same time as the downstairs, but you build to what you build. There is nothing unsightly about our partially finished addition. From the inside, you don't know the extra space is there (all the old walls/ceiling is still in place--we were able to refinance the way it is now--clearly not under construction), from the outside, it is all finished with siding, roof, etc to match the existing. And, it is in my backyard which no one faces.

This requirement of the permit would in no way be a safety issue. Wired fire alarm requirement, maybe (though, I'm not even sure about that). CO requirement, sure. But, not insulation. We don't think we need to upgrade our insulation at all, as our house seems to work rather efficiently. We are not eligible for any energy rebates (to get gas to the house, for example) because our energy use is so low. I really feel like being forced to upgrade to R49 is excessive when we seem to manage and stay efficient with just whatever it was we had before that fit in our 2x10 floor joists.

I am unsure what code our city is using now. Whatever it is, it is different than it was in Spring 2010 when we did part 1 of the addition. I found the "helpful" pdf, linked below, hopefully).

Renovator, thanks for the information about possible wrong interpretations. I'll look into it.

As for the space--the addition is a 4/12 trussed (~24ft wide over 20 foot interior living space) roof that meets at a right angle a 12/12 framed cape style roof (with living space). It is possible, though we are not sure, the city will make us "upgrade" our existing cape area insulation, including at the angled ceilings (which would require a complete gut of upstairs and re-sheetrocking to get the insulation in place without messing up the roof ventilation.) Our roof is continuous ridge vent with soffit vents at the lower side. Total 1 story sq ftage under these 2 sections of roof (cape and trussed addition) is about 1140sq ft. Oh, and walls are 2x6 construction.

Does that help?

Here is a link that might be useful: insulation checklist

    Bookmark   October 28, 2012 at 8:14PM
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Renovator, on your last post, it wasn't there when I posted my reply--
So far, all I have is what my GC has told me (based on what his Sub told him).
I think I will have to wait to sign a construction contract until we know if we can get permits on the scope of work that we actually plan to do, and not all the extras that might be required, or might not be... (ie, I have some more researching to do in city hall--though good luck getting the "head bloodsucker." Last time, I got some gal that went and literally labored over the code reading it aloud with me and interpreting as she went saying, "I think this means..." and "I guess..." I wish it were as simple as finding and talking to the head guy.)

    Bookmark   October 28, 2012 at 8:36PM
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What is the area of the addition?

    Bookmark   October 28, 2012 at 9:06PM
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Washington does not use the IECC; it has it's own energy code but it is obviously modeled after the IECC and allows a decrease in R-value to R-38 for attics where certain energy efficient "Advanced Framing" techniques are used.

I only read it once so I'm not sure but it appears that in addition to a "raised-heel truss" meeting the requirement, it is possible that foam insulation above the exterior wall top plate of a conventionally framed roof might be acceptable. I've never seen so much information presented in such a rambling fashion.

There is a strange section on additions that allows less insulation in the addition if the main house energy efficiency is increased and the calculations are so complicated they require the use of special Excel spreadsheet templates.

Your contractor should be aware of the insulation reductions. If not, and the building department is not helpful, you may need to hire an energy consultant or an architect.

    Bookmark   October 28, 2012 at 9:56PM
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The downstairs addition was 20x15
the upstairs works out to be about 20 x 21 feet of additional sqftage. The current floor area upstairs is around 450sqft (12x35 with a little additional under dormers).

    Bookmark   October 28, 2012 at 9:57PM
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HA! Renovator, this line cracked me up--"I've never seen so much information presented in such a rambling fashion"

Okay, again, thank you for your time in this. I'll see what I can glean from the building department (and hope I get the same person when they review the plans to issue permits).

    Bookmark   October 28, 2012 at 10:34PM
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It's not clear to me what the addition is. It sounds like the shell has already been built. If so, why wasn't it required to be insulated when it was built? If an upper floor was not occupied, was the floor insulated?

It sounds like the prescriptive "addition" part of the energy code might help you because if you upgrade parts of the existing house the addition can have less insulation.

Also, if you are near Bellevue Washington, the IECC would put you in Zone 4 and require a maximum roof/ceiling R value of R-38 instead of R-49.

"Super insulation" was the rage in the 60's and people misunderstood it then as they do now. Each additional inch of insulation saves less energy than the one before it so at some point there are other construction techniques that will be as helpful as adding more insulation. But it's easier to mandate R values in a code. That's why you are allowed to reduce the roof/ceiling insulation if you use Advanced Framing techniques and raised heel trusses, and perhaps other techniques that are presented with somewhat contradictory language and too many poorly drawn diagrams.

One way or another someone who understands the new code in Washington should be able to get the roof insulation reduced to R-38. When it comes to using special construction techniques that person is more likely to be a professional designer than a contractor or a building inspector. You want someone who has a dogeared copy of the energy code with tabs and notes in the margin rather than someone who heard somewhere that the roof R-value had increased to R-49.

To see the code use the link below and look down the page to "CODE TEXT" and select "Chapters 1 through 10 (Single-Family Residence)"

Also select "Chapter 3 & 4" of the "Builder's Field Guide".

Here is a link that might be useful: Washington State Energy Code

    Bookmark   October 29, 2012 at 6:57AM
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I suspect the Washington energy code will be satisfied with R-38 roof insulation that extends over the top plate of the exterior wall (just like the IECC does) but for some reason the Washington code characterizes this detail as "Advanced Framing" or "Raised Heel Trusses" as if that was the only way to achieve that result. Of course that is not the case because it is possible for a truss to be designed with sufficient overhang to allow full height uncompressed R-38 insulation to extend over the top plate. However, it probably requires the addition of some kind of closure between the trusses at the outside face of the insulation.

The 4 in 12 truss you describe (I am now assuming it is already built so this project is an attic conversion/renovation instead of an addition) would probably have a clear dimension above the top plate of about 12" and that would accommodate 10.25" of high density fiberglass insulation and leave enough space for a vent baffle against the bottom of the roof sheathing. If it has less space you would need to use closed cell foam insulation at that location which is referenced in a vague way in the Builder's Guide (I think that's where I saw it).

So, everything depends on the height of that detail but I don't know what it is or if it actually already exists and I suspect the insulation subcontractor doesn't know either. If the truss exists you need to post the original design/shop drawing or go up there and measure the clear height above the outside face of the top plate.

I realize you will have to wait until it stops raining to do that (I had an all expenses paid vacation in Tacoma in '67).

    Bookmark   October 29, 2012 at 8:34AM
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You have it right. We built a 2 story shell with siding and roof, insulated only the finished section and so there is insulation between the 1st and second floor of the addition. The new upstairs space was considered "unfinished (unconditioned) attic" in the refi-appraisal we had recently.

We are very near Bellevue.

And, yes, of course, it is raining. But, I do have an "attic access door" that I may be able to measure in there from within. I'll see if I am tall enough, because I know I can't get a ladder in there.

Tacoma has changed a lot in the last 45 years... It is almost as well-respected, as a city, as Seattle! ;)

    Bookmark   October 29, 2012 at 10:49AM
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I was referring to Ft. Lewis which I suspect has not changed much.

    Bookmark   October 29, 2012 at 10:55AM
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Ah. Well, that is now "Joint Base Lewis McChord--JBLM"

They combined Fort Lewis and McChord AFB. It probably hasn't changed much other than in the name.

    Bookmark   October 29, 2012 at 11:05AM
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About residential permit expiration:

The way this is written in the 2009 IRC is misleading if you read it superficially.

What it actually says is that you have to start work within 180 days of the date that the permit was issued and once work has started, work must not stop for more than 180 days. If you can't show progress within a 180 days period (!), you may apply for an extension documenting why you stopped.

My permit was issued early 2010 and I made sure to have an inspection showing progress at least every 180 days. Total time of construction will be 3 years (I have another 180 days to go approx.) and I will own a mortgage free house, which I could not have afforded (even with a mortgage) had I paid a builder to construct it within 180 days.

The local building department specifically explained to me that I have to schedule inspections not more than 180 days apart for the permit to stay active.

Otherwise it would effectively impossible to build DIY while earning a living with a full time job.

And no, the neighbor's visual inconvenience does not trump my property rights (it helps that my property is secluded, though).

The city has adopted a more stringent energy code after 2010 but my build is grandfathered into the previous one that was valid when the permit was issued.

    Bookmark   October 29, 2012 at 12:26PM
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A different contractor came today--he says he doesn't think I'll have any problems with my insulation--not because of the code, that is clear enough, but because my shell was built to code/requirements when it was permitted and built. He thinks they can't make me redo anything... We'll see.

All on interpretation, I guess.

    Bookmark   October 29, 2012 at 1:16PM
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I don't know what he means. You will have to meet the code for new construction for the new habitable space including any code regulated systems that are disturbed.

    Bookmark   October 29, 2012 at 2:46PM
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Okay. Thanks.

    Bookmark   October 29, 2012 at 3:00PM
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