Comments on: Something Blue http://360winnett.com/2009/02/26/something-blue/ Just another Jeremy Bell Sites site Mon, 15 Nov 2010 06:03:42 +0000 hourly 1 http://wordpress.org/?v=3.1 By: Jeremy Bell http://360winnett.com/2009/02/26/something-blue/#comment-338 Jeremy Bell Sat, 07 Mar 2009 18:30:25 +0000 http://www.360winnett.com/?p=702#comment-338 I'll be writing a detailed post about the price of insulation once all of the costs are all finalized, but your $1 per square foot is pretty accurate. For R-20, it was about $3.50 per inch, per square foot. The cost was also affected by the amount of preparation required. For instance, the two exterior overhangs needed to be completely enclosed to ensure the overspray didn't land on anything. I’ll be writing a detailed post about the price of insulation once all of the costs are all finalized, but your $1 per square foot is pretty accurate. For R-20, it was about $3.50 per inch, per square foot. The cost was also affected by the amount of preparation required. For instance, the two exterior overhangs needed to be completely enclosed to ensure the overspray didn’t land on anything.

]]> By: Dan You http://360winnett.com/2009/02/26/something-blue/#comment-337 Dan You Fri, 06 Mar 2009 15:24:29 +0000 http://www.360winnett.com/?p=702#comment-337 thanks for all the info. thanks for all the info.

]]> By: Scott http://360winnett.com/2009/02/26/something-blue/#comment-336 Scott Thu, 05 Mar 2009 22:05:38 +0000 http://www.360winnett.com/?p=702#comment-336 I guess in the end, it really depends on where the guy decides to take measurements from in terms of how much he adjusts, if at all. But if he used the entire exterior frame dimensions, the 25% figure is pretty accurate plus or minus any roof contribution. I guess in the end, it really depends on where the guy decides to take measurements from in terms of how much he adjusts, if at all. But if he used the entire exterior frame dimensions, the 25% figure is pretty accurate plus or minus any roof contribution.

]]> By: Scott http://360winnett.com/2009/02/26/something-blue/#comment-335 Scott Thu, 05 Mar 2009 22:02:49 +0000 http://www.360winnett.com/?p=702#comment-335 I got that 25% from both Holmes on Homes and Ask Jon Eaves and other publications too. But, I thought, why not calculate it? The following calculation is for a 12" wide width of wall in a 2-store home with 10' and 9' ceilings, where the headers are 12" high and there are double 1.5" thick floor and ceilings plates on each floor. This is pretty typical construction. In fact, maybe a bit conservative in terms of framing as headers are often higher than 12". I am excluding the basement as it is a concrete or block wall. The height of the wall will be 10' floor height + 1' header + 9' floor height + 1' header. For a 12" width of wall, the total of the 2 x 12" headers and the 4 x 1.5" double floor and ceiling plates is 30", so the square footage of wood in this 12" width is 12" x 30" = 360 sq in. With studs at 16", for each 16" width of wall you have 1.5" of stud so therefore for each 12" width you have 12/16 x 1.5" = 1.125" of stud. For the 9' and 10' wall heights the total height of the studs, accounting for the floor and ceiling plates is 10' + 9' = 19' the 6" for the 4 plates so that's 18'6". 18'6" x 1.25" = 222" of height. 222" of height x 1.125" taken up by studs = 249.75 sq inches. 249.75 sq in + 360 sq in = 609.75". 12' width of 21' high wall is 12 x (21 x 12) = 3,024 sq in. Of this, 609.75" is taken up by wood. So 609.75/3,024 = 20.2% of wall area. And, that's not even including any corners, sistered or packed studs, jack studs, cripple studs, protrusions or the effect of window or door openings. So the % could easily be 25% or higher. So it looks like the 25% figure is quite accurate. Let me know where my arithmetic is wrong if you find an error in my calculations. I got that 25% from both Holmes on Homes and Ask Jon Eaves and other publications too.

But, I thought, why not calculate it? The following calculation is for a 12” wide width of wall in a 2-store home with 10’ and 9’ ceilings, where the headers are 12” high and there are double 1.5” thick floor and ceilings plates on each floor. This is pretty typical construction. In fact, maybe a bit conservative in terms of framing as headers are often higher than 12”. I am excluding the basement as it is a concrete or block wall.

The height of the wall will be 10’ floor height + 1’ header + 9’ floor height + 1’ header. For a 12” width of wall, the total of the 2×12” headers and the 4×1.5” double floor and ceiling plates is 30”, so the square footage of wood in this 12” width is 12” x 30” = 360 sq in.

With studs at 16”, for each 16” width of wall you have 1.5” of stud so therefore for each 12” width you have 12/16×1.5” = 1.125” of stud. For the 9’ and 10’ wall heights the total height of the studs, accounting for the floor and ceiling plates is 10’ + 9’ = 19’ the 6” for the 4 plates so that’s 18’6”. 18’6” x 1.25” = 222” of height. 222” of height x 1.125” taken up by studs = 249.75 sq inches. 249.75 sq in + 360 sq in = 609.75”. 12’ width of 21’ high wall is 12 x (21×12) = 3,024 sq in. Of this, 609.75” is taken up by wood. So 609.75/3,024 = 20.2% of wall area.

And, that’s not even including any corners, sistered or packed studs, jack studs, cripple studs, protrusions or the effect of window or door openings. So the % could easily be 25% or higher.

So it looks like the 25% figure is quite accurate. Let me know where my arithmetic is wrong if you find an error in my calculations.

]]> By: Colin http://360winnett.com/2009/02/26/something-blue/#comment-334 Colin Thu, 05 Mar 2009 21:06:34 +0000 http://www.360winnett.com/?p=702#comment-334 For me, they deducted the openings. They didn't make allowances for studs, etc. ... but I'd be hard pressed to say they account for 25% of the wall area. A 1.5" stud every 16" is only 9%. Headers, jack studs, etc., will increase that, of course ... but surely not three-fold. Maybe you're overframing your walls! Oh, and it was suggested to me to use acoustic seal in all the gaps between double joists, where headers meet studs, etc., then cover them with tuck tape. You could also add 1/2" or 1" of rigid insulation on the exterior, and tuck tape the joints, to provide a full thermal break ... but that's going to cost a chunk more! For me, they deducted the openings. They didn’t make allowances for studs, etc. ... but I’d be hard pressed to say they account for 25% of the wall area.

A 1.5” stud every 16” is only 9%. Headers, jack studs, etc., will increase that, of course … but surely not three-fold. Maybe you’re overframing your walls!

Oh, and it was suggested to me to use acoustic seal in all the gaps between double joists, where headers meet studs, etc., then cover them with tuck tape.

You could also add 1/2” or 1” of rigid insulation on the exterior, and tuck tape the joints, to provide a full thermal break … but that’s going to cost a chunk more!

]]> By: Scott http://360winnett.com/2009/02/26/something-blue/#comment-333 Scott Thu, 05 Mar 2009 20:59:29 +0000 http://www.360winnett.com/?p=702#comment-333 Did they calculate it per gross sq ft of wall area or did they make an allowance for studs, headers, protrusions and the like (which comprise about 25% of the total external envelope of a house?). I assume they must take the sq ft of window and door openings out of the equation. Did they calculate it per gross sq ft of wall area or did they make an allowance for studs, headers, protrusions and the like (which comprise about 25% of the total external envelope of a house?). I assume they must take the sq ft of window and door openings out of the equation.

]]> By: Colin http://360winnett.com/2009/02/26/something-blue/#comment-332 Colin Thu, 05 Mar 2009 20:41:12 +0000 http://www.360winnett.com/?p=702#comment-332 $1 per inch per square foot is what I paid for BASF Walltite. $1 per inch per square foot is what I paid for BASF Walltite.

]]> By: Scott http://360winnett.com/2009/02/26/something-blue/#comment-331 Scott Thu, 05 Mar 2009 18:15:19 +0000 http://www.360winnett.com/?p=702#comment-331 It's based on square footage (with probably a premium for small jobs). Interesting to see what he paid, as when I was at the Toronto National Home Show last weekend, I asked one of the companies offering high-density spray foam insulation (both regular and 'eco' versions) and it was in the order of $1+ per square foot per inch of depth + tax, depending on which particular brand is used. With 3 inches (in order to get about R20) usually used on exterior walls that's $3+ per square foot of wall area. but, nothing beats it. It’s based on square footage (with probably a premium for small jobs). Interesting to see what he paid, as when I was at the Toronto National Home Show last weekend, I asked one of the companies offering high-density spray foam insulation (both regular and ‘eco’ versions) and it was in the order of $1+ per square foot per inch of depth + tax, depending on which particular brand is used. With 3 inches (in order to get about R20) usually used on exterior walls that’s $3+ per square foot of wall area. but, nothing beats it.

]]> By: Dan You http://360winnett.com/2009/02/26/something-blue/#comment-330 Dan You Thu, 05 Mar 2009 18:08:09 +0000 http://www.360winnett.com/?p=702#comment-330 Hi Jeremy - I think the house is looking great. Thank you for sharing all of this info for us to learn from. Can you give a rough estimate of what it costs to spray insulate? Thanks - DAN Hi Jeremy –
I think the house is looking great. Thank you for sharing all of this info for us to learn from. Can you give a rough estimate of what it costs to spray insulate?

Thanks – DAN

]]> By: Ken http://360winnett.com/2009/02/26/something-blue/#comment-329 Ken Wed, 04 Mar 2009 06:01:26 +0000 http://www.360winnett.com/?p=702#comment-329 I think Scott has a point. Did some digging and found a reference for unvented roof assemblies under the International Residential Code, 2007 Supplement, section R806.4 "Unvented Attic Spaces". Have a read through the following page: http://www.inspectorsjournal.com/forum/topic.asp?topic_id=6120 At the bottom of the page, there's a link that actually opens up a pdf of the IRC 2007 supplement. On page 73 of the supplement it states the following (paying close attention to point #2): R806.4 Unvented attic assemblies. Unvented attic assemblies (spaces between the ceiling joists of the top story and the roof rafters) shall be permitted if all the following conditions are met: 1. The unvented attic space is completely contained within the building thermal envelope. 2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly. 3. Where wood shingles or shakes are used, a minimum 1⁄4 inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing. 4. In climate zones 5, 6, 7 and 8, any air-impermeable insulation shall be a vapor retarder, or shall have a vapor retarder coating or covering in direct contact with the underside of the insulation. 5. Either Items a, b or c shall be met, depending on the air permeability of the insulation directly under the structural roof sheathing. a. Air-impermeable insulation only. Insulation shall be applied in direct contact to the underside of the structural roof sheathing. b. Air-permeable insulation only. In addition to the air-permeable installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified in Table R806.4 for condensation control. c. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact to the underside of the structural roof sheathing as specified in Table R806.4 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation. I know this is based on US based International code, but it would probably be worthwhile to bring up with your building inspector if there should be a vapour barrier on the ceiling side. The worry is that any moisture that did get in between the closed cell foam and the vapour barrier would have no place to escape, whereas without the vapour barrier then moisture could then escape to the interior side. It also sounds like your setup falls under 5.c. air impermeable + air permeable insulation. sorry for the long message! I think Scott has a point. Did some digging and found a reference for unvented roof assemblies under the International Residential Code, 2007 Supplement, section R806.4 “Unvented Attic Spaces”.

Have a read through the following page:

http://www.inspectorsjournal.com/forum/topic.asp?topic_id=6120

At the bottom of the page, there’s a link that actually opens up a pdf of the IRC 2007 supplement. On page 73 of the supplement it states the following (paying close attention to point #2):

R806.4 Unvented attic assemblies. Unvented attic assemblies (spaces between the ceiling joists of the top story
and the roof rafters) shall be permitted if all the following conditions are met:

1. The unvented attic space is completely contained within the building thermal envelope.
2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly.
3. Where wood shingles or shakes are used, a minimum 1⁄4 inch (6 mm) vented air space separates the
shingles or shakes and the roofing underlayment above the structural sheathing.
4. In climate zones 5, 6, 7 and 8, any air-impermeable insulation shall be a vapor retarder, or shall have a
vapor retarder coating or covering in direct contact with the underside of the insulation.
5. Either Items a, b or c shall be met, depending on the air permeability of the insulation directly under the

structural roof sheathing.
a. Air-impermeable insulation only. Insulation shall be applied in direct contact to the underside of the
structural roof sheathing.
b. Air-permeable insulation only. In addition to the air-permeable installed directly below the structural
sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing
as specified in Table R806.4 for condensation control.
c. Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct
contact to the underside of the structural roof sheathing as specified in Table R806.4 for condensation
control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.

I know this is based on US based International code, but it would probably be worthwhile to bring up with your building inspector if there should be a vapour barrier on the ceiling side. The worry is that any moisture that did get in between the closed cell foam and the vapour barrier would have no place to escape, whereas without the vapour barrier then moisture could then escape to the interior side.

It also sounds like your setup falls under 5.c. air impermeable + air permeable insulation.

sorry for the long message!

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