Insulation confusion

[OldSchool500]

I'm having a (my dream!) 60x120 shop built soon, wood poles and steel roof trusses. I'm not sure what I want to do about insulation, it really depends on the price. Am I correct that they often use a fiberglass blanket under the steel siding? I assume this is the cheapest option?

I would love to do all spray foam but it's such a big place, maybe a "flash and batt" system would be more economical? I like to have it well sealed inside, I'm in very humid NC. I don't think the fiberglass blanket would be good for that. I hope for the whole place to be partially conditioned, and lots of dehumidification.

Also, would it be better to put more money into the ceiling insulation over the walls? I think that would need to be all spray foam, it would be a PITA to do any other way. Might be worth the cost.

I do not need super high R value in this climate. I'm installing a geothermal heat pump and a complete off grid solar system, so running more heating/cooling equipment might be cheaper vs more insulation. There is no monthly bill. I also have unlimited firewood for the winter, I'm thinking maybe two large wood stoves would be nice in the shop.

Thoughts?

 

[u2slow]

When I was quoted for a steel building, it was highly encouraged to get insulation from the beginning because it gets installed between components on assembly - something that's impossible to do well later (so they say).

Avoiding condensation in a metal building would be my #1 reason for insulation.

Fwiw, I decided on a woodframe build in the end. One contractor and paid as I went.

 

[Firebrick43]

If your doing wood poles and girts on the outside face I would have them install 1.5” XPs foam between the girts and before putting the steel R panels on. This will seal the envelope.

Then you can add cheaper fiberglass blanket batts or spray foam on that instead of the steel and not possible have issues that spray foams can cause directly against metal

A ventilated attic with insulation above a ceiling on the bottom chords of the trusses is usually always the highest performance per dollar.

 

[dcg9381]

Insulation is somewhat "regional" with how they do it, so I always defer to regional best practices. Cold states are different than hot states.

1) Yes, building manufacturers often will sell an "insulation package" that is a blanket under siding. This is usually cheapest.
2) Spray foam (IMHO) is the best thing you can buy. It's also the most expensive type of insulation. It's downside is that it will likely "void" your steel warranty on panels (not that they'd honor a warranty with any sort of an install leak anyway). The real downside is if you replace directly sprayed panels, you have to re-spray.
3) Some people will put moisture barrier under the steel and spray that. This prevents the problem where you lose your insulation if you lose your panels, but I have seen spray foam fail on moisture barriers. At least twice. Once it was the foam adhesion. The other time it was the barrier itself that cracked.
4) Bat insulation will be fine. As would most traditional insulation types. Absolutely.
5) Consider foam panels in conjunction with above.

My favorite bang for the buck? 1" of closed cell spray foam, frame the inside, add bat or cellulose insulation to desired R-level.

One super thing about spray foam, they can do that entire building in a day. No trying to hang insulation from the ceiling. I'd almost "just" have the roof deck done as I can handle the sides pretty easily.

I do not need super high R value in this climate. I'm installing a geothermal heat pump and a complete off grid solar system, so running more heating/cooling equipment might be cheaper vs more insulation. There is no monthly bill. I also have unlimited firewood for the winter, I'm thinking maybe two large wood stoves would be nice in the shop.

What climate in particular? Geothermal sounds northern climate. You do want to focus your R value on the roof deck. But I get it, if power is "free" and heating (geothermal) is free also, you could potentially decrease insulation. That's going to be a hard one to calculate.

I like to say "it's batteries that run electric, not solar". Unless you have net metering (grid is your battery). Doesn't matter how many solar panels you have if you can't store the power or sell it back at a reasonable rate. Do not use kWh of solar as your guide. Solar is a bell curve. You have to store it to optimize it. And storing it is expensive. Modern LiFePO4 is great, but not cheap.

My other "consideration" is the for a "partial use" building, I don't insulate to the recommended spec. No reason for me to spend $10k on spray foam, when I can get by with $5k in spray foam and a little higher HVAC BTU for a building that I only cool for a few hours on weekends.... Sure, it costs a little more to keep cool on the weekends I use it, but it takes a LOT of weekends to make up the cost difference.

 

[WisJim]

Sealing the building is probably as important as the amount of insulation. Good sealing will mean that humid outside air won't be coming into the building as fast and will make the dehumidification easier

 

[pcmeiners]

Aside from the insulation on the metal pay attention to the slab particularly the vapor barrier.

 

[OldSchool500]

Insulation is somewhat "regional" with how they do it, so I always defer to regional best practices. Cold states are different than hot states.

1) Yes, building manufacturers often will sell an "insulation package" that is a blanket under siding. This is usually cheapest.
2) Spray foam (IMHO) is the best thing you can buy. It's also the most expensive type of insulation. It's downside is that it will likely "void" your steel warranty on panels (not that they'd honor a warranty with any sort of an install leak anyway). The real downside is if you replace directly sprayed panels, you have to re-spray.
3) Some people will put moisture barrier under the steel and spray that. This prevents the problem where you lose your insulation if you lose your panels, but I have seen spray foam fail on moisture barriers. At least twice. Once it was the foam adhesion. The other time it was the barrier itself that cracked.
4) Bat insulation will be fine. As would most traditional insulation types. Absolutely.
5) Consider foam panels in conjunction with above.

My favorite bang for the buck? 1" of closed cell spray foam, frame the inside, add bat or cellulose insulation to desired R-level.

One super thing about spray foam, they can do that entire building in a day. No trying to hang insulation from the ceiling. I'd almost "just" have the roof deck done as I can handle the sides pretty easily.


What climate in particular? Geothermal sounds northern climate. You do want to focus your R value on the roof deck. But I get it, if power is "free" and heating (geothermal) is free also, you could potentially decrease insulation. That's going to be a hard one to calculate.

I like to say "it's batteries that run electric, not solar". Unless you have net metering (grid is your battery). Doesn't matter how many solar panels you have if you can't store the power or sell it back at a reasonable rate. Do not use kWh of solar as your guide. Solar is a bell curve. You have to store it to optimize it. And storing it is expensive. Modern LiFePO4 is great, but not cheap.

My other "consideration" is the for a "partial use" building, I don't insulate to the recommended spec. No reason for me to spend $10k on spray foam, when I can get by with $5k in spray foam and a little higher HVAC BTU for a building that I only cool for a few hours on weekends.... Sure, it costs a little more to keep cool on the weekends I use it, but it takes a LOT of weekends to make up the cost difference.

Interesting...I did not know you shouldn't foam the steel. Does that cause rust or something? If I have them use the fiberglass blankets, can I still spray foam over that later?

I want the ceiling to stay open (That's why I'm using steel rafters) and I think insulation blanket or foam are the only options. How would I keep spray foam off the ceiling metal if there is no insulation blanket? This is definitely something that will be finished over time, and most of the walls will be framed out and covered.

I'm in North Carolina. The property I am buying has a really big creek, that is what I will be using for geothermal. It's actually around the same cost or cheaper to build an entire solar system than to bring in power around 800 feet. Right now I'm looking at a 25kw inverter and probably about 100kwh in battery storage.

Thanks!

 

[dcg9381]

Interesting...I did not know you shouldn't foam the steel. Does that cause rust or something? If I have them use the fiberglass blankets, can I still spray foam over that later?

There are members that disagree with me and have said that they have experienced rust due to closed cell foam holding water against the steel.

I think that's possible.

But I'm in the south. Water evaporates fast. I know of 10+ steel structures and no issues. Mine, even with a leak - with open cell, we find it and fix it. Leaks happen.

Steel suppliers want to sell whatever they can sell. Including insulation. The reality is that their "warranty" covers the steel and it's not going to cover ANY install where there is water intrusion, including foam or their "blanket". And it only covers the steel. Who gives a S what an 8 x 4 R-panel costs. The money is in getting it up there, replacing it, etc. So I totally throw away their "voids your warranty" as it's all ********. I can afford a new panel. It's the cost of the install and drama that isn't under warrantt,

The downside of foam is that if you replace the R-panel you're replacing the foam. I get that. 100%. Hail is a issue here.

I want the ceiling to stay open (That's why I'm using steel rafters) and I think insulation blanket or foam are the only options. How would I keep spray foam off the ceiling metal if there is no insulation blanket? This is definitely something that will be finished over time, and most of the walls will be framed out and covered.

Depends on what you mean by "open". For me, I want the foam on the metal. That's how I roll.
To answer your question, there are various means of "suspending" fiberglass on an un-framed ceiling, etc. But sounds like a lot of uncomfortable work to me. If you are not going to look at the roof deck, you can always finish it out later.

I'm in North Carolina. The property I am buying has a really big creek, that is what I will be using for geothermal. It's actually around the same cost or cheaper to build an entire solar system than to bring in power around 800 feet. Right now I'm looking at a 25kw inverter and probably about 100kwh in battery storage.

We are talking the same language now. A 24kW inverter is massive. 100kWh is about 10x what I have in my "cargo trailer" and 3x what we have in EV "recharge" vans. I'd love to hear what they are charging you to do this and the tech they are using for it (brand). PM me. If you are rolling your own, happy to help.

Here's where I run out of steam. Up north (perhaps NC qualifies) with tightly insulated structures (foam insulated) you have humidity issues so they install ERV or HRV systems.

I know nothing about practical use of geothermal. I'd love to do it. Here, when I want to heat at "low power" we use propane, but it incurs moisture.


Are you in this structure "full time" because that changes the math?

 

[OldSchool500]

There are members that disagree with me and have said that they have experienced rust due to closed cell foam holding water against the steel.

I think that's possible.

But I'm in the south. Water evaporates fast. I know of 10+ steel structures and no issues. Mine, even with a leak - with open cell, we find it and fix it. Leaks happen.

Steel suppliers want to sell whatever they can sell. Including insulation. The reality is that their "warranty" covers the steel and it's not going to cover ANY install where there is water intrusion, including foam or their "blanket". And it only covers the steel. Who gives a S what an 8 x 4 R-panel costs. The money is in getting it up there, replacing it, etc. So I totally throw away their "voids your warranty" as it's all ********. I can afford a new panel. It's the cost of the install and drama that isn't under warrantt,

The downside of foam is that if you replace the R-panel you're replacing the foam. I get that. 100%. Hail is a issue here.


Depends on what you mean by "open". For me, I want the foam on the metal. That's how I roll.
To answer your question, there are various means of "suspending" fiberglass on an un-framed ceiling, etc. But sounds like a lot of uncomfortable work to me. If you are not going to look at the roof deck, you can always finish it out later.


We are talking the same language now. A 24kW inverter is massive. 100kWh is about 10x what I have in my "cargo trailer" and 3x what we have in EV "recharge" vans. I'd love to hear what they are charging you to do this and the tech they are using for it (brand). PM me. If you are rolling your own, happy to help.

Here's where I run out of steam. Up north (perhaps NC qualifies) with tightly insulated structures (foam insulated) you have humidity issues so they install ERV or HRV systems.

I know nothing about practical use of geothermal. I'd love to do it. Here, when I want to heat at "low power" we use propane, but it incurs moisture.


Are you in this structure "full time" because that changes the math?

I'm not much concerned about warranty either, I can actually buy the metal for cheaper without a warranty, I think I might do that. (Imagine trying to file a claim in 40 years - if they are still even open! And I'll be dead!) "As built" the ceiling will be just the underside of the roof metal and some 2x6 purlins, and I don't want to add much more than that. Would open cell be better for the roof? I won't be spending 40 hour weeks working in here, but it will be used most days and I want the temps to stay pretty constant.

I plan on building some smaller rooms inside, like 20x30, so I can work on a car in there and keep the temp real nice. With cheap modern mini splits being so efficient I probably am way overdoing it with geothermal...but that's the kind of thing I like to play with. Getting a mini excavator too so I can dig trenches all over for pipes and wires.

I didn't go into great detail with the power company, but it was looking like $8-10k to have high voltage brought in, a 25kva transformer, and some poles...or pay even more to bury it. I strongly dislike the PoCo here, they want $43/month just for the privilege of connecting - on top of all the other fees and taxes. The bank says I have 1 year to get that all sorted out, nothing is set in stone yet. I LOVE the fact that I get to choose split phase or 3 phase, even 480v if I want, depending on the inverter. Somewhere between 10 and 20kw in solar panels for charging. Being able to waste energy for free would be amazing!

For temp construction power I have an old pickup with 10kwh of batteries, a 6kw split phase inverter, and a 3500w generator in the back that will start automatically when the batteries need charged. I can also get about 1.5kw charge out of the alternator at idle if needed.

It's really hard to explain to other people my hobbies are electricity and air conditioners. LOL

 

[Dragfluid]

I want the ceiling to stay open (That's why I'm using steel rafters) and I think insulation blanket or foam are the only options. How would I keep spray foam off the ceiling metal if there is no insulation blanket? This is definitely something that will be finished over time, and most of the walls will be framed out and covered.

I'm guessing that you want the ceiling open so you can "store" stuff in the rafters?
Most people that say that, put a bunch of stuff up there and ten years later, all that stuff is still up there without it ever being touched. It's better to have a ceiling and have insulation on it. I recommend cellulose.
For the issue of not letting the foam make contact with the steel walls, a layer of house wrap is the thing to have. In the pole shed that I built, I used dense pack cellulose. Tons cheaper than foam, still cheaper than fiberglass, and better fire protection.

 

[kaymccampbell]

If you do decide to do spray foam up high, I can recommend a layer of the lightweight roll fence between the purlins and below the moisture barrier. It provides attachment for the foam, without depending on the foam sticking to the slippery plastic and avoids the foam directly on tin issues.

 

[NUTTSGT]

I do not need super high R value in this climate. I'm installing a geothermal heat pump and a complete off grid solar system, so running more heating/cooling equipment might be cheaper vs more insulation. There is no monthly bill. I also have unlimited firewood for the winter, I'm thinking maybe two large wood stoves would be nice in the shop.

Thoughts?

Insulation is an investment. It'll continually pay you back on the original investment. You'll use less electricity heating or cooling the structure, even if you're using solar, that stored power will last longer or be used elsewhere.



While you may not be in there much now, it'll be cheaper to insulate now rather than go back in 10 years and tear everything back out to redo the insulation. Futureproof.

 

[Chuckster in NJ]

Insulation is an investment. It'll continually pay you back on the original investment. You'll use less electricity heating or cooling the structure, even if you're using solar, that stored power will last longer or be used elsewhere.



While you may not be in there much now, it'll be cheaper to insulate now rather than go back in 10 years and tear everything back out to redo the insulation. Futureproof.

THIS^
Spray foam may seem expensive now but if you stay in your home for 10 years it is the least expensive. Invest in the future now…….. You will thank me later.

TIP! Listen to your local insulation contractors because they are familiar with the local area.

 

[dcg9381]

THIS^
Spray foam may seem expensive now but if you stay in your home for 10 years it is the least expensive. Invest in the future now…….. You will thank me later.

TIP! Listen to your local insulation contractors because they are familiar with the local area.

I'm 100% down with this advice, but I don't follow it for shops that are "part time use". Recommended R levels are set for "residential" use and full time heating and cooling. Insulation WILL pay back, but when you're heating and cooling the shop 1-2 days out of 7 that payback can be a loong time....

Agree, insulation techniques are regional. What we do it TX won't necessarily work well for up north.

 

[u2slow]

Insulation is an investment. It'll continually pay you back on the original investment.

Mine has paid back very little in 10 years because I do not have heating or cooling in place.

But your are right about strategy - no way would I close up the walls without it. I used R22 batts. There's no ripping my shop apart later - full of stuff and built-in features now.

 

[NUTTSGT]

Mine has paid back very little in 10 years because I do not have heating or cooling in place.

But your are right about strategy - no way would I close up the walls without it. I used R22 batts. There's no ripping my shop apart later - full of stuff and built-in features now.

You may not be heating and cooling currently but that may change.

What it is doing now is preventing wide temp swings and preventing rust from forming when stuff sweats during drastic temp swings.

 

[u2slow]

What it is doing now is preventing wide temp swings and preventing rust from forming when stuff sweats during drastic temp swings.

Good point. Even with an open ceiling and soffits, I still often notice a temperature and humidity change from outside to inside.

 

[OldSchool500]

I'm guessing that you want the ceiling open so you can "store" stuff in the rafters?
Most people that say that, put a bunch of stuff up there and ten years later, all that stuff is still up there without it ever being touched. It's better to have a ceiling and have insulation on it.

You think I'm building a 7200sq ft warehouse so I can hide things in the rafters? Open ceiling, with a fully conditioned space is much better. I want the height inside that metal joists offer, using the angled space all the way up to the roof with a forklift. I am only allowed to build 35' tall at the peak, and I will be within inches of that with a tall wide roof.

Part of this is so all the hot air rises in the summer, and can be sucked out at the highest point. There will be several ceiling fans too, mostly for winter. The roof will be silver to reflect as much as possible.

Insulation is an investment. It'll continually pay you back on the original investment. You'll use less electricity heating or cooling the structure, even if you're using solar, that stored power will last longer or be used elsewhere.



While you may not be in there much now, it'll be cheaper to insulate now rather than go back in 10 years and tear everything back out to redo the insulation. Futureproof.

Who is this you think is paying me for insulation? I am installing a vastly oversized solar system so I can waste energy like it's 1955. Solar panels and batteries at this time are alarmingly cheap. 20kw in solar panels will provide me about 100kwh per day, and the panels themselves only cost $0.34/watt. I'm unlikely to use even half of that, but it's all getting installed so there is plenty even on cloudy days. My old shop was 50x100, and I did not heat or cool, but I only used about 10kwh in a day. It was in a very different climate.

In the winter I will be burning wood and I have an unlimited supply of nice hardwood. It gets into the teens for a few months in the winter, but we don't have a frost line.

I think I would be fine with a thin fiberglass blanket, but that could never seal the place like foam. There definitely will be an ERV for ventilation and an industrial size dehumidifier. It is currently 2:30AM, it's 78 degrees and 92% humidity outside. This is 7 months of the year. Temperature differential is not that bad, but the humidity is a *****. I agree the ceiling is not something I want to finish later, the walls however will take longer.

Does anybody have a picture of steel siding/roof rusted out from spray foam? I tried google but could not find an actual example. (Please let's not argue, I would just like to see a pic)

 

[OldSchool500]

Does anybody have a picture of steel siding/roof rusted out from spray foam? I tried google but could not find an actual example. (Please let's not argue, I would just like to see a pic)

This is funny. Spray foam DOES NOT cause metal to rust! It does not "trap" moisture beneath it, it is the moisture barrier. It is standard practice for metal building builders to spray directly on the metal. There is no other way to seal better. It also deadens noise and stiffens up the panel.

I've been researching for hours, I can't find a single, REAL example of this being an issue, and not a single photo. The only thing I could find worrying about foam in relation to a metal building is doofuses on this website screaming the sky is going to fall if you do so. (And they have no actual experience of such to share)

This is a good read for anybody that might find this in a future search:

Can You Use Spray Foam on Metal Buildings?

Does your client have a metal building that experiences high energy costs and poor insulation? Find out whether you can use spray foam on metal buildings.

sprayfoamsys.com

LOL! Typical forums...