Green Building Forum - How much insulation should a ceiling have?

How much insulation should a ceiling have?

tony — Sun, 07 Jun 2009 12:52:10 +0100

The recent vote seems to be saying that we dont put in enough insulation -- how much should a ceiling have?

How much insulation should a ceiling have?

trule — Sun, 07 Jun 2009 14:04:12 +0100

...to Passiv Haus Standards and beyond...(in a buzz lightyear voice)

How much insulation should a ceiling have?

ralphd — Sun, 07 Jun 2009 15:39:19 +0100

RSI 10.6(R60) is good enough for Alaska, so you shouldn't need any more than that!
http://www.gwscientific.com/cchrc/rtf_data/roof/roof.html

When I calculated insulation vs. heat costs, going beyond RSI8-9 pushed the payback beyond 10yrs.

-Ralph

How much insulation should a ceiling have?

tony — Sun, 07 Jun 2009 15:40:45 +0100

how long will the house be there?

How much insulation should a ceiling have?

ralphd — Sun, 07 Jun 2009 15:51:38 +0100

Posted By: tonyhow long will the house be there?

Much longer than anyone can reasonably forecast energy costs or insulation costs.
However in an open attic it is easy to add more insulation in 10yrs if the economics change. My parent's single-story house built ~30yrs ago has R20 in the attic and I'll be helping them add insulation to bring it up over R40.

-Ralph

How much insulation should a ceiling have?

Mike George — Sun, 07 Jun 2009 16:36:26 +0100

Posted By: tonyhow long will the house be there?

Can't think why this received a negative vote. Seems a reasonable enough question to me

How much insulation should a ceiling have?

ralphd — Sun, 07 Jun 2009 21:09:49 +0100

Posted By: Mike George
Posted By: tonyhow long will the house be there?

Can't think why this received a negative vote." alt="" src="https:///forum114/extensions/Vanillacons/smilies/standard/shocked.gif" >Seems a reasonable enough question to me

Indirect communication is not open and constructive.
http://www.cps.usfca.edu/ob/studenthandbooks/321handbook/indirect.htm

-Ralph

How much insulation should a ceiling have?

Mike George — Sun, 07 Jun 2009 21:19:19 +0100

How much insulation should a ceiling have?

ralphd — Sun, 07 Jun 2009 21:31:35 +0100

Watch out, I've got a mouse loaded with voting points, and I'm not afraid to use them!

How much insulation should a ceiling have?

Mike George — Sun, 07 Jun 2009 21:41:41 +0100

Go for it

How much insulation should a ceiling have?

sinnerboy — Mon, 08 Jun 2009 13:41:34 +0100

For refurbs - it depends . If you can't alter roof fabric for budgetary and planning restriction concerns - then a careful judgement has to be made

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=4074&page=2#Item_15

For new builds - I would take PHI guidelines to be apt .

http://www.sei.ie/Renewables/Renewable_Energy_for_the_Homeowner/SEI_Passive_House_A4.pdf

I think we ( Irish ) and thee ( UK ) are close in many ways - not least geographically- so from page 2 ( PDF Page 8 ) we get U Value of 0.15 W/m2K - not too far off B Regs in case of Attic Roofs . Now whist it is possible to way past this ( 400mm quilt )
- http://www.scanhome.ie/archive/S09%20Super%20Passive%20-%20single%20storey.pdf

What then of the attic space ? Want to lose it as storage space . Some will say yes .... may lead to demand for more m2 ...

For ceilings on slope - here's "one I made earlier" for ceiling-slopes-with rafter 0.12 w/m2K
( using this http://www.xtratherm.com/software/software.php )

Note - 15% factor for bridging of insulation as per BR 443 2006

Roof Slope WARM 600cs rockwool over + between +below to 0.12

U-value [W/m2 K] 0.12

Layers Thickness Conduct'y Resistance
[mm] [W/m K] [m2 K/W]
Outer Resistance 0.100
Tile/Batten Space 1 1.000 0.001
Breather Membrane 1 1.000 0.001
Rockwool Flexi 0.038 100 0.038 1.931
Rockwool Flexi 0.038 200 0.038 3.861
Vapour Control layer 0 1.000 0.000
Rockwool Flexi 0.038 75 0.038 1.448
Plasterboard 13 0.180 0.069
Internal surface resistance 0.100

Upper/lower resistance 8.710 / 7.511 W/m2 K
Correction for air gaps / mechanical fasteners 0.000 W/m2 K

Details of layers with thermal bridging or corrections for air gaps or mechanical fasteners are given below.

Rockwool Flexi 0.038 (3)
Is there repeating thermal bridging? Yes
Bridging conductivity [W/m K] 0.13
Bridging material Softwood
Bridging thickness [mm] 100
Fractional area of bridging [-] 0.15
Correction for air gaps Not applicable
Correction for mechanical fasteners Not applicable

Rockwool Flexi 0.038
Is there repeating thermal bridging? Yes
Bridging conductivity [W/m K] 0.13
Bridging material Softwood
Bridging thickness [mm] 225
Fractional area of bridging [-] 0.15
Correction for air gaps Not applicable
Correction for mechanical fasteners Not applicable

Rockwool Flexi 0.038
Is there repeating thermal bridging? Yes
Bridging conductivity [W/m K] 0.13
Bridging material Softwood
Bridging thickness [mm] 75
Fractional area of bridging [-] 0.15
Correction for air gaps Not applicable
Correction for mechanical fasteners Not applicable

Brief description

100 top battens - across not along rafters + 100 RW
225 rafters + 200 RW
75 soffit battens - across not along rafters + 75 RW

How much insulation should a ceiling have?

sinnerboy — Tue, 09 Jun 2009 13:52:12 +0100

Posted By: tonyThe recent vote seems to be saying that we dont put in enough insulation -- how much should a ceiling have?

How can this question - opening a thread be awarded a negative point ? I am all for occasional bouts of levity but there is some immaturity at play here . Having at first thought community moderation was not bad idea - it won't be if abused like this

PS - why aren't negative point awarders identified ? Why just positive ones ?

PPS - why don't my "qoutes" work properly ?

How much insulation should a ceiling have?

ralphd — Tue, 09 Jun 2009 17:15:00 +0100

Posted By: sinnerboy
Posted By: tonyThe recent vote seems to be saying that we dont put in enough insulation -- how much should a ceiling have?

How can this question - opening a thread be awarded a negative point ?

The question does not state the source for the voting on insulation levels. To me it seems to be an indirect way of stating Tony's belief that more insulation should be used in ceilings.
I think good discussion does not contain weasel words or indirect communication.
http://en.wikipedia.org/wiki/Weasel_word

I also think the Egyptian pigs thread shows that members are still trying to figure out the community moderation, and how they want to use it. I think it shouldn't just be used to stop spam, but to limit discussion to topics that are of interest to the members. This way it less work for the moderator and the members don't have to wait until someone calls someone else Hitler before a thread can get shut down.

-Ralph

How much insulation should a ceiling have?

ralphd — Tue, 09 Jun 2009 17:24:52 +0100

Posted By: sinnerboyPPS - why don't my "qoutes" work properly ?

Format comments as Text is probably selected. Change to Html (that messes me up frequently too).

-Ralph

How much insulation should a ceiling have?

sinnerboy — Tue, 09 Jun 2009 17:56:16 +0100

The question does not state the source for the voting on insulation levels. To me it seems to be an indirect way of stating Tony's belief that more insulation should be used in ceilings.
I think good discussion does not contain weasel words or indirect communication.
http://en.wikipedia.org/wiki/Weasel_word

I also think the Egyptian pigs thread shows that members are still trying to figure out the community moderation, and how they want to use it. I think it shouldn't just be used to stop spam, but to limit discussion to topics that are of interest to the members. This way it less work for the moderator and the members don't have to wait until someone calls someone else Hitler before a thread can get shut down.

-Ralph

Tony does believe in more insulation . His query was conversational - not weasel .

( Or , - Clearly , I feel it was - and most people would think so too .... )

The Egyptian pigs thread contains some pretty malignant stuff . I don't read it as you do .

Thank you for the tip on qoutes - appreciated

How much insulation should a ceiling have?

Mike George — Tue, 09 Jun 2009 19:12:27 +0100

Posted By: sinnerboy
Posted By: tonyThe recent vote seems to be saying that we dont put in enough insulation -- how much should a ceiling have?

How can this question - opening a thread be awarded a negative point ? I am all for occasional bouts of levity but there is some immaturity at play here . Having at first thought community moderation was not bad idea - it won't be if abused like this

I have started to counter negative votes which I feel are unwaranted

How much insulation should a ceiling have?

jolly-green-giant — Tue, 09 Jun 2009 21:32:44 +0100

word to the wise dont use celotex or kingspan between ground floor and first floor ceiling void as it has very poor sound deadening qualitys use rock wool type much more sound absorbtion found this out to late myself .
i would of thought that 120mm celotex type insulation would be more than enough for the uk