Do you heat the building? You should at least meet code, so yes more insulation.

no we don't. regardless the code officer said by sealing the envelope and negating air exchange there was no reason to up the r value past the close cell foam. I've read about this becoming .ore common in spots very slowly but I tend to think adding unfaced Batts long term would be wise.

Interesting. Why would you use 2x6 framing with such thin insulation? Costs a lot more than some batts vs doing 2x4 construction. But I realize this is a regional decision. And in some regions, 2x4 is considered cheap.

People like to think foam is magic. It isn't.

I am curious where in the NE, they would be so slack on code enforcement?

We have a place that is primarily a summer time place but we still go to check on in the winter and heat it at that time. We also have the heat on - set to 50 and it doesn't run much because of our south facing windows ... and insulation.

In the NE, I would want some insulation to keep the pipes protected, to minimize extreme temps for wood movement etc. Batts are cheap....And honestly, you need ceiling insulation also (or roof). My concern with the roof/ceiling is not covering the wood. Assume you meant roof, you have uncovered beams so the r-value there is just wood - ie 1 per inch. Or is that metal? Even worse.

Maybe with metal, you have no hope of a decently insulated structure (without exterior rigid foam). Hadn't though of that. In that case, maybe the insulation is a waste.

Clarify your thermal bridging - is it metal? What kind of framing fraction do you have? Will the home have heat?

hi, as I answered in the first question the cottage will not have heat. it is in upstate NY. there is no exposed metal anywhere in the house. the exterior walls were built with 2x6 to help support the trusses. all plumping is under the house with PEX slanted to easily gravity drain by opening two valves.

I'm not expecting the foam to be magic, but we wanted a sealed building. with it elevated and foamed we have had no issues w rodents, everyone else around here does, including other new constructions. we literally cannot access this place in the winter due to road access so once we close it down in late October we usually don't get back in until late April.

I apologise for the mistake earlier, there is 3 to 4 inches of foam on the roof, not the ceiling. the thermal bridging would be via wood. we do run a small AC during the summer which can keep the building in the 70s on a day that is in the mid 90s outside, but despite my CEO saying we have no need to add additional insulation I am still tempted to add unfaced batts.it could also be that he is waiving the insulation requirements because we have no heat here. we ran into an issue with an assessor that was adamant they would assess the new building as year round regardless of the fact we have no wintertime access. the only way to stave that off was to not put a permanent heat source in the building.

thanks for the comments, look forward to feedback

The applicable building code in your area should specify the required R-value in your climate zone for exterior walls, attics, and slabs or floors over unconditioned spaces. Here in coastal Virginia it's R-15 for walls and R-38 for attics. If your insulator sprayed a low-density spray foam with an R-value of 3.7/in you have R-7 +/- in your walls and R-11 +/- applied under your roof. With high density foam, the R-value could be up to 6.5/in so you'd have R-13 in your walls and R-20 +/- under your roof deck. In either case, you wouldn't meet the prescriptive code requirements in our area.

That said, building codes usually allow some flexibility with respect to the prescriptive code requirements if you can demonstrate equivalent overall energy performance to a home built to the prescriptive code. This "trade off approach" considers the contributions of higher-efficiency HVAC systems, better performing windows, more energy-efficient hot water heating, etc. to the overall energy performance of the home. In our area, if we want to use a trade-off approach we need to submit documentation to the code official proving our case. I can only infer your code official doesn't want to be bothered with the paperwork.

A word of caution: designs which depart from prescriptive codes can produce unintended consequences. At the risk of drawing the ire of houzzers, I don't recommend it as a DIY exercise.

we are no bound by energy and I dilation codes because we do not have a permanent hear source. insulation is to create a thermal envelope for heated or conditioned air, but without a permanent heat source or winter usage we have no conditioned air to keep within an envelope. that's why we have flexibility on the insulation. sorry I touched on that on the last response which I posted while you were commenting.

it sounds like you are advocating for the additional unfaced Batts to be installed, which is what I originally planned to do before the CEO told me it would be a waste

I understand that your lake cottage is designed for seasonal use and will have no system for conditioning the living space. Installing insulation keeps open the possibility of a change from seasonal to year 'round occupancy.

The construction of your exterior walls permits drying only to the interior. However, you don't have any conditioning of the living space. I don't know what your climate zone is, but you--and your cottage-- will likely benefit from installing an appropriately sized dehumidifier.

Good luck with your project.

I now see your third post answering the heat question. Strange - I don't think it was there before. Or I just missed it.

So strange IMO that you are allowed to do that. In my state, if a structure does not have heat, than it is not habitable. Which seems pretty basic.

Honest question, is there no time you would want to be in the house when it is cold out? I lived in Ithaca and Buffalo and I would never want to go back in the winter. But what about a late April time?

We have a NC beach house. We had to heat it and insulate it. And it was a no brainer since it does give the option to be a year-round structure. But the wind at the beach can make it not a lot of fun...

If you aren't heating, then more insulation seems like a waste.

Seems to me your best insulation strategy for adding insulation would be to negate thermal bridging in walls and roof.

Installing taped rigid insulation panels on the exterior of your walls and roof would not only stop any thermal bridging, but would also help with negating air infiltration.

Good luck!

The OP indicated they will occupy the home only seasonally. R-value and thermal bridging aren't particularly relevant for summer occupancy in climate zones 5 or 6 (upstate NY includes both.) The spray foam insulation already installed should provide sufficient air sealing to preclude any appreciable air infiltration.

What is a concern, in my opinion, is that the use of spray foam insulation in the walls and under the roof deck creates a sort of "thermos bottle" with implications for indoor air quality. A fresh air make-up system of some sort is likely needed. The need can be verified by a blower door test. The other concern is the potential for mold and mildew growth since the wall assembly will dry only to the interior and space conditioning includes air conditioning only. I grew up in the southern tier of upstate NY and can tell you that air conditioning is rarely called for in that part of the world. Accordingly, some supplemental dehumidification will likely be required to keep relative humidity levels below that which will support mold/mildew growth.

It's particularly disappointing that the building official has contributed little to the understanding of potential problems with this home.

hey guys, I appreciate everyone's input. to clarify things the building is up, the ccsf is on, and we are working with what we have, so we aren't going to rip exterior panels off the add foam board now, and being a seasonal cottage I'm not concerned with thermal bridging and the same applications of insulation that I would were I building a year round house.this is just a simple, seasonal lake cottage that I'm trying to get clarification if my CEO is right or wrong that with a sealed building the gains from additional Batts would be negligible w the ccsf already installed. I priced out adding r13 Batts to the walls and the price is roughly $500 to do it which is also negligible so I'm going to do that. 2-3" of ccsf with r13 unfaced batts and 5/8" sheetrock should take care of the walls. then later once I move to close the ceilings I will probably add some rolled r30.

for the people speculating and asking why we were allowed to not have heat, I went through all the codes including our state codes and presented them to the town. essentially they only require an envelope if you have conditioned air, and furthermore require that you have a primary structure on your property that proves things such as shelter, cooking source, water source, etc but heat is not required. bus zoning actually has designations for season structures without heat, although most assessors and towns are pushing all new constructions to be build w heat and such so they can be assessed as year round homes. I fought this battle and presented the codes in a town meeting and essentially embarrassed those that were telling me false info.

the other reason I've had flexibility on this project is that it's a smaller building. do to the small assessable sqft we were not required to stamp plans or bound by other codes. we included a massive covered deck in the construction so we basically have double the space but the deck area doesn't count to sqft that would affect how the building had to be built. it was just a matter of circumstances that has made our lives a little easier through the process without as much red tape.

Charles, thanks for the info. I share you sentiments about the CEO not really providing much here. everything you said is correct. the building itself is one giant open space and three smaller rooms. we usually have windows open in the summer for extended periods for air exchange and such but also have many days in the 90s where we close up and run an ac. my wife seems to think she's going to melt any day the temp hits 80. we haven't had humidity issues in the house to this point. aside from the periodical use of ac you would suggest a dehumidifier be installed to keep the building dried out especially when we are not here, that would be your main concern? also, you agree with the CEO that the ccsf essentially negates the need for additional insulation in our application?

@thewolfslair

Your home's construction may be exempt from certain prescriptive building code requirements, but it's not exempt from the laws of basic physics. You will be well served to consult with a HERS rater or energy consultant in your area who has expertise in indoor air quality.

I'm not suggesting I'm immune from the laws of physics. the question that was asked was if a fully sealed building would still benefit from the additional r13 Batts in the wall. after shopping around the additional Batts for the walls would end up costing roughly $250 so it's just a no brainier and I'm going to add it. thanks for the input

Funny, I thought CEO meant your wife.

I know see the code enforcement officer is what you meant....

I have to think the CEO should be limited to the more typical Chief Executive Officer. Which sometimes means your spouse....

Just as CFO often means spouse.

Not sure I would even spend $250 in your application. In your setting, insulation will prevent nighttime cooling. So some sunny 90 days followed by 60 degree nights and you will arrive to a warmer cabin than if you had no insulation. Just a thought....

What is your ventilation plan?

Rodents love spray foam insulation.

The addition of fiberglass batts to the spray foam insulated walls will do little to enhance overall performance of your wall and roof assemblies. For seasonal use in mild weather, it's not worth the effort. I do wonder, if at some point in the life of the structure, whether it will be adapted for year 'round use. They have an invention called a "snowmobile" which would make your cabin accessible in the winter even if the guys who drive snow plows for a living decide to winter in Florida. Hardier types will scoff at the notion of carbon-emissions-producing play toys for access and will strap on the cross country skis or snowshoes (my personal preference is the traditional ones with rawhide webs.) But I digress.

As one poster above noted, spray foam insulation doesn't create much of a barrier for rodents.
It doesn't stop termites or many other insects either.

The important consideration-and it appears that your code compliance inspector could care less about it--is the indoor air quality in your thermos bottle of a cabin. You need a means of controlling indoor relative humidity to minimize the potential for mold and mildew and you need fresh air ventilation. Thus my recommendation to get a HERs rater or energy rater involved to assess the existing conditions and make specific recommendations. Alternatively, you can crowd source that to the usual suspects here on houzz.com Just remember that free advice is worth what you paid for it. Mine included.

I appreciate it and got a laugh out of a couple of the jokes here!

we have been running a small window AC which has done great removing any moisture and controlling the temp. I know this isn't ideal to everyone but it works for us. windows open at night, closed during the day. air is never stale and it's dry. I think the highest humidity that we've seen inside w a tester is 42%. I completely understand some of the comments in here for applications that are more than what this building is suppose to be and I'm not discounting them, but I'm also realistic about what this building is and the utility it's meant to provide.

I had a friend come over with w thermal imager this weekend and we were able to measure temps on the walls and roof with the sun hitting it. most of the building showed no or negligible heat increases, but we found that the absolute ridge/peak had issues. it was a difficult area to spray and it appears the installer did a poor job and we will need to circle back with them. the vast majority of the roof was consistent with temps, but the ridge had so spots reading 20-30 degrees warmer than the inside air while we found a couple other spots that were 10-15 degrees warmer. we will figure out how to proceed soon with them. the walls probably don't need additional Batts with the readings we got, but we may still just install them for additional sound deading and just in case we pursue use during late fall.

I want to make clear I'm not ignoring advice to speak to local resources, but the simple fact is this is a very small town and the local "experts" give advice such as what this code officer gave me, or the complete other extreme where someone told me we needed! to entirely fill a ceiling cavity 4' thick with insulation to prevent us from hearing rain. contractors in this area see/hear lake property and their eyes go $$$$$ and it turns into how can we make out best on these people. for instance, installation of 8 steel fence posts (with and air hammer), just the fence posts and no fencing was 1200 from the lowest quote. it's been a constant battle bc everyone assumes owners are very well off financially which just isn't always the case. so to my original point, finding reasonable and consistent advice and insight locally has been almost impossible.

also regarding the rodents, I know foam is not a miracle cure, but we have battled rodent issues for 6 years prior to this building, as have ALL our neighbors, but since this building went up and was sprayed 16 months ago we haven't had a single issue. I found one pinhole in the foam that a couple ants came through and took care of it. I know things can change but we really tried to have this building animal tight and so far not a single issue.

again, thanks for the conversation and feedback guys