Foam insulation - Making cabin from prebuilt shed

[Raised on a Deere]

Pondering in the interest of time to have a quality shed builder make me one of those 16x32' with the corner porch and swing kinda thing to use for a cabin on some land in KY so I can spend extended vacation times around a bunch of kids and grand kids in the neighborhood. I live in Alabama.

These sheds are very sturdily built with strong roofs with hurricane plates to the rafters etc. I will place it on 5 concrete footings running crosswise to the building and anchor it down for a blizzard. The builder will work with me to have the insulation in the floor as they build, and then I will have walls blown with open cell after on site and plumbed and wired.

My plan is to have 6" closed cell in the floor and regular open cell in stud walls including 6" in ceiling then dry wall it all in. All this can happen by me making phone calls andwriting checks except for plumbing and wiring of course. I can do the rest while I am camping in it including do the HVAC and septic work.

It seems to me with a heat pump this thing would be pretty cozy and easy to heat, understanding that I have to build in some air exchange for such a tight structure.

Any suggestions or no's from your experiences or stories heard? Old wives tales are also to be enjoyed.:laughing:

 

[adventure bob]

My house is sprayed with 6" closed cell and a flash and fill in the attic. The only advice I would have is find an experienced sprayer. You can monkey this up pretty easily with guys who don't know what they're doing and you wont know for a while that they sprayed in voids, sprayed out of mix, or even gapped it. The equipment they use is critical to getting the mix right, and some cheaper guys either didn't pony up for good gear or don't maintain it very well. Are you going to do the ceiling? I'm assuming its just a ceiling, no attic space? That's were you make your money on warm conditioned space. You do have to think about air exchange; my house is extremely tight and we have to vent in the winter for moisture.

 

[Raised on a Deere]

My house is sprayed with 6" closed cell and a flash and fill in the attic. The only advice I would have is find an experienced sprayer. You can monkey this up pretty easily with guys who don't know what they're doing and you wont know for a while that they sprayed in voids, sprayed out of mix, or even gapped it. The equipment they use is critical to getting the mix right, and some cheaper guys either didn't pony up for good gear or don't maintain it very well. Are you going to do the ceiling? I'm assuming its just a ceiling, no attic space? That's were you make your money on warm conditioned space. You do have to think about air exchange; my house is extremely tight and we have to vent in the winter for moisture.

I am filling the 6" rafter space.

I think the biggest un ease I have is concerning the necessity of closed cell foam in the jointed floor. The cabin will be just a few inches off the ground they is built up a few inches higher than surrounding to insure above all water. Would this work with open cell if I tarpaper under the finish flooring? Do mice mess with the insulation etc

 

[AGRIMAN]

I am filling the 6" rafter space.

I think the biggest un ease I have is concerning the necessity of closed cell foam in the jointed floor. The cabin will be just a few inches off the ground they is built up a few inches higher than surrounding to insure above all water. Would this work with open cell if I tarpaper under the finish flooring? Do mice mess with the insulation etc

You will be fine with the open cell in the walls and roof, but I would not use/recommend open cell under the floor/crawl space. I would go with your original plan on using closed cell.

As far as mice, I have never seen them nest in foam, but I have seen the chew through it.

 

[adventure bob]

Id definitely suggest a vapor barrier to the outside (floor side) for either type of foam just to keep condensation off your foam. While its pretty impervious, mold will grow on it if it stays wet. I live in Colorado so water and moisture are only a concern on the human side of the foam.

 

[ustmd]

You will be fine with the open cell in the walls and roof, but I would not use/recommend open cell under the floor/crawl space. I would go with your original plan on using closed cell.

As far as mice, I have never seen them nest in foam, but I have seen the chew through it.

Mice will nest in open cell, but not closed cell

 

[adventure bob]

When they shot our house we opted for the fire retardant spray (the purple colored stuff) over the top of the foam, which in addition to adding fire retardant, makes it very un-tasty to mice and other beasties to burrow in.

 

[AGRIMAN]

Mice will nest in open cell, but not closed cell

I'm wouldn't be surprised. I just haven't seen it for myself yet. My son and I are spray foam contractors.

 

[Ed of all trades]

My shop is a shed like you say. The insulation under the floor is just held up by plastic draped over the flooring joists and will be a problem in the future. Check with your builder to make sure he is not thinking of doing it that way. Ed

 

[Raised on a Deere]

Thanks to all on confirmation of closed cell properties being desirable in floor exposed to outside. Also I am going to do my homework with respect to quality contractors and I like the fire retardant idea to ****** mice. My sister had a place that she left vacant for one one winter. When she came during the summer she found a colony of mice. Messed up a lot of stuff.

 

[Raised on a Deere]

Ed that is why I was looking at closed cell foam. It is pricy but it will stay put. Cures hard and is impervious to moisture. Problem is it will also trap moisture and so should be cut off from moisture from the inside. At least if you have a spill or something yours can be dried out with help of fans.

 

[EddieWalker]

Pondering in the interest of time to have a quality shed builder make me one of those 16x32' ...


Any suggestions or no's from your experiences or stories heard? Old wives tales are also to be enjoyed.:laughing:

Closed cell foam is probably the best stuff out there, but it's expensive. Open cell foam is OK, but it's nowhere near as good as closed cell and if you are filling small areas, like in between the studs of a wall, it's not a great material.

Google the R value of open cell and closed cell. There is a huge difference.

Talk to several installers and get bids in writing before doing anything.

How much space will you have in your ceiling? If it's just the thickness of you rafters, closed cell foam is going to be the best choice, especially if they are 2x6's.


If it was me, I wouldn't use foam. It's just a weekend get away cabin, and probably not where you want to dump a ton of cash. If you have enough room under your building for a guy to spray foam it, you have enough room to crawl under there and install fiberglass and then seal it with plywood to keep out animals.

Wrapping the outside walls is very important. If you are having it built, insist that they do this. Also insist that they tape the windows. Keeping the wind out from the walls is a big part of maintaining your inside temperature. Open cell in the walls fails to do this very well, but closed cell is fantastic. But it's super expensive and rarely done when you find out how much it costs.

For the ceiling, if you are going with a flat ceiling and you have an attic, blowing in two feet of loose insulation is the best bang for your buck. You get the machine to do this free when you buy ten bags, and the new Attic Cat type insulation does not itch or require a face mask. I do a few houses every year with this and energy bills drop 30 to 50 percent on every job.

If you are going with a raised/vaulted ceiling and you only have the thickness of the rafters, then nothing will come close to closed cell foam. In your bid, ask them to give you a price for just the ceiling and then for everything else that you want sprayed. Break it into two bids.

Or you can add another 2x6 under what is already there and create a space of 11 inches for fiberglass insulation bats. I've done this a few times with great results. Here in Texas, heat is what we battle the most, but in Jan and Feb, it gets down into the teens, so we do have some issues there. I've found it to be very easy to heat and cool a room with two layers of R19 fiberglass bats in the ceiling. It's only R 38, but for occasional use, it's a great way to save some money and have a comfortable space.

 

[STx]

If your walls and ceiling are going to be metal, you will want to use closed cell foam or a moisture barrier. If you don't, you will get condensation on the metal from the warm, moist air inside the cabin.

I'm currently living in a 16 x 32 Morgan building that we've converted into a cabin. We sprayed 1" of closed cell on the walls and ceiling and put regular batt over that behind the drywall. The foam itself made a HUGE difference, the roof is still exposed with just the foam and we were able to keep it in the low 70's during our 105* summer. It really helped to stiffen up the building as well.

I foamed it myself using a couple of kits (Touch 'n Seal U2-6 Spray Closed Cell Foam Insulation Kit 6BF | eBay), I found that doing 1" of foam with the batt gave use the benefits of spray foam with the cost savings of batt. It's really not that difficult to do, the most important thing is to make sure that the bottles are 80* or warmer when you do it or it won't flow/spread correctly. Other than that, it's like spraying paint.

 

[EddieWalker]

STx,

Good point about using closed cell on metal walls. Open cell absorbs water and will cause rust on the metal in a short amount of time.


Did you have an insulation company give you a bid before buying the kit and doing it yourself? I'm curious what the price difference would be from the kit to having a company do it. Did you have any issues with the spray gun? I read some reviews in either Fine Home Building or Journal of Light Construction that said they had problems with the guns jamming up and being difficult to keep clean enough to keep working. They recommended buying a higher grade gun if you are going to do it a lot. They also said to be sure to wear a full body protective suit that covered you from heat to feet, and full face protection because it will get all over you when spraying.

I have no experience with the kits, and was hoping you could provide more information on what it was like to use it?

 

[STx]

I'm 2 hours away from anyone that has the equipment to do it professional, the travel time to mobilize a professional rig for a 1200 board foot job would have cost more than the kit did. I did get a quote for a 40 x 50 x 14 steel building with 1" all the way around and it came back at $10,000 so I'm doing batt for $2,100 instead.

I screwed up on the first kit and didn't get it up to temp correctly. It sprayed, stuck and expanded but, it looks like crap. The 2nd kit I warmed up to 85 degrees and it sprayed super easy. The guns in these kits are one time use, throw away guns. They have 2 tubes that come up into the gun and then you connect a mixing nozzle to the 2 outlets on the gun. The nozzle can be replaced if it gets jammed up but, your best bet is to have everything cleared out so that you can just keep spraying until the job is done or you run out of foam. With the second kit properly warmed, I got a nice, even finish and the material went a lot further. I'm sure a professional gun is 1,000 times better than what comes with the kit. When you're only doing 600 board feet at a time though, the cheapo disposable does the job.

The kits I bought came with a Tyvek suit, I wore latex gloves and taped plastic bags over my shoes and wore a full face shield. The stuff is nasty, you need good ventilation and it's going to stick to anything it touches, including you. Overall, after learning what not to do with the first kit, it was a pretty easy job. I've got a 40' high cube container that we're using for storage right now. Once my shop is finished (should be mid Jan) and everything is moved out of the container, I'm going to get a couple more kits and spray it inside as well. Now that the house is sold, we have some furniture to store until we build something on the land and my wife wants it somewhat climate controlled for that and some of her stuff. I figure an inch or so of spray foam and a 12,000 BTU window unit should keep it cool enough in the summer that we can use the container for that purpose.

 

[Cord]

Closed cell is better than open open cell and it doesn't need a vapor barrier. Open cell requires a vapor barrier. Don't use a vapor barrier with closed cell because it would trap moisture behind the plastic. The fire retardant stuff is very expensive, but a layer of drywall will more effective at resisting fire. To keep keep the mice out, you need to seal up all openings. Caulk the plumbing and waste lines. Foam holes which are oversized. If you don't provide any openings, you'll never have a mouse infestation.

Be sure to check with the local authority to make sure you pull the necessary permits.

 

[AGRIMAN]

To the OP. As I said we are spray foam contractors, but we also sale and install fiberglass and it's likely that we will be adding blow-in in the near further,so we are involved in it all.

Some of our residential and commercial jobs are all foam, some are a combination of foam and fiberglass and some are all fiberglass. We are currently working two fiberglass jobs, one 80K sf and the other nearly 100K sf, so we are not opposed to fiberglass.

As stated, foam is not the cheapest option whether using open or closed, but there's nothing out there that provides a better long term value for your insulation dollar than foam. Now, that doesn't mean that it's the best fit for you or your budget. This is the main reason we have expanded our business to include other options.

Foam is not the cheapest option and probably never will be, but the industry is changing at such a fast pace it's hard to keep up with. There are foam now with built in thermal and ignition barriers, there are hybrid foams now which are a combination of open and closed (1.0 to 1.6 PCF). Most of the foams on the market today are far better than the foam of a few years ago. Many of the old does and don't of foam are changing and hopefully this will also lead to a reduction in the cost at some point.

Fiberglass is cheaper and will provide good insulation value for the money. It's been around for a long time and still widely use. It's valve is highly dependent on the quality of the installation, but even with the best of installation jobs, it still can't match the seal of foam. (even open cell in the walls).

Blow-in is similar in that's cheaper than foam and provides good initial valve for the money, but over time it will settle and lose some of its R valve.

You are the person that has to decide which option best fits your needs and budget, but remember there's pros and cons to them all.

 

[AGRIMAN]

There were some past reports of metal rusting after being foamed. This was linked back to a corrosive material that was being used in the ISO. That material has long since been discontinued.

Open cell foam has been applied directly to metal in our area (zone 3) for many years with no reported problem.

 

[Weedy Fields]

We used 15" of open cell spray foam on our house on the roof under sides. At this thickness it acts as a vapor barrier like closed cell but it remains "flexible" so that as house moves you have no cracking to allow air gaps. Additionally the spay foam had to painted by code. Paint was to stop vapor transmission even tho at the thickness we had sprayed it was not needed.
Yes, open cell has a lower R value than closed cell.

 

[Cord]

That's an interesting code interpretation because paint is permeable.