Spray Foam VS Fiberglass for SAME price!?

[Repsolracer22]

Ok, so we've beat to death plus & minuses of spray foam and fiberglass as well.

At this point Ive decided against spray foam for the whole 40x60 building because its just too expensive. So I think we're going traditional blown up in ceiling. But the walls may be a different story

Spray foam Price for walls. 2inches thick closed cell 2lb density (2180sqft) - installed $3700

R19 6in thick fiberglass on walls with white vinyl backing. Installed $3200

So to insulate the walls is about the same price. So what im wondering is what people would choose if they had this option. For basically the same price ....

2 inches of closed cell foam or 6in of fiberglass.

(yes i know people do foam & fiberglass on the walls together sometimes, but that's not what im asking here)

 

[neogenesis2004]

Does 2in of 2lb foam = R19?

I'd go with whatever has the most R personally as heating/cooling costs will be forever. Are you doing conduit electrical, etc.... so you would get a good seal across your building envelope even with fiberglass?

 

[Repsolracer22]

Does 2in of 2lb foam = R19?

I'd go with whatever has the most R personally as heating/cooling costs will be forever. Are you doing conduit electrical, etc.... so you would get a good seal across your building envelope even with fiberglass?

nothing is going to seal quite like spray foam. closed cell stuff is vapor, air, and moisture barrier. its rigid. its nice.

1 inch of spray foam is about R7. So 2in would be R13/14. However, it seals out all air 100%. Fiberglass doesn't do that. Fiberglass is good, but foam is best. Id estimate that an R14 foam is fairly equivalent to an R19 fiberglass.

But just wanted to see what everyone thought

 

[Tim M]

I can't recall the exact numbers since it has been a few years but I was told by an engineer that 70%(or so) of heating/cooling expense is determined by the roof insulation.

When I insulated my detached garage I used 3" of closed cell directly on the roof deck followed with R-19 fiberglass batts. On the walls(2x6) I used 1.5 " closed cell with a 3" thick batt (r13 if I recall correctly).

And as other posters mentioned the closed cell foam has the added benefit of strengthening the structure. It also cuts down on noise transmission.

Tim

 

[Thumper68]

I would (and wish I had) go with the foam, just to seal the structure, if you can keep the cold out it is much cheaper to keep the heat in.

 

[dwegner]

I am in the same position as you. I have a 30x60x14 post frame that I am putting white metal ceiling and walls in. I am gonna 4" open cell in the walls and 12" of blow in fiberglass in the ceiling. I feel that the sealing qualities of the foam are gonna overcome the R5 difference in the walls and with R30 worth in the ceiling it should be comfortable and somewhat economical to condition. I'm looking at about 4000 for insulation according to the quote. The only questions I am wondering is noise factor with nothing on the roof metal to dampen noise and do I need to put plastic between rafters and ceiling metal for a vapor barrier there.

 

[Scsmith42]

A friend of mine recently built a 3 story shop and model train museum, and he used a hybrid approach that was recommended by his insulation company that seems to have provided him with the best performance for the $.

The building is framed with 2 x 6's and standard wall sheathing. The walls and attic have 1" of closed cell spray foam applied directly to the sheathing, and then 3-1/2" fiberglass batt insulation installed in the walls, leaving about a 1" air gap between the fiberglass batts and the spray foam. As I recall the attic has 2 x 8's for the top chords on the rafters with 1" of spray foam and 5-1/2" of fiberglass batts.

He is cooling the entire building with mini-split HVAC systems, and he ran into a problem last summer where the air conditioners do not run enough to dehumidify everything (yet maintaining mid 70's temperature).

Thus far it has been extraordinarily effective, and it only cost a little bit more than standard fiberglass insulation. The same company did both the spray foam and the batts, so they only had one mobilization and one crew on site.

My personal shop has a very unconventional approach to insulation which allows me to cool a 5,300 sq ft building with only 2-1/2 tons of air conditioning.

 

[James-W]

I would go with the spray foam. They say 2 inches but I would bet it will end up being a bit more than that anyway. It is hard for them to get exactly 2 inches and they don't want to spray in less than what they said they would. You will most likely end up with close to R-19 anyway and the building will be well sealed up against air penetration.

 

[nicksL98]

This is good to see the mild cost difference.

 

[yeldogt]

For $500.00 get the foam --- doing everything correctly the batts still leak .. and if you use plastic you risk moisture. The closed cell foam will make you happy.

 

[stikman56]

What's the stuff like to deal with if you find yourself tearing into a wall later on? Seems like it would be a nightmare for any separation of it and the wood, plumbing, electrical etc.

 

[dynahoe]

a spray foam rep told me that metal buildings will sweat between the insulation layer and the metal,the spray foam adheres directly to the metal and seals out everything including insects and rodents,and ground water.i plan to use spray foam if i ever get to build

 

[rburke65]

I think I'd foam it for the price difference.

 

[walrus]

Not only will the foam perform better, it will glue that place together and stiffen it up. Foam without question is the way to go

 

[Notgrownup]

Only problem I have with foam is if you ever had to go into the wall for any reason...that is why I m doing fiberglass, plus it doesn't get cold here but it sure gets hot...r19 fir me will work, plus the drywall will seal it up good.
Plus I can go at my own pace with fiberglass...buy a little bit as I go.

 

[vmusch]

I had my new 38x48 12 foot side walls steel hybrid building insulated with spray foam. During the last cold snap (temps in the teens for several days) the coldest inside was 40. I used a small propane buddy heater brought it up to 60 in one hour. The three garage doors are roll ups, insulated. I cannot believe how warm this building is staying. I have started to install a wood burning furnace I have the hole for the chimney cut. My plan was to have the furnace installed before the cold weather, I started the install on a Monday when it was 70 the next day it rained and stayed cold for over a week I could not get on the roof to install the rubber boot. When I needed to cut through the foam for the triple wall pipe it was not problem, used a hack saw blade, cut the square and pulled down the block of foam. For smaller areas that I need to access, I have cut the foam pulled it out and replaced it with spray foam from a can. It is that easy, no way you could ever touch fiberglass insulation this easy. IMO spray foam. As you will find out every expert will have an opinion, it amazed me how much each one conflicted.

 

[theoldwizard1]

nothing is going to seal quite like spray foam. closed cell stuff is vapor, air, and moisture barrier. its rigid. its nice.

1 inch of spray foam is about R7. So 2in would be R13/14. However, it seals out all air 100%.

The best is a combination of the 2 ! Spray foam all corners and joints. Then install fiberglass.

 

[bcradio]

The best is a combination of the 2 ! Spray foam all corners and joints. Then install fiberglass.

I could agree with this... I would worry with full spray foam that your building would not be able to breath and you would have problems with sticking doors and such

 

[stangkid14]

Now I am really confused. I was reading here that tyvek on the outside is a good idea. I guess it isnt if you are doing spray foam. You wouldn't want to foam the tyvek

 

[curiousB]

Yes but is there additional cost to fireproof the foam that you wouldn't have with the fiberglass? I don't think you can leave foam exposed.


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[Repsolracer22]

Yes but is there additional cost to fireproof the foam that you wouldn't have with the fiberglass? I don't think you can leave foam exposed.


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maybe do 1.5" on walls and 3" on roof. hell, that may be all i need ...

as far as the building "breathing", i dont know. I mean there's 2 garage doors and a man door so it will leak a little i suppose. which is ok

 

[DEnd]

I could agree with this... I would worry with full spray foam that your building would not be able to breath and you would have problems with sticking doors and such

Buildings don't need to breathe, they are not alive.

They do need to be able to dry however. Foam limits drying to either the inside or the outside. Drying to the inside is taken care of by HVAC equipment. Drying to the outside is taken care of by airflow across moisture absorbing materials, and the best way to do that is with a rain screen gap, or not having any moisture absorbing materials on the outside side of the foam.

 

[bcradio]

Buildings don't need to breathe, they are not alive.

They do need to be able to dry however. Foam limits drying to either the inside or the outside. Drying to the inside is taken care of by HVAC equipment. Drying to the outside is taken care of by airflow across moisture absorbing materials, and the best way to do that is with a rain screen gap, or not having any moisture absorbing materials on the outside side of the foam.

Absolutely False statement!

They certainly do need to breathe. Yes, this can be handled by the HVAC system assuming you are home and regularly use it. If you are away for long periods of time with the HVAC system off, you do need other methods to help your home breathe. That is if you don't want to deal with the side effects.

maybe do 1.5" on walls and 3" on roof. hell, that may be all i need ...

as far as the building "breathing", i dont know. I mean there's 2 garage doors and a man door so it will leak a little i suppose. which is ok

I would say that is sufficient also.

 

[DEnd]

Absolutely False statement!

They certainly do need to breath. Yes, this can be handled by the HVAC system assuming you are home and regularly use it. If you are away for long periods of time with the HVAC system off, you do need other methods to help your home breath. That is if you don't want to deal with the side effects.

Absolutely not false. In the building world to breathe is to allow air and moisture to travel freely. The entire purpose in having a building is to eliminate and then control air and moisture flow. Living beings in buildings that have well controlled air and moisture flows also need ventilation for those buildings. I'm not a fan of mechanical ventilation, however it is necessary for building longevity and safety. It also has benefits for human health, even in buildings that don't have well controlled air and moisture flows. I'd much rather see a passive ventilation scheme employed, but I have yet to find one that actually works as well as mechanical ventilation.

 

[bcradio]

Absolutely not false. In the building world to breathe is to allow air and moisture to travel freely. The entire purpose in having a building is to eliminate and then control air and moisture flow. Living beings in buildings that have well controlled air and moisture flows also need ventilation for those buildings. I'm not a fan of mechanical ventilation, however it is necessary for building longevity and safety. It also has benefits for human health, even in buildings that don't have well controlled air and moisture flows. I'd much rather see a passive ventilation scheme employed, but I have yet to find one that actually works as well as mechanical ventilation.

I do agree with you that good HVAC is critical to a building, but you aren't getting what I am saying about breathing. There is a huge difference between having full open airflow (like it is outside) and having some airflow in your house so the inside air does not become stagnant. HVAC systems are not running 24/7 usually and therefore you need some airflow through the house (breathing) so that the air does not become stagnant.

 

[cruzzer]

If your worried about being "too tight" you can always get an air exchanger. Super insulated houses use them, it basically vents out old air for new air but passes the air though a radiator type box that the air leaving heats(or cools) the air entering. Then the air entering is 'fresh' but close to the same temp.

 

[Jack3]

I spray foamed a 60x100 shop/office. The roof was done in 1996. The walls in 2012 when we put in radiant-heat floor. It tightened up the building. Very energy efficient. I like it and would do it again.