mtCDCcb wrote:1) I want to insulate the rafters of my garage with batt insulation (id do it myself). There is no living space above and the garage is unconditioned. If I use batt insulation do I need to vent the rafters, if I do would it just be easier to use spray in insulation?
There are two types of attics: 1) the standard vented attic with insulation laid against the ceiling and the attic is vented to the required minimum (or greater) requirements; 2) the sealed attic with insulation against the underside of the roof decking and no ventilation - thus it is called a sealed attic.
With 1), the standard vented attic, the thermoenvelope is the insulated walls and the ceiling. That creates the envelope which encloses the conditioned space. The attic is basically at outside temperature with exceptions for heat gain; the attic is hotter than outside temperature during the summer because the ventilation is not complete and sufficient to ventilate the attic to replicate the outside temperature, and the attic is warmer than the outside temperature during the winter, and colder than the conditioned space within the thermoenvelope below.
With 2), the sealed attic, the thermoenvelope is the insulated walls and the roof decking. That creates the envelope which encloses the conditioned space. The attic is basically at the same temperature as the conditioned space below, and the attic is considered to be 'conditioned space' for heating/cooling sizing as the ceiling does not act as much of an insulator between the attic and the conditioned space below.
Saying that you want to 'insulate the rafters' indicates you are thinking of 2), a sealed attic. Batt insulation is not a good choice for that use as most batt insulation you will get will be faced (has a paper or foil facing) and the facing is required to be in substantial contact with building material, i.e., such as laying on the drywall ceiling. This is because the facing will burn. Using 'unfaced' insulation is a way to avoid the problem with leaving the facing exposed, however, unfaced creates other problems.
Also, the codes basically do not allow fiberglass insulation batts (faced or unfaced) to be installed on the rafters (there are exceptions in the code).
If you are going to go with 2), the sealed attic, then spray foam insulation is what you want to use. However, the spray foam insulation comes with its own drawbacks, and that is protecting the spray foam insulation from heat and flame, so a thermal barrier and an ignition barrier may need to be installed, of just an ignition barrier - depends on the specific conditions of the attic.
Is the garage going to have a ceiling, or is the garage going to have open trusses with the 'attic' open all the way to the roof decking?
Additionally, if you are to insulation the garage attic, you will want to insulate the garage walls and the garage doors.
I know that I have not answered your questions, and that I have given you a bit to consider, but the answers will help answer the question.
2) My kitchen is a the front of the house and I need to vent my kitchen range. I don't want tje vent from my range at the front of the house for aesthetic reasons. I asked the inspector and he said he didn't care where I vented my range. My question is can I join my range with other ducts in the home so it vents out somewhere other than the from of the house?
No, all the exhausts will need to be vented to the outdoors separately.
Yes, you can vent the exhausts to the outdoors through the sides or back of the house.
Not sure what "somewhere other than the from of the house" means, but - no, you cannot exhaust into the garage, attic, or crawlspace (if present).