Styrofoam board vs Dow foam board
- Thread starter Blkctsv05
- Start date
Highbeam
Well-known member
Both have the same R-value. Your question is really EPS vs. XPS. Most XPS is of higher density than EPS, though you can buy higher strength EPS if you want. XPS costs way way more than EPS. With this topic, there are lots of old wive's tales. Both foams are rated for the same uses under slabs, in walls, in roofs, etc.
Kevin C
Well-known member
Similar R value.... 1" Dow = R5. 1" EPS = R4. If the price is right its not an issue.
Or should I sale this make a 2x4 frame use a vapour plastic on the back of the 2x4 against wall an use r13 in the frame then cover the front. Or use this eps 1/2 on the back of frame against wall an r13 the frame an cover front would that be over kill? it would keep the heat in an also a lot more money but I'm thinking of selling the eps sheets an getting the iso foam board 1/2 or 1" an glueing it to wall
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tdkkart
Well-known member
Huh???
Sorry, but I read this about 5 times and still don't have a clue WTF you said??
rburke65
Well-known member
It all depends on how much money AND time you have. How high of an R you are looking for. It would also help if we knew what you are trying to achieve AND where you live. You probably don't need any of this in Potra Rico. AND you should buy a few commas to use in your sentences. Very hard to read. IMO
It's just a single car garage I do work in. I'm looking to cover the blocks to keep heat inside than loose threw the walls I have a hot dawg 45k an a space ray radiant tube heater. If I do all the walls it should stay more on a comfort zone an have the heaters run less right? I'm also doin ceiling in r19 an 1/2 eps right now I only have 1/2 foam bored an that's at 10.5 ft I'm dropping ceiling to 9ft.
XPS vs EPS is more complicated than first glance as XPS R value degrades to R 4 per 1" over time and then stabilizes,EPS is fairly stable from the start. I would use the foil faced that you have because 1 you have it and 2 it will work as well as anything for your application. Get a Dow pro gun from the local lumber yard and a couple of cans of adhesive and glue it up. It will cut the amount of heat going thru the walls by at least 1/2 so by all means have at it. Also the foil will reflect the radiant heat as well. I would leave the ceiling as high as possible as you may need the extra room some day.
Kevin C
Well-known member
This is the XPS that I'm using... Seems like they are pretty confidant that it will hold its R5 value.
From the Dow site: Most STYROFOAM™ Brand Extruded Polystyrene Foam Insulation products have a stabilized R-value of 5.0 per inch. Unlike other insulation materials, the R-value for STYROFOAM™ Brand Extruded Polystyrene Foam Insulation does not appreciably decrease over time.
http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/721/related/1/session/L2F2LzEvdGltZS8xMzU3ODcyNjk1L3NpZC9UWk5lXy1mbA%3D%3D
I can only go 10ft cause the main I beam ceiling is 10.5-11.5 an beam in middle so I wanna lower it so its level. Also I can use r19 an the eps to keep more heat in an lower ceiling meaning won't lose much heat plus my hot dawg will be lower. How much does the glue run? I'm also gonna layer it in 2s so 1" thick first layer I'm gonna lay 4ft h 8ft long then 2nd layer 8ft upright to make sure the **** joints are covered
Glue is about 15 a can and the gun is 45... last job I used 5 cans for 80 sheets. I apply the adhesive for 4 to 6 sheets so it sets up a bit and then make sure you get good contact. you can also use the gun for spray foam for cracks. Are you using 2 bys so you can install drywall or plywood?
I would sell the hot dawg and keep the spaceray as it will be more efficient and comfortable, you wont need both. What model spaceray do you have? Can it be installed bellow 10'?
I would sell the hot dawg and keep the spaceray as it will be more efficient and comfortable, you wont need both. What model spaceray do you have? Can it be installed bellow 10'?
I would look some where other than marketing claims to get real world long term performance. 20 years ago when I started installing radiant heat as a contractor I believed that XPS was the only product that worked for slab insulation and below grade applications. Not so, EPS and XPS both have their place and EPS is undersold.
http://en.wikipedia.org/wiki/R-value_(insulation)
http://www.foam-control.com/downloads/brochure/foam-face-off-xps-architect.pdf
and there is this concerning water absorption http://www.foam-control.com/downloads/brochure/foam-face-off-xps-architect.pdf
They both are available in different densities.. http://www.buildings.com/Portals/1/images/Magazines/0609/B_0609_SB_ENVELOPE_lg.jpg
Most commercial projects that involve architects and engineers spec EPS as it is generally the most cost effective product.
Kevin C
Well-known member
So your telling me not to look at marketing claims for XPS and then provide a link to a marketing brochure for EPS?
According to the tests I saw, based on ASTM C518, the R value of XPS was at least 5.5 per inch after four years of aging.
Seems like there is a bit of headroom.
I do understand that one reason that XPS performs better is because the blowing agent has a higher molecular weight and that the blowing agent will diffuse out over time.
I also know DOW tested its new CO2 blowing agent and then increased its warranty for R value from 25 to 50 years for 1.5" and thicker foam.
They increased the warranty of the 1 to 1.5" material to 30 years. My take is that the thicker material is more resistant to diffusion (seems reasonable) and DOW factored that into their warranty.
Based on the LTTR test report that I saw as well as a bunch of other info, I think that DOW's claims are believable (no more than a 10% loss below the rated value in 50 years). It also seems like they pad the rated value by 20%. For the first 20 or so years the insulation should perform above spec, at 50 years it's within 10%.
Based on Home Depot's prices, the XPS's dollar to R value is low until you get to the 2" material. Below that the EPS is a much better value. Basicly 1" XPS does not seem like a good deal, better to get a bit thicker EPS to get to a certain R value.
At 2" the Dow XPS is about 10% more expensive ( based on R value, not total price) than EPS, but it offers about 20% better performance.
I agree that both have their place (I have been using both for my projects).
Based on a lot of reading, I still feel that R5 per inch of XPS is a valid number.
Here the cost difference is at least 80% per inch and about 40% on actual r value. Last job had 1.5" eps $12 and xps at $20 per sheet, and 2" eps at $13. I've got 3 quotes for xps on 85 sheets and they range from 20 to 22. There are a lot of local producers of eps scattered through out the country. I do though use both depending on the availability of higher density eps at the time.So your telling me not to look at marketing claims for XPS and then provide a link to a marketing brochure for EPS?
According to the tests I saw, based on ASTM C518, the R value of XPS was at least 5.5 per inch after four years of aging.
Seems like there is a bit of headroom.
I do understand that one reason that XPS performs better is because the blowing agent has a higher molecular weight and that the blowing agent will diffuse out over time.
I also know DOW tested its new CO2 blowing agent and then increased its warranty for R value from 25 to 50 years for 1.5" and thicker foam.
They increased the warranty of the 1 to 1.5" material to 30 years. My take is that the thicker material is more resistant to diffusion (seems reasonable) and DOW factored that into their warranty.
Based on the LTTR test report that I saw as well as a bunch of other info, I think that DOW's claims are believable (no more than a 10% loss below the rated value in 50 years). It also seems like they pad the rated value by 20%. For the first 20 or so years the insulation should perform above spec, at 50 years it's within 10%.
Based on Home Depot's prices, the XPS's dollar to R value is low until you get to the 2" material. Below that the EPS is a much better value. Basicly 1" XPS does not seem like a good deal, better to get a bit thicker EPS to get to a certain R value.
At 2" the Dow XPS is about 10% more expensive ( based on R value, not total price) than EPS, but it offers about 20% better performance.
I agree that both have their place (I have been using both for my projects).
Based on a lot of reading, I still feel that R5 per inch of XPS is a valid number.
Looks good Blkctsv05 A little insulation malkes a huge difference when compared to none. The foil and the radiant go hand in hand.
Finished that side started other side 1 layer an stood the sheets up on garage door to reflect the heat. The heater ran for say 40 mins an shut off got up to temp quicker an I'm not even done! Can't wait to do ceiling be even better you can feel the heat reflecting off the boards feels great. I need ideas on making a footer or if I have extra left I can do It with the sheets
