insulation

[Raider Bill]

What do you figure will be my best bet for insulation?
My way of thinking is to insulate the ceiling to keep heat/a/c inside the living space. There is a bit over 6 ft dead space between my ceiling and roof deck and I can't see letting anything get up into that.
Have plenty of space for batts, blow in or spray foam.
Everything else is ICF so don't want to skimp here which doesn't make sense.

Suggestions please?

[scsmith42]

Bill, to my knowledge spray foam would be the best choice, although it costs significantly more than fiberglass bats.

Properly applied, it will seal all of the gaps, and has excellent insulating properties.

Scott

[Don_Papenburg]

I have been doing a bit of reading on this stuff lately .  Too bad it was not sooner as I have mine all bricked now .     
  Do not skimp on your ceiling Take it up to an R80 or more .  Use the spray foam for th e first layer . It seals all cracks .  That stops air movement and vapour infiltration. Then you can use  cellulous ,blown in   (cheapest perR)  or ThermaX (most R per inch)
  However if you are going to run any utilities in the attic,   Insulate the roof . 

Now onto your side walls R60 is what you want to shoot for .   Insulate the outside of your forms .  The Thermax with the aluminum foil is the cheapest per R for outside walls . It will not hold up to moisture (ground contact) so it needs a good cover. Use extruded poly (pink, owens corning or blue ,dow) for anything in ground contact but it needs some covering also protection from the sun.

[isawlogs]

 Don ... would that high " R " range be to combat the heat ,  here standard would be R20 for the walls and R40 for the ceilling .

[Norm]

The cheapest easiest it to have it blown in. The more the better but your pocketbook will dictate how much.

[Handy Andy]

  I like the fiberglass for ceilings, because of weight.  Cellulose appears to weigh more per r value, so more chance of bowing down your ceiling if it is drywall. Don't know if I caught what your ceiling is made of.  Only thing is, with loose fiberglass, you need to have blocked your overhang and built your vents up above the insulation so the wind doesn't blow it around in your attic.  

[mad dog]

                                                                                                                                                    whatever You use in your attic make sure its properly vented,

[Raider Bill]

 
I'm thinking spray foam is the best way to start as you say it will seal everything in. I can add blow in later if needed.
Ceilings will be mostly wood except in bathrooms and closets.

Don, this is where I'm getting confused, if I insulate the ceilings good do I need to also do the roof deck? I know it will get hot up there but my thinking is to super insulate the ceiling and vent the dead space above?
Also this is a ICF house I'd think the walls were insulated enough?
There shouldn't be anything run up there except for some wires for lights and fans. All a/c ducts will be run under the living space floor which is the ceiling of the ground floor shop/garage.

[Raider Bill]

                                                                           whatever You use in your attic make sure its properly vented,

My thinking here is to have a inch or so vent between the metal roof and decking top to bottom. I'm not sure if I will have gable vents or soffit vents. Have read that you should not use both. Also maybe a couple of those solar roof fans but haven't really read up on them as of yet.
Here at my house in Florida I have the decking and ceiling insulated, soffit vents and a thermostat controlled fan that turns on only when it gets real hot up there. Keeps things almost cool up there.

[scsmith42]

Bill, after a lot of thought I recently decided to spray foam insulation directly to the bottom of metal roofing panels that were installed over skip sheathing (rather than plywood).  This is on an old farmhouse project that I'm remodeling.

My logic was that foam sprayed directly onto the metal would provide a non-condensing surface, which would be beneficial both for the atmosphere inside the house as well as the durability of the metal roofing.  I have heard that there are sometimes issues with metal roofing rusting out "from the inside" when installed over plywood, because humidity and moisture get trapped between the underside of the roofing and the plywood.

I also like the idea of insulating the roof all of the way up to the eaves, rather than just to your ceiling, because if you can keep your attic cooler, then this should mean less thermal transfer into your living areas.

Regards,

Scott

[Raider Bill]

Scott,

What is skip sheathing?

[scsmith42]

Bill, skip sheathing is where you nail down wood strips, such as 1 x 6's, across your rafters, instead of solid plywood sheathing. 

I typically install mine on the same spacing as the rafters - ie if my rafters are spaced on 24" centers, the 1 x 6's will be installed 24" on center.

Scott

[Raider Bill]

Scott,
are the1x6's perpendicular to the rafters or parallel?

[scsmith42]

Bill, they are perpindicular.  Basically you start at the base of the rafter and nail boards all of the way across your rafters, and then nail one board every 24" on your way up to the ridge.  I like to double my ridge boards too (two 1 x 6's nailed side by side - ie a 12" wide board at the top.

When you're done (and before the tin is installed) the roof looks like a giant lattice, with skip sheathing running from side to side and rafters running up and down.

I've got a photo on the camera; I'll see if I can upload it and post it later tonight.

Scott

[Raider Bill]

I was thinking of running 2x4's on their side on top of my decking then attaching my metal roof to that for a air vent [space]  top to bottom. Figure this will allow the hot air a place to go up and out.
So many choices.................

[Larry]

I’ve been studying a little (not much) on what to do on our roof.  There is a new idea that maybe originated north of the border.  Skip the poly vapor barrier and install a gasket when the drywall is installed.  Insulate with cellulose.  Skip the attic venting.  Like I said I need to do a little more research before I buy into this idea but food for thought.  Maybe caulk the drywall and just go with cellulose.

Few thoughts on metal roofs since ya brought it up.  We put a true standing seam roof on a house I built 18 years ago.  The metal was put down over plywood and felt.   Part of the house had cathedral ceilings and part had an attic.  Zero problems in 18 years.  I’ve had experience with a couple of other metal roofing systems also but not near as long time frame.  On the house we are getting ready to build I am going to use conventional metal with exposed screws as it is about 1/3 the cost of standing seam and goes on much faster.  I’m convinced with the new improved screws, if I put them down square, and don’t over torque the roof will outlast me.

[scsmith42]

Bill, one one of my barns I went the 2 x 4 route for the skip sheathing... if I had it to do over again, I'd use 1 x 6's instead.

The 2 x 4's were difficult to walk on, and you can see ridges in the finished roof above each one of them.

Planed 1 x 6's seem to have worked best for me.

Scott

[Don_Papenburg]

Isawlogs,  The R ratings are a minimum that you should use. As all codes are a minimum that should be used for building.  The extra insulation keeps the heat /cool in the building where you put it.The Idea is to cut your fuel use to near zero as possable.

Raider, No you would not need to do the roof deck if you do the ceiling.  But I would do the roof and keep all of the electical penetrations inside the conditioned space.  Every hole is a place for air movement . Air movement takes heat /cool with it .  That is one reasons I have lost interest in using fiberglas inulation in my buildings.  It lets air move through the blanket ,like a furnace filter.

If your inulation is in tight contact with your roof ,Like SIP(structural Inulated Panels) you will not need to vent. If you have airspace you have a place for condensation . Simular to a part full tank of fuel will condense moisture inside the tank a full one will not.

 Bill as far as the ICF goes It is cheaper to add more to the outside than to pay for the energy to cool or heat later.    I added a second 2" EXP sheet to the outside of my house before I bricked it .  That gave me anR value of 30 with 8" of concrete.  I wish I had added two extra sheets at least.  Each 2"layer is cheaper than a half seasons propane cost. If you can keep the concrete from picking up the outside temperature  You can keep your house inner temp balanced . The concrete will helpmoderate temp swings with all the thermal mass..

I know this all sounds ferrun  but it works .   The last issue of Fine Homebuilding had a article fromm a builder thaty remodled three houses . He was shooting for zero enrgy consumtion He got close with the third house . It had R60 walls I do not remember what the roof was but I think it was more than R80.  These were old houses that he worked over . He also said that if he did it again  he would use heatmirror windows with triple pane glass.

[isawlogs]

 Makes a lot of sense to me , thanks for clearing that up . 

So Don on a regular stick frame how would you go about the insulating of it 

[scsmith42]

Bill, here are a couple of photo's of the 1 x 6 skip sheathing that I referred to earlier.  One photo is of the underside of a porch, showing the tin and sheathing installed above the rafters.  The other photo is of the eave of the house, where you can see the skip sheathing underneath the roofing tin.

One thing that I've learned with the various roofs that I've installed, is that it is important to plane the skip sheathing so that they are all the exact same thickness.  If you don't, any minor variations will be visible in the tin.

Regards,

Scott