I realize this topic has been covered numerous times. I just spent 20 minutes looking through old posts and found nothing that dealt specifically with my situation.
New home construction, upstate NY. FG batts used (Yeah, I know but best estimate was 12 grand for spray-in and I can’t swing it). House will be heated with a wood fired boiler, so heating costs aren’t a huge issue.
Anyway I have knee-walls on 2nd and 3rd floors. Sub floor installed in all attic areas as well as wall sheeting on the cold side of the wall. I am not concerned with storage space in these areas. Does it make sense to insulate the knee-walls like an exterior wall with batts and use blown-in cellulose on the floors?
House wrap on the backside of the walls and on top of sub floor worth the money?
Better ideas?
Thanks a lot for any input
Andy
Replies
I wouldn't insulate the knee walls in the attic.
It will keep the heat inside the attic, a bad thing in winter. Ice dams and possible leaks.
It could probably be pulled off with plenty of ventilation.
Thoughts determine what you want,
Action determines what you get
<< I wouldn't insulate the knee walls in the attic.
It will keep the heat inside the attic, a bad thing in winter. Ice dams and possible leaks. >>
Well, I'm confused already... why wouldn't you want to keep heat in? and wouldn't keeping the attic insulated prevent ice dams by keeping the roof from heating up from the inside out? Justin Fink - FHB Editorial
Your Friendly Neighborhood Remodelerator
Well guys, sorry for the confusion. Amazing how difficult it is to describe things effectively sometimes.
Attic space referred to in my original post is the triangular section behind the knee walls, maybe that will help.
Knee walls on 2nd and 3rd floor, living space on each floor.
Knee walls have osb sheathing installed on the side away from living space. Sub flooring installed in the space behind the knee walls.
The storage space I am unconcerned with is the triangular section behind the knee walls.
Look at these.They recommend insualting the ceiling and not the kneewalls.One of the reasons is that it is easy to get sneak air pathes from the kneewalls.http://www.buildingscience.com/documents/profiles/designs-that-work-cold-climate-minneapolis-profile/view?searchterm=knee%20wall
http://www.buildingscience.com/documents/profiles/designs-that-work-very-cold-climate-aspen-profile/view?searchterm=knee%20wall
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Because when the heat gets into the attic it's not going to come back into the house. Let it go man.
Insulated knee walls in the attic retain heat. I was in an attic this winter that had the knee wall insulated. The attic was 60 degrees. When it was 10 degrees outside. THe HO called about her roof possibly leaking due to ice dams.
You really don't want that much snow melting and freezing on your roof.
As for the original post I am still confused so I am going to bow out of this conversation.
Thoughts determine what you want,Action determines what you get
Edited 3/21/2007 2:30 pm ET by Stilletto
andy.. draw a cross section of your house
take a highlighter and mark out which part will be "heated" and which part will be "un-heated"
delineate those two with your highlighter
the higlighter is your insulation line..
and the answer is... if you want ot reduce your heated area ... insulate the kneewall & the floor behind the kneewall
if you want to use the "attic" space behind the knweewall ( like for occasional storage ).. then you have to insulate the rafters over the kneewallMike Smith Rhode Island : Design / Build / Repair / Restore
and that would be the way my house was done.
Thanks Mike. So assume I'm going with the option of insulating the kneewall and the floor behind it.
Can I blow in cellulose on top of the sub floor behind the kneewall rather than insulating joist cavities below? Would foam board be a good idea on the kneewalls to help with air movement? I had thought I would insulate with FG batts, then foam board, then drywall.
Thanks. Andy
if you have access to the joist bays below.. you should build a dam on the warm side of the kneewall above.. and insulate from that dam to the outside band joist
then insulate the kneewall..... AND blow insulation on top of the kneewall floor
you need another dam at the plate line to keep the insulation from filling your soffitsMike Smith Rhode Island : Design / Build / Repair / Restore
Foam board necessary on the kneewalls, immediately under drywall?
The kneewalls are sheathed with osb on what will be the cold side.
Edited 3/22/2007 7:44 am ET by andyb
foam board would be a nice addition.. upstate NY... it'll be mighty cold on the other side
two choices : foam board over the osb .. installed from the kneewall side
or
applied on the warm side.... i would then furr the kneewall horizontally over the foam..
also.. you have to make up blocks to mount your elec. outlets on so they will wind up flush with the finish wallMike Smith Rhode Island : Design / Build / Repair / Restore
I understand where you're coming from, I guess I misunderstood that the attic won't be living space. If it were, then it makes sense to insulate, I would think.Justin Fink - FHB Editorial
Your Friendly Neighborhood Remodelerator
What do you mean when you say there is "wall sheeting" on the cold side of the wall? Assume it's a typo and you meant "sheathing"? Are we still talking about knee walls when you say 'cold side of the wall'?
Will both the 2nd and 3rd floors be living space? I'm not clear on what you mean when you say you aren't concerned with storage.
More information please.
Justin Fink - FHB Editorial
Your Friendly Neighborhood Remodelerator
Are the knee walls in the attic the same kneewalls you are refering to as 2nd and 3rd flooor? I'm a bit confused.
Regardless of where these walls are.....if the space is heated, the walls need to be insulated.
If you are talking about an unheated attic, than no. Do not insulate knee walls. But do insulate the floor, as it is also the ceiling for the heated space below.
J. D. Reynolds
Home Improvements
Knee walls on 2nd and 3rd floors? Sounds like an A-frame chalet or like that. We need more description. If it is as I envision it, in elevation you have living space on 2nd, 3rd floors, with attic space to the sides of the 2nd floor space and to the sides and above the 3rd floor, and between the knee walls and flat ceiling you have sloped ceiling. Correct? So why wouldn't you have insulation everywhere between living space and where it is cold? If you don't, you'll have heat loss into attic space, leading to a log of melting, maybe ice dams if the roof isn't steep enough. I would expect a problem with movement of air between side attic spaces, from 2nd floor space and 3rd floor space, right through any FG insulation above the sloped ceiling areas (great air filtration, not much net R value). I would think that you need either a totally unvented but insulated roof, so that the attic spaces are conditioned, or else a vented attic, with provision for passage of air under the roof deck between floors without compromising the insulation there. For that, closed cell foam would be good. For the rest, horizontal areas under the attic spaces and in vertical wall sections, certainly not FG (come on - a brand new house, and FG???), but blown cellulose in the horizontal floors and densepack in the walls. It'll be interesting to see what others propose.
Edit: even if your heat source give you cheap heat, it's a matter of discomfort resulting from cold spots in the exterior walls where not properly insulated and the resulting draftiness.
Edited 3/21/2007 2:15 pm ET by DickRussell