Which styrofoam / rigid insulation to use?

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Posted by: from Ottawa
10/4/2012 at 3:36:59 PM


I posted a question here and mentioned that I planned to use sprayfoam in my basement finishing project, and one of the answers suggested using styrofoam / rigid insulation instead. In theory, I would be gluing/attaching it to the cinderblock wall and then framing for drywall on top of it.

I started to read up on it. It seems to have really good R-value for the price, but how do I know which kind to buy? There white, blue, pink and green of different thicknesses? Which is 'better' ?

What would you use to stick it to the cinderblock wall? Construction adhesive or contact cement or something else? Do I need a vapour barrier with it?

Thank you

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Branden from Tut's Renovations in Lyn
Date/Time10/4/2012 at 4:10:46 PM


You can actually buy 2" thick pink styrofoam insulation that has slots in it from the factory that you put a aluminum Chanel in and tapcon it to your wall, no adhesive needed and actually works very well.

If money is not a object I personally would go spray foam though.

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Date/Time10/4/2012 at 4:55:02 PM

The best way to go is with one inch high r value per inch rigid foam. glued on to the wall tape the joints. The foam act as a vapour barrier. Frame the wall in front of that and add more insulation between stud like rox all. No other barrier needed. Dont forget to protect the bottom plate on concrete.

Sprayed on foam would be the best but to costly compared to rigid foam and roxal.

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Dave from 360renos in Navan
Date/Time10/5/2012 at 7:05:33 AM

Good Morning Andy,

You may also want to investigate having your insualtion level up to current 2012 Building code which is R20 for basements.

A product by Roxul call Comfort board has an R value of 6. This product against your basement wall then your studded and insualted wall of R14 will offer outstanding insualtion value.

Wether you install rigid styrofoam or Comfort Batt having your studded wall off the cinder blocks will help tremendously with stopping the heat trransfer through the stud wall.



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Marsh's Homes in Bay Roberts
Date/Time10/5/2012 at 9:25:18 AM

There are many different thicknesses and colors, but essentially basically two types. one is extruded polystyrene, the other is expanded polystyrene. expanded is the poly beads commonly white, does not have as good an r value as a piece of extruded (blue stuff) of the same thickness. If your basement is insulated outside we usually go with a 1 inch polybead between your framed wall and foundation. Then batt (loose insulation) between your studs.

By the way, any adhesive that comes in contact with styrofoam is only temporary. there has never been a glue on the planet earth that was made for styrofoam. At least one they're not telling the construction community about. 2 inch extruded (blue one) polystyrene with edges taped is considered a continuous vapor barrier according to the atlantic home warenty program.

Best of luck.!!!

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Andy in Ottawa
Date/Time10/5/2012 at 10:59:57 AM

Hey, thanks guys!

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Jeff from Newson Interiors in Dunrobin
Date/Time10/8/2012 at 2:55:25 PM


Both Dave and Cristopher bring up very good points. After the expense of applying and attaching the rigid foam, (adhesives don't hold) buying and installing fastener systems and sealing the seams, you still only have an r-8. You then still need to insulate your stud wall to achive a resonable r-value (20 is code).

Before you consider spray foam to be too expensive, all of the expenses of doing it the other way. In addition, the joist/rim cavities can be completely sealed/insulated, making a huge difference in total heat/air loss. The walls can be framed, (1" from block wall) wired and plumbed prior to foam installation. The foam will fill between the block and stud wall further decreasing thermal transef through the studs.

When comparing costs, don't forget, your time is worth something, better spent finishing your project.

On another note did you solve your basement window issue?

Hope this helps.

Jeff Newson,

Newson Interiors

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Andy in Ottawa
Date/Time10/9/2012 at 9:52:44 AM

I have to take out my calculator and see how much money I stand to save by not using the sprayfoam. Frankly, if it's a question of a couple hundred dollars I think I will still go with the sprayfoam becasue of better insulation quality and well, my time savings.

Following up Jeff's question regarding my windows, my wife booked an estimate with the company that did other windows in our house and that should be some time this week. Hope it works out - it's often diffcult I find to get fair quotes when you only have a small job. I thknk I have a good idea around what it should cost to have the windows installed, but I think I may have problems when it come to agreeing on a price to enlarge/reduce the size of window openings. I figure it should be "no materials cost" ( I have lots of cinderblocks and mortar) and then I would calculate labour at 30$/hour at about +/- 1/2 day per window. Then maybe a little wear and tear on tools but that ballpark seems fair to me. Oh, I also provide coffee/drinks and snacks cause I like to have them when I work. :)

Does that sound reasonable?

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Date/Time10/22/2012 at 11:23:30 PM

Greetings Andy,

You mention that it is "difficult to get a fair quote when it is a small job". It is difficult for a contractor to get a fair days pay for his service on small jobs. Whether Installing 1 window, or 20 windows, the contractor must first Come to your site, speak to you and go over with you what you want. Assuming you are going the "free estimate" route, This contractor is now running a deficit of at least 2 hours (driving time and on site time). This contractor must now go back to his office, price the window, the labour required, and determine all costs. When this is complete, he must put together an estimate for you, and email, fax, or call you and discuss over telephone. There is another minimum of an hour gone.

Assuming that your contractor is a window and door supplier, his rate is most certainly going to be more than 30$ per hour. He needs to make his wages, he needs to make up his time spent quoting the job ( there is NO SUCH THING as a free quote ). This contractor also has corporate taxes to pay, book keeping expenses, Rent / mortgage / utilities, Fuel, Vehicle expenses, Tool expenses, WSIB, Insurance, and so on and so on.

What I am getting at, is do not beat your contractor up to bad. Get your estimate, look at the job that needs to be done and THEN determine if that is a fair price.

Ask your contractor for a written quote/contract, Identify what is and what is not included, If there is a possibility that additional materials may be required, find out if it is a fixed sum extra, or time and material cost+. If the price and conditions do not seem fair at this point, call two other contractors, and get 2 additional quotes for the same job and compare.

I for one would politely decline your offer of coffee and snacks if there was any hint that my price would need to be dropped as a result of your hospitality. I am polite, informative, and would offer my expertise and experience to a homeowner for free because that's what homeowners expect. If I felt the need to pay for my coffee, I would likely just drive down to the closest coffee shop and buy one.

I doubt this will help you a much in your project, but it is another perspective on what you would consider fair pricing.

Best regards,

Al Walker

Secure Contracting & Renovations Inc.

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