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hi guys,
appreciate any help with this monkey puzzler!
i’m building my own house later this year, and am working out the price and the bugs at the moment.
my roof structure is going to be like so- the house is 30′ wide with a 12/12 pitch,we place the seat cut of the rafter on a 2*6 at the edge of the first floor deck, and start from there. my knee-walls are going to be 5′ from the edge, to make walls and support the middle of the 2*9 rafters @ 16″O.C. spray-on insualtion’s in ireland are not an option for the residential application. i need to insulate and vent the roof taking these factors into account, we don’t have those plastic baffles that you lot put under the plywood roof sheathing; we don’t seem to have recessed lights that can have insulation put near them.
i am in trouble with this one.
our climate is not to bad- we never go below 20f and above 80f in temp.
help!!!
Replies
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Eddie,
I don't think you have a problem roof structure. We call what you are building an "A Frame."
Do your codes mandate venting now?
Is cellulose available in your area?
I would suggest getting IC rated recessed lights, or at least getting some nice american to mail them to you. You guys use 120V?
I suggest you call the entire roof assembly the thermal envelope and sheath, air seal, and insulate it accordingly. Then build your kneewalls. This simplifies the matter of the attic space behind the kneewalls.
-Rob
*thanks for post Rob.we don't have 'codes'. we have reg.'s that are no way near as strenuous as yours', or as informative either. our building system is so traditional, that when you veer away from it, even a little, your creamed for extra problems, and cost of materials.i think there is cellulose, not sure of price. if i blow in cellulose, between the rafters, do i not need to vent?we use 220v electricity. and getting recessed light's that are rated for insulation, is not an option - cost again.also, because our timber does not come in any longer lenghts than 24' (not a problem), or bigger than 9*2, i have to build a knee-wall for the midspan support.appreciate the info, any more?
*Eddie, Rob is off the mark a little, what you have is not anywhere's near an "A" frame.While we can't do too much about your fixtures from here (because of the voltage difference), we could help you order some of those styrofoam baffles from here, in Canada.With your climate you will do well with the space available for insulation. I'm not 100% sure but you may have a higher humidity and that would require some type of Vapour Barrier incorporated in your roof system. I don't know the type of roofing material you want to use so I don't know if you would benefit from ventilation. I really isn't a negative to have ventilation in case I'm wrong.Gabe
*rob... i bet you meant "Cape"..(10/12 to 12/12 ) this is the traditional problem of how to insulate the "knee wall " portion of the cape... actually , the knee wall portion and all behind it can usually get about 12" of whatever insulation you want... the difficult protion is the slant ceiling from the kneewall to the flat attic.. (you do have a flat ceiling portion , right ? )... usually we vent this area with Propavent.. the stuff you can't get.. and we put foam below the rafters and furr the ceiling.. the attic area gets 12" to 18" of cellulose..the area around the kneewall also gets 12"+ (8" to 10" in the rafters below and 6" to 8" on the 5' flat portion of the kneewall floor..)think about setting you kneewall at 4' instead of 5' and put a closet in front.. th closet wall will be 6' + and you can use cut-down doors... you gain 2' of width on the 2d floor by going from 5' to 4' with a 12/12 pitch
*thanks for the post's guys.gabe - i'm going for a traditional roof like you lot, laminated shingles on top of felt, ontop of ply, on top of full 9*2 rafters.our only advantage over you lot is our timber is still the size its' called.mike - i do have a 'flat portion'.for the slant portion between the kneewall and the ceiling, i could rigid foam, could i?but the reason i was going to insulate like a cathedral ceiling, is because i have to keep clear of the recessed lights with the insulation.any more suggestion?good stuff
*would gable end venting work. the house is 90' long x 30' wide, 55' up from one gable end, the house kink's at a 45 degree angle, but there is a large attic space unbroken through the house.if there are any suggestion's, i'll take them allgood stuff
*what price are the styrofoam baffles you were talking about, to see if it's worth my while importing them. and could i use 1" polystyrene as a baffle, would it allow the warm air escape, and would it stop the air washing of the FG, would it take getting wet from condensation falling on it every now and then.appreciate the help guy'sgood stuff
*eddie,recessed lights are a source of heat loss into the attic and in snowy climates can be difficult to seal up enough to stop them being chimneys letting much heat out.Maybe you don't have the ice dam concern that we have in northern US, but you'd like to keep in the heat you paid for, right?So, may I suggest that you consider another approach to lighting rather than recessed lights? The benefit is that you avoid putting penetrations in the most important membrane in your house (the one on 'top' of the heating envelope). - track lighting - sconce lighting along the walls - soffit (or 'cove') lighting (flourescent tubes hiding in a boxed structure that runs all the way around your room, open side facing upward). This approach can provide a very even, natural 'day light' feel to any room (especially ones with low cielings). The box can be simple painted drywall or fancy mouldings that add decoration to the room. The heat is small, and because the top is open the materials you make it from are kept simple.Just a few thoughts for you to ponder.
*When the rafters sit on the first floor deck, I call that an A-frame.-Rob
*rob.. do you mean if they sit on the first floor "sill" ?... i hope eddie is describing a classic cape.. on top of the 2d floor joists he installed a 2x6 shoe and is using that as the seat for the rafter birdsmouth...'course i could be misreading it.. .............nah....say it isn't so, eddie...cause you wouldn't build nothin that ugly .... would ya ?...on the 2d reading, rob... if you take it literally .. then you're absolutely .........RIGHT
*Mike, shame on you! A-frames aren't ugly, they are kitsch! Pure '70s Americana (like using orange, brown and Avacado in your main decorating theme).On the other hand, eddie lives in Ireland, so he could be making a Swiss statement. They were using A-frames long before we were, and with enough gingerbread trim could look quite alpine.But then again, if he is in a Dublin or Cork suburb...
*guy's, you not pass judgement when your not sure of what you are talking about!BUT THANKS FOR ALL THE AMAZING INFORMATION, WHICH HELPED ME VERY MUCH!!!!
*so..... eddie..what tis it ?A-frame ... er .... Cape ?
*neither, it is a bungalow that we call a dormer house.where you live in the roof space also.i don't know what you lot call itgood stuff
*Well, come on. Give us a drawing then.
*I did a search on google. It appears that this is a generic term for what we would call a 1 1/2 story.
*that's it Bill!!some intellect at last
*dormer house, my ass.. it's a bleedin capehttp://kiernan.mayo-ireland.ie/Prop101.htmhah, hah, hah.....
*no-way mike, the owner of that house might not like what i'm about to say, but that house makes me sick.over here, the standard self-build/contractor build is of this type. sickening, but affordable.my plan is different. is almost a gabled barn.on the original issue. i'm going to throw out the shingled roof option, and go with a concrete tile approach, this way the ventilation problems go away.would appreciate some input on another post i just put up.any way, you seem to have more info on ireland than the average yank?good stuff
*2 irish grandmothers... post a pic of what you're building then.. you've got me confused as to what the architectural style is to be...
*no picture, not built yet, remember!but i will.i'm going to build with the craftsman influence.
*Eddie,I'm building a cottage with a similar configuration. I'm using 1/2" foam insulation to construct the vents. Cut 1 1/2" strips of the foam to use as spacers then cut the 1/2" foam in widths to fill the rafter space. I put heavy duty aluminum screen in the bottom of each rafter bay. Once the sheet rock is up I'll fill the rafter bays with cellulose. It's 1/2 the price of fiberglass and 10 times faster.FWIW
*>>we place the seat cut of the rafter on a 2*6 at the edge of the first floor deck, and start from thereThat's the description of an a-frame. Should have said secon- floor deck. Confusion and chaos results! All is forgiven. Would love to see a picture of something similar to what you are talking about, eddie. I like to see regional stuff that's unique.Steve