insulating attic space

[rookie]

My wife and I are about to begin construction on our new house. We are building a modest 1820sq ft home with a bonus room in the attic space above the garage. There will be a door going from the bonus room into the rest of the attic space. This unused attic space is where the heat and air will be located. My question is should we insulate this attic space or just use an insulated exterior door between the bonus room and attic space. I was told that if I insulated this attic space that the heat and air equipment would operate more efficiently. This sounds logical but would there be any problems with moisture or ventilaton if the attic space was insulated? Any help here would be much appreciated.

[montytx]

Insulation is designed to keep heat in or out. IF your garage space has no interior space over it then you dont need to insulate it unless you want to. I cant see how insulating the attic would make the a/c run better. They do make a spray on attic liner that cuts down on heat. You may want to look into that.

Moisture shouldnt be an issue if the insulation is properly installed and the proper vents are in place to allow for air flow.

[giddonah]

I asked a friend of mine who does HVAC this question today (I guess it's technically yesterday). Anyway, he said he didn't know. It's hard to say. I was in an insulated attic today with him on a service call (fixing some poorly installed equipment that started leaking water through the ceiling). It was probably 110F up there. And I've been in sweat lodges. This was pretty close. Anyway, the evaporator was up there cooling air it pulled from the house. Everything was insulated, but the seams weren't taped, so it was pulling this 110F air into the system and leaking cold air into the attic (which didn't really help us out that much). But, the house didn't have any fans for the attic to move that hot air out. An uninsulated space might have been just as hot though (or close to it). But, if the system is sealed right, it's not cooling that air, it's cooling the air from the house, and if the system itself is well insulated, then I'm going to guess it won't make much of a difference. I was hoping rabager would comment on this one, but maybe my rambling might make sense to you.

I would like to add though, that when that hot air was cooled, it made a hell of a lot of water.

[rookie]

OK, so assuming I don't insulate that portion of the attic space I'm guessing that I need to insulate the wall separating the bonus room from the rest of the attic space and also use an exterior door between the two. Should I use a 2x6 partition wall so I can keep as much hot and cold from the attic space from getting into the bonus room? Is this the proper way to separate a insulated room from an uninsulated room?

[giddonah]

It would be just about the same thing as insulating an exterior wall, except for the siding on the outside. Just make sure to insulate every surface that separates insulated from uninsulated.

[danh]

Since the HVAC is in an area that will be exposed to cold during the winter and attic temperatures during the summer, make sure that all the equipment is well insulated & sealed. If your HVAC guys do a poor job of insulating & sealing the equipment, you could still have moisture problems. Unfortunately, when it comes to sealing ducts, most installations are poor...

[montytx]

I agree, a bad a/c install can wreak havoc on your house, your bills and your sanity.

[rbisys]

Greetings.

I'm assuming (oops) that you are insulating rafters.

Rafters are deadly because energy passes directly from the shingles to the interior where it is RADIATED to all other surfaces. Of course this is true for trusses too.

If you want a super insulated home ck my answer to Question.