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dpatch
Attic Insulation dilema
dpatch

I am a widow, trying to do a major remodel. I am trying to educate myself as I go, and although it's slow-going, I have finally completed the framing and electrical, plumbing, and HVAC rough-in. I have installed new energy efficient doors and windows, added new Hardie siding to the exterior, and put on a new metal roof. I am now ready for insulation and sheetrock, but am having a hard time figuring how I should insulate the attic. I have perforated exterior soffit in place, and a ridge vent the length of the roof. Spray foam insulation under the roof decking is not an option. The house is a very simple straight-run ranch type design, 66' x 26'. The roof pitch is not steep. I have put a thermal barrier product called Polaralum under the metal roof. Now I am trying to decide what kind of insulation to put in the attic. In particular, I'm wondering if it would make any sense to put batts in between the roof rafters, and to also put batts in between the ceiling joists. Just wondering if this would enhance the insulating properties of the attic and help to minimize the heat/cold transfer to the conditioned space below. I like the idea of batts between the ceiling joists because then I could still see the 2x4's. (Could I then put a plywood 'floor' over the batts on top of the joists?) The attic is not tall enough to stand up in, so I'm not thinking of it as any kind of 'living space,' but possibly for some additional storage. (I had to put my HVAC system in the attic, as it was really the only option.) One suggestion I've had was to put 5 1/2" of blown-in insulation above the ceiling, which I guess is pretty standard, but what happens if you ever need to find the wiring, plumbing, bathroom exhaust fans, can lights, etc. in the attic? Any help or recommendations would be greatly appreciated.

MtMan54
Re: Attic Insulation dilema
MtMan54

Hi, It is to late to think of insulation, you need to know how you will insulate before you do the framing. Thanks

ed21
Re: Attic Insulation dilema
ed21

Typically with a ridge vent and soffit vents the insulation would be placed on the ceiling to allow airflow through the attic. Baffles should be placed at each rafter bay to keep the insulation from blocking the air flow.
What is the recommended insulation R value where you are? Around me the code says R-38. Chances are it's more than what you have from the rafter depth alone, so no you don't want a plywood deck. No storage. A plywood deck around HVAC unit to allow for maintenance is advisable.
Personally I would use batts, not blown in. The joists are probably 2x6 or 8 at least, not 2x4 on less you have trusses.

dpatch
Re: Attic Insulation dilema
dpatch

Thank you for your response. I really appreciate it. The ceiling joists are 2x4's with trusses. I know I need to keep an un-obstructed air-flow for ventilation, and I think I'm understanding that I won't be able to put any kind of 'floor' for storage in the attic. I guess I just need to make a decision on either blown in or batts and keep moving forward.

keith3267
Re: Attic Insulation dilema
keith3267

With truss roofs, an attic floor is just not practical. If you have a crawl space, consider an all in one, aka gas pack installed outdoors. These do not take up any living space. They are only a little larger than a typical outdoor compressor unit and all the ductwork is in the crawl space. If you are on a slab, then this is not an option.

You will have to hang the HVAC if you put it in the attic. Access to it to work on it will always be difficult. You may be able to run 2x4's along the faces of some of the trusses to support a platform above the insulation and around the HVAC unit.

I have seen all in one units that run the ducts through the attic, so maybe this would work with a slab. But you end up with a big square duct running up the side of the house. You could put a fake chimney around it to hide it I guess.

But to answer your first question, if you are DIY, use batts. You won't need to mess with the baffles as long as you trim off the excess fiberglass near the soffits so that air can flow up through the soffits, into the attic and out the ridge vent.

Putting insulation between the rafters will not do anything to save energy, it would only be a waste of money.

MtMan54
Re: Attic Insulation dilema
MtMan54

Hi, Do you guys actually believe your little work around tricks solve problems, she is going to know they don't when she gets the heating and cooling bills. Thanks

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